Medium Voltage Application Guide

13809.A
SWITCHGEAR
Calculations: fixed capacitor bank for individual motor
To calculate the fixed capacitor bank power (Q) required to improve the power factor of an individual motor:
U = 6.6 kV
Q (kVAr)
1
M
Q
2
P (kW)
P = 1500 kW
= 0.96
pf 1 = 0.88 (initial power factor)
pf 2 = 0.95 (target power factor)
Q = (tan 1 tan 2 )
Where:
Q = capacitor bank power (kVAr)
P = motor shaft power (kW)
= motor efficiency at full load
1 = phase angle of motor power factor at full load (=cos -1 x pf 1 )
2 = phase angle of target power factor at full load (=cos -1 x pf 2 )
Required power is 325 kVAr
Calculations: PFC capacitor bank
To calculate the capacitor value (C) and nominal current value (I nom ) for a power factor correction capacitor bank:
Capacitance
Where:
C = capacitance (µF)
U 2 (2 f)
Q = capacitor bank power (kVAr)
U = supply voltage (kV)
f = supply frequency (Hz)
Nominal current
710-12280-00A Medium Voltage Application Guide Page 137