The difference between the primary and secondary winding. As the resistance to determine the primary winding of the transformer. Simple tips on how to check the transformer multimeter for performance. Definition of intercity closure

The word "transformer" is formed from the English word "TRANSFORM" - Convert, change. I hope everyone remembers the film "Transformers." There cars are easily converted into transformers and back. But ... the transformer is not transformed in appearance. It has even more amazing property - converts an alternating voltage of one value to an alternating voltage of another value!This transformer property is very widely used in electronics and electrical engineering.

Types of transformers

Single-phase transformers

These are transformers that convert a single-phase variable voltage of one value into one-phase variable voltage of another value.

Basically single-phase transformers have two windings, primary and secondary. One voltage value is supplied to the primary winding, and the voltage desired to us is replaced. Most often in everyday life you can see the so-called network transformerswho have a primary winding designed for network voltage, that is, 220 V.

In diagrams, single-phase transformer is indicated as follows:

Primary winding on the left, and the secondary - right.

Sometimes a variety of different stresses are required to power various devices. Why put your transformer on each device if you can get several stresses from one transformer? Therefore, sometimes secondary windings there are several pairs, and sometimes even some windings are displayed directly from the available secondary windings. Such a transformer is called a transformer with a multitude of secondary windings. In schemes you can see something like this:

Three phase transformers

These transformers are mainly used in industry and most often exceeding simple single-phase transformers on dimensions. Almost all three-phase transformers are considered force. That is, they are used in chains where you need to feed powerful loads. These can be CNC machines and other industrial equipment.

In the schemes, three-phase transformers are indicated like this:

Primary windings are indicated by capital letters, and secondary windings - small letters.

Here we see three types of connecting windings (from left to right)

star-star
star-triangle
triangle-star

In 90% of cases, the star star is used.

Principle of operation of the transformer

Consider this picture:

1 - Primary transformer winding

2 - Magnetic Line

3 - Secondary transformer winding

F. - direction of the magnetic flux

U1. - Voltage on the primary winding

U2. - Voltage on the secondary winding

The picture shows the most common single-phase transformer.

The magnetic core consists of special steel plates. It flows the magnetic flow F (shown by arrows). This magnetic flux is created by variable voltage of the primary winding of the transformer. The voltage from the secondary winding of the transformer is removed.

But how is it possible? We have no connection between the primary and secondary windings? How can the current flow through the open chain? It's all about a magnetic stream that creates the primary winding of the transformer. The secondary winding "catches" this magnetic flux and converts it to an alternating voltage with the same frequency.

Currently, transformers are created in another constructive design. Such execution has its advantages, such as the convenience of winding primary and secondary windings, as well as smaller dimensions.

Transformer formula

So what does the voltage depends on, which gives us a transformer on the secondary winding? And it depends on the turns that are wound on the primary and secondary winding!

where

N 1 - Number of turns of the primary winding

N 2 - the number of turns of the secondary winding

I 1 - primary winding current

I 2 - Secondary Winding Current

The transformer also complies with the law of conservation of energy, that is, what power goes into the transformer, this power comes out of the transformer:

This formula is valid for perfect transformer. The real transformer will produce a little less power at the output than at its input. The efficiency of the transformers is very high and sometimes constitutes even 98%.

Types of transformers on output voltage

A step-down transformer

This is a transformer that lowers the voltage. Suppose 220 V comes to the primary winding, and on the secondary we obtain 12 V. That is, we have more voltage converted to less voltage.

Enhancement transformer

This is a transformer that increases the voltage. Here, too, everything is completely pain. Suppose we supply 10 volts to the primary winding, and with secondary removing already 110 V., that is, we raised our voltage several times.

Agreement transformer

Such a transformer is used to match the schemes between cascades.

Separating or unleashing transformer (transformer 220-220)

Such a transformer is used for electrical safety purposes. Basically, this is a transformer with the same number of windings at the input and outlet, that is, its voltage on the primary winding will be equal to the voltage on the secondary winding. The zero output of the secondary winding of such a transformer is not grounded. Therefore, when you touch the phase on such a transformer, you will not hit the electric shock. You can read about it in the article about.

How to check the transformer

Short closure of windings

Although the windings fit very tightly to each other, they are separated by a varnish dielectric, which are covered by the primary and secondary winding. If somewhere occurred, the transformer will warm and make a strong hum of working. In this case, it is worth measuring the voltage on the secondary winding and compare so that it coincides with the passport value.

Open transformer winding

When climbing everything is much easier. To do this, using the multimeter, we check the integrity of the primary and secondary winding.

In the photo below, I check the integrity of the primary winding, which consists of 2650 turns. Are there any resistance? So everything is OK. The winding is not in the cliff. If it were in the cliff, the multimeter would show on the display "1".

In the same way, check and secondary winding, which consists of 18 turns

Transformer work

Work of a lowering transformer

So, we are visiting a transformer from the inland device on the tree:

His primary winding is numbers 1, 2.

Secondary winding - numbers 3, 4.

N 1. - 2650 turns,

N 2. - 18 turns.

His insides look like this:

Connect the primary winding of the transformer to 220 volts

We put a twilka on the multimeter to measure the alternating current and measure the voltage on the primary winding (network voltage).

We measure the voltage on the secondary winding.

It is time to check our formulas

1.54 / 224 \u003d 0.006875 (Voltage Relationship Coefficient)

18/2650 \u003d 0.006792 (coefficient of winding relationship)

Compare numbers ... The error is generally a penny! Formula works! The error is associated with losses to heat the windings of the transformer and magnetic pipeline, as well as the error of the measurement of the multimeter. As for the strength of the current, it works a simple rule: lower voltage, increase current strength and vice versa, increasing the voltage, lower the current strength.

Idle transformer

The operation of the transformer at idle involves the operation of the transformer without load on the secondary winding.

Our experimental rabbit will have another transformer

Secondary windings here are as many as two pairs, but we will use only one.

Two red wires are the primary winding of the transformer. On these wires, we will supply voltage from the network 220 V.

We will remove the voltage from the secondary winding from two blue wires.

In order to make measurements, we will need to set on a circle to measure alternating voltage. If you do not know how to measure alternating voltage and current strength, I recommend reading the article.

We measure the voltage on the primary winding of the transformer, where we are taking 220 V.

Multimeter shows 230 V. Well, what happens).

Now measure the voltage on the secondary winding of the transformer

Received 22 volts.

I wonder what power consumes our transformer from the outlet at idle mode?

Multimeter showed 60 mlm. It is understandable, because our transformer is not perfect.

As you can see, there is no load on the secondary winding of the transformer, but it still "eats" current strength, and consequently electrical energy from the network. If you count the power, then we get p \u003d iu \u003d 230 × 0.06 \u003d 13.8 watts. And if we just have an enabled at least a watch, then we will eat electricity 13.8 watts * hour or 0.0138kvatt * hour. And how much is one kilowatt electricity now? In Russia, 4-5 rubles. A penny ruble coats. Therefore, it is not recommended to leave electrical appliances in the network with a transformer power supply.

Transformer under load

Experience number 1

I wonder if the current will change on the primary winding, if we load the secondary winding of our light bulbs? The light bulbs caught fire, and the power of the current on the primary winding was also changed ;-)

When we measured without a load, we had 60 milliamme apex in the primary winding circuit. The secondary winding circuit was open, since we did not attach any load. As soon as we have connected incandescent lamps to the secondary winding of the transformer, they started immediately consume current strength. But by the way, the strength of the current rose in the chain of the primary winding, to the level of 65.3 milliam. From here, the conclusion suggests:

If the current is growing in the transformer secondary winding circuit, the current is also growing in the primary winding circuit.

Experience number 2.

Let's spend another experience. To do this, measure the voltage without load on the secondary winding of the transformer, the so-called - idle mode of operation

now connect our light bulbs and measure the voltage again.

