Diagram of a device for determining short-circuited turns. Ƒ↓ — Anchor testing device (APD). Stator interturn short circuit
It may happen that the wound coil does not contain short-circuited turns, and during operation doubt arises about its serviceability. How can you be sure of this? Do not disassemble the transformer to check the coil again. In such cases, another device will help, which allows you to check transformers, chokes and other inductors in assembled form.
The device is assembled on two transistors and is a low-frequency generator. The occurrence of oscillations occurs as a result of positive feedback between cascades. The depth of feedback depends on whether there are short-circuited turns in the coil being tested or whether they are absent. In the presence of closed turns, generation is interrupted. In addition, the circuit has negative feedback, which is regulated by potentiometer R5. It allows you to select when testing coils with different inductances desired mode generator operation.
To monitor the generator voltage, the circuit contains an AC voltmeter. It consists of a milliammeter and two rectifier diodes. AC voltage supplied through capacitor C5. This capacitor also serves as a limiter, allowing you to set a certain deviation of the milliammeter needle. Here it is advisable to use a milliammeter with a low deflection current (1 mA, 0.5 mA) so that the measuring circuit does not affect the operation of the generator.
Diodes of type D1, D2 with any letter index are suitable as rectifier diodes. When operating the generator, select the capacitance of capacitor C5 such that the milliammeter needle deviates to the middle of the scale. If this fails, place a resistor in series with the milliammeter and select its resistance according to the required needle deflection.
Take transistors like MP39-MP42 (P13-P15) with an average gain (40-50). Resistors can be of any type with a power starting from 0.12 W. You can take any buttons, switch, terminals too.
The device is powered by a Krona battery or any other source with a voltage of 7-9 V.
To assemble the device, use a wooden, metal or plastic box suitable sizes. On the front panel, attach the control knobs and a milliammeter, and on top there are terminals for connecting the coils under test.
How to use the device? Turn on the Vk toggle switch. The milliammeter needle should deflect approximately to the middle of the scale. Connect the terminals of the coil being tested to the “Lx” terminals and press the Kn1 button. Between the base of transistor T1 and the power plus, capacitor C1 will be connected, which, together with capacitor C2, will form a voltage divider, sharply reducing the coupling between the stages. If there are no short-circuited turns in the winding being tested, then the milliammeter readings may increase or decrease slightly. If there is even one short-circuited turn, the oscillations of the generator are disrupted and the needle returns to zero.
Engine position variable resistor R5 depends on the inductance of the coil being tested. If this is, for example, the winding of a power transformer or rectifier choke, which have high inductance, the motor should be in the extreme right position according to the diagram. As the inductance of the coil being tested decreases, the oscillation amplitude of the generator decreases, and with very small inductances, generation may not occur at all. Therefore, as the inductance decreases, the variable resistor slider needs to be moved to the left according to the circuit. This allows you to reduce the depth of negative feedback and thereby increase the voltage between the emitter and collector of transistor T1
When testing coils of very low inductance - circuits of receivers with ferrite cores, the inductance of which is from 3 to 15 mH, it is additionally necessary to increase the depth of positive feedback. To do this, just press the Kn2 button. The device can test coils with inductance from 3 mH to 10 H.
Attention!
If you cannot find a 1.2 kΩ variable resistor, assemble the circuit section near R5 according to the following diagram:
100Ω R5 1kΩ 100Ω To R3 (---[___]----[___]----[___]---) to R7 | To R6
The variable resistor must be single-turn and non-inductive, such as SP0, SP3, SP4 (or a foreign equivalent). The main thing is that the track is graphite and not wire.
100 Ω resistors should be soldered to the terminals of R5, then a cambric or heat-shrinkable tube should be placed on them.
Any of the following transistors are suitable: MP39B, MP40(A/B), MP41, MP41B, MP42, MP42B (or analogues). If you change the board layout, you can install transistors KT361 (except KT361A), KT209D or any other low power P-N-P with Ku=40...50.
