Why the voltage gets boosted by a capacitor in a capacitor ran AC motor?

[the_mick]

Hi,

I'm doing some work on a capacitor run ac motor. The motor is single phase with auxiliary windings. These windings are feed current through a capacitor which shifts the phase by 90 degrees.

Thats all fine but I've found that the voltage gets boosted by the capacitor. from 230V to about 260-270V.

Could somebody explain this please?

 

[srizbf]

Re: Capacitor Motor

a phasor diagram can give the picture.

 

[the_mick]

Re: Capacitor Motor

Ya a Phasor Diagram is good for explaining the 90 degree phase shift. That's all fine, its the increase in voltage I don't understand???????

 

[FvM]

Capacitor Motor

Simply consider the inductive impedance of the motor, than you'll see.

 

[the_mick]

Re: Capacitor Motor

I think the reason is that there is a back emf created due to the larger size of the aux winding