LED lamps DC or AC. AC LED lighting products are finding their niche and may expand beyond it. Using an incandescent lamp as a ballast

Laura Peters

LEDs Magazine

LED based assemblies alternating current often have light output and efficiency equal to those that use DC LEDs, without the need for an AC/DC converter. But can they find their place beyond the applications in which they are currently used?

The concept of AC-LEDs itself is neat. They do not require AC/DC converters and some of the other electronic components required to power DC-LEDs, and all the electronics between the AC source and the LED are simplified as much as possible. Indeed, when creating AC-LED applications where the LED is capable of driving directly from the AC line or from a step-down transformer, only an LED housing and a ballast resistor may be required for some applications. On the other hand, when using AC-LED, optimization of power management (power factor correction and total harmonic distortion correction) may be required. Until now, the scope of AC-LED applications has been limited to the niche of cornice lighting, garden and decorative lighting. But manufacturers of AC-LED assemblies claim that one day the entire market of retrofit LED lamps will switch to AC-LED.

This article examines the commercial availability of AC-LEDs, assemblies based on them, and power supply devices, and discusses the challenges that will lead to easier integration of AC-LEDs into electrical networks than is the case with DC-LEDs. It also touches on the possibility of AC-LED entering the retrofit lamp market, including MR16 lamps, A-lamps and downlights.

What does AC-LED mean?

It is important to note that the abbreviation AC-LED is actually incorrect: LED refers to diodes, that is, devices that pass current in one direction (direct current). However, using the so-called "AC-LED circuit", light emitting diodes (LEDs) can be connected directly to the power supply (usually 110 V/60 Hz or 230 V/50 Hz) and light up without a conventional driver. In each half-cycle of a sinusoidal alternating voltage, half the LEDs emit light and the other half do not. In the next half-cycle, the LEDs change roles. In this configuration, sometimes called back-to-back, or "true AC", a large number of LEDs connected in series can be driven directly from electrical network.

However, with this approach, the sequential inclusion of many LEDs in one chain becomes a factor limiting their efficiency. Therefore, several years ago, AC-LED manufacturers, including Lynk Labs of Elgin, IL, Seoul Semiconductor (Seoul, South Korea) and Epistar (Hsinchu, Taiwan), began producing LEDs, or rather LED assemblies, operating from low or high AC voltage with using simple control circuits. They are treated as low voltage LED assemblies, and assemblies with rectifiers connected directly to the AC mains. Typical supply voltages for such devices can range from 12 V to 240 V. Individual LEDs are connected in a chain, the peak voltage of which reaches, for example, 55 V in each half-wave of the 110 V mains voltage. “This is truly the use of alternating current based on high-voltage architecture” - said Brian Wilcox, vice president of North America at Seoul Semiconductor, a manufacturer of AC and DC LEDs and LED assemblies.

In comparison, DC-LEDs require a driver to convert AC mains voltage to low voltage. constant pressure, powering the LED. The driver includes an AC/DC converter, usually a high-capacity electrolytic capacitor, as well as other components, the number of which can reach 20, as, for example, in the 7-watt MR16 lamp. High power applications require even more components. However, Wilcox said that despite the simplicity of the electronic design, the development of AC-LED devices involves the need to overcome problems such as reducing total harmonic distortion, improving power factor and providing zone dimming. “Any one of the three problems is not trivial, especially when you try to solve all three at once,” Wilcox concluded.

In fact, it can be argued that all these problems, as well as the low efficiency compared to DC-LED, have limited the adoption of AC-LED to date. However, in the latest AC-LED and high-voltage products based on them, the above disadvantages have been largely eliminated. Also, the flicker problem should be solved in new devices. “Many people complain about AC-LED flickering. But this effect is a consequence of the spatial distance of the LEDs. It occurs when the LEDs are very far apart and the eye notices the 50-60 Hz rectified frequency component,” says Mike Miskin, CEO of Lynk Labs, a manufacturer of AC-LEDs, AC-LED assemblies, and drivers. Some of the company's latest products use high-frequency circuits that step down the voltage using an electronic transformer or some other device and generate a signal high frequency(1000 Hz or more), eliminating the flickering effect.

The fruits of the developers' efforts are latest models AC-LED assemblies with better compatibility with existing infrastructure, increased reliability due to fewer components used, and potentially shorter time to market.

Types of AC-LED

According to Miskin, there are three main types of AC-LEDs on the market today: low-voltage AC-powered, direct-high-voltage AC-LED, and rectified high-voltage AC-LED. Low voltage LEDs operate on 12 V or 24 V and are connected via a magnetic or electronic transformer. Such LEDs, as a rule, independently rectify alternating current. They have found application in gardening lamps, for hidden lighting and illumination of trade counters. In high-voltage assemblies (from 15 to 55 V), a topology with a bridge rectifier is used, where the LEDs are powered by a pulsed current in each half-cycle of the sinusoid. Devices with a rectifier contain built-in control circuits that prevent peak currents from reaching dangerous values ​​for LEDs.

AC-LED technology is scalable, since the number of LEDs included in the chain can be selected according to the mains voltage, and is applicable in lighting fixtures with power supply from 12 to 277 V. In fact, AC-LEDs can even operate in resonant conditions for maximum efficiency mode, which is not possible for DC-LED. Miskin explained that Lynk has developed a new method that allows AC-LEDs to be driven close to the resonance limit, so that even if one lamp is removed from the circuit or fails, the remaining ones will work with the same efficiency. He said: "We believe that in the future frequencies will increase to match RLC components, which will allow efficiency to rise to 98%."

Replacing lamps

Today, the main target market for low-voltage and high-voltage AC-LED designs is the retrofit lamp market, which includes miniature lamps such as G4, G8, GU10 and MR16, as well as B10 chandelier lamps. The companies are also developing products for A-lamps, BR lamps and linear replacement modules fluorescent lamps.

The ceiling luminaire market is also extremely attractive for AC-LED fixtures because such luminaires typically have space available to accommodate additional electronics. In addition, free space can be occupied by cooling radiators. An example of a device designed for such lamps is shown in (Figure 1). The 16-watt Acrich2 LED module from Seoul Semiconductor has a luminous flux of 1250 lm with a color temperature of 3000K and a viewing angle of 120°.

Figure 2a.	IN internal structure of the MR16 lamp based on DC-LED.	Figure 2b.	Lynk Labs 12V AC-LEDs in COB packages.	Figure 2c.	AC-LED assembly from Seoul Semiconductor with a supply voltage of 120 V and 4 W, equivalent to a 35 W MR16 lamp.

Figure 2 compares DC-LED with two functionally similar AC-LED assemblies. An MR16 or GU10 lamp (the latter connects directly to the network) are direct candidates for installing a module with AC-LED.

Ultimately, cost and reliability will tip the scales in favor of AC-LED designs over the now more common DC-LEDs. “We have already significantly reduced package costs, about 40% of the cost of an LED, by moving to die-on-board technology and using SMD components,” Wilcox said. However, he argues that the $10 price target for a 60-watt equivalent lamp, often seen as the point of consumer acceptance, can only be achieved by removing expensive electronic components from LED lamps and luminaires. - “The best way to reduce the price is to introduce AC-LED without drivers.” He added that the first products to hit retail shelves will be dimmable retrofit lamps, some of which will be quite large, like the A19 and BR30.

“I am confident that in the very near future we will see lamps that replace 60-watt incandescent lamps at a price of $15, and a little later the price will drop to $10. These will be products from reputable companies, some of which will not contain drivers. The most suitable applications for the new product will be retrofit lamps and ceiling lights,” Wilcox said.

Another important area of ​​application of AC-LED is backlight or local lighting sources. Figure 3 shows an LED module with a resistor designed for this purpose.
As noted earlier, for such products to dominate the market, their lumen output, efficiency, power factor and harmonic distortion must be at least as good as DC-LED. However, light output and efficiency must be compared using a specific application as an example, but we will consider the problem of AC-LED power management.

Power management

As mentioned, poor power management in terms of power factor correction and harmonic distortion has limited the penetration of AC-LED into the wider market. Power factor is equal to the ratio of the active power consumed by a lamp or luminaire to the total power. In AC-LED devices, the load is non-linear, so special attention must be paid to the power factor.

Harmonic distortion is a numerical representation of the degree of distortion of the current waveform compared to the sine wave of the mains voltage. Harmonics are unwanted current components that are multiples of the mains frequency (50 or 60 Hz) and cause power loss. Although beyond the scope of this article, it is worth noting that AC-LED devices use various types of matching circuits, including resistors and switching power supplies, to reduce harmonic distortion.

Wilcox noted that in the Acrich2 product line, the power management unit has 90% efficiency and less than 25% harmonic distortion.

Dimming

One of the main advantages of AC-LED is its compatibility with phase-cutting (triac) dimmers. “We can reduce the brightness by up to 2%, which is a real advantage,” says Miskin. In addition, Lynk Labs introduced technology that “heats” the glow color when dimming from 4000K to 2000K using AC-LED and current-limiting components.

conclusions

AC-LED based assemblies represent a competitive platform, especially in the retrofit lamp market. Whether they will be the choice of lamp and luminaire manufacturers will depend on the characteristics and cost of such solutions compared to assemblies based on already proven DC-LEDs. The race to create a ten-dollar replacement for 60-watt incandescent light bulbs could be won by one technology or both.

