power factor of an induction motor.

The answer lies in your question.

we use a running/starting capacitor in a single phase induction motor.

Single phase motor usually unless some methodology is used can not create a rotating magnetic field. To simulate the rotating field several possible methods are there , usage of capacitor - to create a phase difference, is one of them.

Three phase automatically crates the rotating field.

Effect of capacitor on pf is only secondary here (for single phase motors) . Primary is Creation of the field.

These links may also help:

http://www.allaboutcircuits.com/vol_2/chpt_13/9.html

http://www.emt-india.net/equipment_tips/electric_motors/pdf/0507SinglePhaseInductionMotor.pdf

http://www.tpub.com/content/neets/14177/css/14177_96.htm (click 'Next' at upper right corner to go to next page)

- MS

any inductive load like induction motor draws activre power (kw),reactive power(kvar)from the source (kva).wherein active power kw is converted into useful work whereas reactive power (kvar)is required for flux creation in case of induction motor. power factor is ratio between actual power(kw) and kva.

power factor=kw/kva

this ratio has to be above 0.95 for effective utilization of electrical power .

3 phase shunt capacitors in differant ways are connected with load to correct power factor.

if you want to know more about power factor mail at ezp@ctr.in