what is crawling of induction motor?

Answer 1

"Crawling", when applied to an induction machine, refers to the very slow rotation of the rotor caused by the asynchronous nature of the harmonic content put out by a variable speed (either frequency OR voltage) drive.

Basically, the mmf of the machine is distorted enough that the rotor tries to follow the asynchronous pattern, rather than the synchronous one.

It can also happen when DC harmonics are present in the system.

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Regarding a previous answer - "growling" is a result of a loose connection. Usually, this means that one of the rotor bars is broken somewhere inside the rotor core, and hence can rattle around as the machine rotates. The "growler test" is the application of a very small electromagnetic field (through a pair of close-set points) to each individual bar, trying to excite the vibration mode and discover which bars are "loose".

Answer 2

Sometimes induction motor (particularly of squirrel cage type) runs at very lower speed, near 1/7th of its rated speed. This phenomenon is called as crawling. To know the phenomenon of crawling in detail, read at

http://selectrical.blogspot.in/2014/02/crawling-and-cogging-in-induction-motors.html

Answer 3

due to the presence of basically 5th and 7th harmonics in the flux wave the speed of the induction machine becomes 1/7th times the synchronous speed and the machine is unable to pick up its speed.this phenomenon is known as crawling.

Answer 4

its called growling and caused by induction feed back in the armature loop, usually caused by several laps of wire that are nolonger insulated from the wrap along side it, effectively shorting out the armature. this could also happen in the field coils. basically the insulation is or has failed.

Answer 5

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Answer 6

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