• I believe that the main problem with LED lighting is that with the introduction of a fundamentally new technology, a new standard of connectors for new lamps was not created. Along with the ban on the use of incandescent lamps, it was necessary to ban the use of threaded sockets of the Edison “E” standard (E27, E17, E14). The absurdity of the situation is that old cartridges are generally not suitable for LED lamps but continue to be reproduced en masse. Lamp manufacturers focus on existing lamps, lamp manufacturers focus on existing lamps, money is invested in this, new production facilities are created that replicate a standard that is long overdue for death. Obviously, the situation will not be corrected without administrative intervention, but the fact of the matter is that no one dares to legitimize any of the suitable connectors as a new standard. It would be logical to adopt a constant voltage of 12v as the standard for new lamps and thus combine the range of lamps for cars and for everyday life. Some of the car lamp connectors are quite suitable for the basis of the new standard. This would make it possible to quickly switch cars to LEDs, which, in general, should have been done a long time ago. Personally, I don’t understand why cars still use incandescent lamps, which are not only not economical and quickly drain batteries, but simply cannot withstand shock and vibration; these lamps constantly have to be changed. Removing the rectifier converter from the lamp itself will not only reduce the cost of the lamp, but will also radically increase its reliability and durability, and eliminate flickering and the stroboscopic effect. In general, I would create panels in which multi-colored LEDs, not white ones, together create normal lighting; it is cheaper and the spectrum can be selected more accurately. In general, the situation has long been ripe... but what am I reading in this article? Manufacturers are still trying to adapt to a standard that is more than 100 years old! I have a lot of respect for inventors, but in my opinion they waste their energy in bad ways.
• I think that the main problem now is the reduction in cost of LED matrices. And the rest is trifles.
• Don't worry, as production volumes increase, the price will fall and there is nothing we can do to speed up or slow down the process. But the final luminaires stubbornly reproduce the standard of sockets from 100 years ago, and this creates a lot of problems for manufacturers. It is impossible to place a normal rectifier with smoothing capacitors in the E27 base and this creates a lot of problems. 1. The supply voltage is not constant but pulsed and the lamp blinks at a frequency of 100 Hz. It seems to be imperceptible, but nevertheless the eyes get tired. There is a possibility of a stroboscopic effect. 2. High-frequency pulses from the power driver are not filtered by this unfinished filter and this creates interference and unnecessary electromagnetic radiation. 3. But the most the main problem in price, reliability and durability. In such a small volume it is impossible to place a full-fledged device on reliable elements; in order to save space, you have to sacrifice either reliability or functionality and, in any case, use more expensive parts. In addition, it would be very appropriate to unify lighting elements for cars and households by bringing everything to 12v DC. Such a radical reduction in the range will in itself reduce the price, and besides, the lamps will be produced without rectifiers, which will also affect the price. In the future, it is possible to create a separate 12v lighting network in houses with battery backup. Various low-power consumers such as mobile phone chargers and any other low-power electrical equipment, including televisions, can be connected to this network. 12 V is absolutely safe and allows you to do without galvanic isolation, which all together will significantly simplify and reduce the cost of all household appliances. The new standard easily integrates a wind turbine or solar panels. In the future, all this equipment will be able to be used everywhere, from a tent in the forest, a summer house, a car cabin and to the office, there is a single standard everywhere; there is no need to create separate mobile and non-mobile devices. In this case, of course, the house must have high voltage connectors to power powerful devices such as washing machines, electric. stoves and kettles...
• As I understand it, the original idea was to increase reliability by eliminating converters, but here we have the same converters and what’s the point?
• What is ingrained into this standard? There are plenty of bases without Edison E, for example GU5.3 And light bulbs are available with 12 volts and rectifiers. Buy what you like. How quick - ban, ban!
• I’m not worried about this. I’m worried about what LED lamps with a deliberately overvoltage mode will do to us. And if you don’t get into it, you won’t be able to fix the matter, they say, just take what they give.
• GU5.3 is symmetrical, designed for AC mains, designed for low current but can withstand overheating well. I would make the connector simply in the form of a plate of foil plastic. On one side there is one contact, on the other there is another contact. The plate itself is also a mounting platform for microcircuits and LEDs. Large contact surface area, compactness and mechanical strength. But the main thing is simplicity and manufacturability within the limits of proven technologies. You can make a key so that it is impossible to insert it incorrectly. And as for “ban E27”... do you go to stores and what do you see in the assortment? Indeed, the situation cannot be reversed without administrative intervention. I have already installed 12V light bulbs. But not everyone is skilled.
• I completely agree. A device consisting of more than one part must be subject to at least an attempt to repair it. And in this case, they glued everything to the board and voila, welcome that trash, like a contraceptive: D it’s worth watching a film about that same light bulb effect http://www.youtube.com/watch?v=ssSlodrPY3M
• There is such a thing
• As for the 12V standard, currents must be taken into account. In order to transmit power at low voltage, the current must be increased, and therefore the cross-section of the wires. Electrical installation will cost more. But there is a big plus - electrical safety. And there is a minus - fire safety.
• Soon there will be no light bulbs, we will choose lamps, and tell our grandson that in the past, there were light bulbs that periodically burned out. But now they say, buy a lamp, hang it up, and the concept of a light bulb will become a thing of the past.
• Unfortunately, while we are discussing issues of increasing durability, bankers have already decided everything a long time ago and hired engineers who will take measures to ensure that LED bulbs didn't last long. The problem is in the financial system itself. But there is a cure, it was invented a long time ago but was well described by Silvio Gesell. This medicine is called "Freigeld" and was used several times, but each time it was destroyed by bankers. Maybe to hell with this light bulb. Let's introduce alternative means of payment. For example, based on vodka. Well, “liquid currency” has long become the norm, so let’s turn it into paper or even electronic money, so that you can’t drink in the gateway. Anyone who doesn’t believe in vodka can use anything as a basis.
• So it is, but keep in mind that the 12V network was initially positioned as power supply for low-power devices, well, maximum TV, computer. Stoves, washing machines, irons, boilers... all this must be powered from other sources. Yes, it would seem there is more wiring. But in your house there are a maximum of 4 - 6 powerful consumers, and there are ten times more low-power consumers. Each such device, starting with a mobile phone charger, requires a converter with galvanic isolation. And power supply from 12 volts will require a very primitive series stabilizer. Constant voltage will eliminate the need for bulky capacitors in each device. It will be possible to easily and cheaply back up power with batteries and connect alternative energy sources. And complete unification of automotive, household and office equipment. I'm sure that the 12V network is much more convenient for transmitting signals. In general, there are a lot of winnings, but the inertia of the old pulls. And there are some advantages: New standard can develop in parallel as mobile but with the prospect of displacing the old standard.
• Sorry Garik, have you watched this video? http://www.youtube.com/watch?v=ssSlodrPY3M You don’t seem to understand that the problem of durability lies not in the area of ​​technical solutions but in the area of ​​politics and finance. These guys are interested in us always playing that game where everyone runs around chairs, and there are always fewer chairs than butts to sit down. And not because there are not enough chairs, but simply the rules in this game are like that. But there is only one ass that is always on the chair - the one to whose tune everyone runs, pushing each other. There is a way out, not to participate in these races, to create your own system where people do not kill each other to please the shepherd. Moreover, such communities exist, but corrupt media prefer not to talk about this topic. Search the Internet for "Freigeld", "Silvio Gesell money", "WARA", "WIR francs", "alternative money"...
• I’ve lived long enough for me to not understand: D There is a story when an inventor comes to the director of a large company. He offers an eternal razor, and the director willingly buys the invention, not in order to make eternal razors, but in order to... no one would ever see this invention.
• Not so simple. The base does not slow down the introduction of LED lamps. Their price is holding them back. When switching to CFLs, we thought that they would justify themselves. It didn't work out. For example, lighting takes up a small part of my total consumption. The main ones are an electric stove and a water heater. The idea of ​​switching to 12 V power supply is puzzling. Why 12 and not 36? And why does it need to be unified with car light bulbs, which also switch to 24 V? By the way, about the fragility of car lamps. They are very reliable. My car is 10 years old, I only changed 2 front light bulbs. But with LED daytime running lights installed by some owners, you can often see that only half of the diodes are lit. And what is more reliable? Let's imagine that we switched to the 12th century. It turns out that in addition to the phone charger, landline phone and there are more routers and there are no low-power consumers. My TV, for example, with a 40" LED matrix consumes 140 W, I’m generally silent about plasma ones. This is 12 amperes. With a wiring length of 10 m with a copper cross-section of 1.5 mm^2, the losses will be almost 3.5 V. Still, in each the room will have to leave 220 V sockets, otherwise where will you turn on the vacuum cleaner, electric heater? You will have to forget about doubles, tees, extension cords. God forbid, this idea will be realized.
• I completely agree. So he also offers to connect a modern computer to a 12V network. So it eats, God forbid, especially the gaming one:eek: He writes that there will be no bulky filter capacitors. Who will filter? Power plant or substation? Well, if only not solar energy, but where is it in Russia? Where is 2/3 north.
• I read everything, but stopped at your statement. Let's start with history, when the "Ilyich light bulb" with a filament was brought to 250,000 hours of operation, by the 1940s, after a collection of light bulb manufacturers, their resource was reduced to 100,000 hours, now you will rummage through everything and find 1 - the light bulb has a resource of 50 hours. As for LED lamps, if today an ordinary LED is a device with r-n transition ohm high-tech) and an alternating current LED, well, the p-n junction is 2 different metals and nothing more, this is all an ordinary spark gap, well, a lens was attached. As for the service life - that you hand over several pieces of luminescent lamps during the warranty period, that LEDs, the electronic part does not change at all. As for the standards, let’s say you make 12V light bulbs, you can use 1 stabilizer for everything - but why charge money? Many manufacturers, like this GARIK, raise prices for lamps - yes, raise them, probably few people have thought about how the system works - who will fuck whom. Today, with your salary, buy 10 - 15 light bulbs, or let’s say 1 LED lamp instead of 4_x 20 W. fluorescent lamps. Due to the unreliability of LED lighting devices today - many manufacturers are scratching their heads - why did we give a 3 or 5 year warranty? The question arises - if you sell at such prices and don’t want to give a guarantee - why the hell do you need your lamps? Now there are 600 lamps in production instead of 4*20W fluorescent lamps, there is still a year of warranty, but they are already thinking about what to change, as they burn like candles, repairs under warranty are a hassle and it’s a hell of a time when they will be bought.
• I agree with some thoughts. With overproduction for example. I won’t say anything about the spark gap and won’t even install it. I have been making LED lamps myself for two years now. At 1 W, 3 W. and so far 5730 LEDs. the schemes are different. the first ones are very simple with a quenching capacitor. Do not like. They work in the village, at the end of the street, the distribution networks have been rebuilt, they are old, the voltage fluctuates and the brightness fluctuates. For the pantry, I’m patient for now. But the LEDs don’t die. The radiators are standing. The current does not exceed the rated current. What am I doing wrong? Now I do it on controllers. I buy ready-made Chinese ones. Again, radiators, ventilation, current. At work we were repairing a ready-made industrial lamp (for Armstrong ceilings, I don’t remember the name), although it wasn’t very expensive. The radiators are insufficient, the current is unstable (the microcircuit was replaced from a donor), everything is packed, there is no ventilation. I had to polish both lamps installed in the workshop. Everything is fine now. The truth is that it has only been working for six months so far. But he will live a long time. I saw good German (imported from Germany) lamps. Radiator, ventilation. I didn’t measure the current, but I believe that it’s not naughty. The main advantage of LEDs over incandescent lamps is efficiency. I think you understand what is behind this, and the main thing is not your money.
• You most likely measured the current with a conventional tester. If possible, try to take 3 different “Ilyich bulbs”, fluorescent and LED, and see the difference - how much active and reactive energy each of them consumes - through the meters. By this I want to say that yes, the LED light bulb consumes less, then the fluorescent light bulb, and only then the Ilyich light bulb - but is this the difference that is written on the box of each of the light bulbs and the actual one (I don’t specifically write numbers, in order to avoid disputes). And then another interesting topic for thought - which of the “former CIS countries” do you personally live in and how much do you actually pay today. I do not take into account the rise in prices for energy sales in recent years, only light bulbs.

In principle, fluorescent lamps are alternating current devices. However, they can also operate on direct current. The following factors must be taken into account:

• Operating on direct current, the lamp produces 75-80% of the light, in a mode similar to operating on alternating current.
• A resistor is used as a current limiter, which results in higher power losses.
• Lighting a lamp is usually more difficult. In most cases, a regular starter will not work.
• One end of the lamp may darken after several hours of operation. This is due to the movement of electrons to one electrode and positive mercury ions to the other. This leads to the fact that at one of the ends there is no generation of ultraviolet radiation necessary for phosphorus to glow. This can also lead to faster burnout of the electrodes. To eliminate this effect, you must regularly change the polarity of the supplied voltage.

Sometimes an inductor is connected in series to limit the starting current.

Using an incandescent lamp as a ballast

This option is sometimes used in circuits with a starter. The lamp filament is used as a current limiter. In principle, any resistor can be used as long as it allows the required power to be dissipated. The main disadvantages of using a lamp as ballast are:

• The efficiency of the circuit is very low because the incandescent lamp dissipates a lot of heat - it is a resistive load, unlike an inductance
• The fluorescent lamp does not operate in an optimal mode - light output, service life, etc. are reduced. The ballast is specially designed for a specific lamp, an incandescent lamp is unlikely.
• The heat generated (can reach up to 40-50 W) causes a decrease in the light output of the fluorescent lamp due to increased temperature.
• It is usually stated that an incandescent lamp provides additional light. However, when operating at full intensity, an incandescent lamp produces very little light in the visible range

We can say that you should not use such a scheme - it is better to purchase a special ballast.

However, there are some data that allow you to choose an incandescent lamp. A feature of incandescent lamps is that the resistance of the filament changes with increasing temperature. This table designed for the most common bi-spiral incandescent lamps with a bulb filled with an inert gas. The calculation was made as follows: first, a lamp was calculated, which at a rated voltage of 220V has the appropriate power and luminous flux, then the resistance of the spiral was recalculated to other current values.

Ballast for gas discharge lamp

A gas-discharge lamp - mercury or metal halide, similar to a fluorescent lamp, has a falling current-voltage characteristic. Therefore, it is necessary to use a ballast to limit the current in the network and ignite the lamp. Ballasts for these lamps are in many ways similar to ballasts for fluorescent lamps and will be described here very briefly.

The simplest ballast (reactor ballast) is an inductive choke connected in series with the lamp to limit the current. A capacitor is connected in parallel to improve the power factor. Such ballast can be easily calculated in a similar way to what was done above for a fluorescent lamp. It is necessary to take into account that the current of a gas-discharge lamp is several times higher than the current of a fluorescent lamp. Therefore, you cannot use a choke from a fluorescent lamp. Sometimes a pulse ignition device (IZU, inginitor) is used to ignite the lamp.

If the mains voltage is not enough to ignite the lamp, then the inductor can be combined with an autotransformer to increase the voltage.

This type of ballast has the disadvantage that when the network voltage changes, the luminous flux of the lamp changes, which depends on the power proportional to the square of the voltage.

rice. 2

This type (Fig. 3) of ballast with constant power (constant wattage) is now most widespread among inductive ballasts. A change in mains voltage by 13% leads to a change in lamp power by 2%.

In this circuit, the capacitor plays the role of a current-limiting element. Therefore, the capacitor is usually installed quite large.

