Different forms of Electrical Power-

Active power, reactive power & Apparent power are different forms of electrical power & they come into picture when electrical power is applied to an inductive load. This happens due to power factor.

First let’s understand the meaning of these different powers –

Active Power –

Active power is the power which is actually utilized by the load. It is denoted by Watts or KW.

Reactive Power –

Reactive power is the power which is not utilized (or wastage) by the load but is added in the power consumption by the load. It is denoted by VAr or KVAR.

Apparent Power –

Apparent power is the power which is given to the load that includes both active & reactive power. It is denoted by VA or KVA.

The above picture is a glass of liquid with foam (it could be any cold drink) where liquid is the main drink which is to be consumed & foam is not the actual drink but it is occupying the space & makes the glass full. Now if we compare it with power applied to an inductive load where liquid represents active power, foam represents reactive power & full glass (liquid+foam) represents apparent power.

Hence, we can say in terms of electrical power that reactive power is the wastage of power which is not being used by the load but is a part of full power (Apparent power) which is applied to the load. Therefore, it is very important to avoid reactive power in the system. But, practically it is not possible in case of inductive loads, therefore, reactive power could be avoided by improving power factor.

Technically this could be explained further by phasor diagram given below. There is a relation between active, reactive & apparent power which is given below –

Note – For leading current, the power triangle become reversed. This characteristic of current helps to improve the power factor.When a leading power factor device is connected in parallel with load, the lagging power factor partially neutralized, thus power factor is improved.

Active, Reactive & Apparent in power in AC & DC circuit –

Power in DC Circuit –

In DC circuit, there is only one type of power utilized by the load as there is no concept of power factor (or phase difference between volage & current). Power in DC circuit is given below-

P = V * I (Where P = Active /Real .. power, V = Voltage, I = Current). Power is measured in Watts (or W)

Power in AC Circuit –

In AC circuit because of power factor – active power, reactive power, apparent power come into picture.

Active Power –

P = V * I CosØ ……Single phase power

P = Г3 * V * I CosØ ……Three phase power

(Where P = Active /Real .. power, V = Line Voltage, I = Line Current, CosØ = Power factor). Power is measured in Watts (or W)

Reactive Power –

Q = V * I SinØ ……Single phase power

Q = Г3 * V * I SinØ ……Three phase power

(Where Q = Reactive power, V = Line Voltage, I = Line Current, SineØ = phase difference between voltage & current). Power is measured in VAr (or Volt-Ampere reactive)

Apparent Power –

It is a total power (including both active & reactive power) whose formula is given below –

S = V * I ………….. Single phase power

S =  Г3 * V * I  ………. Three phase power

(Where S = Apparent power, V = Line Voltage, I = Line Current. Power is measured in VA (or Volt-Ampere).

Frequently Asked Questions (FAQs) on Active Power, Reactive Power & Apparent Power –

Q1) What is the difference between Active Power & Reactive Power?

Ans) Active power is the power which is actually utilized by the load while reactive power is the waste power (not used by the load due to inductive load).

Q2) What is alternate words used for Reactive power?

Ans) Alternate words of reactive power are watt-less power, waste power, Use-less power.

Q3) What is alternate words used for Active power?

Ans) Alternate words of reactive power are Real power, True power, Watt-full power, Use full power.