Wow, the voltage caught up with 0.2 V.

Let's measure the current strength in the secondary winding with light bulbs

Received 105 million.

All the same similar operations are carried out for a powerful rating in 10 ohms and a 10 watt dispersion capacity. We measure the voltage on the secondary winding, when the resistor is turned on

Received 18.9 V. Seen how voltage looked much? If at idle it was 22.2 V, then it was 18.9 V!

I wonder what the current current flows in the secondary chain, which includes a resistor

Wow, almost 2 amps.

Conclusion: When the load is turned on, there is a stress permanent. The voltage drops the greater, the greater the strength of the current eats the load. Another important factor also plays the role here - transformer power. The greater the power of the transformer, the smaller there will be a voltage drawdown.The power of the transformer depends on its dimensions. The more dimensions, the greater its size of the core. Consequently, such a transformer can produce a decent strength of the current in the secondary winding with minimal stress drawdown.

The main purpose of the transformer is the current and voltage conversion. And although this device performs enough complex transformations, in itself it has a simple design. This is a core around which several wire coils are wound. One of them is introductory (the primary winding is called), other output (secondary). Electric current is fed to the primary coil, where the voltage induces the magnetic field. The latter in the secondary windings is formed by the alternating current of exactly the same voltage and frequency, as in the winding of the input. If the number of turns in two coils will be different, then the current at the input and output will be different. Everything is simple enough. True, this device often fails, and its defects are not always visible, so many consumers have a question how to check the transformer with a multimeter or other device?

It should be noted that the multimeter is useful and if you have a transformer with unknown parameters. So they can also be determined using this device. Therefore, starting to work with it, you must first of all deal with the windings. To do this, all the ends of the coils pull out separately and call them, thereby looking for paired connections. At the same time, the ends are recommended to numbered, determining which winding they relate to.

The easiest option is four end, two for each coil. More often there are devices that have more than four ends. It may also be that some of them are "not nicknamed", but this does not mean that there was a breakdown. This may be the so-called shielding windings, which are located between the primary and secondary, they usually be connected to the "Earth".

That is why it is so important when talking to pay attention to resistance. In the network primary winding it is determined by tens or hundreds. Please note that small transformers have greater resistance of primary windings. It's all about more turns and a small diameter of copper wire. Resistance to secondary windings is usually approximate to zero.

Transformer checking

So, the windings are defined using the multimeter. Now you can go directly to the question how to check the transformer using the same device. Talking is about defects. They are usually two:

cliff;
isolation wear, which leads to a closure to another winding or on the device body.

Options to determine easier than simple, that is, each reel is checked for resistance. The multimeter is set to the module mode, the arrows are connected to the device two end. And if the display shows the lack of resistance (readings), this is guaranteed to break. Checking a digital multimeter may be unreliable if the winding is tested with a large number of turns. The thing is that the more turns, the higher the inductance.

The closure is checked like this:

One multimeter probe closes on the output ending.
The second probe alternately connects to other ends.
In the case of a closure on the case, the second probe is connected to the transformer housing.

There is another frequently encountered defect - this is the so-called intersensional closure. It occurs in the event that the insulation of two adjacent turns wear out. Resistance in this case in the wire remains, therefore overheating at the absence of insulating varnish. Usually, the smell of Gary is distinguished, the winding, paper appears, the fill appears. Multimeter This defect can also be detected. At the same time, you will have to learn from the reference book, what resistance should have the windings of this transformer (we assume that its brand is known). Comparing the actual indicator with reference, you can say for sure whether there is flaw or not. If the actual parameter differs from the reference halfway or more, then this is a direct confirmation of the intersensible closure.

Attention! Checking the transformer winding to resistance, does not matter which probe to which end is connected. In this case, the polarity does not play any role.

Measuring current of idling

If the transformer after testing the multimeter turned out to be properly, then experts recommend checking it and on such a parameter as a current of idling. Usually a serviceable device is 10-15% of the nominal. In this case, subject to the current under load under load.

For example, a transformer of the TPP-281 brand. Its inlet voltage is 220 volts, and the idle current is 0.07-0.1 A, that is, it should not exceed one hundred million. Before checking the transformer to the idling current parameter, the measuring instrument is necessary to transfer to the ammeter mode. Please note that when the power supply is supplied to the windings, the power current force may exceed a nominal to several hundred times, so the measuring instrument is connected to the tested device with a closed spice.

After that, it is necessary to smash the conclusions of the measuring device, while the number will be praised on its display. This is current without load, that is, idling. Next, the voltage without load on the secondary windings is measured, then under load. A voltage decrease by 10-15% should lead to current indicators that do not exceed one amper.

To change the voltage to the transformer, you must connect a retail, if any, you can connect a few light bulbs or a spiral from tungsten wire. To increase the load, you need to or increase the number of light bulbs, or shock the spiral.

Conclusion on the topic

Before checking the transformer (lowering or enhancing) by a multimeter, you need to understand how this device works, as it works, and what nuances must be considered by conducting checking. In principle, there is nothing complicated in this process. The main thing is to know how to switch the measuring device itself into an ohmmeter mode.

Related records:

Have a transformer two windings, four conclusions, it is not worth calling anything. The problem is due to the significant difference of real structures. The transformer is equipped with a plurality of secondary winding conclusions to obtain the desired voltage ratings. The entrance side is not easy. Two separate transformers can be wound on one magnetic circuit. How to evaluate the use of use? Let's see how to check the transformer.

Check transformer Chinese tester

Not every transformer is made to eat 220 volts with a frequency of 50 Hz. In industry, the measuring industry, other devices are applied to higher education. Observing inappropriate characteristics, the use of devices in industrial circuits will be a bad idea. Therefore, the first, we pay attention to the labeling. Support is underway. The problem appears: an individual document released each type of transformers.