The best are electronic ballasts, which are similar to the electronic ballasts of fluorescent lamps. Everything that is said about those ballasts is true for gas-discharge lamps. In addition, in such ballasts you can regulate the lamp current, reducing the amount of light. Therefore, if you are going to use a discharge lamp to illuminate your aquarium, then it makes sense for you to purchase an electronic ballast.

rice. 3

Electronic ballasts

These ballasts come in both low-frequency and high-frequency types. Low frequencies power the lamp with frequent network, for example, hybrid ballasts (hybrid), which are a starterless ballast (rapid start), in which an electronic circuit is added that turns off the secondary circuit for heating the electrodes after the lamp is ignited, which gives a slight increase in the efficiency of the ballast. Aquariums

High-frequency electronic ballasts supply voltage to the lamp with a frequency of about 20,000 Hz and higher (they should not be confused with high-frequency induction lamps, which operate in the megahertz range). Such ballasts consist of a rectifier and a transient (or thyristor) breaker. Ballast has many advantages over magnetic ballast:

• The efficiency of the lamp increases. The ballast coefficient increases by 20-30%, i.e. lamp produces more light
• Losses in ballast have been reduced several times - a huge piece of iron is missing. Accordingly, energy consumption decreases and the temperature decreases, which is important for the operation of the lamp.
• The ballast becomes compact, which is important when placing it in a tight place.
• The ballast does not produce noise in the audio range.
• Lamp pulsations are reduced
• Many ballasts can be changed luminous flux lamps (dimming)

Electronic ballast also has its disadvantages:

• Relatively high cost compared to magnetic ones.
• Some older ballast designs had a small amount of current leaking into the ground wire, causing the GFCI system to trip.
• These ballasts (especially cheap ones) may have increased harmonic distortion. They can affect a radio receiver working nearby (although unlikely - within a radius of no more than half a meter)

However, when purchasing new system lamps, especially HO, VHO lamps, it makes sense to think about using electronic ballast

The figure shows the increase in lamp efficiency with increasing current frequency, relative to the mains frequency of 60Hz

Circuit diagram for switching on a fluorescent lamp without a starter

The disadvantages of the starter circuit (long time for warming up the electrodes, the need to replace the starter, etc.) led to the appearance of another circuit, where the electrodes are heated from the secondary winding of the transformer, which is also an inductive reactance.

Distinctive external feature Such a ballast is that both network wires are connected to the ballast, four wires from the ballast are connected to the lamp electrodes.

There are many varieties of such a circuit, for example, when an electronic circuit turns off the electrode heating circuit after turning on the lamp (trigger start), etc. Ballasts of this type are also used in a circuit with several lamps.

You cannot use a lamp designed for a starter switching circuit in such a circuit, since it is designed for longer heating of the electrodes and will fail prematurely in such a circuit. Only lamps marked RS (Rapid start) should be used. The circuit must provide a grounded reflector along the lamp (sometimes there is a metal strip on the lamp). This makes lighting the lamp easier.

The figure shows the internal view of such a ballast. It consists of a choke (core and coil), a capacitor for power factor correction (power capacitor) and a thermal fuse (thermal protector). Everything inside the case is filled with thermal dissipative material

Wiring diagram for a fluorescent lamp with a starter

A traditional circuit, used for a very long time, in the case when the mains voltage is sufficient to light the lamp. It uses a ballast, which is a large inductive reactance - a choke, and a starter - a small neon lamp that serves to preheat the lamp electrodes. There is a capacitor in the starter parallel to the neon lamp to reduce radio interference. A capacitor can also be included in the circuit to improve the power factor.

When you turn on the lamp in the network, first, a discharge occurs in the starter and a small current passes through the electrodes of the lamp, which heats them up, thereby reducing the ignition voltage of the lamp. When a discharge occurs in the lamp, the voltage between the electrodes drops. disconnecting the starter circuit. In old schemes, instead of a starter, a button was used, which had to be held for several seconds.

The ballast is used only to limit the current. It’s easy to calculate the ballast parameters yourself (if you found a choke in the trash and want to use it).

The parameters of an inductive ballast can be determined very easily using the rules for calculating AC circuits. For example, consider a 40W lamp (F40T12) 48" (122 cm) long, connected to a 230V network

The operating current of the lamp is about 0.43A. The power factor of the lamp is approximately 0.9 (in principle, the lamp can be considered an active load). The voltage on the lamp is: 40W/(0.43A*0.9)=102V. The active component of the voltage is equal to: 102V*0.9=92V, the reactive component is equal to 102V*sqrt(1-0.9^2)=44V.

Power losses in ballast are 9-10W. Hence, the total power factor is equal to: (40W+10W)/(230V*0.43A)=0.51 (this clearly requires a correction capacitor). The active component of the voltage drop across the ballast is equal to: 230V*0.51-102V=15V, the reactive component 230V*sqrt(1-0.51^2)-44V=154V. The active resistance of the ballast is 15V/0.43A=35 Ohm, the reactive resistance is 154V/0.43=358 Ohm. The ballast inductance at a frequency of 50Hz is 358/(2*31.4*50)=1.1H

A similar calculation for a 30W lamp (F30T12) 36" (91 cm) long, with an operating current of 0.37A, gives the ballast parameters - active resistance is 59 Ohms, reactive 450 Ohms. The total power factor is 0.45. Ballast inductance 1.4H

From here, it is generally clear what will happen if you use a ballast for a 40W lamp in a circuit with a 30W lamp - the current will exceed the rated value, which will lead to faster failure of the lamp. Conversely, using ballast from a less powerful lamp in a circuit with a more powerful lamp will result in current limitation and reduced light output.

A capacitor can be used to improve the power factor. For example, in the first example, for a 40W lamp, a capacitor connected in parallel is calculated as follows. The current through the capacitor is 0.43A*sqrt(1-0.51^2)=0.37A, the reactance of the capacitor is 230V/0.37A=622Ohm, the capacitance for a 50Hz network is: 1/(2*3.14*50*622)=5.1uF. The capacitor must be 250V. It can also be connected in series (calculated similarly), but you must use a 450V capacitor. Aquarium

Ultra-high-pressure arc lamps (UHPA) include lamps operating at a pressure of 10 × 10 5 Pa and higher. At high pressures of gas or metal vapor, with close proximity of the electrodes, the near-cathode and near-anode areas of the discharge are reduced. The discharge is concentrated in a narrow spindle-shaped region between the electrodes, and its brightness, especially near the cathode, reaches very high values.

Such an arc discharge is an indispensable light source for projector and floodlight devices, as well as a number of special applications.

The use of mercury vapor or inert gas in lamps gives them a number of features. The production of mercury vapor at the appropriate pressure, as can be seen from the discussion of high-pressure mercury lamps in the article "", is achieved by dosing mercury in the lamp bulb. The discharge ignites as low pressure mercury at ambient temperature. Then, as the lamp flares up and heats up, the pressure increases. The operating pressure is determined by the steady-state temperature of the bulb, at which the electrical power supplied to the lamp becomes equal to the power dissipated in the surrounding space by radiation and heat transfer. Thus, the first feature of ultra-high pressure mercury lamps is that they light up quite easily, but have a relatively long burn-up period. When they go out, re-ignition can be carried out, as a rule, only after complete cooling. When the lamps are filled with inert gases, the discharge almost instantly enters a steady state after ignition. Ignition of a discharge in gas at high pressure presents certain difficulties and requires the use of special ignition devices. However, after going out, the lamp can be relit almost instantly.

The second feature that distinguishes the short-arc ultra-high-pressure mercury discharge from the corresponding gas discharges is its electrical mode. Due to the large difference between the potential gradients in mercury and inert gases at the same pressure, the combustion voltage of such lamps is significantly higher than with gas filling, due to which, at equal powers, the current of the latter is much greater.

The third significant difference is the emission spectrum, which in gas-filled lamps corresponds in spectral composition to daylight.

The noted features have led to the fact that arc lamps are often used for filming and film projection, in solar radiation simulators and other cases where correct color rendition is required.

Lamp arrangement

The spherical shape of the lamp bulb was chosen to ensure high mechanical strength at high pressures and small distances between the electrodes (Figure 1 and 2). A quartz glass spherical flask has two diametrically located long cylindrical legs, in which leads connected to the electrodes are sealed. The long leg length is necessary to remove the lead from the hot flask and protect it from oxidation. Some types of mercury lamps have an additional ignition electrode in the form of a tungsten wire soldered into the bulb.

Figure 1. General view of ultra-high pressure mercury-quartz lamps with a short arc of various powers, W:
A - 50; b - 100; V - 250; G - 500; d - 1000

Figure 2. General view of xenon ball lamps:
A- DC lamp with a power of 100 - 200 kW; b- AC lamp with a power of 1 kW; V- AC lamp with a power of 2 kW; G- DC lamp 1 kW

Electrode designs vary depending on the type of current that powers the lamp. When operating on alternating current, for which mercury lamps are intended, both electrodes have the same design (Figure 3). They differ from the electrodes of tubular lamps of the same power by being more massive, due to the need to reduce their temperature.

Figure 3. Short arc AC mercury lamp electrodes:
A- for lamps with power up to 1 kW; b- for lamps with power up to 10 kW; V- solid electrode for high-power lamps; 1 - core made of tungsten; 2 - covering spiral made of tungsten wire; 3 - oxide paste; 4 - gas absorber; 5 - base made of sintered tungsten powder with the addition of thorium oxide; 6 - forged tungsten part

When operating lamps on direct current, the burning position of the lamp becomes important, which should only be vertical - anode up for gas lamps and preferably anode down for mercury lamps. The location of the anode at the bottom reduces the stability of the arc, which is important because of the counterflow of electrons directed downward and hot gases rising upward. The upper position of the anode forces it to increase its size, since in addition to its heating due to the greater power dissipated at the anode, it is additionally heated by the flow of hot gases. For mercury lamps, the anode is located at the bottom in order to ensure more uniform heating and, accordingly, reduce the burn-up time.

Due to the small distance between the electrodes, mercury ball lamps can operate on alternating current from a mains voltage of 127 or 220 V. The operating pressure of mercury vapor is in lamps with a power of 50 - 500 W, respectively (80 - 30) × 10 5, and in lamps with a power of 1 - 3 kW - (20 - 10) × 10 5 Pa.

Ultra-high pressure lamps with a spherical bulb are most often filled with xenon due to the convenience of its dosage. The distance between the electrodes is 3 - 6 mm for most lamps. Xenon pressure in a cold lamp (1 - 5) × 10 5 Pa for lamps with power from 50 W to 10 kW. Such pressures make ultra-high pressure lamps explosive even when not in use and require the use of special casings for their storage. Due to strong convection, lamps can only operate in a vertical position, regardless of the type of current.

Emission from lamps

The high brightness of mercury ball lamps with a short arc is obtained due to an increase in current and stabilization of the discharge at the electrodes, which prevents the expansion of the discharge channel. Depending on the temperature of the working part of the electrodes and their design, different brightness distributions can be obtained. When the temperature of the electrodes is not sufficient to ensure the arc current due to thermionic emission, the arc contracts at the electrodes into bright luminous points of small size and acquires a spindle-shaped shape. The brightness near the electrodes reaches 1000 mcd/m² or more. The small size of these areas means that their role in the overall radiation flux of the lamps is insignificant.

When the discharge is contracted near the electrodes, the brightness increases with increasing pressure and current (power) and with decreasing distance between the electrodes.

If the temperature of the working part of the electrodes ensures that the arc current is generated due to thermionic emission, then the discharge seems to spread over the surface of the electrodes. In this case, the brightness is more evenly distributed along the discharge and still increases with increasing current and pressure. The radius of the discharge channel depends on the shape and design of the working part of the electrodes and is almost independent of the distance between them.

The luminous efficiency of lamps increases with their specific power. With a spindle-shaped discharge, the light output has a maximum at a certain distance between the electrodes.

The radiation from mercury ball lamps of the DRSh type has a line spectrum with a strongly pronounced continuous background. The lines are greatly expanded. There are no radiations with wavelengths shorter than 280 - 290 nm, and due to the background, the share of red radiation is 4 - 7%.

Figure 4. Brightness distribution along ( 1 ) and across ( 2 ) discharge axis of xenon lamps

The discharge cord of spherical xenon DC lamps, when operating in a vertical position with the anode up, has the shape of a cone, resting its tip on the tip of the cathode and expanding upward. A small cathode spot of very high brightness is formed near the cathode. The brightness distribution in the discharge cord remains the same when the discharge current density changes over a very wide range, which makes it possible to construct uniform brightness distribution curves along and across the discharge (Figure 4). Brightness is directly proportional to the power per unit length of the arc discharge. The ratio of the luminous flux and luminous intensity in a given direction to the length of the arc is proportional to the ratio of the power to the same length.

The emission spectrum of ultra-high pressure ball xenon lamps differs little from the emission spectrum of tubular xenon lamps.

Powerful xenon lamps have an increasing current-voltage characteristic. The slope of the characteristic increases with increasing distance between the electrodes and pressure. The anode-cathode potential drop for xenon lamps with a short arc is 9 - 10 V, with the cathode accounting for 7 - 8 V.

Modern ultra-high pressure ball lamps are produced in various designs, including with collapsible electrodes and water cooling. The design of a special metal collapsible lamp-luminaire of the DKsRM55000 type and a number of other sources used in special installations have been developed.

