Difference between Active and Reactive Power (Active vs Reactive)

The most important difference between active and reactive power is that Active Power is a real power that is used in the circuit while Reactive power bounces back and forth between load and source.

Before comparing the Active and Reactive power, I want to explain active and reactive power. So let see the introduction of Active, Reactive power.

Active power:

Active power is also called actual power, real power, or working power. It is the power that actually powers the equipment and performs useful work. It is measured in kilowatt (kW) or MW.

Reactive Power:

Reactive Power is the power that magnetic equipment (transformer, motor, and relay) needs to produce the magnetizing flux. It flows back and forth which means it moves in both the directions in the circuit.

The reactive energy produces an overload in lines, transformers, and generators, without producing a useful performance. However, it’s recorded in the bill, so it can considerably increase the total amount to pay. The reactive power is measured in kilo volt-ampere reactive (kVAR) or MVAR.

Let see the power triangle to understand the relationship between active, reactive, and apparent power.

Active, Reactive and Apparent Power

In the mentioned image you can see that the complex power is the vector sum of active and reactive power. The apparent power is the magnitude of the complex power. let see the terminology which has been used In image,

  • P => Active power
  • Q => Reactive power
  • S => Complex power
  • |S| => Apparent power
  • φ => Phase of voltage relative to current

Therefore, the following expression shown below gives the active, reactive, and apparent power respectively.

  • Active power P = V x I cosϕ = V I cosϕ
  • Reactive power Pr or Q = V x I sinϕ = V I sinϕ
  • Complex power S = P + jQ
  • Apparent power = |S| = √P² + Q²

 

Now I think we can see the difference between Active and Reactive power using a chart.

Basis for Comparison

Active Power

Reactive Power
Definition The active power is the real power that is dissipated in the circuit. The power which moves back and forth between the load and source such type of power is known as the reactive power
Formula P = V x I cosϕ = V I cosϕ Q = V x I sinϕ = V I sinϕ
Measuring Unit Watts,  kW, MW VAr,  kVAr, MVAr
Represented By P Q
Causes Produces heat in a heater, light in lamps, and torque in the motor. Measures the power factor of the circuit.
Measuring Instrument Wattmeter VAR Meter

 

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