A balanced delta connected load of 8+j6 Ω per phase is connected to a 415 V, 50 Hz, 3-phase supply lines. If the input power factor is improved to 0.9 by connecting a star connected capacitor bank, then the required kVAR of the bank is

• A. 10.98 kVAR
• B. 8.98 kVAR
• C. 16.98 kVAR
• D. 14.98 kVAR

Answer: (A)

Current flow through the circuit,
I = V/Z
= 400/10
= 41.5 A
Power factor = 8/10
= 0.8
After connecting a capacitor bank, the reactive power component of current changes but the active power component of current is unchanged.
I1*cosφ1 = I2*cosφ2
41.5*0.8 = I2*0.9
I2 = 36.88 A
Q1 (before connecting capacitor) = √3*VL*IL*sinφ1
= √3*415*41.5*sin(36.86)
= 26.847 kVAR
Q2 (after connecting capacitor) = √3*VL*IL*sinφ2
= √3*415*36.88*sin(25.84)
= 15.867 kVAR
kVAR supplied by capacitor bank = Q1 - Q2
= 26.847 - 15.867
= 10.98 kVAR