Conditional symbols for power (GOST 52719-2007) transformers

Logo of the manufacturer. There is such an icon, on the official website of the plant, you can certainly learn a lot of useful information. The problem is limited to the cessation of existence. You understand the liveliness of the question for a collapsed country. The second queue concerns the search for a brief digital marking, puzzling search engine: Yandex, Google. The chance of immediate finding characteristics, as well as an electrical diagram of the device. Next, nothing easier than to ring the transformer, determine, the presence of a breakdown, the integrity of the windings. We remind the insulation resistance (for magnetic core, for example) is at least 20 MΩ according to existing standards. It concerns any neighboring, electrically unleashed windings. Buying a Chinese tester, lovers can make measurements with their own hands.
Product name We consider a key factor. You need to understand: various classes are intended to be their goals. You can, of course, use the transformer input, forming a galvanic junction, while understanding the resulting result. In devices, the voltage is usually not normalized separately, the operation is deprived of meaning. The secondary winding of the current transformer is connected to the appropriate coil of the control device, measurement. Voltage, if necessary, is estimated separately. Marking may contain the words "transformer", "Autotransformer". Immediately disassemble the meaning. Yandex will help. For example, the autotransformer is distinguished by the lack of electroplating union between the primary, secondary winding. In fact, when the electric trains move, it is convenient to place autotransformers through the intervals, remove the voltage by the typical method. The current trajectory will allow significantly reduced losses. The distance between the source and grounding (through the rails) is reduced. There are many other varieties of transformers. The type is defined, we will find the GOST of the relevant class of the device, then moving, equipped with reliable information support. Regarding this class of instruments, we find: marking is conducted according to GOST 11677-75. Different GOS, according to which the consideration began, is explained by a different area of \u200b\u200baction. GOST 11677 is international. Consequently, you need to know: even one class of products, the tag is brought unequal.
The factory number will help get technical support. I know exactly exactly, in Taiwan, specialists who know English live in China, we strongly recommend that you try to contact. For Soviet products, information is rather useless.
The conditional designation of the type will help to disassemble the design features. For example, meet TZRL. According to GOST 7746-2001, there are tables (2 and 3), leading decoding. As for the first letter, characterizes the word "transformer". Non-unknown - the plate is devoid of decryption of the letter Z. Delivered? We visit Yandex, we find a shortness: since means "protective". Further simply: the letter O according to the table - the "support", L characterizes the type of insulation. We find climatic execution U2. The decoding is conducted according to GOST 15150, the category of placement of type 2 GOST 15150. Having information on the hands, you can find the distinctive features of the transformer. It concerns future accommodation, they undertook to check the transformer for no accident. Surely cooked a warm place corresponding to the specified standards.
We consider information regarding regulatory documentation. The standard according to which the transformer is made is shown. It remains to open a document, decipher the inscription. In each particular case, there may be small deviations of the designations, the search engine (Yandex, Google) will help.
Manufacture date is specified by soft aluminum signs. Information will be useful to have a desire to contact the manufacturer's technical support.
The nameplate provides drawn electrical circuits of windings connections, pin numbers (colors, other conventions). According to information, nothing is easier than to find malfunctions of transformers. Even if the nameplate is half a gun, you can probably find a sign of a similar device. You can redraw, print the necessary information. At specialized forums, lovers willingly share such information. Having trouble lose heart. Finally, much watched from reference books. Find using Yandex. Look for electronic versions of books, network resources suffer from small accuracy. The search string contains file extensions: DJVU, PDF, TORRENT. Do not worry about copyright, the book swings to familiarize yourself. We looked, deleted. It is impossible to transfer the information received, understandable. A brochure was born, developed by ABS electro, leading the necessary information on products. Inside some devices are thermal relays, some other elements. Therefore, the transformer is though more difficult to call the transformer. In consumer electronics, there is more often a fuse for 135 degrees Celsius, hidden by turns of the primary, secondary winding, a truly complex product will be presented by a surprise to experienced researchers. By the way, the thermal power plants sometimes decorate the magnetic circuit, the tester showed the burst of the winding, find the protective elements.
The nominal frequency of Hz may be absent if the network corresponds to the standard (industrial). The high-frequency transformer is not for the usual. There will be a completely different resistance of the windings, the characteristics will change. The transformer will work incorrectly, it will become stronger than.
The characteristics of the working mode are indicated if the nature of the transformer is knocked out beyond the term "long". According to the accepted standards, the device can work for a long time. Otherwise, the operating cycle is given. After a certain period of activity, the transformer will take rest. Otherwise, it burns, the protection will work (relays, fuses), or the winding fails due to overheating.
Nominal full power KVA is indicated for meaningful windings. It is useful to know: Under NN is understood as low, under the high voltage. Easy to understand by studying the transformer of the welding machine. The current electrodes is large, low voltage. The coils are formed with a thick wire, the resistance is small. Nominal total power will allow to agree on a source with the consumer. Suppose there is low-voltage equipment, it is required to quickly pick up a transformer. Avoiding breaking his head, you should compare power: consumption, permissible secondary transformer winding. Aspects will clarify. Maximum power consumption capacity is below the working (nominal) secondary winding of the transformer.
Tok transformer signboard
The voltage rating of the main secondary winding acts characteristics at which you can understand whether the transformer is working. It is enough to enlist the lack of short circuit, turn on the primary winding into the network. The tester (calculated on the specified range) will measure. Much more reliable than measuring resistance, attempts to calculate the transmission coefficient.
In voltage stabilizers, transformers with variable turns are more often used. Special slider bypasses a secondary winding, removing the desired voltage. Marking some transformers contains voltage change limits. Of course, accountable. By the way, the transformers malfunction takes more often in this place. Or closes neighboring turns, or bad contact runner. Found breakdown by correcting.
The rated currents of the windings will sometimes allow not looking to choose the components of the network. For example, automatic protection. Many devices provide the maximum current load parameters. Useful ampermeter Measure to measure, you will need to connect the consumer. It is clear, the short circuit should not be made.
The short-circuit voltage of the secondary winding is indicated by the percentage of the nominal. It is clear that, unlike the ideal source of energy, studied by teachers of physics lessons, real devices are powerless to issue indicators. Therefore, with a sharp increase in current, the voltage is rapidly falling. Interest is given relative to the nominal value. Specific meaning to consider themselves, having enlisted using Windows Calculator. Is it worth trying to organize a short circuit with your own hands, they find it difficult to say. Risk: Tubes will choose, the transformer is susceptible to risk.

We hope, quite told about ways to eliminate transformer faults. The main thing is to detect the cause, then each one spins around its own axis. The simplest (often only) solution solution will be rewinding a faulty coil. Made by the wire purchased on the market, to calculate the number of turns - separate art. It is easier to make a request forum. The answer will certainly give:

reference to a specialized computer program;
share experiences;
advise.

Please note the conditional notation, the list of parameters, are determined by the type of transformer. You will not necessarily be identical to your portal review of your portal.

How to check the transformer?

The transformer that is translated as a "converter" entered our life and is used everywhere in everywhere and industry. That is why you need to be able to check the transformer for performance and serviceability to prevent breakage to fail. After all, the transformer is not so cheap. However, not every person knows how to check the current transformer on its own and often prefers to attribute him to the master, although the case is completely unclear.

Consider how you can check the transformer yourself.

How to check the transformer multimeter

The transformer works on a simple principle. In one of its chain, a magnetic field is created due to the variable current, and an electric current is created in the second chain due to the magnetic field. This allows you to isolate two currents inside the transformer. To test the transformer, it is necessary:

Find out whether the transformer is damaged. Carefully inspect the transformer sheath for the presence of dents, cracks, holes and other damage. Often the transformer is spoiled by overheating. Perhaps you will see traces of melting or bloating on the housing, then the transformer does not make sense to further look and give it to repair.
Inspect the transformer winding. There should be clearly printed tags. It does not prevent and have a transformer scheme with you, where you can see how it is connected and other details. The scheme should always be present in the documents or, as a last resort, on the website of the developer on the Internet.
Find also the input and output of the transformer. The voltage of the winding that creates a magnetic field must be marked on it and in the documents in the diagram. It should also be marked on the second winding where the current is generated, voltage.
Find filtering at the output, where the power transformation from the variable into constant occurs. Diodes and capacitors are connected to the secondary winding, which are filtered. They are indicated in the diagram, but not on the transformer.
Prepare a multimeter to measure the voltage measurement on the network. If the panel cover interferes getting to the network, remove it for the check time. Multimeter can always buy in the store.
Connect the input chain to the source. Use the Multimeter in AC mode and measure the voltage of the primary winding. If the voltage falls lower than 80% of the expected value, the primary winding malfunction is likely. Then simply disconnect the primary winding and check the voltage. If it rises, the winding is faulty. If not rose, a malfunction in the primary input circuit.
Also measure the output voltage. If there is filtration, the measurement is performed in DC mode. If it is not, then in the AC mode. If the voltage is incorrect, then you need to check the entire block. If all the details are in order, the transformer itself is defective.

Often you can hear the buzzing or hissing sound from the transformer. This means that the transformer is about to burn and it should be urgently turned off and minimized.

In addition, often windings have different grounding potential, which affects the calculation of the voltage.

In modern technique, transformers are used quite often. These devices are used to increase or decrease the parameters of the variable electrical current. The transformer consists of an input and several (or at least one) output windings on a magnetic core. This is its main components. It happens that the device fails and the need for repair or replacement occurs. Install, whether the transformer is working, it is possible using a home multimeter on its own. So how to check the multimeter transformer?

Basics and principle of work

The transformer itself refers to elementary devices, and the principle of its action is based on a bilateral transformation of an excited magnetic field. Which is characteristic, it is possible to induce the magnetic field exclusively using AC. If you have to work with constant, first it must be converted.

