The power factor of an electric load can be defined as the ratio of real power to apparent power.
- Real power is, as implied by its name, the actual power the load is consuming. It is represented by the letter P and measured in kilowatts (kW).
- Reactive power is a type of power drawn by inductive or capacitive loads -
- it flows back and forth between the load and the voltage supply, without being consumed. It is represented by the letter Q and its measurement unit is kilovolt-ampere reactive (kVAR).
- Real and reactive power are out of phase by 90°, and their vector sum is apparent power. It is represented by the letter S and its measurement unit is kilovolt-ampere (kVA).
The following diagram illustrates the concept of power factor:
For instance, if we have 40 kW of real power and 15 kVAR or reactive power, the apparent power would be:
In this scenario, the power factor would be:
- PF = 40 kW / 42.72 kVA = 0.9363 = 93.63%
If the load is predominantly inductive, the power factor is considered lagging. On the other hand, capacitive loads have a leading power factor.