The kvar of capacitor will not be same if voltage applied to the capacitor and frequency changes. The example given below shows how to calculate capacitor power in kvar from the measured values at site and name plate details.

Qm =( fm / fn ) × ( Um / Un )2 × Qn
Un = Rated Voltage
fn = Rated Frequency
Qn = Rated power
Um = Measured voltage
fm= Measured frequency
Qm = Available power in kvar

Example: 1.
Name plate details – 15kvar, 3 phases, 440V, 50Hz capacitor.
Measured voltage - 425V
Measured frequency - 48.5Hz

Qm =( fm / fn ) × ( Um / Un )2 × Qn
Qm = (48.5/50) × (425 / 440 )2 × 15 = 13.57kvar

Released for: Schneider Electric India