The primary winding is wound on the core of the device, on which an external variable voltage with certain characteristics is supplied. It is followed by or several secondary windings, in which alternating voltage is induced. The transmission coefficient depends on the difference in the amount of turns and the properties of the core.

Varieties

Today on the market you can find many varieties of the transformer. Depending on the design selected design, a variety of materials can be used. As for the form, it is chosen exclusively from the convenience of placing the device in the electrical appliance body. On the calculated power only configuration and core material affect. At the same time, the direction of turns is not affected by anything - the windings are wound up both towards and from each other. The only exception is the identical selection of directions in the event that several secondary windings are used.

To check this device, a fairly ordinary multimeter, which will be used as the current transformer tester. No special devices will need.

Procedure for verification

Checking the transformer begins with the definition of windings. This can be done using the labeling on the device. The output numbers must be specified, as well as the designations of their type, which allows you to set more information on reference books. In some cases there are even explanatory drawings. If the transformer is installed in some electronic device, the principal electronic circuit of this device can clarify the situation, as well as the detailed specification.

So, when all the conclusions are defined, the tester turns. With it, you can set the two most frequent malfunctions - closure (on the housing or adjacent winding) and breaking the winding. In the latter case, all windings in turn are transferred in the module mode (resistance measurements). If some of the measurements shows a unit, that is, infinite resistance, then there is a break.

There is an important nuance here. Checking better on an analog device, since digital can issue distorted readings due to high induction, which is especially characteristic of windings with a large number of turns.

When the housing closure is conducted, one of the probe is connected to the output of the winding, while the second conclusions are made by all other windings and the housing itself. To check the latter, you will need to pre-clear the contact site from varnish and paint.

Definition of intercity closure

Another frequent breakdown of transformers is an intersless closure. Check the pulse transformer for a similar fault with one multimeter is almost unrealistic. However, if you attract the sense of smell, attentiveness and acute vision, the task may well be solved.

A bit of theory. The wire on the transformer is isolated solely with its own varnish coating. If the insulation breakdown occurs, the resistance between the neighboring turns remains, as a result of which the contact site is heated. That is why the first thing should be carefully inspecting the device for the appearance of flutters, blackened, burnt paper, blooms and smell of Gary.

Next, we try to determine the type of transformer. As soon as it turns out, on specialized directories you can see the resistance of his windings. Next, we switch the tester to the mode of the megaommeter and begin to measure the impact resistance of the windings. In this case, the pulse transformers tester is an ordinary multimeter.

Each measurement should be compared with the directory specified in the directory. If there is a difference in more than 50%, then the winding is faulty.

If the resistance of the windings for one or another reasons is not specified, other data must be given in the reference book: the type and cross-section of the wire, as well as the number of turns. With their help, you can calculate the desired indicator yourself.

Checking household reduction devices

It should be noted the moment of verification by the tester-multimeter of classical slide transformers. It is possible to find them in almost all blocks of power, which reduce the incoming voltage from 220 volts to the 5-30 volt exit.

The first thing is checked the primary winding, which serves a voltage of 220 volts. Signs of malfunction of the primary winding:

the slightest visibility of smoke;
the smell of burning;
crack.

In this case, you should immediately stop experiment.

If everything is fine, you can move to the measurement on the secondary windings. You can only touch them with tester contacts (suctions). If the results obtained are less than 20% control minimum, then the winding is faulty.

Unfortunately, you can test such a current block only in cases where there is a completely similar and guaranteed working unit, since the control data will be collected from it. It should also be remembered that when working with indicators of about 10 ohms, some testers can distort the results.

Measuring current of idling

If all testing have shown that the transformer is fully working, it will not be superfluous to carry out another diagnosis - on the current of the idle transformer. Most often, it equals 0.1-0.15 from the nominal indicator, that is, current under load.

To test the test, the measuring device is switched to ammeter mode. Important moment! The multimeter to the test transformer should be connected to a closed spice.

This is important because during the supply of electricity to winding the transformer, the current of the current increases to several hundred times in comparison with the nominal. After that, the tester probes are swapped, and indicators are displayed on the screen. It is they who reflect the amount of current without load, no idle current. Similarly, indicators are measured and on secondary windings.

To measure the voltage to the transformer, the retaint is most often connected. If it is not at hand, a spiral of tungsten or a row of light bulbs can go into the move.

To increase the load, the amount of light bulbs increases or reduce the number of spiral turns.

As you can see, it doesn't even need any special tester to check. Suitably quite ordinary multimeter. It is extremely desirable to have at least an approximate concept of the principles of operation and a device of transformers, but for a successful dimension, just just be able to switch the device into an ohmmeter mode.

Often you need to read in advance with the question of how to check the transformer. After all, when it is out of order or unstable work it will be difficult to seek the reason for the refusal of equipment. This is a simple electrical device can be diagnosed with a conventional multimeter. Consider how to do it.

What is the equipment?

How to check the transformer if we do not know its design? Consider the principle of operation and varieties of simple equipment. The copper wire of a certain section is applied to the magnetic core so that the conclusions for the feed winding and the secondary are left.

Energy transmission to the secondary winding is carried out by contactless way. It already becomes almost clear how to check the transformer. Similarly, the usual inductance by an ohmmeter is nicknamed. The coils form resistance that can be measured. However, this method is applicable when a given value is known. After all, resistance can change in a large or smaller side as a result of heating. This is called Mixless Circuit.

Such a device will no longer give out the reference voltage and current. Ommeter will show only a break in the chain or a complete short circuit. For additional diagnostics, it is used to check the closure on the body with the same ohmmeter. How to check the transformer, not knowing the outlines of the windings?

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Transformers are divided into the following groups:

Lowering and boosting.
The strengths more often serve to reduce the supply voltage.
Current transformers for feeding the consumer of a constant current value and its deduction in a given range.
Single and multiphase.
Welding destination.
Pulse.

Depending on the purpose of the equipment, the principle of approach to the question is changing how to check the transformer winding. Multimeter you can ring only small-sized devices. Power machines already require a different approach to malfunction diagnostics.

Transplex method

The diagnostic method of the Ommeter will help with the question of how to check the power transformer. The resistance between the conclusions of one winding is started. So establish the integrity of the conductor. Before that, inspection of the housing on the absence of Nagarov, the influx as a result of the heating of the equipment.

Next measure the current values \u200b\u200bin Omah and compare them with passports. If there are no such, then additional diagnostics are required. It is recommended to call each output relative to the metal body of the device, where the ground is connected.

Before performing measurements, turn off all ends of the transformer. Disconnect them is recommended for their own security. Also check the presence of an electronic circuit, which is often present in modern power models. It should also be dropped before checking.

Infinite resistance speaks about the whole isolation. Values \u200b\u200bin a slight kilome already cause suspicions of the breakdown on the body. It may also be due to the accumulated dirt, dust or moisture in the air gaps of the device.

By tension

Tests with supplied food are held when there is a question of how to check the transformer to the inter-touch closure. If we know the magnitude of the supply voltage of the device for which the transformer is intended, then the value of idling is measured by a voltmeter. That is, the wires are in the air.

If the voltage value differs from the nominal, then draw conclusions about interstitious closures in the windings. If the device is kept when the device is kept, sparking, then such a transformer is better to turn off immediately. It is faulty. There are permissible deviations when measuring:

For voltage, the values \u200b\u200bmay differ by 20%.
For resistance, the norm is the spread of values \u200b\u200bof 50% of the passport.

Memmeter measure

Tell how to check the current transformer. It is included in the chain: the staff or actually made. It is important that the current value is no less nominal. Measures ampermeter are carried out in the primary chain and in secondary.

