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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Newer Post Older Post Home. Would you please elaborate it in more details.
This phenomenon is called cogging or magnetic locking of induction motor. What is meant is to arrange the stack of rotor laminations so that the rotor slots niduction “skewed” or motod with respect to the axis of rotation. Effect of Crawling The problem of Cogging is overcome by making the number of rotor slots prime to the number of stator slots. 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.
As we know that there is series of slots in the stator and rotor of the induction motor. Constructing the rotor with skewed slots and providing more or fewer rotor slots than stator slots is the remedy for both cogging and crawling.
Sometimes it happens because of low supply voltage. P Please frame your question properly, include as much information as possible! Even after applying full voltage to the stator winding, the rotor of a mootr phase induction motor fails to start. But generally, three constants R, L indiction C are considered and the The basic od of crawling is a stator magnetic flux wave that is distorted rather than purely sinusoidal.
There may be a bit more risk with electronic reduced-voltage starters. Now the question arises why this happens?
Crawling and Cogging in Induction Motors |
Cogging and Crawling are less eminent in wound rotor motors because of the higher starting torques. As a result in addition to the fundamental torque ,harmonics torques also developed whose synchronous speed for fundamental torque. 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.
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Cogging in Induction Motor
Newer Post Older Post Home. When the number of stator teeth is equal to number of rotor teeth, there is possible locking tendency of the stator and rotor teeth. Thus, a locking is created between the stator and rotor teeth. 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.
See the How to Ask page for help clarifying this question. Read articles related to various Electrical Engineering topics. Here is a bit more detail on the reason that distorted flux waves cause problematic torque variations. It can also be reduced by using the skewed rotor. Hence total motor torque has there components. Please clarify your specific problem or add additional details to highlight exactly what you need. If the mechanical load on the shaft involves constant load torque, the torque developed by the motor may fall below this load torque.
Crawling and Cogging Effect in the Induction Motor | Electrical Revolution
The content on this website is copyrighted and may not be reproduced. This action is due to the motod that harmonics fluxes produced in the gap of the stator winding of odd harmonics like 3 rd5 th7 th etc. By my electrical Reaction: I really have no idea what you are asking and the link you are referring to doesn’t really help.
In your link, that statement is under the heading “Cogging. Your the link’s author?
The primary method of avoiding or minimizing these problems is to select an optimum number of stator and rotor slots and an optimum winding distribution scheme. The torque produced by the 5 th harmonic rotates in the backward direction. Manoj Sahu 25 1 2 5. Crawling Sometime the squirrel cage induction motor refuses to start particular at low voltage, it is known cotging crawling effect. 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.
The number of the stator slots equal to or an integral multiple of the rotor slots, strong alignment forces is produced between the stator and the rotor. Methods to overcome Cogging This problem can be easily solved by adopting several measures. The shapes of the slots can also be optimized to reduce flux wave distortion.
When the slots of the rotor are equal in number with slots in the stator, they align themselves in such way that both face to each other and at this stage the reluctance of the magnetic path is minimum and motor refuse to start. This is happens due to fact that when stator teeth and rotor teeth face to other, the magnetic path becomes minimum. How are induction motors designed to minimize cogging and crawling?