Can anyone provide a mathematical expression that i can use for a given value of Var to provide a capacitor value in Microfarads?

I want the new expression so that i only have to change the Var rating to find out an equivalant capacitor size.

 

Responding to Martin's query:

The formula(s) you seek can be found in the List Archive under "APPS: HT Capacitor Bank Failure"!

Regards,
Phil Corso, PE
Boca Raton, FL
[[email protected]] ([email protected]) {[email protected]}

 

Power Factor (pf) is the ratio of real power to total power. Real, or productive power, is the actual power used in a building, measured in kilowatts (kW). Reactive power generates the magnetic field for inductive loads such as motors, transformers, lighting ballasts, etc. Reactive power is measured in kilovars (kVAR). Total power (measured in kVA) is a combination of real power and reactive power.

The basic formula for Power Factor is the mathematical ratio of real power to total power. This ratio is an effective measure of system electrical efficiency and is represented as a percentage or decimal (e.g., 90% or 0.9).

Power Factor = PF = KW (REAL POWER)
KVA (TOTAL POWER)

 

Martin,

I apologize for sending you on a wild-goose chase. The Aug '99 post referencing the formula(s) is no longer available in the Archives. So, here it is again:

Given a 3-phase system in which the total capacitive reactive power is kVARc, and line-to-line voltage is kV, then 3 capacitors are used. They can be delta-connected, or wye-connected.

A) Delta Arrangement.
Letting Cd equal one of the line-to-line connected capacitors, then its capacitance (in microfarads) equals,

Eq 1) Cd = (kVARc x 10^3) / (3 x 2 x pi x f x kV^2 )

B) Wye (Star) Arrangement.
Letting Cy equal one of the line-to-midpoint connected capacitors, then its capacitance (in microfarads) equals,

Eq 2) Cy = 3 x Cd.

For a single-phase system use Eq 1, but delete the 3 in the denominator.

Regards,
Phil Corso, PE
Boca Raton, FL
[[email protected]] ([email protected]) {[email protected]}

 

Phil,

Thank you for your information on power factor mathematical equation.

regards
martin