What is KVA KVAR And KW?

Description of KVA KVAR and KW:

KVA, KVAR, and KW are various types of power. In this post, we will identify the major difference between 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.

• whereas 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 effects in 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 the Inductive nature of Loads.
• Example of Lagging Reactive power loads is Induction Motors and Transformers for producing their magnetizing currents.

  2.  Leading Reactive Power:

• Produced by Synchronous Capacitors and Capacitor Banks.
• Consumed by the Capacitive 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. The 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.

• 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 the 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-kilowatt hour (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.

2.Three Phase KVA to Amps:

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

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 nameplate details consist of voltage rating, ampere rating and power factor at which it operates are required.

2.Three Phase KVA to KW:

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