The current in the primary chain is compared with secondary readings. More precisely, the first values \u200b\u200bfor measured in the secondary winding are divided. The transformation coefficient should be taken from the directory and compare with the calculations obtained. The results must be the same.

The current transformer cannot be measured at idle. On the secondary winding, in this case, too high voltage can be formed, capable of damageing isolation. You should also comply with the polarity of the connection, which will affect the operation of the entire connected scheme.

Typical malfunctions

Before checking the microwave transformer, we present frequent varieties of breakdowns eliminated without a multimeter. Often the nutrition device fails due to short circuit. It is set by inspecting the mounting boards, connectors, connections. Less often, mechanical damage to the transformer body and its core occurs.

Mechanical wear of the connections of the transformer conclusions occurs on moving machines. Large feeding windings require constant cooling. With its absence, overheating and melting isolation is possible.

TDKS.

Tell how to check the pulse transformer. Ommeter will only be installed only the integrity of the windings. The performance of the device is installed when connected to the scheme where the capacitor is involved, load and sound generator.

The primary winding is allowed a pulse signal in the range from 20 to 100 kHz. On the secondary winding make measurements of the oscilloscope. Set the presence of impulse distortions. If they are missing, draw conclusions about the working device.

Oscillogram distortions speak of the backup windings. Repair such devices are not recommended independently. They are configured in laboratory conditions. There are other schemes for checking pulse transformers, where they explore the presence of resonance on windings. Its absence indicates a faulty device.

You can also compare the shape of the pulses filed on the primary winding and published from the secondary. The deviation in form also speaks of a transformer malfunction.

Several windings

For measurements of resistance, they free the ends from electrical connections. Choose any output and measure all the resistance relative to the rest. It is recommended to write values \u200b\u200band label proven ends.

So we will be able to determine the type of connection of the windings: with medium conclusions, without them, with a common point of connection. More often encountered with separate connection of windings. Measurement will be done only with one of all the wires.

If there is a common point, then the resistance is measured between all available conductors. Two medium output windings will be values \u200b\u200bonly between three wires. Several conclusions are found in transformers designed to work in several networks with a face value of 110 or 220 volts.

Nuances diagnostic

The buzz when the transformer is normal if it is specific devices. Only sparking and trinity indicate a malfunction. Often and heating windings is the normal operation of the transformer. It is more often observed in lowering devices.

A resonance can be created when the transformer housing vibrates. Then it should be simply fixed with insulating material. The work of the windings changes significantly with loosely tightened or contaminated contacts. Most of the problems are solved by stripping metal to shine and new conclusions.

When measurements of voltage and current values, the ambient temperature, the magnitude and nature of the load should be taken into account. Driving voltage control is also necessary. Checking the frequency connection is required. Asian and American technique is designed for 60 Hz, which leads to underestimated output values.

Ineptly connecting the transformer can cause a device malfunction. In no case are constantly connected to the windings. The turns quickly pay otherwise. Accuracy in measurements and competent connection will help not only find the cause of the breakdown, but also, perhaps, eliminate it with a painless way.

12.12.2017

What is the equipment?

Views

Transformers are divided into the following groups:

Lowering and boosting.
The strengths more often serve to reduce the supply voltage.
Current transformers for feeding the consumer of a constant current value and its deduction in a given range.
Single and multiphase.
Welding destination.
Pulse.

Transplex method

By tension

For voltage, the values \u200b\u200bmay differ by 20%.
For resistance, the norm is the spread of values \u200b\u200bof 50% of the passport.

Memmeter measure

Typical malfunctions

TDKS.

You can also compare the shape of the pulses filed on the primary winding and published from the secondary. The deviation in form also speaks of a transformer malfunction.

Several windings

Nuances diagnostic

Basics and principle of work

Varieties

To check this device, a fairly ordinary multimeter, which will be used as the current transformer tester. No special devices will need.

Procedure for verification

Definition of intercity closure

Each measurement should be compared with the directory specified in the directory. If there is a difference in more than 50%, then the winding is faulty.

Checking household reduction devices

The first thing is checked the primary winding, which serves a voltage of 220 volts. Signs of malfunction of the primary winding:

the slightest visibility of smoke;
the smell of burning;
crack.

In this case, you should immediately stop experiment.

Measuring current of idling

To test the test, the measuring device is switched to ammeter mode. Important moment! The multimeter to the test transformer should be connected to a closed spice.

To measure the voltage to the transformer, the retaint is most often connected. If it is not at hand, a spiral of tungsten or a row of light bulbs can go into the move.

To increase the load, the amount of light bulbs increases or reduce the number of spiral turns.

How to check the transformer?

Consider how you can check the transformer yourself.

How to check the transformer multimeter

Find out whether the transformer is damaged. Carefully inspect the transformer sheath for the presence of dents, cracks, holes and other damage. Often the transformer is spoiled by overheating. Perhaps you will see traces of melting or bloating on the housing, then the transformer does not make sense to further look and give it to repair.
Inspect the transformer winding. There should be clearly printed tags. It does not prevent and have a transformer scheme with you, where you can see how it is connected and other details. The scheme should always be present in the documents or, as a last resort, on the website of the developer on the Internet.
Find also the input and output of the transformer. The voltage of the winding that creates a magnetic field must be marked on it and in the documents in the diagram. It should also be marked on the second winding where the current is generated, voltage.
Find filtering at the output, where the power transformation from the variable into constant occurs. Diodes and capacitors are connected to the secondary winding, which are filtered. They are indicated in the diagram, but not on the transformer.
Prepare a multimeter to measure the voltage measurement on the network. If the panel cover interferes getting to the network, remove it for the check time. Multimeter can always buy in the store.
Connect the input chain to the source. Use the Multimeter in AC mode and measure the voltage of the primary winding. If the voltage falls lower than 80% of the expected value, the primary winding malfunction is likely. Then simply disconnect the primary winding and check the voltage. If it rises, the winding is faulty. If not rose, a malfunction in the primary input circuit.
Also measure the output voltage. If there is filtration, the measurement is performed in DC mode. If it is not, then in the AC mode. If the voltage is incorrect, then you need to check the entire block. If all the details are in order, the transformer itself is defective.

Often you can hear the buzzing or hissing sound from the transformer. This means that the transformer is about to burn and it should be urgently turned off and minimized.

In addition, often windings have different grounding potential, which affects the calculation of the voltage.

The transformer is a simple electrical device and serves to convert voltage and current. On the total magnetic core, the input and one or more output windings are wound. The variable voltage supplied to the primary winding induces the magnetic field, which causes the appearance of an alternating voltage of the same frequency in the secondary windings. Depending on the ratio of the number of turns, the transmission coefficient changes.

To check the transformer malfunctions, first of all, it is necessary to determine the conclusions of all its windings. This can be done by it, where the numbers are indicated, the designation type (then you can use directories), with a sufficiently large size there are even drawings. If the transformer is directly in a kind of electronic device, then all this will clarify the circuit diagram on the device and the specification.

By defining all the conclusions, the multimeter can be checked two defects: breaking the winding and closing it on the housing or other winding.

To determine the break, you need to "ring" in the ohmmeter mode in turn every winding, no readings ("infinite" resistance) indicates a break.

In a digital multimeter, there may be false testimony when checking windings with a large number of turns due to their high inductance.

To search for a closure on the housing, one multimeter probe is connected to the output of the winding, and the second conclusions conclusions from other windings (just one of two) and the case (contact location must be cleared of paint and varnish). There should be no short circuit, it is necessary to check this output.

Multivated transformer closure: how to determine

Another common transformer defect is an inter-touch closure, it is almost impossible to recognize it with a multimeter. There can help attentive, acute vision and smell. Wire is isolated only due to its lacquer coating, with a test of insulation between adjacent twists, the resistance remains anyway, which leads to a local heating. With a visual inspection, a working transformer should not be sponsored, drunks or blown fill, charring paper, gary smell.

