What is the purpose of using DC voltage on measuring the winding resistance of a transformer?

The purpose of measuring the DC winding resistance of the transformer windings is to check the welding quality of the winding joints and whether the windings have short circuits between the windings; whether the contact positions of the voltage tap switches are good and whether the actual positions of the taps match; …

What is the purpose of DC resistance test for a transformer?

DC winding resistance testing is performed during transformer commissioning, after the occurrence of internal faults, and during periodic maintenance as recommended by the manufacturer [3]. Winding resistance tests are performed to assess the integrity of a transformer’s windings, tap changer, and internal connections.

What is DC resistance test?

DC Loop Resistance is the total resistance through two conductors looped at one end of the link. This is usually a function of the conductor diameter and varies only with distance. This measurement is sometimes done to ensure there are no gross misconnections which can add significant resistance to the link.

Why doesn’t a transformer work with direct current Why is AC required?

The basic reason is that you need a changing magnetic field in order to induce a voltage in a loop of wire. So transformers work with AC since the magnetic field is oscillating at 60 Hertz. If you plug the transformer into a DC circuit, the magnetic field is a constant, after a short initial spike.

Which test is used for measurement of winding resistance?

Winding resistance tests are a measurement of the applied DC voltage and current to the device under test -DUT. Using Ohm’s law the resistance is calculated in µΩ (micro Ohms) or mΩ (milli Ohms) by the winding analyzer.

Which instrument is used to measure winding resistance?

ohmmeter
The windings resistance can be directly measured with an ohmmeter.

What is the use of DC test on induction motor testing?

To calculate the resistance (R2) of the rotor we should have the idea of R1 (stator resistance) so that it can subtract from the total resistance. The test is done on the motor to find the resistance (R1) of the stator is named as dc test of induction motor.

What happens if DC is applied to transformer?

When a DC voltage is applied to the primary winding of a transformer, due to low resistance, the winding acts as a short circuit across the terminals of the DC source that lead to the flow of heavy current through the winding resulting in overheating of the winding.

How is winding resistance measured in a dc motor?

For the winding resistance use an ohmmeter. For a dc motor measure the resistance between the 2 armature wires. If it is a WYE connected BLDC motor, the resistance is the line-to-line resistance. Thus divide the resistance(l-l) by 2 to get the phase resistance.

What is resistance in winding?

Winding resistance is defined as the resistance of a length of copper wires from one end to the other. It is a measurement of DC voltage and current in regard to Ohm’s law, where R (resistance) is equal to V (voltage) divided by I (amps).

How do you measure the resistance of a transformer winding?

Transformer winding resistance measurements are obtained by passing a known DC current through the winding under test and measuring the voltage drop across each terminal ( Ohm’s Law ).

Why is the insulation resistance test performed using a DC voltage?

If the insulation resistance test is performed using an AC voltage, we end up measuring the impedance of the capacitive component and prevents us from obtaining the required insulation resistance. This is the reason why the insulation resistance test is performed using a DC voltage.

Why do we use DCDC instead of AC for insulation testing?

DC alone is used because we need to measure only the resistance of the winding insulation. If we use AC to conduct the insulation test, we will be measuring impedance instead of the resistance as the insulation has a substantial capacitive reactance. The health of the winding is best indicated by its resistance and not its impedance.

What precautions should be taken before conducting a transformer winding resistance test?

Before conducting a transformer winding resistance test, it is important to observe all safety warnings and take proper precautions. Ensure that all equipment to be tested is properly grounded and treat all high-voltage power equipment as energized until proven otherwise by using the proper lockout/tagout procedures.