Printed circuit board: 
(download in Sprint-Layout 5 format)
The diagram is taken from the brochure “The First Steps of a Radio Amateur - Issue 4/1971”, printed circuit board- Alexander Tauenis.
ATTENTION! 05/13/2013 board layout updated, a new version available available via the same link. In addition to the original version for transistors MP39-42, the .lay file also includes versions with transistors KT361 (regular mounting) and KT361 (surface mounting, size 0805). The SMD version includes 1KΩ resistors, so you can use a regular 1KΩ variable resistor R5 without unnecessary distortions a la the 1960s.
People who often deal with engines will find this device very useful. It is very simple in design and use. Using this device, you can test the windings of transformers, chokes, electric motors, relays, magnetic starters, contactors and other coils with inductance from 200 μH to 2 H. It is possible to determine not only the integrity of the winding, but also the presence of an interturn short circuit in it. The figure shows the device diagram:
(click on image to enlarge)
The basis of the device is a measuring generator using transistors VT1, VT2. Its operating frequency is determined by the parameters oscillatory circuit, formed by capacitor C1 and the inductor being tested, to the terminals of which probes XP1 and XP2 are connected. Variable resistor R1 sets the required depth of positive feedback, ensuring reliable operation of the generator.
Transistor VT3, operating in diode mode, creates the necessary voltage level shift between the emitter of transistor VT2 and the base of VT4.
A pulse generator is assembled on transistors VT4, VT5, which, together with a power amplifier on transistor VT6, ensures the operation of the HL1 LED in one of three modes: no glow, blinking and continuous burning. The operating mode of the pulse generator is determined by the bias voltage based on transistor VT4.
The device works as follows. When the probes XP1 and XP2 are closed, the measuring generator is not excited, transistor VT2 is open. The constant voltage at its emitter, which means based on transistor VT4, is not enough to start the pulse generator. At the same time, transistors VT5, VT6 are open, and the diode lights up continuously, signaling the integrity of the circuit being tested.
When a working inductor, say, a motor winding, is connected to the probes of the device and the variable resistor R1 is installed in a certain position, the measuring generator is excited. The voltage at the emitter of transistor VT2 increases, which leads to an increase in the bias voltage at the base of transistor VT4 and the start of the pulse generator. The diode begins to blink.
If there are short-circuited turns in the winding being tested, the measuring generator is not excited and the probe operates as if the probes are short-circuited (the diode simply glows).
When the probes are open or the circuit of the coil being tested is open, transistor VT2 is closed. The voltage at its emitter, and therefore at the base of transistor VT4, increases sharply. This transistor opens to saturation, and the oscillations of the pulse generator are interrupted. Transistors VT5, VT6 close, diode HL1 does not light up.
In addition to those indicated in the diagram, transistors VT1 - VT3 can be KT315G, KT358V, KT312V. KT361B transistors can be replaced with any of the KT502, KT361 series. It is advisable to use the VT6 transistor of the KT315, KT503 series with any letter index. Fixed resistors - MLT-0.125; capacitor C1 - KM; C2 and SZ - K50-6; LED AL310A, AL 307A, AL307B, you need to connect a 68 Ohm resistor in series to the circuit; power source - 3V (regular batteries or crown).
It may happen that in the extreme right position of the resistor slider and with the probe probes open, the diode will light up. Then you will have to select resistor R3 (increase its resistance) so that the diode goes out.
When checking coils of small inductance, the sharpness of the “tuning” of the variable resistor may turn out to be excessive. It is not difficult to get out of this situation by connecting in series with resistor R1 another variable resistor with low resistance, or using instead of a variable resistor a resistance store or a set of resistors connected by a small multi-position switch (roughly, smoothly). Information taken from Radio magazine No. 7, 1990.
And this is how I made it:
Whoever is interested, write, there is a signet in Sprint-Layout format
In the video I demonstrated it in operation, obviously taking a non-working engine.
If physics was taught well at your school, then you probably remember an experiment that clearly explained the phenomenon of electromagnetic induction.
