Active Power – Formula, Definition, and Explanation

The term active power is related to AC power systems and it defined as the average power delivered from a source to a load. It is also known as real power or average power.

The active power is the amount of electric power in an AC electric circuit that is actually consumed or utilized.

Active power is measured in Watts (W). For larger quantities prefixes kilo, mega and giga are used for kilowatts (kW), mega-watts (MW), and gigawatts (GW).

Active power is symbolized using P.

Active Power in case of Purely resistive loads

In case of a simple alternating current (AC) circuit comprising of a source and a linear time-invariant load, both the current and voltage are sinusoidal at the same frequency.

If the connected load is purely resistive, both current and voltage reverse their polarity at the same time and for all instants the product of voltage and current is either positive or zero. As a result the direction of energy flow does not reverse and for such case, only active power is transferred.

Active Power Formulas

In case of DC CircuitsP = V x I
in Single phase AC CircuitsP = V x I x Cosθ
in Three Phase AC Circuits (Line to Line)P = √3 x VLx IL x Cosθ
in Three Phase AC Circuits (Phase to Phase)P = 3 x VPh x IPhx Cosθ
In terms of complex and reactive powerP = √ (S2 – Q2)or P =√ (VA2 – VAR2)

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