What are cogging and crawling in induction motors?

Cogging (magnetic locking) occurs when stator and rotor slot numbers are equal or have common factors, causing magnetic alignment that can prevent starting. The motor locks at standstill positions. Crawling is operation at a stable sub-synchronous speed (typically 1/7 of synchronous speed) due to space harmonics in the air gap flux. Both are avoided by proper slot number selection - rotor slots should differ from stator slots by 1-2, and certain combinations are avoided per design rules.