S.I. Palamarenko, Kyiv

Part 3. Methods for starterless ignition of lamps and classification of circuits, circuits for switching on fluorescent lamps using semiconductor devices, operation of fluorescent lamps on direct current, operation of fluorescent lamps at an increased frequency, regulation of the brightness of fluorescent lamps

Methods for starterless ignition of lamps and classification of circuits

The presence of starters complicates maintenance, delays the ignition process, sometimes leads to unpleasant blinking of individual lamps; in some cases, starter malfunctions (“sticking”) can lead to failure of serviceable lamps. Therefore, a large number of different ballasts for arterless ignition have been proposed.

Depending on the mode used, existing starterless ignition circuits for LL arc discharges are divided into two groups: fast ignition circuits - with preheating of the cathodes, which should ensure “hot ignition” (they can be used for lamps in which the cathodes have two terminals), and instant ignition circuits - without preliminary heating of the cathodes, designed for “cold ignition” (in these circuits, lamps with special cathodes should be used). To create economical starterless devices, it is necessary to reduce the lamp ignition voltage to a value less than the network voltage, taking into account its drop. The most effective ways to reduce the ignition voltage are to preheat the cathodes and use conductive strips on the bulb (or near the lamp).

In the presence of a strip connected to the electrode and the cathodes are heated, the ignition voltage for lamps of 30 and 40 W can be reduced to 130-150 V. In addition, the ignition voltage is greatly influenced by such factors as humidity and temperature of the ambient air, composition and pressure of the filling gas, design and condition of electrodes, etc.

The ignition voltage, even for one lamp, can only be spoken of as a statistical quantity that has some distribution. Therefore, the dependence of the ignition voltage on various factors should be depicted in the form of a zone, the width of which should be constructed according to the laws of statistics. On

Fig.10 areas corresponding to different ignition conditions are shown.

In region I the lamp does not ignite, region II corresponds to ignition with cold cathodes - the region of “cold” ignitions. It is the least favorable for the service life of lamps with heated cathodes. Region III corresponds to ignition when the cathodes are sufficiently heated - the region of “hot” ignition. In region IV, cold ignitions are possible, despite the cathode heating current sufficient for “hot” ignition.

Fast ignition circuits must provide preliminary heating of the cathodes sufficient for the lamps to operate in the “hot” ignition region; supplying the lamp with a voltage that guarantees “hot” ignition of the arc discharge, taking into account possible variations in lamp parameters, low voltage in the network and other unfavorable factors and, if possible, excluding “cold” ignitions. To guarantee the ignition of lamps without a “strip” (the upper limit of region III), an effective open-circuit voltage of at least 250-300 V is required (i.e., higher than the mains voltage).

The presence of strips and pre-heating of the cathodes make it possible, at a network voltage of at least 210-220 V, to do without an additional increase in voltage, which greatly simplifies the ballast circuits. Therefore, in all circuits without increasing the voltage, it is necessary to use “strips”. For this purpose, special lamps are produced with a conductive transparent strip or a general coating applied to the surface. It should be emphasized that in networks with a significant voltage drop, such schemes do not ensure reliable ignition of lamps.

Fig.11 diagrams designed to work with strips are shown. Preliminary heating of the cathodes is carried out from special filament windings through an autotransformer, the primary winding of which is connected in parallel with the lamp. Winding resistance Z 3 is selected significantly greater than Z so that when the lamp is not lit, the entire network voltage drops across Z 3 and an emf sufficient to heat the cathodes arises in the filament windings

(Fig. 11, a). After the lamp is ignited, the voltage at Z 3 drops, as a result of which the EMF of the filament windings and the heating of the cathodes automatically decreases. Scheme

Fig. 11.6 similar to the diagram in Fig. 12a, but to slightly increase the no-load voltage, a capacitor is connected in series with the primary winding of the autotransformer. Such circuits usually use the phenomenon of ferroresonance. In fast start-up circuits, LLs with low-resistance cathodes should be used.

Since starterless ballasts for LL have significantly greater weight, dimensions and power losses than starter ones, they should be used only in special cases when starter circuits are not applicable.

The luminous flux (brightness) of the LL can be adjusted by changing the discharge current. At the same time, in order to avoid rapid destruction of the cathodes and extinction of the discharge with a significant decrease in the current, it is necessary to constantly maintain the heating of the cathodes and provide conditions for re-ignition of the discharge. The lamp current can be changed by changing the supply voltage, ballast resistance and discharge ignition phase.

In the simplest case

Fig. 12, a) In addition to the inductor, a resistor with variable resistance is connected in series with the lamp. The cathodes are heated by a filament transformer, and a conductive strip is used to facilitate ignition and re-ignition. The circuit is acceptable for a small number of lamps.

Changing the resistance of the inductor is usually carried out by magnetizing its core with direct current. To do this, two windings are made on the inductor without an air gap: one is connected in series with the lamp, and the second is used for magnetization. The choke is designed so that when the additional winding is open, the lamp current is several percent of the rated one. When you turn on the load in the additional winding of the inductor and change it up to short circuit you can increase the current in the lamp circuit to the rated value. In the scheme under-

independent heating of the cathodes is maintained. There are other magnetic control schemes, for example, by moving the core. The disadvantages of this method are the bulkiness of the apparatus and large losses.

rice. 12.6 The luminous flux is regulated by changing the supply voltage through a voltage regulator, and to expand the control limits, an auxiliary low-power high-frequency source (5-15 kHz) is connected in parallel to the supply voltage source through decoupling and blocking filters, which ensures ignition and re-ignition of lamps at low supply voltage. The power of the auxiliary RF source is about 1% of the power of the lamps. The circuit allows for smooth adjustment of the luminaire brightness within the range of 1-200, and it can be used in any existing lighting installation without significant modification.

Fig. 12, c shows a schematic diagram of phase control of LL brightness. Typically, regulation is carried out by thyristors T1 and T2. With increasing current pauses, the ignition voltage increases. Therefore, as in other similar schemes, continuous heating of the cathodes and the use of lamps with a conductive grounded strip are necessary. When operating at a frequency of 50 Hz, as the current pauses increase, the brightness pulsations increase.

Schemes for switching on fluorescent lamps

using semiconductor devices

Bypassing the lamp electrodes with diodes or thermistors with a negative temperature coefficient in combination with a conventional starter circuit allows you to increase the service life of the lamps, reduce the power consumed by the ballasts and increase the light parameters of the lamps.

rice. 13,a shows a circuit with shunting of lamp electrodes, in which thermistors (TR) with a negative temperature coefficient are used as a shunting element. The scheme works as follows. During the starting period, when the starter contacts are closed, a starting current begins to flow in the circuit. Since the resistance of the TP in the cold state is 10 times greater than its resistance in the hot state, approximately 90% of the inrush current will flow through the lamp electrodes. This ensures preliminary heating of the electrodes, and after several successive contacts of the starter electrodes, the lamp lights up. In operating mode, the lamp current, flowing through the TR, heats it up, and after 15-30 s, thermodynamic equilibrium occurs when the resistance of the TR reaches its minimum value. In this case, the operating current of the lamp is redistributed and passes partly through the TP and partly through the electrode. By choosing the minimum resistance TP approximately equal to the resistance of the lamp electrode in a hot state, it is possible to ensure that the operating current of the lamp will branch into two currents. Then both ends of the electrode will be equipotential, and the lamp will begin to operate in a mode close to the mode with two cathode spots.

With this mode of operation of the lamp, its service life increases. The presence of a shunt TR also protects the lamp from overload when the starter electrodes are shorted. In this emergency mode, the starting current heats up the TP, and with a decrease in its resistance, approximately half of the starting current will flow through the TP, bypassing the lamp electrodes, and thereby protecting the lamp from overload.

The scheme also has a number of disadvantages. In starting mode, the circuit works like a regular starter circuit with its inherent disadvantages. Another disadvantage is that after turning off the lamp, you need to give the thermistor time to cool down. If this is not done, then the shunting effect of the TR will lead to underheating of the lamp electrodes and its cold ignition. This reduces the reliability of lamp ignition.

The thermistor used to bypass the lamp electrodes must meet certain requirements. It must be designed for a rated current of at least 0.65 A, its cold resistance (at 20°C) must be at least 350-400 Ohms, the resistance after 0.5-1 minutes after turning on the circuit must be at least 100 Ohms , the hot resistance should be no more than 20 ohms.

rice. 13.6 A diagram is shown in which semiconductor diodes connected opposite each other are used as a shunt element. The scheme works as follows. In the starting mode, each half-cycle the current passes through only one shunt diode and after 0.01 s it reaches an almost steady value (for 40 W lamps the current is 0.35 A at a network voltage of 200 V). In this case, shunting the lamp electrode with a diode leads to a decrease in the preheating current, which can cause either a delay in the lamp ignition process or a cold ignition. In operating mode, each half-cycle one diode is open and the other is closed. The diode that bypasses the electrode operating in cathode mode will be open. When the diode is open, the operating current of the lamp passes through both terminals of the electrode. As the cathode spot moves along the turns of the electrode, the current in one wire decreases and increases in the other, remaining on average over the period less than the rated current in each part of the electrode. It has been experimentally proven that in this scheme the temperature of the cathode spot decreases and its area increases. At the same time, the service life of the lamps increases slightly, power losses in the lamp are reduced and their luminous efficiency increases by 4-5%.

To improve the starting characteristics of the circuit, you can use an additional coil w d

(Fig. 13,c), wound on a magnetic circuit common with the main choke (counter to the main one). In this case, in the starting mode, the total resistance of the circuit decreases and the preheating current increases (approaches the heating current for a conventional starter circuit). Diodes with a permissible reverse voltage of at least 10 V and a forward current of at least 0.3 A can be used as shunt diodes.

Instead of glow discharge starters, dinistors can be successfully used. The current-voltage characteristic of the dinistor has a section with a negative differential resistance. In startup mode

(Fig. 14, a) When supply voltage is applied to the lamp in each positive half-cycle, the dinistor remains closed as long as the instantaneous voltage applied to the dinistor is lower than the turning-on voltage. The resistance of the dinistor in the closed state is several tens of megaohms, so the current in the circuit will be very small. After switching the dinistor to the conducting state, a preheating current is established in the circuit and the process of heating the electrodes begins. In this case, the voltage on the lamp decreases to approximately 2 V (residual voltage on dinistor DT1 and voltage drop on diode D2). A diode is included in the circuit when the reverse voltage of the dinistor is less than the voltage amplitude in the network.

During negative half-cycles, the dinistor is closed, no current passes through the electrodes of the lamp, and the voltage across the lamp is equal to the mains voltage. The described process is automatically repeated until the lamp electrodes warm up and an arc discharge occurs in the lamp. After the lamp is ignited, the voltage on it will drop to the operating voltage, and the dynistor will remain closed if the operating voltage on the lamp is lower than the switch-on voltage of the dynistor.

The process of igniting a lamp in a circuit with a dinistor, compared to a conventional starter circuit, has the difference that the starter contacts can break at any moment (at different values ​​of the preheating current, including the maximum), and in a circuit with a dinistor - at the moment turning it off. The lamp ignition time for ballasts with a dinistor is usually 0.5-2 s.

The disadvantage of the scheme is the following. As the lamp burns, re-ignition peaks are observed, which can reach up to 30% of the amplitude of the operating voltage on the lamp and have a duration of up to 400 μs. Because of this, it is necessary to increase the dinistor switch-on voltage, since false triggering of the dinistor is possible due to re-ignition peaks. Increasing the turn-on voltage leads to a decrease in the cutoff angle, which worsens the performance characteristics of the circuit.

To eliminate this drawback, a scheme is proposed

rice. 14, b, where, to suppress the re-ignition peak, an additional inductance in the form of a small inductor L fl is connected in series with the dinistor and diode, and in parallel - a resistor g d. It has been experimentally established that the resistance g d should not be lower than 10 kOhm. The time constant of the additional circuit t d = L d / r d is selected from the condition that it is equal to half the duration of the re-ignition peak, i.e. approximately 200 µs. Based on this, the inductance of the inductor must be at least 2 H. But the introduction of such an element reduces the starting current of the lamp. Therefore, the additional inductance must have a nonlinear current-voltage characteristic, which ensures high inductance at low currents (operating mode) and low inductance at high currents (starting mode). Such inductance can be obtained by using a choke with a ferrite ring magnetic core. An experimental test showed that the voltage across the dinistor is reduced by 50-75%.

Fig. 14, c shows a circuit in which two dinistors and an rC chain are used. At the moment the circuit is turned on, capacitor C is charged through a diode and resistor r1, and the voltage across it is close to the amplitude

mains voltage. As soon as the voltage on C becomes equal to the switch-on voltage of dinistor DT2, it turns on, and the entire network voltage will be applied to dinistor DT1, which also turns on. After this, the heating mode of the lamp electrodes begins. Then the circuit works in the same way as the circuit in Fig. 14, a. Resistor r limit limits the current through DT2 when capacitor C is discharged, and resistor r 2 is the discharge resistance of the capacitor. Resistor resistance r1 = 50 kOhm; g 2 = 500 kOhm, and capacitance C = 2000 pF.

