LED, DRIVERS & ELECTRICAL
Power factor is real power (watts) divided by apparent power (volt-amps). Enter both to find the power factor, reactive power, and phase angle of an LED driver or other load.
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Power factor
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Reactive power (VAR)
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Phase angle
Power factor = watts divided by volt-amps. Reactive power = square root of (VA squared minus W squared).
How it works
Apparent power (VA) is the total the supply must deliver; real power (W) is what does useful work. Their ratio is the power factor, from 0 to 1. The gap shows up as reactive power, which loads the wiring without doing work. A low power factor means more current for the same watts, which matters for circuit and breaker sizing.
Driver power factor. Quality LED drivers run a power factor of 0.9 or higher. Cheap drivers can drop to 0.5, drawing nearly double the current their wattage implies.
See the Power Formula and the LED Driver Calculator.
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