Ƒ↓ — Anchor testing device (APD). How to detect short-circuited turns Homemade short-circuited turns indicator diagram

“By admitting our mistakes, we find a source of strength.”

I decided to make a device for checking armatures for short-circuited turns and so on. Useful if you decide to renovate brushed motor and check if it was wound correctly. A very useful thing and was once produced in the USSR. But now you won’t find it during the day with fire.

We won’t go into complex formulas, I’ll try to explain in a moment what I did. I will split the article into 2 parts. “Part one. Magnetic core." “Part two. Electricity". Then I will explain why there are 2 parts.

Part one. Magnetic core.

Firstly, we need a magnetic circuit, or in other words, a stator from the vacuum cleaner motor. Then we need to cut out a part at an angle of 90 degrees in one side of it, where the anchor itself will lie for testing. You can use a grinder, a saw, a spoon - whatever is more convenient for you.

Next, we need to create a platform for winding the coil. Many people write that you need to take electric cardboard or some other kind, but I don’t have it and it’s not planned in the next 50 kilometers around, there’s nowhere to buy it. This means we need an alternative. Remember, when motorcycle and car engines are being repaired and there is no gasket, it used to be cut out from the “Case No.” folder. That’s what we’ll do, but you need to keep in mind that the folder is rough, a notebook cover will do. I had a similar magnetic circuit and there was electrical cardboard, but a little narrower than needed. But it’s enough for us to measure the thickness and select an approximate one. If only there was a layer between the wire and the stator itself.

P.S. The device on the stator of a vacuum cleaner is inspired by a topic on one forum. Original. Thanks to the author for the push in the right direction.

We measure the thickness:

Electrical cardboard from a different engine, but in which the windings were once placed.

and notebook cover

Now we cut:

And we wrap it in one layer on the magnetic circuit, securing the whole thing with tape:

Then we need cheeks so that the wire rests on the sides and we get a full-fledged coil. We cut them out of plywood, having previously calculated the dimensions.

And use a chisel to remove the excess. You can clean it up a little with sandpaper.

Don’t forget to take into account the angle of the stator and adjust it with the same sandpaper - a small angle on the cheeks themselves

It is desirable that the cheeks themselves become tight on the magnetic circuit.

If not, take a notebook and cut a piece of sheet to the size of the cheeks and wind it with sizing. Until the wall becomes more or less tight.

We insert the cheeks and glue them with glue. I used almost half a pack of PVAK. I glued and filled it about a dozen times. The next morning everything was ready.

That's all for the Magnetic Core part.

Part two. Electricity.

Let's begin. We need wire. I found a wire that was once wound from a kinescope from an old TV. The resistance immediately seemed insufficient to me - only 13 ohms, with a diameter of 0.4 with a wire length, as I later calculated 93 m. 1 mm square copper wire can withstand 3.2 -3.5 amperes. For us, if it survives half of it, it will already be happiness, this should be enough for us. I thought so.

(According to calculations (number of turns = 50 / S * 220v) on this site, I calculated the required number of turns, it turned out to be 660. But I didn’t like that this applies to all thicknesses of wires! How so?? The site seems to be good, but I’m in the calculations I doubted it or I misunderstood something.)

But then, vague doubts began to overcome me. Although I’m not an electrician, I still know from Ohm’s law (here I = U\R) - if we apply 220 Volts to a conductor with a wire resistance of 13 Ohms, then a current of about 16 A will flow through it. Our wire can withstand somewhere around 1.25A. In short, it will simply puff and disappear through the window. I thought and thought and attributed the rest to the miraculous magnetic saturation of the core and the inductance (energy storage) of the coil itself, which I know little about, but decided to wind it. After all, trying is not torture. And any attempt, even a failed one, is a lesson for those who want to learn.

I spent about 4-5 hours. Turn by turn, diligently. Believing less and less in success. It turned out about 800 turns.

Having finished, I went to bed and left it for the morning.

I checked it today. I set the tester and ammeter to the required modes to take readings.

20 Volts - about 1 Ampere

50 Volts - 2 Amps

And taking a risk, realizing that he was right yesterday, he applied a hundred volts:

100 Volts - 4.5 Amps.

So what kind of 220 are we talking about? It will definitely “dissipate”, this wire.

Have you forgotten how much it was supposed to be? No more than 1.25A, but here 4.5A only at 100 Volts. The experiment ended in smoke from under the electrical tape, melting of the wire and complete failure. But it’s better than sitting and looking out the window with a drunken mug, drinking endlessly.

And now about the Parts. The “Magnetic Circuit” part is completely suitable for implementation. But as for the “Electricity” part, I think the mistake here was that you need to increase the resistance - in other words, take enough wire to withstand 220 Volts.

There is already a suitable donor, some old inductor from a TV with a resistance of 240 Ohms, wire diameter 0.08 mm. I think it will hold up. Or maybe not. So to be continued.

I assembled it today and tested it. Works.
R at least 20 kOhm... on the board 10 kOhm... (tuning, for calibration) I had to install an 8 kOhm cutter in series, because R2, R5, R6 at 470 Ohm.
R1 10Ohm
R2, R5, R6 820 Ohm... less is possible, but then R needs to have a higher resistance.
R3 47 kOhm
R4 365 Ohm
R7 10kOhm
C1 - C3 30 nF
C4 0.5 nF
L1 5 Ohm 360 turns with 0.13 wire insulation
L2 10 Ohm 460 turns with 0.09 mm wire insulation
They are wound on 5 mm reels. I wound it at 10 mm and with a larger cross-section and a larger coil because there were no smaller ones at hand.
The distance between the centers of the coils is 27 mm (important).
VD1 any diode
VD2 LED. Or 2 different or 2 colors.
VT1 - VT5 any low-frequency transistor (in this case kt361). It is better to use not the ones on the board, but modern analogues.

S1 switch.
Power supply 3V.
The generator frequency should be 34.5 kHz.... there was nothing to check... because... The oscilloscope was written off and disassembled, there is no money for personal use.

p.s. On the diagram, I used a green marker to mark what I drew on the printed circuit board.

The rosin didn't wash off because... This is an experimental device.
in the future I plan to do the same on a transistor assembly or common logic.
I drew the board in SL 6.0.

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 diagram of the device:

(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 of the 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 the VT4 transistor, is not enough to start the pulse generator. 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 motor 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.

It may happen that the wound coil does not contain short-circuited turns, and during operation doubts arise 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, there is a voltmeter in the circuit AC. 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 of suitable dimensions. 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.
The position of the variable resistor R5 slider depends on the inductance of the coil being tested. If it is, for example, a winding 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 amplitude of the generator's oscillations 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.

PCB:


(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, 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.

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 said 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 of the induction 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 induction 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 force DC 1A 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, the 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 the standard circuit for switching on 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 with polarity is installed parallel to the winding back emf power supply. 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 devices- samples. 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.