INSULATION OF MOTOR AND MEGGER TESTING?

In this Article I am going to discuss about Motor Insulation and Megger Testing ?

Motors insulation is tested using a MEGGER. It is a portable instrument used to measure insulation resistance. It consists of a direct ohm meter and a hand driven DC generator or battery.

Causes of insulation failure:

1. Moisture

2. Dust and dirt deposits

3. Oil and grease

4. Vibration

How to test:

1. Short the two probes together and switch to “MΩ” and press the test button. The pointer should

indicate approx. Zero.

2. Disconnect the motor from live power supply and lock off acc. to the standard procedure.

3. Confirm that a reliable earth connection is obtained by connecting the probes of 2 separate earth

points on the equipment frame for low res. Continuity.

4. Measure and log the phase-to-phase insulation resistance values. (for eg. U-V, V-W, U-W).

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