What Is Complex Power? Active, Reactive, and Apparent Power Explained

In AC electrical systems, phase-shifting between voltage and current introduces the concept of complex power, which has active power, reactive power, and apparent power as its components. Understanding complex power is fundamentally important for AC electrical system analysis, operation, and control.

In this video you will learn:
- The relationship between voltage and current in resistors, inductors, and capacitors
- What instantaneous power looks like in resistors, inductors, and capacitors
- How to use vector representations of voltage and current to calculate complex power
- How complex power is separated into active power, reactive power, and apparent power
- How power factor gives insight into system efficiency

Learn more:

[zuhairalsaffar]

Sir, how could one thank you for your help and support us to understand and overcome that difficult subject 🎉❤😊

[windward]

In the USA NEC the convention is to always use RMS values for steady state AC current and voltage. Also, in the USA the real part of complex power is called Average power (and many times called Real power) we don't use the word active power.

When given a power factor (pf) you have to know the type of reactive VARs. So for inductive pf we use the prefix lagging (current lagging voltage) and for capacitive pf we use leading (current leading voltage). So, to correct pf you often will see the addition of leading VARs (capacitors).

To take the conjugate of phasor current in polar form all that is needed is to change the numeric sign of the angle. The use of RMS values will reduce the divide by two seen when using peak values which is another type of useful mathematical simplification.

So, in reality we have two beneficial techniques from Mr. Steinmetz, the AC phasor transform (which is really an application of Euler's identity) and the RMS equivalence (which is described as the effective value, equivalent heating in a purely resistive load). With the understanding that the techniques are used for steady-state AC.

Given this we see that instantaneous power occurs at twice the line frequency, which is how energy (power) can move in an RLC circuit between the source and the load with a pf less than one in one cycle. I should stress that the complex power strictly relies on the use of pure sine waves. If the source is not a pure sine wave (the sine wave is distorted) then we can have differences in actual losses. Also, steady-state AC is not derived from switching on an AC source. It is a mathematical concept which assumes the effects are beyond any transient (power first applied) effects. Like transformer magnetization current.

[DrJALAGHARI]

Very well explanation of the most confused terms in electrical engineering.