Instead of dinistors, you can use a thyristor

(Fig. 14, d). A zener diode is included in the circuit of the thyristor control electrode, the stabilization voltage of which is selected close to the switching voltage of the thyristor. In this case, the circuit will work similarly to a circuit with one dinistor.

The use of thermal resistances with a positive temperature coefficient (posistors) in the switching circuits of fluorescent lamps makes it possible to ensure starterless ignition of lamps without the use of incandescent transformers.

Fig.15 two variants of circuits using resistors are shown. In Fig. 15, and the posistor is connected in parallel with the lamp instead of the starter. Ignition of the lamp is carried out as follows. In a cold state, the posistor has such a resistance that the initial preheating current of the electrodes is approximately equal to the rated current of the lamp. As the posistor heats up, its resistance decreases until it reaches the Curie point. During this period, the preheating current increases. Starting from the Curie point, the resistance of the posistor increases sharply, and at the same time the voltage across the lamp increases, and when the ignition voltage is reached, the lamp lights up. After ignition, the current through the posistor becomes small, and the losses in it amount to 4-5% of the lamp power. The ignition time of a 40 W lamp during an experimental test of this circuit was 8.7 s. The lamp must be provided with a grounded conductive strip or a grounded metal luminaire must be used. The resistance of a posistor depends on its temperature, therefore, to re-ignite the lamp, the posistor must cool to a temperature close to the ambient temperature, which takes 4-5 minutes. This is a drawback of all circuits involving the use of thermal resistances.

The advantages created by the use of posistors are high reliability, durability (provides more than 106 starts), increased lamp life by reducing the likelihood of cold ignitions and low power losses in ballasts compared to starterless devices.

In Fig. Figure 15.6 shows a diagram for switching on a lamp with a posistor, when an increased open-circuit voltage is required to ignite the lamp. A branch is connected in parallel to the lamp, containing a capacitor C and a posistor rl, and a second branch with a posistor r2. When supply voltage is applied to the lamp, resonance phenomena occur in the circuit formed by the inductor Dp and capacitor C, and the voltage across the lamp increases. The posistor g2 has a low “cold” resistance, so the preheating current is large. After preheating the electrodes, the lamp lights up, at the same time the resistances rl and r2 increase and the capacitor C is practically disconnected from the circuit using a posistor r2.

rice. 16 shows variants of devices with two parallel chains: one of which is switching, the second is forming pulses. In Fig. 16, and the switching circuit consists of a dinistor VD1, and the pulse formation circuit consists of a diode VD2 and a capacitor C connected in series, with a resistor R connected in parallel. In the starting mode, the device operates in both half-cycles. During one half-cycle, the dinistor breaks through and the lamp electrodes are heated; during the second half-cycle, a ignition pulse is applied to the lamp. The pulse amplitude should not be sufficient to ignite a cold lamp. After the lamp is lit, the switching circuit is switched off. In Fig. 16.6, the switching circuit consists of two dinistors VD1 and VD2, the first of which is shunted by resistor R. Using this resistor, you can select the appropriate switching voltage for the dinistors and provide optimal starting current depending on the power of the lamp.

An interesting direction in the field of using semiconductor devices in lamp ignition circuits is the creation of semiconductor ballast, which is used instead of conventional inductive ballast. As an example, a device on

Fig. 17. The fluorescent lamp is connected to the network using an NT filament step-up transformer. The primary winding of the NT is connected to the network through a triac VS1 and a capacitor SZ. In parallel with triac VS1, circuit R1C1 is connected through symmetrical dinistor VD1. A second similar cell, consisting of a triac VS2, a dinistor VD2 and a chain R2C2, is connected in parallel with the filament transformer NT and the capacitor SZ. Choke Dr of small inductance prevents VS2 from opening before VS1 opens. When supply voltage is applied to the circuit, VS1 is locked, the current through resistor R1 charges C1. After charging capacitor C1, dinistor VD1 breaks through, and a control pulse is applied to the control electrode VS1. VS1 opens and after primary winding NT and capacitor SZ begin to flow a current, the value of which is limited by SZ. In the secondary winding of the NT, voltage and current appear sufficient to ignite and burn the lamp. At the same time, charging of capacitor C2 begins, breakdown of dinistor VD2 and opening of triac VS2. The opening phase shift of VS2 relative to VS1 is regulated by the inductance of the inductor Dr. When VS2 opens, VS1 closes, and the discharge current of the capacitor SZ induces a current in the lamp in the direction opposite to the original one. After the SZ discharge, the process is repeated. Thus, a current of increased frequency flows through the lamp.

This scheme is effective when undervoltage network and application for powering a high-frequency lamp 800... 1000 Hz. Compared to a conventional ballast circuit, this circuit has advantages: lower power losses in the ballast, increased luminous efficiency of the lamp and a longer service life.

Operation of fluorescent lamps on direct current

When fluorescent lamps are connected to a DC network, a number of phenomena occur that introduce certain features into their operation; The circuits for connecting lamps to the network differ from the AC circuits discussed above.

When powering lamps with direct current, the polarity of the electrodes remains unchanged, so the lamp electrodes operate in different modes: the electrode, which is the anode, overheats, and different anode and cathode designs are required to maintain the required lamp life. But in practice, such lamps are almost never produced and standard ones must be used. And for standard lamps, it is necessary to reverse the polarity of the lamps from time to time so that the electrodes wear evenly.

In addition, when lamps operate on direct current, the phenomenon of cataphoresis is observed, due to the fact that positive mercury ions under the influence of an electric field move to the cathode during lamp operation, as a result of which the anode end of the lamp is depleted of mercury. At the cathode, positive mercury ions are neutralized into mercury atoms, and excess mercury condenses on the walls of the tube. In operating mode, the density of mercury vapor along the length of the tube is unequal, the brightness of the lamp decreases, and after several tens of hours of lamp operation, its brightness can be halved. The appearance of cataphoresis also forces polarity reversal to be carried out at certain intervals.

As a ballast when powering lamps with direct current, active resistance is used either in the form of a resistor or in the form of an incandescent lamp. The voltage on the active ballast is equal to the difference between the mains voltage and the operating voltage on the lamp. Therefore, power losses in the ballast can be 1.5-2 times higher than the lamp power, for this reason this method of lamp stabilization turns out to be economically unprofitable. The use of an incandescent ballast lamp improves the overall efficiency of the set due to the additional luminous flux created by the incandescent lamp.

When using a standard fluorescent lamp in a DC circuit, in order to maintain its luminous flux at the level that it had when powered by alternating current, the operating current of the lamp must be reduced by 10-20% compared to the current when operating on alternating voltage.

The requirements for preheating the lamp electrodes and providing a certain level of open-circuit voltage for the ballast to ignite the lamp remain approximately the same as for alternating current. To prevent cold ignition of lamps, the ignition pulse must be supplied when the electrodes are sufficiently warmed up. In contrast to the operation of a lamp on alternating current, when a choke is used to form the ignition pulse, the size of the pulse is not affected by the moment the circuit switches from the preheating mode to the operating mode, since a constant current flows in the choke. The resistance of the throttle is determined only by its active resistance.

Let's consider the simplest circuits for switching on fluorescent lamps using direct current. On

Fig. 18a shows a diagram for switching on a fluorescent lamp with preheating of the electrodes, operating from a network with a voltage sufficient to ignite it. The DC ignition voltage is higher than the AC ignition voltage. This is explained by the fact that the electric field in the “electrode-wall” sections and between the electrodes is uniform. Standard lamps, when included in the circuit under consideration, must be equipped with a conductive strip, and the network voltage must exceed 3-4 times the operating voltage of the lamp. Preheating of the electrodes is ensured when switch B2 is closed. The transition from start-up mode to operating mode will occur when the lamp ignition voltage decreases and becomes less than the mains voltage. In operating mode, switch B2 is open.

A more rational diagram is shown in

rice. 18.6. To reduce the required supply voltage and make it possible to use standard lamps without a conductive strip, a choke is included in the lamp circuit and a DC starter is used, operating on the principle of a thermal starter. In normal condition, its contacts are closed. When supply voltage is applied to the lamp, preheating of its electrodes begins. At the same time, the thermal

The starter motor ensures the opening of the starter contacts with a certain time delay. When the starter contacts break, due to the inductance of the inductor, a voltage pulse appears, which is necessary to ignite the lamp. In this circuit, the mains voltage should be approximately 2 times higher than the operating voltage of the lamp.

In all cases, it is possible to reverse the polarity of the lamps after a certain period of time. When powering lamps through a rectifier from an alternating current network, it seems advisable to install the ballast on the alternating current side and use a choke or leakage transformer for this.

Operation of fluorescent lamps at higher frequencies. With increasing frequency of the supply voltage, the values ​​of currents, voltages and power factors of lamps with various types ballasts (R, L, C) become closer to each other, and starting from frequencies of 800-1000 Hz, they practically cease to depend on the type of ballast. The decrease in the influence of the type of ballast on the electrical characteristics of lamps with increasing frequency is explained by the fact that with increasing frequency the dynamic characteristics of the discharge approach equilibrium. The shape of the current and voltage curves for all types of ballasts is shown in

Fig. 19, where the first column refers to inductive ballast, the second to resistive, and the third to capacitive. With increasing frequency the coefficient

The rate of light flux pulsations decreases monotonically (50 Hz - 60%, 1000 Hz - 25%, 5000 Hz - 10%). The drop occurs due to the inertia of the phosphor glow and the appearance of a constant component in the discharge radiation, starting from 400 Hz.

With increasing frequency, an uneven increase in luminous efficiency is observed, continuing up to approximately 20,000 Hz. With a further increase in frequency, the output increases slightly. The parameters of an energy-saving lamp with a power of 58 W when operating at frequencies of 50 Hz and 35 kHz are given in

table.

The table shows that when switching to a higher frequency, the light output of the lamp-ballast set increases by 20%.

The service life of lamps at a frequency of 1 kHz is approximately 15% higher than at industrial frequency in the same mode. But with a further increase in frequency, the combustion duration quickly drops: at a frequency of 10 kHz it is already 15% less than at the industrial frequency.

The conditions for stabilizing the discharge at an increased frequency remain generally the same as at the industrial frequency. Therefore, inductive, capacitive or mixed ballasts can be used as a stabilizing resistance. With increasing frequency, the mass and dimensions of the ballasts will noticeably decrease. For example, when moving from a frequency of 50 Hz to a frequency of 3000 Hz, the mass of the inductor decreases by more than 30 times (as

As a core, it is necessary to use not electrical steel, but ferrite or alsifer). Moreover, at high frequencies it is more advisable to use capacitance rather than inductance.

Fig.20 shows a block diagram of a lighting installation with lamps powered at a higher frequency. Power frequency alternating current must first be converted to direct current using a rectifier. Next, the direct current is inverted into high-frequency alternating current and supplied through the distribution network to ballasts and lamps.

Fig.21 simple circuits for turning on lamps at higher frequencies are given. At these frequencies, starters do not provide reliable ignition of fluorescent lamps due to a decrease in contact time and the inability to obtain a sufficient ignition voltage pulse on the lamp due to a decrease in the inductance of the circuit, so only starterless lamp ignition circuits can be used.

Fig. 21 a, b Resonant fast ignition circuits are shown. Preheating of the electrodes is carried out by the current of a resonant circuit formed by inductance and capacitance. Due to the voltage drop on the circuit parallel to the lamp, in the starting mode, the necessary ignition voltage is created, exceeding 1.5-2 times the rated network voltage.

The required open circuit voltage of the ballast is created by resonant phenomena in a circuit of inductance and capacitance.

Scheme on

Fig. 21, c differs from previous resonant circuits in that a special filament transformer is introduced to preheat the electrodes, and a capacitance is used as ballast. It is possible to use a ballast choke, but the mains voltage must be sufficient to ignite a lamp with heated cathodes.

Adjusting the brightness of fluorescent lamps

Unlike incandescent lamps, for which smooth dimming is quite simple, fluorescent lamps require certain conditions to be met. The difference in control methods is explained by the different nature of the dependence of the luminous flux on the current through the lamp for incandescent and fluorescent lamps. In addition, the falling current-voltage characteristic of fluorescent lamps and the increase in re-ignition voltage when the current through the lamp decreases makes it impossible to regulate their brightness by further reducing the voltage across the lamp. The brightness of a fluorescent lamp can be reduced by adjusting the current through the lamp, but while maintaining the same or even slightly increased voltage across it. In this case, lamps with preheated electrodes, equipped with a conductive strip, should be used.

There are three possible methods for adjusting the brightness of fluorescent lamps: by changing the voltage supplied to the adjustable

element; changing the ballast impedance; adjusting the lamp ignition phase. In all three methods, the brightness of the lamp is controlled by changing the current passing through the lamp. The first two methods have limited use due to disadvantages. The most economical method is the phase adjustment of the lamp ignition time.

