Basic AC Power
AC power relationships are summarized below.
AC Power Relationships Summary
Observe the equations for apparent, true, and reactive power, and power
Apparent power (S) = I2Z = ITE
True power (P) = I2R = EI cosq
Reactive power (Q) = I2X = EI sinq
Power factor (pf) =
From observation, you can see that three power equations have the angle q in
common. q is the angle between voltage and current. From this relationship,
a power triangle, as shown in Figure 1, is formed.
ELI the ICE man is a mnemonic device that describes the reactive
characteristics of an AC circuit.
Current (I) lags voltage (E) in an inductive circuit (L)
Current (I) leads voltage (E) in a capacitive circuit (C)