What is KVA KVAR And KW?

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Description of KVA KVAR and KW:

KVA, KVAR and KW are various types of power. In this post we will identify the major difference among these terms. Also see how to convert one form of power to another.

  • KVA means Kilo volt ampere. V*I*1000
  • KVAR means Kilo Volt Ampere Reactive. V*I*Sinϕ*1000
  • KW means Kilo Watt. V*I*Cosϕ*1000

                where V is in volts

                 I is in Amps.

  • Actual Power consumed by loads is called Kilo Watt Power.
  • All the Power given to the load is not utilized as useful power, some power is being wasted. The power which is not consumed is called Reactive power i.e KVAR.
  • where as apparent power KVA is the vector sum of KW and KVAR.

i.e. VI = VICosϕ + VISinϕ (Added vectorially)

Active Power: KW

  • Active Power is produced by Generators in power plants.
  • Active Power is Consumed by resistive part of the loads. A pure resistive load consumes only active power.
  • Example of Active power loads are Incandescent Bulbs, Heaters, Iron Box etc.

Reactive Power: KVAR

  • Although Reactive power doesn’t do any work it is needed to create magnetic flux in the windings. Magnetic flux is responsible to produce Induction effect in the electrical machines like transformers, alternators and Induction motors.

Reactive power is two types.

  1. Lagging Reactive Power:

  • Produced by Inductive Reactors known as Reactive Transformers.
  • Consumed by Inductive nature of Loads.
  • Example of Lagging Reactive power loads are Induction Motors and Transformers for producing their magnetizing currents.

  2.  Leading Reactive Power:

  • Produced by Synchronous Capacitors and Capacitor Banks.
  • Consumed by Capacitve nature of Loads.
  • Example of Leading Reactive power loads are Electric Motors with Capacitor for starting and running, Long Transmission Lines.

Ratio between KW and KVA:

  • The ratio between active power, measured in kW, and apparent power, measured in kVA, is known as the Power factor. Power factor is used to assess the utilization of electrical power.
  • The value of the power factor varies between one and zero.It depends on the amount of reactive power consumed by the Electrical Machine.
  • If the machine doesn’t require any reactive power then its power factor is unity.
  • If the machine consumes only reactive power and no active power then its power factor is zero.

Measurement of KVA, KVAR And KW:

Trivector Meter is used to measure KW, KVAR and KVA of a power line. Trivector Meters are normally used in Substations to measure the power flowing through the feeders.

Difference between KVA and KW ratings:

If we see the rating of any alternator it is expressed in both KVA and KW ratings.

KVA KVAR and KW ratings of Alternator
Name Plate of Alternator
  • The KVA rating denotes the capacity of the alternator. Here Capacity is the maximum electric output a generator can produce under specific conditions. Nameplate capacity is determined by the generator’s manufacturer and indicates the maximum output a generator can produce without exceeding design thermal limits.
  • The KW rating denotes the amount of generation the alternator. Here Generation is the amount of electricity a generator produces over a specific period of time.
    For example, a generator with 1 kilowatt (KW) capacity that operates at that capacity consistently for one hour will produce 1 kilowatthour (KWH) of electricity. If it operates at only half that capacity for one hour, it will produce 0.5 KWH of electricity.

Conversion Formulas:

Some important conversion formulas which are needed to calculate efficiency, losses and power factor of the machine are given here.

KVA to Amps Conversion:

This conversion is used to determine the load on the transformer or alternator.

1.Single Phase KVA to Amps:

The secondary side voltage of transformer or load voltage is required.

Single Phase KVA formula
Amps to KVA conversion formula

2.Three Phase KVA to Amps:

The secondary side voltage of transformer or load voltage is required.

Three Phase KVA formula
Amps to KVA Conversion Formula

KVA to KW Conversion:

This conversion is used to determine the electrical  input giving to the motor or power delivered by the alternator.

1.Single Phase KVA to KW:

The Single Phase machine name plate details consist of voltage rating, ampere rating and power factor at which it operates are required.

Single Phase KVA formula
KW to KVA conversion formula

2.Three Phase KVA to KW:

The Three Phase machine name plate details consist of voltage rating, ampere rating and power factor at which it operates are required.

Three Phase KVA Formula
KW to KVA conversion formula

6 thoughts on “What is KVA KVAR And KW?

  1. Smithk68

    I do accept as true with all of the concepts you have offered in your post. They’re really convincing and will definitely work. Still, the posts are very brief for beginners. May you please extend them a little from next time? Thanks for the post.

    Reply
      1. SHAMSUZZOHA

        Sir,
        I have worked in different places like India, Kuwait, and Saudi in Power plant and Substation even, I get dedicated concept from your post.
        I am very much appreciated and obliged you

        THANK U FOR GOOD SUGGESTION

        Reply

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