How to test the transformer with a multimeter? Instructions

It is often necessary to familiarize in advance with the question ofhow to check the transformer. After all, if it breaks down or is unstable, it will be difficult to find the cause of the equipment failure. This simple electrical device can be diagnosed with a conventional multimeter. Consider how to do this.

What is the equipment?

How to check a transformer if you do not know itconstruction? Consider the principle of operation and a variety of simple equipment. The magnetic core is wound with coils of copper wire of a certain cross-section so that the pins for the supply winding and the secondary wire remain.

Transmission of energy to the secondary windingis made in a non-contact way. Here it is almost clear how to test the transformer. Similarly, the usual inductance is called with an ohmmeter. The turns form a resistance that can be measured. However, such a method is applicable when the predetermined value is known. After all, resistance can change to a greater or lesser extent as a result of heating. This is called interturn closure.

Such a device will no longer issue a referencevoltage and current. The ohmmeter will show only a break in the circuit or a complete short circuit. For additional diagnostics, a short circuit test is used with the same ohmmeter. How to check the transformer without knowing the winding leads?

This is determined by the thickness of the outgoing wires. If the transformer is lowering, the lead wires will be thicker than the feeders. And accordingly, on the contrary: the input lead is thicker. If two windings are output, then the thickness may be the same, it should be remembered. The surest way to look at the marking and find the technical characteristics of the equipment.

Kinds

Transformers are divided into the following groups:

• Lowering and raising.
• Power is more often used to reduce the supply voltage.
• Current transformers for supplying the consumer with a constant current value and keeping it in a predetermined range.
• Single- and multiphase.
• Welding purposes.
• Pulsed.

Depending on the purpose of the equipmentthe principle of approach to the question of how to check the transformer windings also changes. A multimeter can only ring small devices. Power machines already require a different approach to fault diagnosis.

Vertebra method

The ohmmeter diagnostic method will help with the question ofhow to check the power transformer. The resistance between the terminals of one winding begins to ring out. This establishes the integrity of the conductor. Before this, the body is inspected for the absence of deposits, influxes as a result of heating the equipment.

Next, measure the current values ​​in Ohms andcompare them with the passport. If there are none, then additional diagnostics under voltage will be required. It is recommended to call each terminal relative to the metal case of the device, where the ground connections are connected.

Before taking measurements, disable alltransformer ends. It is recommended to disconnect them from the circuit and for your own safety. Also check for the presence of an electronic circuit, which is often present in modern power models. It should also be removed before checking.

Infinite resistance speaks of the wholeisolation. Values ​​of a few pounds already cause suspicions about the breakdown on the body. It can also be due to accumulated dirt, dust or moisture in the air gaps of the device.

Under stress

Feed tests are carried out whenthere is a question about how to check the transformer for interturn circuit. If we know the magnitude of the supply voltage of the device for which the transformer is intended, then measure the value of idling with a voltmeter. That is, the lead wires are in the air.

If the voltage value is different fromrated, then draw conclusions about the interturn circuit in the windings. If a crackling sound is heard when the device is operating, it is better to turn off such a transformer immediately. It is faulty. There are tolerances in the measurements:

• For voltage values ​​may differ by 20%.
• For resistance, the norm is the spread of values ​​in 50% of passport.

Measurement with an ammeter

We will understand how to check the current transformer. It is included in the chain: regular or actually made. It is important that the current value is not less than the nominal. Measurements with an ammeter are carried out in the primary circuit and in the secondary circuit.

The current in the primary circuit is compared with the secondaryindications. More precisely, they divide the first values ​​into those measured in the secondary winding. The transformation ratio should be taken from the directory and compare with the obtained calculations. Results must be the same.

Current transformer cannot be measured at idlego. In this case, too high a voltage can be generated on the secondary side, which can damage the insulation. You should also observe the polarity of the connection, which will affect the operation of the entire connected circuit.

Typical malfunctions

Before checking out the transformermicrowave, we give frequent varieties of breakdowns, fixed without a multimeter. Often, power devices fail due to short circuits. It is installed by inspecting circuit boards, connectors, and connections. Less commonly, mechanical damage occurs to the transformer case and its core.

Mechanical wear of connections of conclusionstransformer occurs on moving machines. Large feed windings require constant cooling. In its absence, overheating and melting of the insulation is possible.

TDX

We will understand how to check the pulsetransformer. An ohmmeter will be able to establish only the integrity of the windings. The operability of the device is established when connected to the circuit where the capacitor, the load and the sound generator are involved.

A pulse signal is sent to the primary winding.range from 20 to 100 kHz. On the secondary winding make measurements of the magnitude of the oscilloscope. Establish the presence of pulse distortion. If they are absent, make conclusions about the good device.

Waveform distortions speak of spoiledwindings. Repairing such devices is not recommended on their own. They are set up in the laboratory. There are other test circuits for pulse transformers, where they investigate the presence of resonance on the windings. Its absence indicates a faulty device.

You can also compare the shape of the pulses fed to the primary winding and released from the secondary. The deviation in form also indicates a malfunction of the transformer.

Several windings

For measuring resistance free ends fromelectrical connections. Choose any output and measure all resistances relative to the rest. It is recommended to record the values ​​and label the checked ends.

So we can determine the type of connection of the windings: with average outputs, without them, with a common connection point. More common with a separate connection of the windings. Measurement will be done with only one of all the wires.

If there is a common point, then the resistancemeasure between all available conductors. Two windings with an average output will have values ​​only between three wires. Several conclusions are found in transformers designed for operation in several networks of 110 or 220 volts.

Nuances of diagnosis

The buzz of the transformer isnormal if it is a specific device. Only sparking and crackling indicate a malfunction. Often the heating of the windings is the normal operation of the transformer. More often it is observed at the lowering devices.

Resonance may be created when vibrating.transformer housing. Then it should just be fixed with insulating material. The operation of the windings varies considerably with loose or contaminated contacts. Most of the problems are solved by stripping the metal to shine and new wearable conclusions.

When measuring the values ​​of voltage and current shouldtake into account the ambient temperature, the size and nature of the load. Voltage control is also required. Checking the connection frequency is required. Asian and American equipment is designed for 60 Hz, which leads to underestimated output values.

The inept connection of a transformer cancause device malfunction. In no case do not connect a constant voltage to the windings. The coils will quickly melt otherwise. Accuracy in measurements and proper connection will help not only to find the cause of the breakdown, but also, possibly, to eliminate it in a painless way.