In AC circuits, the power factor is the ratio of the real power that is used to do work and the apparent power that is supplied to the circuit. The power factor can get values in the range of 0 to 1.
Power factor definition
The power factor is equal to the real or true power P in watts (W) divided by the apparent power |S| in volt-ampere (VA):
PF = P(W) / |S(VA)|
PF - power factor.P - real power in watts (W).
|S| - apparent power - the magnitude of the complex power in volt·amps (VA).
Power factor calculations
The power factor PF is equal to the absolute value of the cosine of the apparent power phase angle φ (which is also is impedance phase angle):
PF = |cos φ|
PF is the power factor.φ is the apprent power phase angle.
The real power P in watts (W) is equal to the apparent power |S| in volt-ampere (VA) times the power factor PF:
P(W) = |S(VA)| × PF =
|S(VA)| × |cos φ|
When the circuit has a resistive impedance load, the real power P is equal to the apparent power |S| and the power factor PF is equal to 1:
PF(resistive load) = P
/ |S| = 1
The reactive power Q in volt-amps reactive (VAR) is equal to the apparent power |S| in volt-ampere (VA) times the sine of the phase angle φ:
Q(VAR) = |S(VA)|
× |sin φ|
Power factor correction
Power factor correction is an adjustment of the electrical circuit in order to change the power factor near 1. This will reduce the reactive power in the circuit and most of the power in the circuit will be real power. The power factor correction is usually done by adding capacitors to the load circuit, when the circuit has inductive components, like an electric motor.Electric power ►
See also
- Power factor calculator
- Power calculator
- Amps to kW calculator
- Amps to kVA calculator
- Electric power
- Efficiency
- Electrical voltage
- Electrical current
- Electric charge
- Watt
- Power conversion
- Ohm's law
- Electrical calculators
- Electrical calculations
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