Fig.22 shown simplest scheme adjusting the brightness of one lamp using the third method. In series with the lamp, in addition to the ballast choke, there is a resistor Rn with an adjustable resistance, the value of which is determined by the power of the lamp (for a 40 W lamp it is 1...1.5 MOhm). Preliminary heating of the electrodes is carried out by a filament transformer. By changing the resistance of the resistor, the brightness of the lamp is adjusted. This circuit is also applicable for several lamps connected in series. When connecting lamps in parallel, each lamp must have its own ballast and filament transformer. An adjustable resistance is included in each parallel

line branch and connect it with a common wire. This method allows brightness adjustment of approximately 300 times and can be used in small installations with 8-10 lamps. With a large number of lamps, this method becomes uneconomical.

Fig.23 shows a schematic diagram of adjusting the brightness of a fluorescent lamp with a choke magnetized by direct current - a magnetic amplifier (MA). One winding of the inductor is connected in series with the lamp and acts as a ballast resistance, the second (control) is powered by direct current from a full-wave rectifier. To change the current in the control winding, an adjustable resistor is connected in series with it. As the current in the control winding increases, the inductor's resistance to alternating current decreases, and the lamp current increases. A filament transformer is used to preheat the lamp electrodes.

The disadvantages of this method are the bulkiness of the control devices and increased power losses, so the use of magnetic amplifiers for control can be recommended for a small number of lamps.

A promising scheme for regulating the brightness of fluorescent lamps, which uses two power sources: one main, having an industrial frequency, and a second auxiliary, connected in parallel with the first and supplying a high frequency voltage to the lamps is shown in

Fig.24. A group of parallel-connected lamps, having individual ballast chokes and filament transformers for preheating the electrodes, is powered through an AT autotransformer from the network with a frequency of 50 Hz. An auxiliary VHF high-frequency source, for example 5-15 kHz, is connected between the autotransformer and the lamps. To prevent these power supplies from shorting to each other, a decoupling and blocking filter is included in series with each of them, designed for frequencies of 50 Hz and 5-15 kHz, respectively.

At the rated supply voltage, the effect of additional high-frequency voltage is small and has virtually no effect on the brightness of the lamps. When the voltage on the lamps is reduced using an autotransformer, the power supplied to the lamps changes and their brightness decreases. Instead of an autotransformer, a thyristor unit can be used to regulate the voltage. Such a regulator unit consists of two thyristors connected back-to-back (or a si-mistor) and a ignition pulse sensor. By adjusting the phase of the ignition pulses supplied to the control electrodes of the thyristors, it is possible to change the current passing through the load. When the supply voltage is reduced to zero, the lamps are switched on to a high-frequency source, the current through the lamps becomes very small, but at the same time sufficient to maintain stable burning of the lamps. Thus, the high-frequency source ensures ignition and re-ignition of lamps at low supply voltage, i.e. at minimum brightness. The power of the high-frequency power supply should be approximately 1% of the power of the lamps.

The above circuit allows you to smoothly adjust the brightness of fluorescent lamps by 200 times and can be used in any existing lighting installation, since no significant alteration is required.

Fig.25 shows a circuit of a frequency converter using transistors with a master oscillator, which makes it possible to obtain a frequency and amplitude of the output voltage that is almost independent of changes in the load. The master oscillator is assembled on transistors VT1 and VT2 with a saturable inductor Dr in the circuit feedback. A push-pull power amplifier is assembled using two transistors VT3 and VT4. The converter is designed for an output frequency of 5 kHz. Such a converter can provide brightness control for 50-60 fluorescent lamps with a power of 40 W. The use of thyristors instead of transistors makes it possible to create more powerful converters.

The disadvantage of this converter is that its operation is strongly influenced by the capacitive nature of the load, as a result of which the output power is limited. This disadvantage of the circuit can be eliminated if the capacitive load is included as a component of the resonant driving circuit.

Fig.26 A converter circuit based on this principle is shown. Due to the fact that the capacitive load is introduced into the master resonant circuit, this circuit becomes not only the master, but also the load. The currents through the base and collector of each transistor are in phase and have a half-sine wave shape, so switching losses in the transistors are reduced to almost zero, which allows the converter to be used at maximum power. In this circuit, transistors of the KT805B type were used. The converter is started from a relaxation generator assembled from an RC circuit and switching diodes VD1, VD2. A prototype of the converter assembled according to this scheme had a power of 200 W and provided brightness control for 150 lamps of the LB-40 type.

CONTENT

Introduction

1. 
   Classification and main parameters of electric light sources
   1. 
      Incandescent lamps
   2. 
      Low pressure fluorescent lamps
   3. 
      High pressure fluorescent lamps
2. 
   Power supply circuits for fluorescent lamps
3. 
   Basic lighting quantities
4. 
   Safety precautions when servicing electric lighting installations

INTRODUCTION

Electric lighting installations are used in all industrial and domestic premises, public, residential and other buildings, on streets, squares, roads, crossings, etc. This is the most common type of electrical installation. There are three types of electric lighting.

Work lighting Intended for normal activities in all indoor and outdoor areas with insufficient natural light. It should provide normal illumination in the workplace.

Emergency lighting is intended to create conditions for the safe evacuation of people in the event of an emergency shutdown of working lighting in premises or the continuation of work in areas where work cannot be stopped due to technology conditions. Emergency lighting must create an illumination of at least 5% of the total to continue work or at least 2 lux, and evacuation lighting - at least 0.5 lux on the floor, along the main passages and stairs.

Security lighting along the borders of the protected area is an integral part of working lighting, will create illumination of the area on both sides of the fence.

According to the rules for electrical installations, lighting is divided into three systems.

General lighting in industrial premises it can be uniform (with uniform illumination throughout the room) or localized when lamps are placed so that increased illumination is created at the main workplaces. The local system provides illumination of workplaces, objects and surfaces.

Combined is a lighting system in which local lighting is added to the general lighting of a room or Space, creating increased illumination in the workplace. The main element of a lighting electrical installation is a light source - a lamp that converts electricity into light radiation.

Two classes of light sources are widely used: incandescent lamps And gas-discharge(luminescent, mercury, sodium and xenon).

The main characteristics of the lamp are the nominal voltage values, luminous flux power (sometimes luminous intensity), service life, as well as dimensions (total length L , diameter, height of the light center from the central contact of the threaded or pin base to the center of the thread).

The most common types of bases: E- threaded; INs - pin single-contact, Vd - pin two-pin(subsequent letters indicate the diameter of the thread or base).

In addition, focusing R, smooth cylindrical soffit SV some other bases.

In the marking of general purpose lamps, the letters mean: V - vacuum, G - gas-filled, B - double-spiral gas-filled, BK - double-spiral krypton.

Of great importance is the dependence of the characteristics of incandescent lamps (IL) on the actual voltage supplied. As the voltage increases, the temperature of the filament increases, the light becomes whiter, the flux increases rapidly and the luminous efficiency is somewhat slower, as a result of which the service life of the lamp sharply decreases.

Widely used in lighting installations, low-pressure tubular fluorescent mercury lamps (LMs) have a number of significant advantages compared to FLs; for example, high luminous efficiency reaching 75 lm/W; long service life, reaching up to 10,000 hours for standard lamps: the ability to use a light source of different spectral composition with better color rendering for most types than incandescent lamps; relatively low (albeit creating glare) brightness, which in some cases is an advantage.

The main disadvantages of LL lamps are: the relative complexity of the switching circuit; limited unit power and large dimensions of the assigned power; impossibility of switching lamps operating on alternating current to power from a direct current network: dependence of the characteristics on the ambient temperature. For conventional lamps, the optimal ambient temperature is 18 - 25°C; if the temperature deviates from the optimal temperature, the luminous flux and luminous efficiency are reduced; at t
Under current standards, in which the gap between the illuminance values ​​for incandescent and gas-discharge lamps in most cases does not exceed two steps, the high luminous efficiency and long service life of LLs, as well as DRL lamps, make them in most cases more economical than incandescent lamps.

The advantages of DRL lamps are: high luminous efficiency (up to 55 lm/W); long service life (10,000 hours); compactness; resistance to environmental conditions (except for very low temperatures).

The disadvantages of DRL lamps should be considered: the predominance of the blue-green part in the spectrum of rays, leading to unsatisfactory color rendering, which precludes the use of lamps in cases where the objects of discrimination are human faces or painted surfaces; ability to operate only on alternating current; the need to switch on through a ballast choke; duration of flare-up when turned on (approximately 7 minutes) and the beginning of re-ignition even after a very short interruption in power supply to the lamp after cooling (approximately 10 minutes); pulsations of the light flux, greater than that of fluorescent lamps; significant reduction in luminous flux towards the end of its service life.

Incandescent lamps are manufactured for voltages of 12-20 V with a power of 15-1500 W. The service life of general-purpose incandescent lamps is 1000 hours. The luminous flux, measured in lumens, per 1 W of power consumed by the lamp ranges from 7 (for low-power lamps) to 20 lm/W (for high-power lamps). The bulbs of incandescent lamps are filled with neutral gas (nitrogen, argon, krypton), which increases the service life of the tungsten filament and increases the efficiency of the lamps.

Currently, mirror incandescent lamps of the ZK and ZSh types are produced for increased voltage: 220-230, 235-245 V.

Halogen incandescent lamps of the KG-240 type (tubular in shape with a tungsten filament in a quartz bulb) with a power of 1000, 1500 and 2000 W have become widespread due to their increased light output.

Fluorescent lamps are a glass tube filled with gas - argon, the inner surface of which is coated with a phosphor. There is also a drop of mercury in the tube. When connected to the electrical network, mercury vapor is formed in the lamp and light appears close to daylight.

The electrical industry produces a series of energy-efficient LL lamps designed for general and local lighting of industrial, public and administrative premises (LB18-1, LB36, LDTs18, LB58). For residential premises, lamps LETS18, LETS36, LETS58 are used, which, compared to standard LLs with a power of 20, 40, and 65 W, have increased efficiency, reduced electricity consumption by 7-8%, lower material consumption, and increased reliability during storage and transportation. For administrative premises, LLs with improved color rendering (LEC and LTBTS) with a power of 8-40 W are produced. The lamps have linear and shaped shapes (U and W-shaped, ring-shaped). All lamps, except ring lamps, have two-pin sockets at the ends.

According to the spectrum of emitted light, LLs are divided into types: LB - white, LCB - cold white, LTB - warm white, LD-daylight and LDC - daytime with correct color rendering.

Color-corrected high-pressure DRL mercury arc lamps consist of a glass bulb coated with a phosphor, inside of which a quartz gas-discharge tube filled with mercury vapor is placed.

DRI gas-discharge metal halide lamps are produced with a luminous efficiency of 75-100 lm/W and a burning duration of 2000-5000 hours. These lamps provide better color rendition than DRL lamps.

To illuminate dry, dusty, and damp rooms, metal halide mirror lamps of the DRIZ type are produced.

400 and 700 W HPS sodium lamps emit golden-white light; their luminous efficiency is 90-120 lm/W, burning duration is more than 2500 hours.

1. 
   Classification and main parameters of electric light sources

Electric light sources can be divided into temperature(incandescent lamps) and luminescent(fluorescent and gas-discharge lamps).

Basic parameters of electric light sources: supply voltage; rated power; luminous efficiency, measured by the number of lumens per watt (lm/W); starting and operating currents; nominal luminous flux; decline in luminous flux through certain time operation; average lamp operating time.

1.1. Incandescent lamps

Electric incandescent lamps are still widely used for lighting purposes, due to their ease of operation and connection to the network, reliability and compactness.

The main disadvantage of incandescent lamps is their low efficiency (about 2%), i.e. incandescent lamps provide more heat than light. The service life of incandescent lamps is on average 1000 hours. Incandescent lamps are very sensitive to changes in the voltage supplied to them. Increase voltage by 1 % in excess of the nominal leads to an increase in luminous flux by 4% and a decrease in service life by 13-14 %. When the voltage decreases, the service life increases, but the luminous flux of the lamp decreases, which affects the productivity of workers.

The service life of incandescent lamps is reduced by vibration, frequent switching on and off, and non-vertical position. The light of incandescent lamps differs from natural light by the predominance of rays of the yellow-red part of the spectrum, which distorts the natural colors of objects.

Incandescent lamps can be vacuum(type B with power from 15 to 25 W) and gas-filled(types G, B, BK with power from 40 to 1500 W).

Gas-filled lamps of type G (monospiral) and B (bispiral) are filled with argon with the addition of 12-16% nitrogen.

Structurally, a bispiral lamp differs from a monospiral lamp in that its filaments have the shape of double spirals, i.e., a spiral twisted from a spiral. These lamps have a luminous efficiency that is approximately 10% higher than that of conventional (monospiral) lamps.

