Under Basic Electrical Engineering

Lesson No 1:

Electric Power Single and Three Phase Power Active Reactive Apparent

Under Basic Electrical Engineering

Complex Power, Single Phase Power, Resistance, Inductance, Capacitance, Active Power and Reactive Power Active Power, Resistive Power, Reactive Power, Inductive Power, Capacitive Power, Active Component and Reactive Component, Three Phase Power Definition, Advantages of Three Phase System, Three Phase Power Equation, Use of Reactive Power • In Transmission Lines • Compensation

Complex Power

It is very conceptual and essential to understand. For establishing the expression of complex power, we have to first consider a single phase network that's voltage and current can be represented in complex form as V.e^jα and I.e^jβ. Where α and β are angles that voltage vector and current vector subtend with respect to some reference axis respectively. 

The active power and reactive power can be calculated by finding the product of voltage to conjugate of current.

That means, This (α − β) is nothing but the angle between voltage and current, hence that is phase difference between voltage and current which is normally denoted as φ.

Therefore the above equation cab be re-written as, Where P = VIcosφ and Q = VIsinφ.

This quantity S is called the complex power.

The magnitude of complex power i.e. |S| = (P² + Q²)^½ is known as the apparent power and its unit is volt-ampere. This quantity is a product of absolute value of voltage and current. Again absolute value of current is directly related to heating effect as per Joule's law of heating. Hence, rating of an electrical machine is normally determined by its apparent power carrying capability within allowable temperature limit.