Re: SIngle phase ac motor question


"HardySpicer"

My understanding is that you must have a rotating magnet field to
drive an ac motor. Hence often a capacitor start system is used with a
second winding (for single phase) which is switched off once the motor
is started. Essentially this is a two-phase motor for starting.Am I
therefore wrong with the idea that a single phase on its own will not
rotate a motor since there is a single phase and one coil only after
the thing has started? How does a single phase give a rotating field?


** No Google where you live ????

Most commonly, single phase motors use a capacitor to shift phase and make
the field rotate.

Low powered ( sub 100 watt input ) examples often use a "shaded pole" to
achieve a similar result.

Plenty of good, basic AC motor stuff here:

http://www.allaboutcircuits.com/vol_2/chpt_13/10.html



...... Phil



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