HOW TO CALCULATE KVAR CAPACITY FOR CAPACITOR IN CASE OF POWER FCTOR IMPROVEMENT

HOW TO CALCULATE KVAR CAPACITY FOR CAPACITOR IN CASE OF POWER FCTOR IMPROVEMENT

5 KW 3 phase induction motor has a power factor of 0.7 lagging. A bank of capacitors is connected in delta across the supply terminals and power factor raised to 0.9 lagging. 

Determined the of its capacitors rating connected in each phase.

A given data

power=5KW
COSΘ1=0.7
COSΘ2=0.9

WE HAVE THE EQUATION

KVAR=P(TANΘ1- TANΘ2) ........ equation 1

FIND

 cos^-1 (0.7) = 45.57

 cos^-1 (0.9) = 25.84

TANΘ1=TAN(45.57)

TANΘ1=1.020

TANθ2=TAN(25.84)

TANθ2=0.49

put this value in the equation 1

KVAR =5(1.020-0.49)

KVAR =2.65 KVAR

KVAR =2.65/3

= 0.88 rating capacitor connected in each phase to raised the power factor from 0.7 to 0.9