what is cogging and crawling

Answer Posted / raul

COGGING : when the stator and rotor poles of a 3-phase
Induction motor r either equal or have an integral
ratio......there is a strong alignment or magnetic locking
b/w the stator n rotor teeths.......so due to this the
motor is unable to start inspite of applying full rated
voltage across the motor........
CRAWLING : it is inability of a 3-phase induction motor to
speed up to desired slip speed and has a tendency to run at
a stable speed of 1/7th of the synchronous speed. this
normally occurs due to the 7th harmonic present in the non-
sinusoidal flux wave.......it can be avoided by using short
chorded windings.......

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