What is crawling and cogging?

When rotor bars are made to run parallel with stator , the

torque rises & falls correspondingly causing more

pulsations. This is termed as cogging in other qords

magnatic locking. This is reduced by making the rotor bars

run at an angle to the stator ie crawling in order to make

the torque uniform.

Crawling on the other hand signifies running of motor at

almost one seventh of the rated speed due to interference

of seventh harmonics.