Power factor

Power factor is the ratio of real power to apparent power in an AC circuit. It measures how effectively electrical power is converted into useful work.

Real power: The average rate at which an electrical circuit transfers energy to useful work or heat. It forms the numerator of power factor.
Power factor correction: Techniques that reduce reactive power demand and improve an AC system’s power factor. It is the direct remedy when a system draws excess current for its real-power load.
Alternating current: Electric current that periodically reverses direction, usually with voltage varying in step. Power factor describes energy use in circuits supplied by this kind of current.
Copper loss: Resistive heating loss in conductors and windings caused by electric current. For fixed real power and voltage, low power factor raises current and increases these losses.
Apparent power: The product of root-mean-square voltage and current, measured in volt-amperes. It forms the denominator of power factor.
Power factor capacitor: A capacitor installed in an AC system to offset inductive reactive power demand. Capacitors supply leading reactive power to counter lagging loads.
Root mean square: A measure of a varying quantity equal to the square root of the mean of its squared values. RMS voltage and current define apparent power in AC circuits.
Voltage drop: The reduction in electrical potential between two points as current flows through circuit impedance. Higher current associated with low power factor can increase drop along a feeder.
Reactive power: The oscillating exchange of energy between an AC source and reactive circuit elements, measured in vars. It accounts for current that contributes to apparent power without adding average real power.
Synchronous condenser: An unloaded synchronous motor operated to supply or absorb reactive power in an electrical grid. Its adjustable reactive output can improve power factor at large installations.

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