In case the transformer type is defined, then on the reference book you can find out the resistance of its windings. To do this, use a multimeter in a megommeter mode. After measuring the insulation resistance of the transformer windings, compare with reference: the differences than 50% indicate the winding malfunction. If the resistance of the transformer windings is not specified, then the number of turns is always driven, and the type of wire and theoretically, if desired, it can be calculated.

Is it possible to check household reduction transformers?

You can try to check the multimeter and the common classic lowering transformers used in the power blocks for various devices with 220 volts input voltage and the output constant from 5 to 30 volts. CAUTION, eliminating the ability to touch the bare wires, is fed to the primary winding of 220 volts.

When smelling, smoke, it is necessary to turn off immediately, the experiment is unsuccessful, the primary winding is faulty.

If everything is fine, then touching only the tester arrows, the voltage on the secondary windings is measured. The difference from expected by more than 20% in a smaller side speaks of a malfunction of this winding.

For welding at home, a functional and productive apparatus is needed, the acquisition of which is now too expensive. It is quite possible to collect from undergraduate materials, after having previously studied the corresponding scheme.

What is solar batteries and how to create a system of home power supply, will tell on this topic.

Can help the multimeter and in case there is the same, but obviously good transformer. The windings are compared, the spread of less than 20% is the norm, but it must be remembered that for values \u200b\u200bless than 10 ohms, not every tester will be able to give true testimony.

Multimeter did everything that could. There will also be an oscilloscope for further inspection.

Detailed instructions: How to check the transformer multimeter on video

Transformer checking

So, the windings are defined using the multimeter. Now you can go directly to the question how to check the transformer using the same device. Talking is about defects. They are usually two:

cliff;
isolation wear, which leads to a closure to another winding or on the device body.

The closure is checked like this:

One multimeter probe closes on the output ending.
The second probe alternately connects to other ends.
In the case of a closure on the case, the second probe is connected to the transformer housing.

Attention! Checking the transformer winding to resistance, does not matter which probe to which end is connected. In this case, the polarity does not play any role.

Measuring current of idling

Conclusion on the topic

Related records:

Nikolai Petrushov

How to deal with the transformer windings, how to properly connect it to the network and not "burn" and how to determine the maximum currents of secondary windings ???
Such and similar questions ask themselves many novice radio amateurs.
In this article I will try to answer such questions and on the example of several transformers (photos at the beginning of the article), deal with each of them .. I hope this article will be useful to many radio amateurs.

First, remember the general features for armor transformers

The network winding, as a rule, dulls the first (closer than all to the core) and has the greatest active resistance (if only this is not an increase in the transformer, or a transformer has an anode winding).

Network winding can have taps, or consist example of two parts with removal.

The serial connection of the windings (parts of the windings) in armor transformers is made as usual, the beginning with the end or conclusions 2 and 3 (if for example there are two windings with leads 1-2 and 3-4).

Parallel connection of the windings (only for windings with the same number of turns) is made as usually started with the beginning of one winding, and the end with the end of another winding (nn and k, or conclusions 1-3 and 2-4 - if for example, The same windings with leads 1-2 and 3-4).

General rules for connecting secondary windings for all types of transformers.

To obtain various output voltages and loading currents of windings for personal needs other than those available on the transformer, you can get through various connections of the available windings with each other. Consider all possible options.

The windings can be connected sequentially, including windings wrapped by different by diameter, then the output voltage of such a winding will be equal to the sum of the voltages of the connected windings (UAV. \u003d U1 + U2 ... + UN). Load current of such a winding, will be equal to the smallest load current from the available windings.
For example: there are two windings with voltages 6 and 12 volts and load currents 4 and 2 amps - as a result, we obtain a total winding with a voltage of 18 volts and a load current - 2 amps.

Winding can be connected in parallel, only if they contain the same number of turns , including wiring wound differently in diameter. The correct connection is checked so. We connect together two wires from the windings and on the remaining two measure the voltage.
If the voltage is equal to double, then the compound is not correct, in this case we change the ends of any of the windings.
If the voltage at the remaining ends is zero, or so (the drop in more than half-volt is desirable, the winding in this case will be basked on the XX), boldly connect the remaining ends together.
The total voltage of such a winding does not change, and the load current will be equal to the amount of load currents, all connected parallel windings.
(Ip. \u003d i1 + i2 ... + in) .
For example: there are three windings with a 24 volt output voltage and load currents of 1 ampru. As a result, we will get a winding with a 24 volt voltage and a load current - 3 amps.

Winding can be connected in parallel and sequentially (features for a parallel connection, see above). The overall voltage and current will be, as with a serial connection.
For example: we have two successively and three parallel to the connected windings (the examples described above). We connect these two components sequentially. As a result, we obtain a total winding with a voltage of 42 volts (18 + 24) and the load current by the smallest winding, that is, 2 amps.

The windings can be connected ones, including wrapped different by different diameter (also in parallel and sequentially connected windings). The total voltage of such a winding will be equal to the difference in voltages included in the windings, the total current will be equal to the lowest winding load. Such a connection is used in the case when it is necessary to lower the output voltage of the available winding. Also, to lower the output voltage of any winding, you can get a dressing over all windings an additional winding with a wire, preferably not smaller diameter The winding, the voltage of which it is necessary to lower, so that the load current would not decrease. The winding can be wounded, even without disassembled the transformer, if there is a gap between windings and core and enable it meet with the desired winding.
For example: we have two windings on the transformer, one 24 volt 3 amps, the second 18 volt of 2 amps. We include them meet and eventually we obtain a winding with an output voltage of 6 volts (24-18) and a 2 amp load current.
But this is a purely theoretically, in the practice of the efficiency of such an inclusion will be lower than if the transformer had one secondary winding
The fact is that the current flowing over the windings - creates in the windings of EMF, and in b aboutleather winding voltage decreases with respect to the voltage of XX, and in m e.nysh - increases, and the larger the current flowing on the windings - the greater this is the impact.
As a result, the total calculated voltage (during the calculated current) will be lower.

Let's start with a small transformer, following the features described above (left in the photo).
Carefully inspect it. All conclusions are numbered and the wires are suitable for the following conclusions; 1, 2, 4, 6, 8, 9, 10, 12, 13, 22, 23, and 27.
Next, it is necessary to call all the conclusions with each meter to determine the number of windings and draw a transformer schema.
The following picture is obtained.
Conclusions 1 and 2 - resistance between them 2.3 Ohm, 2 and 4 - between them 2.4 Ohm, between 1 and 4 - 4.7 Ohm (one winding with the average derivation).
Further 8 and 10 - resistance 100.5 Ohm (another winding). Conclusions 12 and 13 - 26 ohms (still winding). Conclusions 22 and 23 - 1.5 Ohm (last winding).
Conclusions 6, 9 and 27 are not nicknamed with other conclusions and between themselves are most likely screen windings between network and other windings. These conclusions in the finished design are connected between themselves and attach to the housing (general wire).
Once again, carefully inspect the transformer.
Network winding, as we know, dulls first, although there are exceptions.

The photo is badly visible, therefore I duplicate. To the conclusion 8, the wire coming out from the core itself (that is, it is closer to the core of all), then it goes to the conclusion 10 - that is, the winding 8-10 is wound up first (and has the highest active resistance) and most likely it is a network.
Now according to the received data from the transvers, you can draw a transformer scheme.

It remains to try to connect the intended primary transformer winding to the 220 volt network and check the idling current of the transformer.
To do this, collect the next chain.

