PowerLogic™ PM5500 / PM5600 / PM5700 series – User manual PDF
HRB1684301-18

Real, reactive, and apparent power (PQS)

A typical AC electrical system load has both resistive and reactive (inductive or capacitive) components.

Real power, also known as active power (P) is consumed by resistive loads. Reactive power (Q) is either consumed by inductive loads or generated by capacitive loads.

Apparent power (S) is the capacity of your measured power system to provide real and reactive power.

The units for power are watts (W or kW) for real power P, vars (VAR or kVAR) for reactive power Q, and volt-amps (VA or kVA) for apparent power S.

The image illustrates the four quadrants of power factor sign conventions, showing how active power (W) and reactive power (VAR) interact under different conditions. Each quadrant represents a unique combination of power flow and power factor behavior. Quadrants 1 and 3 correspond to lagging power factor conditions, while Quadrants 2 and 4 represent leading power factor conditions. The diagram also compares IEEE and IEC sign conventions: IEEE uses positive signs for Quadrants 1 and 2, and negative signs for Quadrants 3 and 4; IEC uses the opposite. Arrows indicate the direction of active and reactive power, and labels identify apparent power (VA) and active power (W).

Power flow

Positive real power P(+) flows from the power source to the load. Negative real power P(-) flows from the load to the power source.

QR Code is a registered trademark of DENSO WAVE INCORPORATED in Japan and other countries.

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