Technical Information

Most loads on an electrical distribution system fall into one of three categories; resistive, inductive or capacitive. In your own plant, the most common is likely to be inductive. Typical examples of this include transformers, fluorescent lighting and AC induction motors. Most inductive loads use a conductive coil winding to produce an electromagnetic field, allowing the motor to function.
All inductive loads require two kinds of power to operate:

  • Active power (kWatts) - to produce the motive force
  • Reactive power (kVAr) - to energise the magnetic field

 

The operating power from the distribution system is composed of both active (working) and reactive (non-working) elements. The active power does useful work in driving the motor whereas the reactive power only provides the magnetic field. The bad news is that you are charged for both!


Reactive power can also be interpreted as wattless, magnetising or wasted power and it represents an extra burden on the electricity supply system. 
An inductive load requires a magnetic field to operate and in creating such a magnetic field causes the current to be out of phase with the voltage(the current lags the voltage).  Power Factor Correction is the process for compensating for the lagging current by connecting sufficient capacitance, so that the power factor is adjusted to be as close to unity as possible.