Outwardly, it looked something like this: the teacher came to the class, the attendants brought some instruments and placed them on the table. After explaining the theoretical material, a demonstration of experiments began, clearly illustrating the story.
To demonstrate the phenomenon of electromagnetic induction, a very large size, a powerful straight magnet, connecting wires and a device called a galvanometer were required.
Galvanometer appearance It was a flat box slightly larger than a standard A4 sheet, and behind the front wall, covered with glass, there was a scale with a zero in the middle. Behind the same glass one could see a thick black arrow. All this was quite distinguishable even from the very last desks.
The galvanometer leads were connected to a coil using wires, after which a magnet inside the coil was simply moved up and down by hand. In time with the movements of the magnet, the galvanometer needle moved from side to side, which indicated that current was flowing through the coil. True, after graduating from school, one physics teacher I knew told me that on the back wall of the galvanometer there was a secret handle, which was used to move the needle by hand if the experiment was unsuccessful.
Now such experiments seem simple and almost unworthy of attention. But electromagnetic induction is now used in many electrical machines and devices. In 1831, Michael Faraday studied it.
At that time there were not yet sufficiently sensitive and accurate instruments, so it took many years to figure out that the magnet should MOVE inside the coil. Magnets of different shapes and strengths were tried, the winding data of the coils also changed, the magnet was applied to the coil in different ways, but only the alternating magnetic flux achieved by moving the magnet led to positive results.
Faraday's research proved that the electromotive force arising in a closed circuit (coil and galvanometer in our experiment) depends on the rate of change of the magnetic flux limited by the inner diameter of the coil. In this case, it is absolutely indifferent how the magnetic flux changes: either due to a change magnetic field, or due to the movement of the coil in a constant magnetic field.
The most interesting thing is that the coil is in its own magnetic field created by the current flowing through it. If the current in the circuit under consideration (coil and external circuits) changes for some reason, then the magnetic flux causing the EMF will also change.
Such an EMF is called self-induced EMF. The remarkable Russian scientist E.Kh. studied this phenomenon. Lenz. In 1833, he discovered the law of interaction of magnetic fields in a coil, leading to self-induction. This law is now known as Lenz's law. (Not to be confused with the Joule-Lenz law)!
Lenz's law states that the direction induced current, arising in a conducting closed circuit is such that it creates a magnetic field that counteracts the change in the magnetic flux that caused the appearance of the induced current.
In this case, the coil is in its own magnetic flux, which is directly proportional to the current strength: Ф = L*I.
In this formula there is a proportionality factor L, also called the inductance or self-inductance coefficient of the coil. The SI unit of inductance is called the henry (H). If, with a direct current of 1A, the coil creates its own magnetic flux of 1Wb, then such a coil has an inductance of 1H.
Just like a charged capacitor has a store of electrical energy, a coil through which current flows has a store of magnetic energy. Due to the phenomenon of self-induction, if the coil is connected to a circuit with an EMF source, when the circuit is closed, the current is established with a delay.
In exactly the same way, it does not immediately stop when disconnected. In this case, a self-inductive emf acts at the coil terminals, the value of which significantly (tens of times) exceeds the emf of the power source. For example, a similar phenomenon is used in car ignition coils, in line scans of televisions, as well as in a standard switching circuit fluorescent lamps. These are all useful manifestations of self-induced emf.
In some cases, the self-induction EMF is harmful: if the transistor switch is loaded with the winding of a relay coil or electromagnet, then to protect against self-induction EMF, a protective diode is installed parallel to the winding with the polarity of the back EMF of the power source. This inclusion is shown in Figure 1.
Figure 1. Protection of the transistor switch from self-induction EMF.
Doubts often arise as to whether there are short-circuited turns in the transformer or motor windings? For such checks, various devices are used, for example, RLC bridges or homemade probes. However, you can check for short-circuited turns using a simple neon lamp. Any lamp can be used - even from a faulty Chinese-made electric kettle.
