A three-phase, 12 kV, 50 Hz and 300 kW load is operating at 0.8 pf lag. If the pf is to be improved to unity, using star connected capacitor, the per phase value of the reactive VAR required is:

• A. 50 kVAR
• B. 75 kVAR
• C. 25 kVAR
• D. 100 kVAR

Answer: (B)

The reactive VAR required = kW*(tanφ1 -tanφ2)
Cosφ1 = 0.8
φ1 = 36.87 deg.
Cosφ2 = 0
φ2 = 0 deg.
kVAR required = kW*(tan(36.87) - tan(0))
= 300*1000(0.75)
= 225.00 kVAR
Per phase value = 225.00/3
= 75 kVAR