how to calculate capacitor values

KVAR of the Capacitance needed to be added in the circuit = kW ( tanΦ1 -tan Φ2)

Cos Φ1 the present Power factor of the system

Cos Φ2 The Value of the required Power factor improvement

Calculation of Required Power Factor

The reactive power which is necessary to achieve a desired power factor is calculated by the following formula:

Q_C = P • F
Q_C - Reactive power of the required correcting capacitor
P - Active power of the load to be corrected
F - Conversion factor according to chart

For Example

a.Consumption of active energy: ………E_W = 300000kWh

b.Consumption of reactive energy: ………E_B = 400000 kvarh
c.Number of working hours: …………t = 600 h

Resulting average active power:

P =

= 500kW

Calculation of the original power factor cosφ₁:

cosφ 1=

For the improvement of the power factor from 0.6 to 0.9 we read the factor 0.849 from the chart above.

The required capacitor power is: QC = 500kW•0.849 = 425 kvar

To Calculate Capacitors capacitance, Formulae are as under:

Xc= 1/(2*3.142857*fC)

Xc=(Kv²)* 1000/Kvar

C=(Kvar*1000)/((2*3.142857*f)*(Kv²))

Kvar=1000*(Kv²)/Xc

Where

f = Frequency

C = Capacitance

Xc = Capacitive reactance

Kvar = Kilo Reactive Power

Kv = Kilo volts

Its Very simple.

Required capacitance value is KVAr= KVA*SinPhi = KVA ( Sin ( Cos inv. ( Power facror) )

OK?

Another modified way of calculating the Capacitor rating

1. Capacitor Rating Required (KVAr) = KW x M.F.

2. M.F. = tan (phi -1) - tan(phi-2)

Where as cos(phi -1) is present p.f. & cos(phi-2) is desired p.f.