Accurate Power Factor Correction: Capacitor Bank Calculator (kVAR & µF)

How to Calculate the Capacitor Bank in kVAR & Microfarad for Power Factor Improvement? Calculator & Example

Capacitor Bank Calculator

The following Power factor improvement calculator will calculate the required capacitor bank value in kVAR reactive power “Q” and Microfarad “µF”. The power factor correction capacitor must be connected in parallel with each phase load. In addition, both kVAR and μ-farad are terms used in capacitor banks and power factor improvement & correction to eliminate the reactive components from the load side which has multiple advantages.

• Related Calculator: Power Factor Correction Calculator – How to Find P.F Capacitor in µF & kVAR?

To calculate the value of capacitance of a capacitor bank in kVAR and µF , just enter the values of real or active power in kW, existing power factor and targeted power factor “P.F needs to be corrected” and hit the “Calculate” button to the get the result of capacitance of a capacitor bank in μF and kVAR.

The value of voltage in volts, and frequency in Hz (50 or 60Hz) is optional in case if you only want to calculate the kVAR rating of capacitor bank. If you need to calculate the value of capacitor bank in microfarad, you must enter the known value of frequency and voltage.

Related Calculators:

• kVAR to Farad Calculator – How to Convert kVAR to μ-Farads?
• μ-Farad to kVAR Calculator – How to Convert Farads to kVAR?

Capacitor Bank in kVAR & µF Calculation Formula

Capacitor Bank in kVAR

The following formulas can be used to calculate the required capacitor bank in kVAR for power factor improvement.

Required Capacitor Bank in kVAR = P in kW (Tan θ₁ – Tan θ₂)

Also

• kVAR = C x f x V² ÷ (159.155 x 10⁶)      …     in kVAR
• kVAR = C x 2πx f x V² x 10^-9     …     in kVAR

Where:

• kVAR = Required volt-ampere-reactive in kilo.
• C = Capacitance value of capacitor in µF
• f = frequency in Hertz “Hz”
• V = Voltage in volts
• θ₁ = Cos^-1 = Existing power factor
• θ₂ = Cos^-1 = Target or desired power factor “which is needed to be corrected”.

Capacitor Bank in Microfarad “µF”

The following formulas can be used to calculate the required capacitor bank in µF for power factor correction.

Required Capacitor Bank in µF = kVAR x 10⁹ ÷ (2π x f x V²)

Also

• C = 159.155 x 10⁶x Q in kVAR ÷ f x V²     …     in microfarad
• C = kVAR x 10⁹ ÷ (2πx f x V²)     …     in microfarad

Where:

• C = Capacitance value of capacitor in µF
• kVAR = Required volt-ampere-reactive in kilo.
• f = frequency in Hz
• V = Voltage in volts

Good to know:

The following are useful formulas and equation while calculating the power factor, active power, reactive power and apparent power.

• Power Factor = Cosθ = Active Power/ Apparent Power
• P.F = Cosθ = kW / kVA
• kW = √ (kVA² – kVAR²)
• kVA = √ (kW² + kVAR²)
• kVAR = √ (kVA² – kW²)

Where:

• kW     = Active Power       = P = V x I x Cosθ
• kVAR = Reactive Power   = Q = V x I x Sinθ
• kVA    = Apparent Power  = S = V x I

How to Calculate the Capacitor Bank in kVAR & µF for P.F Correction

The following example shows how to calculate the required correction capacitor bank rating in microfarad and kVAR. You may compare the result of the solved example with the power factor calculator results.

Example 1:

A Single phase 480V, 60Hz, motor takes a supply current of 55.5A at a power factor “p.f” of 0.60. The motor power factor has to be corrected to 0.98 by connecting a capacitor in parallel with it. Calculate the required capacity of Capacitor both in kVAR and µF.

Solution:

Load in kW = P = V x I x Cosθ₁

P = 480V x 55.5A x 0.60

P = 16 kW

Required Capacitor Bank in kVAR

Required Capacitor kVAR = P in kW (Tan θ₁ – Tan θ₂)

θ₁ = Cos^-1 = (0.60) = 53°.130; Tan θ₁ = Tan (53°.130) = 1.333

θ₂ = Cos^-1 = (0.98) = 11°.478; Tan θ₂ = Tan (11°.478) = 0.203

kVAR = 16kW x (1.333 – 0.203)

VAR = 1808 VAR

Required kVAR = 18.08 kVAR

Required Capacitor Bank in µF

C = kVAR x 10⁹ ÷ (2π x f x V²)     …     in microfarad

C = 18.08 kVAR x 10⁹ ÷ (2π x 60Hz x 480² V)

C = 208.2 µF

Example 2:

A factory have a load of 300kW at 0.6 P.F. If they need to improve the power factor from 0.65 to 0.97, find the value of capacitor bank in kVAR and microfarad they need to install in parallel with the load phases.

Solution:

Given data:

• Active load = 300kW
• Existing Power Factor Cosθ₁ = 0.65
• Target Power Factor Cosθ₂ = 0.97

Required Capacitor bank in kVAR = P in kW x Tan (Cos^-1(θ₁) – Cos^-1(θ₂))

kVAR = 300kW x Tan (Cos^-1(0.65) – Cos^-1(0.97))

kVAR = 300kW x x Tan (49°.458 – 14°.069)

kVAR = 300kW x (1.169 – 0.250)

kVAR = 275.7 kVAR

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