alt.engineering.electrical

On Mon, 03 Sep 2007 00:14:41 -0700 Mitian wrote:

| I want someone who can help me to easly understand how rotating
| magnetic field is created in induction you can it would
| good with drawing and mathematical analysis. thank you...

The field is created by current in the various coils arranged in a circle.
The phases are connected so that each current peak of a given polarity
follows in sequence around the circle. The is easy with 3 phase power,
where coils opposite each other (180 degrees) are connected to the same
phase source, but in opposite polarity. With 6 such coils it should be
easily seen (understood) to be a fairly uniform field with N and S on
opposite sides that rotates in the power supply frquency.

Now once you have the field rotating, the change induces current in the
initially stationary "squirrel cade" rotor. That induced current then
caues a field that pulls the rotor to follow the field. I can't follow
it as fast as the field turns, however, because there is a speed in which
the dimishing field change as seen by the rotor because it is rotating
will cause it to slow down. It will reach an equalibrium at some point
based on stator field strength, mechanical load, etc.

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