ACTIVE,REACTIVE,APPARENT AND COMPLEX POWER

REAL POWER: 

Real Power is the actual power which is really transferred to the load such as motors,transformers etc.,

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 powe 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.

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

Reactive Power: (Q) 

It is also  known as (Use-less Power, Watt less Power)

Power merely absorbed and returned in load due to its reactive properties is referred to as reactive power. denoted by Q

Reactive power represent that the energy is first stored and then released in the form of magnetic field or electrostatic field in case of inductor and capacitor respectively.

Reactive power is given by Q = V I Sinθ which can be positive (+ve) for inductive loads and negative (-Ve) for capacitive load.

The unit of reactive power is Volt-Ampere reactive i.e. VAR where 1 VAR = 1V x 1A.

In Inductor or Capacitor, how much magnetic or electric field made by 1A x 1V is called the unit of reactive power.

Apparent Power: (S)

The combination of reactive power and true power is called apparent power

In an AC circuit, the product of the r.m.s voltage and the r.m.s current is called apparent power which is denoted by (S) and measured in units of Volt-amp (VA).

S=V*I

It is the product of Voltage and Current without phase angle.

The unit of Apparent power (S) VA i.e. 1VA = 1V x 1A.

When the circuit is pure resistive, then apparent power is equal to real or true power, but in inductive or capacitive circuit, (when Reactances exist) then apparent power is greater than real or true power.

Complex Power: (S )

The Complex sum of Real Power (P) and Reactive Power (Q) is known as Complex Power which can be expressed like S = P+jQ and measured in terms of Volt Amps Reactive (generally in kVAR).

It may also be expressed as S=VI* where I* is the conjugate of the complex current I. This current “I” flows through a reactive load Z caused by the Voltage.

Categories: CIRCUIT THEORY