Tutorial on how to calculate kilovolt ampere reactive or reactive power (kVAR)
KVAR (Kilo Volt Ampere Reactive or Reactance)
is a reactive power. It is the power that magnetic equipments like transformer, motor or relay produces to magnetize flux. The below tutorial explains you on how to calculate kVAR.
It is essential to understand kW and kVA in order to understand kVAR.
kW is the power that actually powers the equipment and converts the power into work. It is also called as Working Power, Actual Power, Active Power or Real Power.
kVAR is the power that magnetic equipment such as transformer, motor and relay needs to produce the magnetizing flux. It is also called as Reactive Power. Use the formula provided below for kVAR calculation.
kVA is the vectorial summation of KVAR and KW. It is also called as Apparent Power or the Alternating Current (AC). It is computed by multiplying the root-mean-square (rms) current by the root-mean-square voltage.
The relation between the real power (kW), the apparent power (kVA) and the reactive power (kVAR) can be represented by the below kVAR triangle as follows.
From the above kW-kVA-kVAR relationship triangle (kVAR Triangle), you can calculate the reactive power (kVAR) using the aparent power (kVA) and the true power (kW). kVAR (Reactive Power) is the vectorial difference between kVA (Apparent Power) and kW (Real Power). kVAR calculation formula:
(Reactive Power)2 = (Apparent Power)2 - (True Power)2
which inturn is given as:
kVAR(Reactive Power) = √ (Apparent Power)2 - (True Power)2
The POWER FACTOR also defines the relationship between kW and kVA. It is the ratio of kW (true power or useful power) to kVA (total power or apparent power). It is a measure of how efficiently electrical power is converted into useful work output. The ideal power factor is one.
The power factor can be increased by adding capacitors to the system. Capacitors are also called as kVAR generators. When the power factor is increased, KW capacity of the system is also increased.
Example of calculating kVAR:
Consider an 1000 KVA transformer with an 80% power factor providing 800 KW of power to the main bus. Calculate the kVAR.
Subsituting the values in the formula:
kVAR = √ (Apparent Power)2 - (True Power)2
= √(KVA)2 - (KW)2
= √(1000)2 - (800)2
= √(1000000) - (640000)
kVAR = 600