Electrical Engineering XYZ MCQs
Cogging and crawling are phenomena associated with:
- The former at a fraction of its rate speed and the latter during starting
- Cage induction machines and they are essentially the same
- The former during starting and the latter at a fraction of its rated speed
- Any of the above
Correct answer: 3. The former during starting and the latter at a fraction of its rated speed
Explanation: Cogging occurs during the starting of a cage induction motor, where the motor may fail to start or jerks when it starts. This is due to the torque not being sufficient due to magnetic locking between the stator and rotor slots alignment. Crawling, on the other hand, refers to the phenomenon where the motor operates at a fraction of its rated speed, usually around 1/7 or 1/6 of the full speed, mainly due to harmonics in the motor.