Calculation formula for the capacitor

Calculation formula for the capacitor

Capacitor output single-phase

Example: 66.5 μF with 400 V / 50 Hz
0.0000665 · 4002 · 2 · 3.14 · 50 = 3,340 var = 3.34 kvar

Capacitor output with delta connection

Example: 3 x 57 μF with 480 V / 50 Hz
3 · 0.000057 · 4802 · 2 · 3.14 · 50 = 12,371 var = 12.37 kvar

Capacitor output with star connection

Example: 3 x 33.2 μF with 400V / 50 Hz
3 · 0.0000332 · (400 / 1.73)2 · 2 · 3.14 · 50 = 1670 var = 1.67 kvar

Capacitor current in the phase conductor

Example: 25 kvar with 400 V
25,000 / (400 · 1.73) = 36 A

Example: p = 0.07 (7 % de-tuning) in the 50-Hz network

Which capacitor should be used for this?
This means, for a 50-kvar stage, a 440-V-56-kvar capacitor is required.

Power factor and cos and tan conversion

Conversion of the capacitor power subject of the mains voltage

Determination of the reactive power Qnew · C is constant here.

Example:

Network: 400 V, 50 Hz, 3-phase
Nominal capacitor data: 480 V, 70 kvar, 60 Hz, 3-phase, delta, un-choked
Question: Resultant nominal capacitor power?

The resultant correction power of this 480-V capacitor connected to a 400-V-50-Hz network is just 40.5 kvar.

Definition

QC Nominal capacitor power
P Degree of de-tuning
UC Capacitor voltage
UN Nominal voltage
NC Effective filter output
Qnew New reactive power
Unew New voltage
fnew New frequency
fR Nominal frequency of the capacitor

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