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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Apart from this, there is one more reason for cogging. Your the link’s author?

Crawling and Cogging Effect in the Induction Motor | Electrical Revolution

This phenomenon is called as crawling of an induction motor. Yes helloworldi am the author. Sometimes it happens because of low supply voltage. Crawling and cogging both are particularly related to squirrel cage induction motors. The phenomenon of Magnetic Locking between the stator and the rotor teeth is called Cogging or Teeth Locking. The torque produced by the 5 th harmonic rotates in the backward direction.

In your link, you wrote “This can be easily overcome by making number of rotor slots more than the number of stator slots and by giving slightly slop to the rotor slots to the rotor slots skewed.

The basic induxtion of crawling is a stator magnetic coghing wave that is distorted rather than purely sinusoidal. ACD 2, 6 The primary method of avoiding or minimizing these problems is to select an optimum number of stator and rotor slots ineuction an optimum winding distribution scheme. These harmonics create additional torque fields in addition to the synchronous torque.

Thank you Charles Cowie. Cogging of Induction Annd This characteristic of induction motor comes into picture when motor refuses to start at all. You can also use this website as reference for your Projects, Exams.

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I would like to know what are the various causes behind this. In your link, that statement is under the heading “Cogging. You may also like: The total motor torque now consist three components as: These characteristics are the result of improper functioning of the motor that means either motor is running at very slow speed or it is not taking the load.

This phenomenon is called as crawling in induction motors. Now the question arises why this happens? Further elaboration re comment: The rotor tends to remain fixed in this condition and causes serious problem in starting.

Cogging And Crawling of Induction Motor – Electrical Engineers Guide

Connects Facebook Youtube Videos. I really have no idea what you are asking and the link you are referring to doesn’t really help. This is happens due to fact that when stator teeth and rotor teeth face to other, the magnetic path becomes minimum. If the total load torque assume remain constant, the resultant torque may fall below load torque.

Crawling of Induction Motor It has been observed that squirrel cage type induction motor has a tendency to run at very low speed compared to its synchronous speed, this phenomenon is known as crawling.

Skewing of the rotor slots, that means the stack of the rotor is arranged in cpgging a way that it angled with the axis of the rotation. A transmission line has four constants R, L, C and shunt conductance. Cogging and Crawling are less eminent in wound rotor motors because of the higher starting torques. This characteristic of the induction motor is called cogging. This action is due to the fact that, flux wave produced by a stator winding is not purely sine wave.

This torque produced by fifth harmonic which works as a braking action is small in quantity, so it can be neglected. This condition is known as Cogging or Magnetic locking.

The 5 th harmonic produces small torque in the reverse direction but it is neglected. Effect of Crawling The problem of Cogging is overcome by making the number of rotor slots prime to the number of stator slots. Sometimes, squirrel cage induction motors exhibits a tendency to run at very slow speeds as low as motr of their synchronous speed.


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 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.

It is also helpful to design the motor so that the torque vs.

Cogging And Crawling of Induction Motor

When the rotor teeth and stator teeth face each other, the reluctance of the magnetic path is minimum, that is why the rotor tends to remain fixed. As a result in addition indduction the fundamental torque ,harmonics torques also developed whose synchronous speed for fundamental torque. Why does the induction motor performance phenomena known as “cogging” and “crawling” occur and how can motors can be designed to minimize them? Methods to overcome Cogging This problem can be easily solved by adopting several induciton.

This condition arises when the number of stator and rotor slots are either equal or have an integral ratio. Leave a Reply Cancel reply Your email address will not be published. This characteristic is also known as magnetic teeth locking of the induction motor.

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