To carry out the measurement, a lamp without a limiting resistor must be connected to the winding under test. The winding should have the highest inductance; if it is a mains transformer, then connect the lamp to the mains winding. After this, a current of several milliamps should be passed through the winding. For this purpose, you can use a power source with a resistor in series, as shown in Figure 2.
Batteries can be used as a power source. If at the moment the supply circuit is opened, a flash of the lamp is observed, then the coil is in good condition, there are no short-circuited turns. (To make the sequence of actions clearer, Figure 2 shows a switch).
Similar measurements can be carried out using a pointer avometer, such as TL-4, as batteries in the *1 Ohm resistance measurement mode. In this mode, the specified device produces a current of about one and a half milliamps, which is quite enough to carry out the described measurements. It cannot be used for these purposes - its current is not enough to create the necessary magnetic field strength.
Similar measurements can be carried out exactly the same way if the neon lamp is replaced with your own fingers: to increase the resolution " measuring instrument» fingers should be slightly wet. If the coil is working properly, you will feel a fairly strong electric shock, of course not fatal, but not very pleasant either.
Figure 2. Detection of shorted turns using a neon lamp.
Probably, many people noticed when checking the integrity of the windings of electric motors, transformers, chokes using a tester that if you break the inductor-tester circuit and then immediately accidentally touch the coil terminals, you can feel a weak electric shock. You can not attach any significance to this effect, you can think that the EMF of the self-induction of the coil is probably manifested, or you can think: is it possible to somehow benefit from this?
It turned out that it is possible, because... The self-induction emf of an inductor is a very specific voltage surge, the amplitude of which depends on the supply voltage of the circuit being broken, on the inductance of the coil and on its quality factor. During experimental testing, it turned out that if a neon light bulb of type TN-0.2, TN-0.3, etc. is connected parallel to the coil being tested, then when the power source-coil circuit is broken, the EMF of the self-induction of the coil causes flashes of the neon light bulb, which are all the brighter , the higher the supply voltage of the circuit being tested, the inductance of the coil and its quality factor.
It is this condition that is met by the network windings of power transformers, simply high-voltage windings of transformers, windings of chokes with significant inductance, windings of electric motors, i.e. precisely those electrical equipment components that are most susceptible to failure due to electrical overloads, leading to overheating of the windings, disruption of the insulation between the winding turns and the appearance of short-circuited turns. K.z. turns can also appear due to mechanical damage to the windings. But in any case, when they appear, the inductor (winding) sharply reduces its quality factor, its resistance to industrial frequency currents decreases and it will heat up above the permissible value, i.e. it will become unsuitable for further use.
It turned out that if you assemble the test circuit shown in the figure, then serviceable inductors, when the power circuit is broken (pressing a button), give off bright flashes of a neon light bulb. And if there are short-circuited turns in the inductor, then there are either no flashes at all, or they are very weak. It is this effect that is useful, because it makes it possible to identify unusable electrical products that are subject to rejection or repair.
It is obvious that windings wound with thick wire and having a small number of turns, i.e. low inductance, it will not be possible to check this method - even serviceable coils will not produce flashes of a neon light bulb. This must be taken into account so as not to draw erroneous conclusions. But for inductors having ohmic resistance DC on the order of tens to hundreds of Ohms or more, this scheme identifying short-circuited turns is very convenient. Connector X1 can be of any type and is intended for connecting a source DC voltage. The supply voltage is not critical and can be in the range of 3 - 24 V, i.e. You can use any batteries or accumulators you have on hand. Toggle switch S1 is used to turn off the device during long breaks in operation. The HL1 lamp can be of any type with a voltage not lower than Epit. It is needed to control the supply voltage to the circuit (to prevent erroneous conclusions about the unsuitability of the tested coil). It is useful to have a known good coil of the same type next to the coils being tested for comparative control. Button S2 can be of any type and is used to break the power circuit when checking the coil. Resistor R1 Tr. (Dr.) serves to limit the current flowing through the neon lamp HL2. X2, XZ -pins of type LU4 with clamps of type put on them<крокодил>, which with flexible conductors soldered to them are connected directly to the terminals of the inductor being tested.