Bispiral lamps with krypton filling (BK type lamps) are externally distinguished by their mushroom-shaped shape and have a luminous efficiency 10-20% higher than lamps with argon filling. Due to the high cost of krypton gas, BK type lamps are produced with a power of 40 to 100 W.

Note that the tungsten filament can be folded not only into a spiral and bi-spiral, but also into a tri-spiral and form various structural shapes (cylindrical, ring, rectangular, etc.). Scale of rated power of general purpose incandescent lamps (W): 15, 25, 40, 60, 75, 100, 150, 200, 300, 500, 750, 1000.

Lamps with a power of 15 and 25 W are produced vacuum, 40-100 W - bispiral with argon or krypton filler, 150 W - monospiral or bispiral and 200 W and above - monospiral with argon filler. Luminous output of lamps is 7-18 lm/W.

For lamps with a power from 15 to 200 W, the E27/27 base is used, for lamps with a power of 300 W with a bulb 184 mm long - the E27/30 base, for lamps with a power from 300 to 1000 W - the E40/45 base.

Lamps with a power of up to 300 W can be manufactured in both transparent and frosted (MT), opal (O), milk (ML) flasks. Note that opal is a mineral of the hydroxide subclass (SiO 2 x nH 2 O).

Conventional designations for general purpose incandescent lamps: the word “lamp”, type of filling and filament body, type of lamp bulb (if it is opaque), voltage range, rated power, GOST number. For example, the designation “Lamp B 125-135-25 GOST 2239-79” is deciphered as follows: vacuum lamp, transparent bulb for voltage 125-135 V, power 25 W, manufactured according to GOST 2239-79.

The designation “Lamp GMT 220-230-150 GOST 2239-79” reads as follows: gas-filled monospiral argon lamp in a frosted flask for a voltage of 220-230 V, power 150 W, manufactured in accordance with GOST 2239-79.

Incandescent lamps for local lighting are manufactured for a voltage of 12 V with a power of 15 to 60 W and for a voltage of 24 and 36 V with a power of 25, 40, 60 and 100 W. The designation of these lamps, for example MO-36-60 or MO-12-40, is deciphered as follows: an incandescent lamp for local lighting with a voltage of 36 V with a power of 60 W and an incandescent lamp for local lighting with a voltage of 12 V with a power of 40 W. In addition, miniature incandescent lamps of type MH with a voltage of 1.25 V and a power of 0.313 W are produced; 2.3 V power 3.22 W; 2.5 V power 0.725 W, 1.35 W, 2.8 W; 36 V power 5.4 W. The luminous flux of lamps may decrease over time. There are standards for reducing the luminous flux of each lamp after 750 hours of operation at the design voltage.

Recently, incandescent lamps, the bulbs of which are covered with a mirror or white diffuse reflective layer, have become widespread. Such lamps are called luminaire lamps. The mirror part of the bulb is given the appropriate shape in order to obtain a certain luminous intensity curve (Fig. 2.2). Since lamps with reflective coatings have the necessary luminous intensity curve, they are used for lighting devices without optical devices, which significantly reduces the cost of lamps for them. These lamps do not require cleaning, and their luminous flux is more stable during operation.

Incandescent lamps with reflective layers (lamps) are divided into: general lighting lamps with a diffuse (D) layer of the NGD type (incandescent lamps, gas-filled with argon, monospiral with a diffuse layer); local lighting lamps with a diffuse layer of the MOD type; mirror lamps with medium (G) light distribution, type NZS; mirror lamps with wide (W) light distribution, type ZN27-ZN28; mirror lamps with concentrated light distribution, type NZK; mirror lamps for local lighting type MOZ.

General lighting lamps with a diffuse layer of the NGD type are manufactured for a voltage of 127 V with a power of 20, 60, 100, 150 and 200 W and for a voltage of 220 V with a power of 40, 100, 150, 200 and 300 W.

Local lighting lamps with a diffuse layer of the MOD type are manufactured for a voltage of 12 V with a power of 25, 40 and 60 W and for a voltage of 36 V with a power of 40, 60 and 100 W.

Mirror lamps with a medium (G) light distributor of the NZS type are available for voltages of 127 and 220 V with a power of 40, 60, 75 and 100 W.

Mirror lamps with a wide (W) light distribution of type ZN30 are produced only for a voltage of 220 V with a power of 300, 500, 750 and 1000 W.

Mirror lamps with concentrated light distribution of the NZK type are available for voltages of 127 and 220 V with a power of 40, 60, 75, 100, 150, 200, 300, 500, 750 and 1000 W. The service life of all lamps with a voltage of 220 V and lamps with a power from 150 to 1000 W at a voltage of 127 V is 1500 hours.

Mirror lamps for local lighting of the MOZ type are available only at a voltage of 36 V with a power of 40, 60 and 100 W.

The service life of all lamps not noted above is 1000 hours. The luminous efficiency of the lamps is 8.5-20.6 lm/W.

The industry also produces halogen incandescent lamps, the service life of which is 2000 hours or more, i.e. 2 times more than the above lamps.

Iodine is added to the gas filling of the bulb of a halogen incandescent lamp, which, under certain conditions, ensures the reverse transfer of evaporated tungsten particles from the walls of the lamp bulb to the filament body. It is this circumstance that makes it possible to double the service life of an incandescent lamp with increased luminous efficiency. Halogen lamps have linear and compact filament bodies. Linear filament bodies are made in the form of a long spiral (the ratio of the length of the spiral to the diameter is more than 10), which fits into a tubular quartz flask with end inputs. Compact filament bodies have a shorter spiral length. These lamps also have a smaller bulb.

Designation halogen lamps: KG220-1000-5 - halogen lamp with a quartz glass bulb, iodine, voltage 220 V, power 1000 W, development number 5; KGM (small-sized) for voltages of 30, 27 and 6 V.

Tubular halogen incandescent lamps are available for a voltage of 220 V with a power of 1000, 1500, 2000, 5000 and 10,000 W, as well as for a voltage of 380 V with a power of 20,000 W. The luminous flux of halogen lamps ranges from 22 klm (1000 W lamps) to 260 klm (10,000 W lamps). The luminous efficiency of these lamps is 22-26 lm/W.

Due to the instability of the supply voltage, incandescent lamps are currently produced that allow a voltage deviation in the range of ±5 V from the calculated one. The voltage range is indicated on the lamp, for example 125-135 V, 215-225 V, 220-230 V, 225-235 V, 230-240 V.

For increased voltage of the electrical network, special incandescent lamps are produced for a rated voltage of 235 V and 240 V. Here the voltage range is 230-240 V and 235-245 V. A rated voltage of 240 V is used only for lamps with a power of 60, 100 and 150 W. Lamps for voltages of 235 and 240 V should not be used with a stable voltage of 230 V due to a sharp decrease in their luminous flux in such a network.

1.2. Low pressure fluorescent lamps

Low-pressure fluorescent tubular lamps are a glass tube sealed at both ends, the inner surface of which is coated with a thin layer of phosphor. The lamp is evacuated and filled with the inert gas argon at very low pressure. A drop of mercury is placed in the lamp, which when heated turns into mercury vapor.

The tungsten electrodes of the lamp have the form of a small spiral coated with a special composition (oxide) containing carbon dioxide salts of barium and strontium. Two hard nickel electrodes are located parallel to the spiral, each of which is connected to one end of the spiral.

In low-pressure fluorescent lamps, a plasma consisting of ionized metal and gas vapor emits in both the visible and ultraviolet parts of the spectrum. With the help of phosphors, ultraviolet rays are converted into radiation visible to the eye.

Low-pressure fluorescent tubular lamps with an arc discharge in mercury vapor are divided according to the color of the radiation into white light lamps (LB type), warm white light lamps (LTL), and color corrected daylight lamps (LDC).

Scale of rated powers of fluorescent lamps (W): 15, 20, 30, 40, 65, 80.

The design features of the lamp are indicated by letters following the letters indicating the color of the lamp (P - reflector, U - U-shaped, K - ring, B - quick start, A - amalgam).

Currently, the so-called energy-efficient fluorescent lamps, having a more efficient electrode design and an improved phosphor. This made it possible to produce lamps with reduced power (18 W instead of 20 W, 36 W instead of 40 W, 58 W instead of 65 W), a bulb diameter reduced by 1.6 times and increased luminous efficiency.

White light lamps of the LB type provide the highest luminous flux of all listed types of lamps of the same power. They approximately reproduce the color of sunlight and are used in rooms where significant visual strain is required from workers.

Warm white light lamps of the LTB type have a pronounced pink tint and are used when there is a need to emphasize pink and red tones, for example, when rendering the color of a human face.

The color of fluorescent lamps of the LD type is close to the color of fluorescent lamps with corrected color of the LDC type.

Cold-white light lamps of the LHB type occupy an intermediate position in color between white light lamps and daylight lamps with corrected color and in some cases are used on a par with the latter.

The average burning time of fluorescent lamps is at least 12,000 hours.

Luminous flux of each lamp after 70 % The average burning time must be at least 70% of the nominal luminous flux.

The average surface brightness of fluorescent lamps ranges from 6 to 11 cd/m2. The luminous efficiency of LB type lamps ranges from 50.6 to 65.2 lm/W.

Fluorescent lamps, when connected to an alternating current network, emit a luminous flux that varies over time. The pulsation coefficient of the luminous flux is 23% (for LDC type lamps - 43 %). As the rated voltage increases, the luminous flux and power consumed by the lamp increase.

Erythematic and bactericidal fluorescent lamps are also produced. Their flasks are made of special glass that transmits ultraviolet radiation. Erythema lamps use a special phosphor that converts mercury discharge radiation into ultraviolet radiation with a range of wavelengths that most cause tanning (erythema) of human skin. Such lamps are used in installations for artificial ultraviolet irradiation of people and animals. Germicidal lamps are used in air disinfection installations; These lamps do not have a phosphor.

Fluorescent lamps are designed for normal operation at ambient temperature +15...+40 °C. If the temperature drops, the pressure of argon and mercury vapor drops sharply and the ignition and combustion of the lamp deteriorate.

The duration of operation of the lamp is longer, the fewer times it is turned on, i.e., the less the oxide layer of electrodes wears out. A decrease in the voltage supplied to the lamp, as well as a decrease in ambient temperature, contribute to more intensive wear of the electrode oxide. If the voltage decreases by 10-15%, the lamp may not light up or its inclusion will be accompanied by repeated blinking. Increasing the voltage makes it easier to ignite the lamp, but reduces its light output.

Disadvantages of fluorescent lamps: a decrease in the power factor of the electrical network, the creation of radio interference and a stroboscopic effect due to pulsation of the light flux, etc.

The stroboscopic effect consists of creating in a person under fluorescent lighting the illusion that an object moving (rotating) at a certain speed is at rest or moving (rotating) in the opposite direction. In production conditions, this is dangerous to human life and health. At the same time, the stroboscopic effect is used to check the correct operation of electricity meters. There are depressed depressions (marks) on the rotating disk of the electric meter. If you look at the disk from above, illuminated by fluorescent light, then if the disk moves correctly, it seems that the recesses (marks) are at rest.

To eliminate stroboscopy phenomena, reduce radio interference, and improve power factor, special circuits for switching on fluorescent lamps are used.

1.3. High pressure fluorescent lamps

High-pressure mercury lamps of the DRL type (mercury arc fluorescent) are produced with a power of 50, 80, 125, 175, 250, 400, 700, 1000 and 2000 W.

A DRL lamp consists of an ellipsoidal glass cylinder (flask), on the inner surface of which is applied a layer of phosphor - magnesium fluorogermanate (or magnesium arsenate). To maintain the stability of the properties of the phosphor, the cylinder is filled with carbon dioxide. Inside the glass cylinder (flask) there is a quartz glass tube filled with mercury vapor under high pressure. When an electrical discharge occurs in the tube, its visible radiation passes through a phosphor layer, which, by absorbing ultraviolet radiation from the quartz discharge tube, turns it into red visible radiation.

The average operating time of DRL lamps ranges from 6,000 hours (lamps with a power of 80 and 125 W) to 10,000 hours (lamps with a power of 400 W or more).

For DRL lamps, the percentage of red radiation is also regulated (6 and 10%). The rated network voltage for all DRL lamps is 220 V. The pulsation coefficient of DRL lamps is 61-74%.

The most modern light sources include metal halide lamps, in which sodium, thallium and indium iodides are added to the mercury discharge in order to increase the luminous efficiency of the lamps. Metal halide lamps of the DRI type (mercury-iodide arc) have ellipsoidal or cylindrical bulbs, inside of which a quartz cylindrical burner is located. Inside this burner, a discharge occurs in vapors of metals and their iodides.

The power of DRI lamps is 250, 400, 700, 1000, 2000 and 3500 W. The luminous efficiency of DRI lamps is 70-95 lm/W.

