Page 237 - Electrician - TT (Volume 1)

ELECTRICIAN - CITS

MODULE 7 : Electrical Power, Power Factor &
Electrical Energy

LESSON 38-40 : Work, power, energy & power factor

Objectives

At the end of this lesson you shall be able to:
• define active, reactive power,
• simple calculation on A.C. circuit work, power energy
• define power factor explain the causes of low power factor
• list out advantages of higher power factor in a circuit
• explain the methods to improve the power factor in an A.C. circuit.

Type of power in ac circuits
Active power [True power]

Reactive power
Apparent power
The active power to be measured is the product of voltage , current and power factor
The active power indicates that with a load which is not purely resistive and where the current and voltage are
not in phase , only that part of the voltage will produce power P = in phase , current which is in phase with the
only that part of the V x I x cos Ø
Units of Active power is Watts/ kilowatts and is measured by using Wattmeter

Reactive power only that part of current which is 900 out of phase with the voltage is used in this case. Capacitors,
inductors, on the other hand, alternatively store energy and return it to the source. Such transferred power is
called reactive power measured in volt ampere reactivePr =V x I sin ø
Apparent power
• It is the simply the product of the total applied voltage and the total circuit current and its unit is volt-ampere
[VA], Pa = V x I

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