In this article, we are going to discuss what is Electrical power and its significance.
Electrical Power Definition:
In
general science power is simply defined as the capacity to do work. In other word, it is defined as the rate of doing work.
Whereas In Electrical Engineering, An
Electrical power is the rate per unit time at which the amount of electrical energy that is transformed into some other form of energy (such as heat, light, mechanical power, etc). Electrical power is one of the key concepts associated with Electrical
Engineering.
Mathematically it is defined as the product of voltage drop across the electrical element in the circuit and current flowing through it. It is measured in terms of Electrical Energy per unit time.
Unit of Electrical Power:
When we talk about Electrical Power then it is considered Active power consumed by the circuit element. So the unit of Electrical power (Active power) becomes Watt.
Watt is the SI unit of the power which is defined as the rate of conversion of 1-joule electrical energy per unit second.
If
we assume V = 1 volt,
I = 1
Amp.
Then
Electrical power (P) = V*I = 1*1 =
1 Watt
Hence the Power
consumed in an electrical circuit is said to be 1 watt if one ampere current flows through the circuit when a potential difference of one volt maintains across it.
Watt
is a smaller unit of power. Whereas a bigger unit of Electrical power is kW, MW,
GW, etc.
1 kW = 1000 Watt
Types of Electrical Power:
The classification of Electrical power depends on the nature of the current. So electrical power is mainly divided into two types.
They
are DC power and AC power.
1. DC Power
Power consumed in the DC circuit is known as DC
power. It is produced by a fuel cell, batteries, DC generators, etc.
Mathematically DC power is defined as the product
of voltage and current through the circuit.
So P = V * I
2. AC Power
Electrical power associated in AC circuit is known
as Complex Power. Complex Power is the combined form of Active, Reactive and
Apparent Power in AC circuit. So AC power is further classified into three
types.
These are Active Power, Reactive Power, and
Apparent Power.
Active Power (P):
The power which is actually consumed or utilized in
AC circuit is known as Active Power. It is also known as True Power or Real
Power in AC circuit. It is denoted by an English alphabet 'P'. It is measured in Watt (W),
kilowatt(kW), or Megawatt ( MW). In the case of DC circuit or in Pure
Resistive AC circuit, It is calculated as the product of voltage and current in
the circuit. Whereas in the case of AC circuit it is calculated as:
Reactive Power (Q):
The power associated
with reactive components (Inductors and Capacitors) of the circuit is known as
Reactive Power. It flows in both (i,e back and forth) direction of circuit. It
is not a useful power so it is interpreted as wattless power. It represents an extra burden on the electricity supply system and on the consumer's bill. Whereas it is required in the circuit to produce the electric
and magnetic field for working of capacitors and inductors in the circuit.
A pure inductor and a pure capacitor do not
consume any power in the circuit. Because in a half cycle whatever power is
received from the source by these reactive components, the same power is
returned to the source in the next half-cycle. Then the power which returns and
flows in both the direction in the circuit is known as Reactive power. This
reactive power does not perform any useful work in the circuit. It is denoted by an English alphabet Q. It is measured in VAR, kVAR,
or MVAR.
In the case of DC circuit, there
are no concepts of Reactive Power. Whereas for the AC circuit it is calculated
as
Apparent Power (S):
The combination of Active Power and Reactive Power is known as Apparent Power.
It
is total power of the circuit. Mathematically it is defined as the product of root
mean square (RMS) value of voltage and current. It is denoted by an English alphabet 'S' and It is measured in kVA, MVA. In the case of DC circuit, it is total Power. Whereas for the AC circuit it is
calculated as :
Power Triangle
The relation between Active, Reactive and Apparent power can be expressed by representing quantities as a vector in geometrical form is known as Power Triangle. In this phasor diagram, voltage is considered as reference phasor.
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