WHAT IS REAL POWER IN ELECTRIC ENGINEERING

What Is Real Power?

Real Power: (P)

Real Power is the actual power which is really transferred to the load such as transformer, induction motors, generators etc. and dissipated in the circuit.

Alternative words used for Real Power (Actual Power, True Power, Watt-full Power, Useful Power, Real Power, and Active Power) and denoted by (P) and measured in units of Watts (W) 

i.e. The unit of Active or Real power is Watt where 1W = 1V x 1 A

Real Power in DC Circuits:

In DC Circuits, power supply to the DC load is simply the product of Voltage across the load and Current flowing through it.

i.e., P = V I because in DC Circuits, there is no concept of phase angle between current and voltage.

In other words, there is no frequency (f) or Power factor in DC Circuits.

Real Power in AC Circuits:

But the situation in Sinusoidal or AC Circuits is more complex because of phase difference (θ) between Current and Voltage. 

Therefore average value of power (Real Power) is P = VI Cosθ is in fact supplied to the load.

In AC circuits, When circuit is pure resistive, then the same formula used for power as used in DC as P = VI

Real Power Formulas:

• P = V I  (In DC circuits)

• P = VI Cosθ    (in Single phase AC Circuits)

• P = √3 VL IL Cosθ   or       (in Three Phase AC Circuits)
• P = 3 VPh IPh Cosθ

• P = √ (S2 – Q2) or

• P =√ (VA2 – VAR2) or

Real or True power = √ (Apparent Power2– Reactive Power2)
 or
• kW = √ (kVA2 – kVAR2)

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