Sequentially with the proposed primary winding of the transformer (we have 10-10 conclusions), connect the usual incandescent lamp with a power of 40-65 watts (for more powerful transformers 75-100 watts). In this case, the lamp will play the role of a kind of fuse (current limiter), and protects the transformer winding from the output when it is connected to the 220 volts to the network, if we chose the wrong winding or winding is not calculated on the voltage of 220 volts. The maximum current flowing in this case over the winding (with a lamp power 40 watts), will not exceed 180 milliam. It will save you and a test transformer from possible troubles.

And in general, take yourself a rule, if you are not sure about choosing a network winding, its switching, in the installed winding jumpers, then the first connection to the network is always made with a consecutable incandescent lamp.

Observing caution, we connect the collected chain to the 220 volt network (I have a slightly more network, or rather 230 volts).
What do you see? Incandescent lamp does not burn.
So the network winding is selected correctly and the further connection of the transformer can be made without a lamp.
We connect a transformer without a lamp and measure the idling current of the transformer.

Idling current (xx) transformer is measured so; A similar chain is assembled that we collected with a lamp (I will not draw anymore), only instead of the lamp turns on an ammeter, which is designed to measure the AC (carefully inspect your device for the presence of such a mode).
The ammeter is first set to the maximum measurement limit, then, if there is a lot of it, the ammeter can be translated to a lower measurement limit.
Observing caution - we connect 220 volts to the network, better through the separation transformer. If the transformer is powerful, then the impoverishment of the ammeter at the time of turning on the transformer to the network is better to reveal or an additional switch, or simply navigate each other, since the starting current of the primary transformer winding exceeds the idling current of 100-150 times and the ammeter can fail. After the transformer is included in the network - the ammeter probe is disconnected and the current is measured.

The idling current of the transformer should be ideally 3-8% of the rated current of the transformer. It is quite considered normal and current XX 5-10% of the nominal. That is, if a transformer with a calculated rated power of 100 watts, the current consumption of its primary winding will be 0.45 A, which means the current XX should be ideally 22.5 mA (5% of the nominal) and it is desirable that it does not exceed 45 mA (10 % of the nominal).

As you can see, the idling current is just over 28 milliamme apex, which is permissible (well, it may be overgrown with a bit), since the view of this transformer with a capacity of 40-50 watts.
We measure the stroke of the stroke of the secondary windings. It turns out on withdraws 1-2-4 17.4 + 17.4 volts, the conclusions 12-13 \u003d 27.4 volts, the conclusions 22-23 \u003d 6.8 volts (this is at 230 volts network voltage).
Further, we need to determine the possibilities of windings and their load currents. How it's done?
If it is possible and allows the length of the windings suitable to wires to the wires, then it is better to measure the diameters of the wires (roughly up to 0.1 mm - caliper and exactly micrometer), and on the table, with an average current density of 3-4 A / mm.KV. - We find currents that are able to give windings.
If the wire diameters are not possible, then we do it as follows.
We load each of the windings of the active load, which can be anything, for example, incandescent lamps of different power and voltage (incandescent lamp with a power of 40 watts to voltage 220 volts has an active resistance of 90-100 ohms in a cold state, a 150 watt lamp - 150 watt lamp - 30 ohms), wire resistance (resistors), nichrome spirals from electric tiles, risostats, etc.
We load until the voltage on the winding decreases by 10% relative to the idle stroke voltage.
Then we measure the load current.

This current will be the maximum current that the winding is capable of issuing a long time without overheating.

Conditionally adopted the value of the voltage drop to 10% for the constant (static) load in order not to overheat the transformer. You can easily take 15%, or even 20%, depending on the nature of the load. All these calculations are approximated. If the load is permanent (lamps, such as a charger), then a smaller value is taken if the load is pulsed (dynamic), for example UMLC (with the exception of the mode "A"), then you can take a value and more up to 15-20%.

I take in the calculation of the static load, and I did it; Winding 1-2-4 load current (with a decrease in the winding voltage by 10% relative to the idle stroke voltage) - 0.85 amps (power of about 27 watts), winding 12-13 (in the photo above) load current 0.19-0, 2 amps (5 watts) and winding 22-23 - 0.5 amps (3.25 watts). The rated power of the transformer is about 36 watts (round up to 40).

Yes, I also want to tell about the resistance of the primary winding.
For low-power transformers, it can make tens, or even hundreds of Ohm, and for powerful - units of OM.
Very often, the forum ask such questions;
"I measured the multimeter resistance to the primary winding of the TC250, and it turned out to be 5 ohms. It is not never known for the network of 220 volts, I'm afraid to include it on the network. Tell me - is it normal?"

Since all multimeters measure constant current resistance (active resistance), it is not worth worrying, because for AC frequency 50 hertz this winding will have a completely different resistance (inductive), which will depend on the inductance of the winding and the frequency of the AC.
If you have than measuring inductance, you yourself can calculate the variable current winding resistance (inductive resistance).

For example;
The inductance of the primary winding at the measurement was 6 Gn, we go here And we enter this data (the inductance of 6 GG, the frequency of the network of 50 Hz), we look - it turned out 1884,959 (rounded 1885), it will be the inductive resistance of this winding for a frequency of 50 Hz. From here you can calculate the idling current of this winding for a voltage of 220 volts - 220/1885 \u003d 0.116 A (116 milliamper), yes, you can also add the active resistance of 5 ohms, that is, it will be 1890.
Naturally, for the frequency of 400 Hz there will be a completely different resistance of this winding.

Other transformers are also checked.
The photo of the second transformer shows that the conclusions are swept towards contact petals 1, 3, 4, 6, 7, 8, 10, 11, 12.
After the transvers, it becomes clear that the transformer has 4 windings.
The first on the outputs 1 and 6 (24oms), the second 3-4 (83 Ohm), the third 7-8 (11.5 ohms), fourth 10-11-12 with a tap from the middle (0.1 + 0.1 ohms) .

And it is clearly seen that the winding 1 and 6 is wound up first (white conclusions), then the winding 3-4 (black conclusions).
24 Ohm active resistance of the primary winding is quite enough. For more powerful transformers, the active resistance of the winding reaches units of OM.
The second winding 3-4 (Ohm), possibly increasing.
Here you can measure the diameters of the wires of all windings, except for winding 3-4, the findings of which are made by black, stranded, mounting wire.

Continue the transformer through the incandescent lamp. The lamp does not burn, the transformer on the type of 100-120, measure the idling current, it turns out 53 milliamperes, which is permissible.
Measure the stress of idle windings. It turns out 3-4 - 233 volts, 7-8 - 79.5 volts, and a winding of 10-11-12 to 3.4 volts (6.8 with an average output). The winding 3-4 is loaded to the voltage drop by 10% of the idle stroke voltage, and measure the flowing current through the load.

The maximum current of the load of this winding, as can be seen from the photo - 0.24 amps.
Toki other windings are determined from the current density table, based on the diameter of the winding wire.
Winding 7-8 wounds with a wire of 0.4 and the roller wire 1.08-1.1. Accordingly, the currents are obtained 0.4-0.5 and 3.5-4.0 amps. The rated power of the transformer is about 100 watts.

Another transformer remained. He has a contact plan with 14 contacts, top 1, 3, 5, 7, 9, 11, 13 and bottom, respectively. It could switch to various network voltages (127,220.237) It is possible that the primary winding has several taps, or consists of two semi-windings with removal.
Nickname, and it turns out such a picture:
Conclusions 1-2 \u003d 2.5 ohms; 2-3 \u003d 15.5 ohms (this is one winding with a tap); 4-5 \u003d 16.4 ohms; 5-6 \u003d 2.7 ohms (another winding with a tap); 7-8 \u003d 1.4 Ohm (3rd winding); 9-10 \u003d 1.5 Ohm (4th winding); 11-12 \u003d 5 ohms (5th winding) and 13-14 (6th winding).
We connect to the conclusions 1 and 3 network with a consecutive inclusion lamp.

