Insulation Resistance Test of Transformer

An insulation resistance test (IR) is commonly performed during the development and production phases of electrical and electronic equipment.

It allows the electrical testing of the insulation resistance between the primary coil and the ground of the transformer.

The insulation resistance test of transformers is an important task in the production process and it’s performed by using an ohmmeter, which measures the electrical impedance between two points in the circuit.

Our insulation resistance test article addresses transformers, how they vary from capacitors and the purpose and technique for conducting insulation resistance tests on transformers.

Basic Transformer

Transformers are widely used in electronics, power systems, motor control, and power transmission. They are electrical devices that can change the voltage or frequency of a source of energy.

Transformers are designed to improve electrical power transmission and distribution efficiency. It has majorly three basic functions.

A voltage regulator is one of the most common applications for a transformer. Regulators are used to stepping down voltages from higher levels to lower levels.

A battery charger is a typical example of this use. Moreover, it increases the current capacity and provides isolation from high voltages.

Capacitors vs Transformer

Capacitors are really small pieces of metal that store energy. They are used in electronic equipment, radios, computers, and cell phones.

If you think about it, capacitors look a lot like transformers, and they do some of the same things transformers can do.

So, what is the difference between capacitors and transformers? The answer is simple. Transformers have a primary and secondary winding. Capacitors have just a single winding.

Purpose of The Insulation Resistance Test Merger

The insulation resistance test in a transformer measures the amount of current the insulation will allow to pass between the primary and secondary windings.

The amount of voltage induced in the secondary winding is measured when a direct current (DC) voltage is supplied across the main and secondary windings.

Whereas, insulation resistance is measured by dividing the voltage induced in the secondary winding by the applied DC voltage. Hence, this test determines the maximum safe voltage output to which a transformer will be exposed.

The technique of Insulation Resistance Test of Transformer

The insulation resistance is measured in ohms by using the following technique:

  • Place the meter at the end of the winding wire and turn on the power supply.
  • After inserting the probes into the the wires center, this wire is used for winding. Turn on the power supply until the voltage reaches the rated voltage of the transformer (120VAC for a 60/60-V transformer)
  • Turn off the power supply.
  • Place the probe on the outer copper ring of the core and record the reading. The insulation resistance is usually printed on the side of the transformer.

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