How to test insulation resistance of motor

1.                  Switch on megger

2.                  Connect two probes together in MΩ. it should show zero (megger test)

3.                  Isolate motor, breaker off.

4.                  Connect two probes to different earth point (different point in frame) on motor. It                            should show zero (earth test)

5.                  Keep megger knob in MΩ position.

6.                  Ensure that machine temperature is near to the working temperature. (IR is leaky at                        high temperature.)

7.                  Remove all short connections incase of star connected motor

8.                  Suppose u1, v1, w1 are the terminals connect one probe to w1 and other to earth. It                         should    show min 0.5 MΩ.

               Alternatively connect one probe to vi and other to w1 and test