# Power Factor Correction Caps



## WantsPE (Mar 27, 2009)

Can someone please share some information on power factor correction capacitors and some of the effects of using them on motors. Will the current at the motor terminals decrease? Will the voltage increase??

Thank You


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## niurou (Mar 27, 2009)

the Cap will provider some reactive power / current to the motor, hence the reactive and apparent power drawn from the power source will be less.

at the motor terminals, current is unchanged. voltage also unchanged.

NCEES sample questions #130 is a good example.



WantsPE said:


> Can someone please share some information on power factor correction capacitors and some of the effects of using them on motors. Will the current at the motor terminals decrease? Will the voltage increase??
> Thank You


arty-smiley-048:


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## WantsPE (Mar 28, 2009)

Thanks for the response. I don't understand why the voltage won't increase. Isn't one of the advantages of power factor correction caps to reduce voltage drop? Meaning voltage is increased?


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## niurou (Mar 28, 2009)

WantsPE said:


> Thanks for the response. I don't understand why the voltage won't increase. Isn't one of the advantages of power factor correction caps to reduce voltage drop? Meaning voltage is increased?




In your original post, you didn't mention the feeder, so I didn't count this part in.

but you are right ,the voltage is different if you add the capacitor.

I think this voltage change is usually negligible. since feeder cable is usually chosen to make VD lower than 5%, typically the improved power factor may reduce the apparent current from power source by 25%(say .8 pf improved to 1.0 pf). Translated to VD is 5%x25%=1.25%(assume the feeder has no Reactance). so there is only approximately 1% voltage increased on the motor terminal.

it really depends on the impedance of the feeder, and how much apparent current is reduced.


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