What is Power Factor?

We speak of “adjusting” the power factor of an inductive motor. Why is this done, and what does it accomplish?

It is similar in concept to aligning the wheels of your car.

We all know that if a car’s wheels are not aligned, the efficiency of the car is affected. The driven wheels want to go straight ahead, but the misaligned wheels do not. Overcoming this means the engine has to work harder, and tires wear out quicker.

The power wasted resisting the misalignment is called reactive (nonworking) power, for obvious reasons.

The power used to take the car in the direction you want is called real power, since that is the work you want to do. The power the engine is making is called apparent (total) power. The ratio between these two is the power factor. It is usually stated as a percentage.

Increasing the power factor brings the two – real power and apparent power – into closer alignment; the wheels are now  all going the same direction.

Which means that the reactive, nonworking power is less. The motor doesn’t need to work as hard. It uses less energy to do the same work. It runs cooler, and will have a longer service life.

In summary, in an electric power system, a load with a low power factor draws more current than a load with a high power factor for the same amount of useful power. This costs the user more, in both energy consumed and the useful life of the components of the system, including the motor.