The luminous efficiency of high-pressure sodium lamps reaches 100-130 lm/W. These lamps have a discharge tube made of floor and crystalline aluminum oxide, inert to sodium vapor and highly transmitting its radiation, placed inside a glass cylindrical flask. The pressure in the tube is about 200 kPa. At this pressure, the sodium resonance lines expand, occupying a certain spectral band, as a result of which the color of the discharge becomes whiter. The operating time of the lamps is 10-15 thousand hours.

To illuminate large areas, powerful (5, 10, 20 and 50 kW) xenon tubular ballastless lamps of the DKsT type are used. They are ignited using a starting device that generates a high-voltage (up to 30 kV) high-frequency voltage pulse, under the influence of which a discharge occurs in the xenon lamp.

Lamps with a power of 5 kW have a nominal voltage of PO V, with a power of 10 kW - a voltage of 220 V, with a power of 20 and 50 kW - a voltage of 380 V. The luminous efficiency of these lamps is from 17.6 to 32 lm / W.

2. Power supply circuits for fluorescent lamps

Fluorescent lamps are connected to the network in series with an inductive reactance (choke), which ensures stabilization of the alternating current in the lamp.

The fact is that an electric discharge in a gas is unstable, when minor voltage fluctuations cause a sharp change in the current in the lamp.

There are the following lamp power supply schemes: pulse ignition, quick ignition, instant ignition.

In the pulse ignition circuit (Fig. 1), the ignition process is provided by a starter (starter). Here, the electrodes are first heated, then an instantaneous voltage pulse occurs. The starter is a miniature gas-discharge light bulb with two electrodes. The bulb bulb is filled with the inert gas neon. One of the starter electrodes is rigid and stationary, and the other is bimetallic, bending when heated. In normal condition, the starter electrodes are open. At the moment the circuit is connected to the network, the full network voltage is applied to the electrodes of the lamp and starter, since there is no current in the lamp circuit and, therefore, the voltage loss in the inductor is zero. The voltage applied to the starter electrodes causes a gas discharge in it, which in turn ensures the passage of a small current (hundredths of an ampere) through both lamp electrodes and the choke. Under the influence of the heat generated by the passing current, the bimetallic plate, bending, short-circuits the starter, as a result of which the current strength in the circuit increases to 0.5-0.6 A and the lamp electrodes quickly heat up. After the starter electrodes close, the gas discharge in it stops, the electrodes cool down and then open. An instantaneous break in the current in the circuit causes the appearance of an electromotive force of self-induction in the inductor in the form of a voltage peak, which leads to the ignition of the lamp, the electrodes of which by that moment are red-hot. After the lamp is lit, the voltage at its terminals is about half the network voltage. The rest of the voltage is extinguished at the inductor. The voltage applied to the starter (half the mains voltage) turns out to be insufficient to trigger it again.

Rice. 1. Pulse circuit for connecting a fluorescent lamp to the network:

1 – starter (starter); 2 – lamp; 3 – throttle.

In the fast ignition circuit (Fig. 2), the electrodes of the lamps are connected to separate windings of a special incandescent transformer. When voltage is applied to a non-burning lamp, the voltage loss in the inductor will be small, the increase in voltage of the filament windings is completely applied to the electrodes, which quickly and strongly heat up, and the lamp can light up at normal mains voltage. When a discharge occurs in the lamp, the filament current of the ballast automatically decreases.

Rice. 2. Scheme for fast ignition of a fluorescent lamp:

1 – throttle; 2 – lamp; 3 – filament transformer.

The instant ignition circuit (Fig. 3) uses a choke-transformer and a separate resonant circuit, which creates an increased (6-7 times the operating) voltage on the lamp at the moment of switching on. Instant ignition circuits are used only in certain cases, for example in explosive areas with lamps containing special reinforced electrodes. Electrodes of normal type lamps in the circuit shown in Fig. 3, wear out quickly. High voltage supplied to the lamp in starting moment, poses a danger to operating personnel.

Rice. 3. Diagram of instant ignition of a fluorescent lamp

1 – lamp; 2 – capacitor; 3 – choke-transformer.

When the throttles operate, noise occurs. To provide the required current and voltage at the lamp terminals in starting and operating modes, increase the power factor, reduce the stroboscopic effect and reduce the level of radio interference, special ballasts are attached to fluorescent lamps. The ballasts include chokes, capacitors (to increase the power factor and suppress radio interference) and resistors, placed in a common metal casing and filled with bitumen mass.

According to the ignition method, ballasts are divided into three groups: starter ( symbol UB), fast and instant ignition (symbol AB).

The main types of ballasts for fluorescent lamps: 1UBI-40/220-VP-600U4 or 2UBI-20/220-VPP-110HL4, which means the following: the first digit indicates how many lamps are switched on with the device; UB - starter control gear; I - inductive phase shift of the current consumed by the device (can be E - capacitive or K - compensated, i.e. compensating the stroboscopic effect); 40 and 20 - lamp power, W; 220 - supply voltage, V; B - built-in device (maybe N - independent); P - with reduced noise level; PP - with especially low noise level; 600 and software - series number or modification of the ballast; U and HL - the ballast is intended for operation in areas with a temperate or cold climate, respectively (can also be TV - tropical humid climate; TC - tropical dry climate; T - tropical wet and dry; 0 - any climate on land); 4 - placement in rooms with an artificially controlled climate (maybe 1 - in the open air; 2 - rooms poorly isolated from the surrounding air, and canopies; 3 - ordinary naturally ventilated rooms; 5 - rooms with high humidity and unventilated underground rooms).

Ballasts for arc mercury fluorescent lamps (MAFL), arc mercury iodide lamps (MAI), high-pressure sodium lamps (HPL) are designated as follows: 1DBI-400DRL/220-N or 1DBI-400DNaT/220-V. Here DB is a ballast choke; DRL and DNAT - type of lamp (DNaT means the same as NLVD); N - independent ballast.

Electrical diagram starter two-lamp ballasts are given in Fig. 4.

Rice. 4. Electrical diagram of starter ballast 2 UBI for two lamps

1 – throttle; 2 – lamps; 3 – starters.

Ballasts for arc mercury fluorescent lamps of the DRL type are made with a choke (Fig. 5).

Fig.5. Scheme for switching on DRL type lamps through a choke.

1 – throttle; 2 – lamp; C – capacitor.

To turn on DRI and HPS lamps, ballasts with standardized pulse ignition devices are used, the main elements of which are diode thyristors (Fig. 6). Here, however, the re-switching on of an extinguished non-equipped special block Instant relighting of the lamp is possible only after it has cooled, i.e. after 10-15 minutes.

Fig. 6 Connection diagram for lamps of the DRI or HPS type.

1 – pulse ignition device; 2 – ballast choke

3. Basic lighting quantities

The amount of light emitted by a source is called luminous flux and is designated F. The unit of luminous flux is lumen(lm).

The luminous flux contained within the solid angle , at the vertex of which a point source of light with force J is located, is determined by the formula Ф = J.

The power of light J is the luminous flux density in one direction or another; measured in candelas (cd).

Candela is the luminous intensity emitted from an area of ​​1/600,000 m 2 of the cross-section of the full emitter in a direction perpendicular to this cross-section, at an emitter temperature equal to the solidification temperature of platinum (2045 K) and a pressure of 101,325 Pa.

Solid angle b is equal to the ratio of the surface area o cut out on a sphere by a cone with its apex at point S to the square of radius r (Fig. 2.1). If r = 1, then the solid angle is numerically equal to the surface area cut out by a cone on a sphere of unit radius. The unit of solid angle is steradian(Wed).

Thus, a lumen is the product of a candela and a steradian. The illumination of the working surface will be better, the greater the luminous flux falling on this surface. The degree of surface illumination, i.e. the density of the luminous flux onto the illuminated surface, is characterized by illumination E, which is measured in suites(OK). If a luminous flux equal to 1 lm falls on 1 m 2 of any surface, then the illumination E will be 1 lux, i.e. lm/m 2.

When the working surface is illuminated, light and dark details stand out in it, differing in their brightnessI., which depends not only on illumination, but also on the reflective properties of the surface. Brightness determines the sensation of light received by the eyes. If the brightness of the surface is very low, it is difficult to discern details on it, and vice versa, if the brightness is very high, then the surface will blind the eyes. Brightness is equal to the ratio of luminous intensity to the projection area of ​​a reflecting (emitting) body in a given direction; measured in candelas per square meter (cd/m2).

4. Safety precautions when servicing electric lighting installations

The organization of safety work at electrical installation work sites provides for: the appointment of persons responsible for the safety of work (work foreman, site supervisors, foremen and foremen of installation teams); instruction on safe working methods in the workplace; hanging warning posters, installing fences, assigning people on duty when performing installation work that is dangerous to others.

All installation work on or near live parts must be carried out with the voltage removed.

When installing electrical installations, various machines, mechanisms and devices are used to facilitate the work of installers and ensure safe working conditions. Incompetent handling of these mechanical equipment can cause injuries.

In electrical installation practice, special vehicles and mobile workshops are widely used. Thus, a special SK-A type vehicle with a trailer is designed for transporting and laying cables in earthen trenches. To install overhead lines, telescopic towers are used, equipped with a basket in which the installer can be lifted to a height of up to 26 m. To lift supports and parts of overhead line structures, jib cranes on wheels and tracks are used.

Electrical work tools are used for electrical installation work. According to protective measures against electric shock, electrified hand tools are divided into 3 classes:

Class I - machines with insulation of all live parts; the plug has a grounding contact;

Class II - machines in which all live parts have double or reinforced insulation; these machines do not have grounding devices;

Class III - machines with a rated voltage not higher than 42 V.

The rated voltage of AC machines of classes I and II should not exceed 380 V.

Electrified tools include:

Drilling manual electric machines with both commutator single-phase motors for a rated voltage of 220 V, and with three-phase asynchronous motors for a rated voltage of 36 and 220 V;

An electric hammer designed for punching openings and niches in brickwork and concrete when installing passages through walls and ceilings, when installing group panels and shields in the event of hidden electrical wiring(rated motor voltage 220 V);

An electric hammer drill designed for drilling deep holes with a diameter of up to 32 mm in the walls and ceilings of buildings made of brick or concrete to a depth of up to 700 mm;

An electric furrow cutter designed for cutting furrows in brick walls for laying hidden electrical wiring (the width of the cut furrow is 8 mm and the depth is 20 mm).

Workers who have completed industrial safety training are allowed to work with manual electric machines. Each machine must have an inventory number.

Hand-held electrical machines are prohibited from being used in explosive areas, as well as in areas with a chemically active environment that destroys metal and insulation.

Machines that are not protected against splashes are not permitted to be used in open areas during rain or snowfall.

Before working with the machine, it is necessary to check the completeness and reliability of fastening of the parts, the serviceability of the cable (cord) and plug, the integrity of the insulating parts of the case, the handle and brush holder covers, the presence of protective covers, the operation of the switch and the operation of the machine at idle speed. When operating Class I machines, it is necessary to use individual electrical protective equipment(dielectric gloves).

To change the cutting tool, make adjustments, when carrying a manual machine and taking breaks in work, it must be turned off.

It is prohibited to operate a manual electric machine if at least one of the following faults is present: damage to the plug connection, cable (cord) or their protective tube; damage to the brush holder cover of a machine with a commutator electric motor; unclear operation of the switch; the appearance of smoke, an all-round fire on the collector, a pungent smell of burnt insulation; lubricant leakage; increased knocking, noise, vibration; breakage or cracks in the body, handle or protective guard; breakage of the cutting tool.

Work on the installation of overhead power lines (external lighting networks) involves lifting people and materials to heights using lifting machines and mechanisms. In this case, there is a danger of injury in case of falling from supports or other structures, as well as injury from lightning current when working during a thunderstorm or induced voltage from neighboring lines.

While lowering the lower end of the support into the pit, none of the workers should be in it. Climbing to the support should be carried out using a telescopic tower, assembly claws, manholes, and ladders. To avoid bruises and injuries as a result of parts and tools falling from a height, it is prohibited to be under the support and basket of the tower during work, and it is not allowed to throw any objects from the height of the support.

When rolling out bare wire from a drum, the worker must wear canvas gloves. During the installation of lines longer than 3 km, the installed sections of wires must be short-circuited and grounded in case induced voltage appears in this section from neighboring lines or from a thundercloud.

To lay cables along walls or building structures at a height of 2 m or more, durable scaffolding with fencing in the form of railings and a side board (at the deck) should be used. Cable laying from stairs is not permitted. Lifting the cable to secure it on the supporting devices of the cable structure to a height of more than 2 m must be done using slingshots and hand blocks. At angles of rotation of the cable line, you should not pull the cable by hand when unrolling. When heating the cable in winter with an electric current of 220 V, its sheath must be grounded to avoid electrical injury in the event of a short circuit of the current-carrying conductor to steel armor or aluminum (lead) sheath.