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2 Different Types of Power in Electrical Circuit. [Explained with Formulas]

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I am writing the tutorial base on electric power which is useful everywhere. When we study, the first arises

  • What is Electric Power?
  • Which are the 2 types of Electric Power?

Let’s go to this tutorial,

What is Electric Power?

The basic definition of Power is ‘the rate of doing work’. It means,  work has consumed energy with respect to a particular time.

The formula of power (P) is represented as,

Power = (Work / Time) = (Energy / Time)

On the bases of the technical term, the basic definition of electric power is

The rate of electrical energy which consumed in an electrical circuit or electrical work.

And it also defines as,

The rate of electrical energy which transferred to the other forms of energy.

In the electrical circuit,  power consumes through connecting load or device. And also it converts into other forms like light energy, heat energy, motion energy, etc.

Electric power is denoted by the capital letter P.

The SI unit of the electric power is Watt (W) or Joule per sec (j/s) or Volt-ampere (VI). It can be measured in the watt (W), kilowatt (kW) or megawatt (MW) by the energy meter.

The equation of the electric power is,

P = (Workdone in an electric current / Time) = (Voltage * Current ) = [(Voltage* Charge)/ Time]

What are the types of Electric Power?

In the electrical system, power is classified into two types. This classification of electric power depends upon the nature of the flowing current.

The classification of electric power is,

  1. AC Power
  2. DC Power

Let’s see each type in detail,

1. AC Power

AC power is defined as the rate of flows of electrical energy in sinusoidal nature through an electrical circuit.

In the electrical circuit, this AC power is consumed by the connecting load to the circuit. It consumes in the resistive load, inductive load and capacitive load.

According to the nature of connecting load in the electrical circuit, AC power is classified into three parts.

  • Active Power
  • Reactive Power
  • Apparent Power

AC power is mostly used because it can easy to power step up and step down.

Calculation of AC Power:

Power = ( Voltage * Current ) or P(t) = ( V(t) * I(t) )

Where,

P(t) – AC power with respect to time (t)

V(t) – Voltage with respect to time (t)

I(t) – Current with respect to time (t)

In the AC circuit, both voltage and current sinusoidal in nature with respective time.

I. Active Power (P)

Active power also is known as Real Power or Actual Power or Watt full Power or True Power.

The power flows from sources to load in the circuit is called as Active Power. It flows in only one direction.

It is identified by the capital letter P. And It is expressed in Watt (W) or Kilowatt (kW) or Megawatt (MW).

Formula as,

Active power, P  = (Voltage * Current * Cos θ)

In the below circuit diagram, the AC source supply connected to the resistive load.  This resistive load resistor is absorbed Active power.

And it is dissipated in the form of heat energy or light energy.

Properties of Active Power:

  • It is always positive.
  • It does not change its direction.
  • Power flows always from sources to load.

II. Reactive Power (Q)

Reactive power also is known as Imaginary Power or Watt less Power or Useless Power .

The Power that continuously flows from source to load and from load to sources in the circuit is called Reactive power.

The Power taken by the reactance (capacitive & inductive) in the circuit is called Reactive Power.

It is identified by the capital letter Q. And It is expressed in Volt ampere reactive (VAR).

Formula,

Reactive Power, Q = (Voltage * Current * Sin θ)

In the below circuit diagram, the AC source supply connected to the inductive load. The main function of the inductive load absorbs reactive power.

Important Notes:

  • Inductor absorbs Reactive Power and dissipated in the form of the Magnetic field.
  • Capacitor absorbs Reactive Power and dissipated in the form of an Electrostatic field.

Properties for Reactive Power :

  • It has a positive and negative peak.
  • It is not used for useful work. Because Power merely absorbed and returned in load.

III. Apparent Power (S)

Apparent Power is the combination of Active power and Reactive power. In an AC circuit, the product of the RMS voltage and the RMS current is called Apparent Power.

It is identified by the capital letter S. And It is expressed in Volt Ampere (VA) or KiloVolt-Amp (kVA).

Represent as

Apparent Power, S = ( Voltage * Current )

According to the definition,

(Apparent Power)² = ((Active Power)² + (Reactive Power)²) or  (S²) = ( P² + Q² )

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

When the circuit is purely resistive, then apparent power is equal to active power. When resistance exists in the inductive or capacitive circuit, then apparent power is greater than active power.

2. DC Electric Power

DC power is defined as the rate of flows of electrical energy in an electrical circuit. This power is generated by the cell battery, etc.

In the electrical circuit, this power is consumed by the connecting load to the circuit. DC power consume in the resistive load.

Simply Represent as,

Power = (Voltage * Current)= ((Current)² * Resistance) = ((Voltage)²/Resistance)

In DC, if the circuit is purely resistive, voltage and current both are in the same phase. In this circuit, the Power factor is not occurring. Because there is no concept of the phase angle between voltage & current.

What is Power Factor?

The power factor is the ratio of the active power (P) to the apparent power (S). The cosine of the angle between voltage and current.

Power Factor is always expressed in percentage (%).

Power Factor Diagram

The power factor is also a measure of the phase angle (θ) between the voltage and
current.

The equation represents as,

Power Factor (PF) =[(Active Power)/(Apparant Power)] =( cosθ)

In an Inductive circuit, the power factor is said to be lagging if the current lags behind the voltage. In a capacitive circuit, the power factor is said to be leading if the current leads the voltage.

Calculation of the Electric Power:

You can calculate the value of electric power from different four quantities (voltage, current, time, charge).





Important conversions:

  • 1 Kilowatt (kW) = 10³ W
  • 1 Megawatt (MW) =10^6 W

Mostly the electrical and mechanical power is express in Horsepower (hp). It is measured in Watt or Joule/sec or Foot pounds/sec.

  • In the mechanical or hydraulic energy, horsepower converts into watt.
1 hp (M)  = 745.699872 W
  • In Electrical energy,  horsepower converts into watt.
1 hp (E) = 746 W = 0.746 kW = 0.000746 MW

In this tutorial, I have explained about the power and its types. If you want any queries about this topic, you will drop me a comment below.

Thanks for Reading!

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