Power Factor: The ratio of the total power in watts (resistive load) to the total apparent power in voltamperes (VA) (reactive load). The difference between watts and VA is due to reactive load impedance. Apparent power equals watts only for a purely resistive load (i.e., zero degrees phase shift between the applied voltage and the resultant current). Power factor is best thought of intuitively as the multiplier (ranging between 0 and 1) that you must use to obtain the real power from the apparent power. For example if the rms voltage and current of a circuit is measured and multiplied together, the apparent power is obtained, but this value must be multiplied by the power factor to obtain the real power. If the load is purely resistive then the phase difference between the voltage and current will be zero and the power factor will be one, and the apparent power will equal the true power -- but only for a resistive load. For a reactive load (any load with inductive and/or capacitive reactance, i.e., any real world load) there will be a phase difference between the voltage and the current due to the phase delay introduced by the reactive elements. Simply put, since the maximum voltage and current do not occur at the same instant of time the amount of power developed is less than the measured rms voltage and current multiplied together.

 

Related Words

Power Factor: The ratio of the total power in watts (resistive load) to the total apparent power in voltamperes (VA) (reactive load). The difference between watts and VA is due to reactive load impedance. . . . View Full Definition

Average Power: The result of multiplying the rms value of the voltage by the rms value of the current in an electronic circuit. It is expressed in watts (W) for resistive loads and in voltamperes (VA) for . . . View Full Definition

Apparent Power: The result of multiplying the rms value of the voltage by the rms value of the current in an electronic circuit. It is expressed in watts (W) for resistive loads and in voltamperes (VA) for . . . View Full Definition

Power Spectrum: intensity [= squared amplitude] of the Fourier transform, presented either in the form of an image (= the outcome of the PW operation) or as a profile (= the outcome of averaging the 2D powe . . . View Full Definition