how to check a three phase induction motor by multimeter &
megger?

Answer Posted / will bg

Prove your meter/megger on a known resistance block. You
should remove any star or delta connection/bridges if at all
possible. If your earth/ground reference is not the motor
frame itself (i.e. a conductor in a cable) then first prove
your earth/ground by measuring on ohms the resistance
between your earth test point to various places on the motor
frame. You should get almost 0 ohms. Now measure your
phase resistances and they should always be fairly equal.
Rule of thumb is 10% variance. Remember the bigger the
motor the lower the resistance. Now on 500 volts DC measure
all phases to earth. Now switch megger to 1000V DC and
measure phase to phase resistance.

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