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ELECTRICAL TERMSRAPID TABLES
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Power Factor
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..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 in volt·amps (VA).
Power factor calculations
The power factor is also equal to the resistance R in ohms (Ω) divided by the impedance Z in ohms (Ω):
PF = R(Ω) / Z(Ω)
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|
The resistance R in ohms (Ω) is equal to the impedance Z in ohms (Ω) times the power factor PF:
R(Ω) = Z(Ω) × PF = Z(Ω) × |cos φ|
Power factor correction
Power factor correction is an adjustment of the electrical circuit in order to change the power factor to 1.
When PF=1, φ=0º and the reactive power Q=0, the efficiency of the circuit is optimal since all the supplied power is used for work on the load.
The power factor correction is usually done by adding capacitors to the load circuit, since the circuit has inductive components, like electric motor.
See also
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