Sizing Power Factor Capacitors on 3 phase motors? 1

[william76123]

I have been looking for the best way for calculating the
KVAR required for reaching .95 Power Factor on my three
phase motors. The information I have on one example =
52 KWatts
39 KVAR
65 KVA
80 PF
Any help would be appreciated.

 

[RalphChristie]

http://www.lmphotonics.com/pwrfact.htm

http://home.earthlink.net/~jimlux/hv/pfc.htm

 

[ladengr]

Here is a calculation procedure:

KVAR= KW( tan(phi1)- tan(phi2))
where KW= 59
tan(phi1)= 0.75 calculated from powerfactor =0.8

tan(phi2)= 0.33 caluclated from powerfactor = 0.9

KVAR= 59(.75-.33)=59*0.42= 21.84
USE 20KVAR capacitor.

Also you need to make sure you match the capacitor size with motor RPM and also may consider switching the capacitor off when the motor is turned off.