What is Apparent Power(KVA), Active Power (KW) and Reactive Power (KVAr)

APPARENT POWER (KVA): Kilo Volt Ampere is the measure of apparent power in ac circuit. It used to rate how much power the supply can deliver. KVA is usually used to rate sourses such as transformers, generators, UPS etc. It is also called imaginary power. The actual power(KW) consumed by the loads connected in a circuit can be obtained by multiplying apparent
power(KVA) with power factor. It can be expressed in complex form as
apparent power(KVA)=active power(KW) + i reactive power 
ACTIVE POWER(KW): The unit of active or real power in an ac circuit is KW. The active power obtained by multiplying apparent power with power factor. It is the power consumed by loads connected in an AC circuit. If only resistive loads are connected in an AC circuit the power factor will be one and the apparent power became equal to active power.
     active power(KW)= apparent power(KVA)*power factor

REACTIVE POWER(KVAr): Reactive power is the imaginary part of apparent power when it is expressed in complex form. If the load in an ac circuit is only resistive the power will always flow from sourse to load. If reactive loads (inductor or capacitor) connected in ac circuit it causes reactive power to develop in the circuit. The reactive power is continually bounces back and forth between the source and load. It represents the energy that is first stored and then released in the magnetic field of the inductor, or in the electric field of a capacitor connected in the circuit. Since reactive power bounces back and forth between source and load it does not provide any energy to the load and draws more current from mains so more heat loss take place on the circuit lines. The reactive power can be reduced by increasing the power factor (reducing the phase angle). This can be achieved by providing a designed capacitive bank in the circuit.

About the Author 
Mr.Manoj He is a marine engineer sailing with ESM. He handles Advertising department and technical support at Marinesite. Apart from this he is having keen interest on Electrical.You can catch him on Facebook  Google+.


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  2. please explain what is happening for purely inductive and purly capacitve or at combination of all load,,

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