Dc Motor Insulation Resistance Test

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.

Dc motor insulation resistance test.

How to measure insulation resistance of a motor the measurement of insulation resistance is carried out by means of a mega ohmmeter a high resistance range ohmmeter. These electrical standards apply to testing cables generators circuit breakers and many other electrical systems where insulation quality around the conductors must be at its best. Step 1 remove all electrical power from the dc motor. Dc alone is used because we need to measure only the resistance of the winding insulation.

The test may be non destructive for in service equipment. Minimum insulation resistance of the winding to ground is measured with 500 v dc. Testing and data processing were carried out on site using a pc. For each system megger has the product best suited to conducting a comprehensive diagnostic insulation test.

The megger tester uses a high voltage generally in the 1000 to 10 000 volt range to identify insulation leakage in motor coils and adjacent wiring. Abstract this paper presents one of the maintenance test methods and the results of its application in the determination of the insulation condition of hv electric motors. The health of the winding is best indicated by its resistance and not its impedance. To measure insulation resistance a dc voltage of 500v or 1000v is applied between the windings and the ground of the motor as shown below.

This test may take place on installing or on the reel cable tools appliances transformers power distribution subsystems capacitors motors and any type of electrical equipment or wiring. B kv is the rated machine terminal to terminal voltage. Electrical motor insulation conditions dc testing. The leakage current through insulation expressed as resistance is displayed so it can be graphed.

The winding temperature should be 25 c 15 c.