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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Crawling and Cogging in Induction Motors
Home Questions Tags Users Unanswered. This is happens due to fact that when stator teeth and rotor teeth face to other, the magnetic path becomes minimum. Now the question arises why this happens?
How to minimize this effects? The answer to ahd related question may be helpful. It can also be reduced by using the skewed rotor. Circuit Globe All about Electrical and Electronics. This is known as crawling of induction motor.
This phenomenon is called cogging or magnetic locking of induction motor. Group Drives Photo Credit – http: At this stage motor does not reach up to its normal speed and continue to rotate at a speed which is anc lower than its normal speed.
xrawling Classification of Electric Drives. 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. Instead, it is a complex wave consisting a fundamental wave and odd harmonics like 3rd, 5th, 7th etc.
If the harmonic frequencies coincide crawilng the slot frequency due to the harmonics present in the supply voltage then it causes torque modulation. Please clarify your specific problem or add additional details to highlight exactly what you need.
Crawling and Cogging in Induction Motors |
Induction Motor Photo Credit – www. Cogging can be caused by the number of stator and rotor slots being equal to each other or perhaps one being an integral multiple of the other. If the total load torque assume remain constant, the resultant torque may fall below load torque.
Newer Post Older Post Home. This 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. As a result, of it cogging occurs.
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. The 5 th harmonic produces small torque in the reverse direction but it is neglected. Thank you Charles Cowie. 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.
This characteristic of the induction motor is called cogging. 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.
Crawling Sometime the squirrel cage induction motor refuses to start particular at low voltage, it is known as crawling effect. The phenomenon of Magnetic Locking between the stator and the rotor teeth is called Cogging or Teeth Locking. I have mentioned one or two in my blog post.
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What is Cogging in Induction Motor? – Magnetic Locking – Circuit Globe