The device, assembled without errors, does not require adjustment. It can be placed in any small-sized housing. I would like to draw the attention of novice radio amateurs that this method of checking inductor coils for the absence or presence of short-circuited turns should in no case be used to test radio frequency coils, because the tuning cores may become demagnetized or even the coil conductors may burn out.
The turn-to-turn tester circuit and its operation are quite simple and can be assembled even by novice electronics engineers. Thanks to this device, it is possible to test almost any transformers, generators, chokes and inductors with a nominal value from 200 μH to 2 H. The indicator is capable of determining not only the integrity of the winding under test, but also perfectly detects interturn short circuits, and in addition it can be used to check p-n junctions in silicon semiconductor diodes.
In addition to checking for a break, you must also check the coil for the absence of short-circuited turns inside it. Check availability short circuit inside the winding using an ohmmeter without first disassembling it is impossible. Therefore, to identify such a defect, it is better to use a simple device, the diagram of which is shown in Fig. 40.
Using this device, you can determine the presence of short-circuited turns inside inductors or windings of small transformers, the internal diameter of which does not exceed 35 mm. In some cases, the device is able to detect short-circuited turns in coils of larger diameter. It should be noted that the device can be adapted to test coils various sizes, for this it is only necessary to provide for the use of replaceable coils wound on rods of the appropriate diameter.
Diagram and principle of operation of the device. The device is assembled on a transistor, which makes it small-sized and very convenient to use. The HF oscillation generator is assembled on a P11A type transistor, but any other transistor that has the same parameters can be used. In case of using transistors type p-p-p The polarity of connecting the generator to the power system must be reversed. The device is powered by a KBS-0.5 battery. Inductors L1—L3 are wound on a ferrite rod and have the following data: L1 contains 110 turns of PEL 0.15 wire; L2 - 210 turns of PEL wire 0.15; L3—55 turns of PEL wire 0.12—0.17. When assembling the device, the coils must be installed so that part of the ferrite rod (35-50 mm) is located above the upper part of the device body, since the test coil is placed on this part of the rod during testing. The operation of the device is based on the principle of absorbing vibration energy induced by a high-frequency generator in coil L3 when installed on a coil rod with short-circuited turns.
Change in induced e. d.s. is fixed by an indicator, with which you can determine the presence of defects in the coil. The device can use any microammeter of a magnetoelectric system with a total deviation current of 50-100 µA. Devices of the types M4204, M494, M49 are most suitable for this purpose (the latter type of device can be recommended in cases where the dimensions of the device are not critical, for example, when operating the device in stationary conditions).
The resistance of the additional resistor R2 should be selected experimentally when setting up the device, depending on the sensitivity of the indicator used. It is necessary to pay attention to the fact that if there is no test coil on the ferrite rod, the angle of deflection of the indicator needle would be at least 3/4 of the entire scale. This will allow you to clearly monitor changes in the indicator readings in the case when a defective coil is placed on the rod.
Mains powered version of the device. To sort coils under production conditions, you can use a simpler device, in which an incandescent light bulb is used instead of a dial indicator. The diagram of such a device is shown in Fig. 41. A light bulb (6.3 V, 0.1 A) is connected to the collector circuit transistor amplifier. The operating mode of the transistors is set using resistors R1 and R2.
It should be borne in mind that if, when setting up the device, a lack of generation is detected, then the ends of the coil L1 or L2 must be changed. The presence of generation can be judged by the deflection of the instrument needle or by the brightness of the light bulb.
The device is easy to manufacture and is made from standard parts. For the second device it is necessary to make a rectifier. To do this, you can use any low-power power transformer, from the secondary winding of which you can remove 12-15 V.
Operating hours and output voltage stabilizer, which includes diode D808 and transistor P201, are installed using resistor R5.