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Generator sizes

WHAT SIZE GENERATOR DO I NEED?

Hi, it’s Alex here. Technical & Operations director for Progen Power.

We get asked a lot about the units of measurement shown on the screens of our generators, so we thought we’d take the opportunity in this week's blog to explain exactly what they mean and how they are related.

Many of us have seen the pint of beer analogy below but we want to go a bit further to help you understand exactly what the relationship is between the three units of measurement.

 

beer analogy

 

Many businesses misjudge the kVA capacity they require by trying to link their maximum power requirement (kVA) to their total annual energy usage (kWh). This is not advisable, as there is no direct link between kVA requirement and annual energy usage.


KVA stands for "kilovolt-amperes" and is a measure of the apparent power in an electrical circuit. It is the product of the voltage and current in a circuit, and it is expressed in units of volt-amperes (VA).

KVAR stands for "kilovolt-ampere reactive" and is a measure of the reactive power in an electrical circuit. Reactive power is the power associated with the flow of alternating current (AC) in an electrical circuit, and it is expressed in units of volt-amperes reactive (VAR).

kW stands for "kilowatt" and is a measure of the real power in an electrical circuit. Real power is the power that is actually used to perform work, and it is expressed in units of watts (W).

In an electrical circuit, the apparent power (KVA) is equal to the sum of the real power (kW) and the reactive power (KVAR). This relationship is known as the "power triangle."

Imagine that you have a hose pipe with water flowing through it. The water flowing through the hose represents the electrical current flowing through a circuit. The pressure of the water in the hose represents the voltage in the circuit.

KVA is like the volume of water flowing through the hose. It is a measure of the total power in the circuit, and it takes into account both the pressure and the flow of the water.

KVAR is like the waves or ripples in the water flowing through the hose. It represents the reactive power in the circuit, which is the power associated with the flow of alternating current.
kW is like the work that the water is able to do as it flows through the hose. It represents the real power in the circuit, which is the power that is actually used to do work.

In this analogy, the apparent power (KVA) is like the total amount of water flowing through the hose, which is equal to the sum of the real power (kW) and the reactive power (KVAR). This relationship is similar to the "power triangle" in an electrical circuit.