Megger Test motor
Set your Megger Tester to 2X the motor’s
rated voltage (250V in this instance), and
attach the testers red lead to one of the plug
spades, and the testers black lead to the
ground prong. Press the TEST button on the
Megger and record readings after 20
seconds. Repeat test with the other plug
spade to ground.
Resistance values between 20 MΩ and 1 MΩ
indicate that the insulation system is starting
to fail. Readings under 1 MΩ after 20
seconds indicate a shorted motor, and the
unit cannot be economically repaired.
If any reading is less than 20 MΩ, test motor
and cable separately to isolate the problem
to either the cable or the motor.
If the problem is in the cable, replace cable
and re-test. If MOTOR resistance is less than
1 MΩ, there is evidence that the motor is
damaged, and the motor should not be
used. Further disassembly and inspection
will be necessary.
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