The units are of the same “size”, but are used for different properties of the feed:
kW – Real Power
kVA – Apparent Power
kvar – Reactive Power
The relationship between the three values can be summarized in the following figure:
The real power and the reactive power together (root of the sum of the squares) give you the apparent power. On your bill, if you are on a demand tariff, you will be billed for the apparent power (kVA). The power factor determines how close the apparent power is to the real power (a PF of 1 would have the apparent power = real power).
I hope this info helps!
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EMPLOYEEI’m still happy1Just found a very good analogy for this on the internet:
Compare the delivery of electrical energy to a motor, and the delivery of milk to a home, in the days when refillable glass bottles were used.
The bottles were esential to the transaction, but were not paid for or consumed by the customer. They were washed and returned to the dairy each day. The load the milkman had to carry to the house consisted of both milk and glass.
Milk = Watts, (True Power) the product consumed and paid for by the customer.
Glass = Vars, (Reactive power) required to supply the magnetic field, returned to the power generator each cycle, not consumed or paid for by the customer.
Milk + Glass = VA, (Apparent Power) the vector sum of the Watts and Vars, which is what the transformers and conductors have to carry.
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