The lamp is lit in half the heat. We measure the voltage at the outputs of the transformer, it equals 131 volts.
So it was not guessed and the primary winding here consists of two parts, and the connected part at a voltage of 131 volts begins to enter the saturation (the idling current increases) and on this thread the lamps fucked.
Connect the jumper conclusions 3 and 4, that is, sequentially two windings and connect the network (with a lamp) to the outputs 1 and 6.
Hurray, the lamp does not burn. Measure idling current.

The idling current is 34.5 ml. Here most likely (as part of the winding 2-3, and part of the second winding 4-5 have greater resistance, then these parts are calculated by 110 volts, and parts of the windings 1-2 and 5-6 to 17 volts, that is, the total for One part 1278 volts) 220 volts was connected to the terminals 2 and 5 with the jumper on the outputs 3 and 4 or vice versa. But you can leave and so, as we have connected, that is, all parts of the windings sequentially. For the transformer it is only better.
All, network found, further actions are similar to those described above.

A little more about rod transformers. For example, there is such (photo above). What are common features for them?

The soda transformers, as a rule, two symmetric coils, and the network winding is divided into two coils, that is, on one coil, turns around 110 (127) volts, and on the other. The numbering of the conclusions of one coil - similar to the other, the numbers of the conclusions on the other coil are marked (or relatively marked) with the stroke, i.e. 1 ", 2", etc.

Network winding, as a rule, dulls the first (closer to the core).

Network winding can have taps, or consist of two parts (for example, one winding - conclusions 1-2-3; or two parts - conclusions 1-2 and 3-4).

The terminal transformer has a magnetic stream along the core (by "circle, ellipse"), and the direction of the magnetic flux of one rod will be opposite to the other, so for the sequential connection of two half of the windings, on different coils connect the same contacts or start with the beginning (end with the end) . 1 and 1 ", the network is fed by 2-2", or 2 and 2 ", the network is then fed by 1 and 1".

For a sequential connection of windings consisting of two parts on one coil - windings are connected as usual, beginning with the end or end with the beginning, (n-K or KN), that is, output 2 and 3 (if, for example, 2 windings with The numbers of the conclusions are 1-2 and 3-4), as well as on another coil. Further consecutive connection of the two semi-windings of the two semi-windings on different coils, see the item above. (An example of such a compound on the TC-40-1 transformer scheme).

For parallel winding connection ( only for windings with identical number of turns ) On one coil, the compound is made as usual (nn and k, or conclusions 1-3 and 2-4 - if for example, there are the same windings with leads 1-2 and 3-4). For different coils, the compound is made as follows, to-n-taps and n-k-taps, or conclusions 1-2 "and 2-1" are connected - if, for example, there are the same windings with leads 1-2 and 1 "-2" .

Once again I remind you of observance of safety equipment, and it is best for experiments with a voltage of 220 volts to have a house separation transformer (a transformer with windings 220/220 volts for galvanic junction with an industrial network), which will protect against damage to the current, with a random touch to the bare end of the wire .

If any questions about the article arise, or find a transformer in the honeycombs (with suspicion that it is powerful), ask questions, help you deal with its windings and connecting to the network.

How to deal with transformer windingslike it connect correctly To the network and not "burn" and how to determine the maximum currents of secondary windings ???
Such and similar questions ask themselves beginner radio amateurs.
In this article I will try to answer such questions and on the example of several transformers (photos at the beginning of the article), deal with each of them .. I hope this article will be useful to many radio amateurs.

For a start, scholars have common features for armor transformers

- Network winding It usually wines the first (closer to all to the core) and has the greatest active resistance (if only this is not an increase in the transformer, or a transformer has an anode winding).

Network winding can have taps, or consist example of two parts with removal.

- Serial connection of windings (parts of the windings) in armor transformers are made as usual, the beginning with the end or conclusions 2 and 3 (if for example there are two windings with 1.-2 and 3-4 conclusions).

- Parallel connection of the windings (only for windings with the same number of turns), is produced as usual beginning with the beginning of one winding, and the end with the end of another winding (nn and k-k, or conclusions 1-3 and 2-4 - if for example, there are the same windings with with conclusions 1-2 and 3-4).

General rules for connecting secondary windings for all types of transformers.

Winding can be connected in parallel, only if they contain the same number of turns , including wiring wound differently in diameter. The correct connection is checked so. We connect together two wires from the windings and on the remaining two measure the voltage.
If the voltage is equal to double, then the compound is not correct, in this case we change the ends of any of the windings.
If the voltage at the remaining ends is zero, or so (the drop in more than half-volt is desirable, the winding in this case will be basked on the XX), boldly connect the remaining ends together.
The total voltage of such a winding does not change, and the load current will be equal to the amount of load currents, all connected parallel windings. (Ip. \u003d i1 + i2 ... + in) .
For example: there are three windings with a 24 volt output voltage and load currents of 1 ampru. As a result, we will get a winding with a 24 volt voltage and a load current - 3 amps.

It remains to try to connect the intended primary transformer winding to the 220 volt network and check the idling current of the transformer.
To do this, collect the next chain.

Idling current (xx) transformer is measured so; A similar chain is assembled that we collected with a lamp (I will not draw anymore), only instead of the lamp turns on an ammeter, which is designed to measure the AC (carefully inspect your device for the presence of such a mode). The ammeter is first set to the maximum measurement limit, then, if there is a lot of it, the ammeter can be translated to a lower measurement limit. Observing caution - we connect 220 volts to the network, better through the separation transformer. If the transformer is powerful, then the impoverishment of the ammeter at the time of turning on the transformer to the network is better to reveal or an additional switch, or simply navigate each other, since the starting current of the primary transformer winding exceeds the idling current of 100-150 times and the ammeter can fail. After the transformer is included in the network - the ammeter probe is disconnected and the current is measured.

As you can see, the idling current is just over 28 milliamme apex, which is permissible (well, it may be overgrown with a bit), since the view of this transformer with a capacity of 40-50 watts.
We measure the stroke of the stroke of the secondary windings. It turns out on withdraws 1-2-4 17.4 + 17.4 volts, the conclusions 12-13 \u003d 27.4 volts, the conclusions 22-23 \u003d 6.8 volts (this is at 230 volts network voltage).
Further, we need to determine the possibilities of windings and their load currents. How it's done?
If it is possible and allows the length of the windings suitable to the wires to the wires, then it is better to measure the diameters of the wires (roughly up to 0.1 mm - caliper and exact micrometer).
If the wire diameters are not possible, then we do it as follows.
We load each of the windings of the active load, which can be anything, for example, incandescent lamps of different power and voltage (incandescent lamp with a power of 40 watts to voltage 220 volts has an active resistance of 90-100 ohms in a cold state, a 150 watt lamp - 150 watt lamp - 30 ohms), wire resistance (resistors), nichrome spirals from electric tiles, risostats, etc.
We load until the voltage on the winding decreases by 10% relative to the idle stroke voltage.
Later we measure the load current .

This current will be the maximum current that the winding is capable of issuing a long time without overheating.
Conditionally adopted the value of the voltage drop to 10% for the constant (static) load in order not to overheat the transformer. You can easily take 15%, or even 20%, depending on the nature of the load. All these calculations are approximated. If the load is permanent (lamps, such as a charger), then a smaller value is taken if the load is pulsed (dynamic), for example UMLC (with the exception of the mode "A"), then you can take a value and more up to 15-20%.
I take in the calculation of the static load, and I did it; Winding 1-2-4 load current (with a decrease in the winding voltage by 10% relative to the idle stroke voltage) - 0.85 amps (power of about 27 watts), winding 12-13 (in the photo above) load current 0.19-0, 2 amps (5 watts) and winding 22-23 - 0.5 amps (3.25 watts). The rated power of the transformer is about 36 watts (round up to 40)