This is known as crawling of induction motor. This action is due to,the fact that the AC winding of the stator produces a flux wave which is not. It can also be reduced by using the skewed rotor. Cogging and Crawling are less eminent in wound rotor motors because of the higher starting. Induction motors will not accelerate to full speed if they cog or crawl. Cogging motors do not accelerate at all, and crawling induction motors stop accelerating.

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The shapes of the slots can also be optimized to reduce flux wave distortion.

Cogging And Crawling of Induction Motor

Skewing of the rotor slots, that means the stack of the rotor is arranged in such a way that it angled with the axis of the rotation. This characteristic is also known as magnetic teeth locking of the induction motor.

Instead, it is a complex wave consisting a fundamental wave and odd harmonics like 3rd, 5th, 7th etc.

This phenomenon is called as crawling in induction motors. Read articles related to various Electrical Engineering topics.

Crawling and Cogging in Induction Motors

Constructing the rotor with skewed slots and providing more or fewer rotor slots than stator slots is knduction remedy for both cogging and crawling. You may also like: Recieve free updates Via Email! What is meant is to arrange the stack of rotor laminations so that the rotor slots are “skewed” or angled with respect to the axis of rotation.


But generally, three constants R, L and C are considered and the If the mechanical load on the shaft involves constant load torque, the torque developed by the motor may crawilng below this load torque.

Please clarify your specific problem or add additional details to highlight exactly what you need. About Terms Sitemap Contact. At this stage motor does not reach up to its anf speed and continue to rotate at a speed which is much lower than its normal speed.

This phenomenon is called as crawling of an induction motor. Thank you Charles Cowie. This can be easily overcome by making number of rotor slots more than the number of stator slots and by giving slightly skew to the rotor slots skewed.

Cogging And Crawling of Induction Motor – Electrical Engineers Guide

The phenomenon of Magnetic Locking between the stator and the rotor teeth is called Cogging or Teeth Locking. These harmonics create additional torque fields in addition to the synchronous torque. You can also use this website as reference for your Projects, Exams. Leave a Reply Cancel reply Your email address will not be published. P Please frame inductiob question properly, include as much information as possible!

Hence, the net forward torque is equal inductipn the sum of the torque produced by 7 th harmonic and fundamental torque.

Newer Post Older Post Home. In your link, that statement is under the heading “Cogging. Further elaboration re comment: Hence total motor torque has there components. Methods to overcome Cogging This problem can be easily solved by adopting several measures. But the main reason for starting problem in the motor is because of cogging in which the slots of the stator get locked up with the rotor slots.


Constructing the rotor with skewed slots and providing more or fewer rotor slots than stator slots is the remedy for both cogging and crawling. Motot happens especially when number of rotor teeth is equal to number of stator teeth, because of magnetic locking between the stator teeth and the rotor teeth.

What is Cogging in Induction Motor? – Magnetic Locking – Circuit Globe

This is an open and free to study website for Electrical Engineering students, Professionals and everyone who wants to learn. Sometimes, squirrel cage induction motors exhibits a tendency to run at very slow speeds as low as one-seventh of their synchronous speed. Classification of Electric Drives. Would you please elaborate it in more details.

Construction and Working of Induction Motor. Distortion can be caused by stator windings that are not well distributed among the slots, an insufficient number of stator slots, a poor relationship between the number of stator slots and rotor slots, or distortion of the voltage supplied to the motor.

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