Basic Concept

Most loads on an electrical distribution system can be placed in one of three categories:

• Resistive
• Inductive
• Capactitive

The most common of these three on modern systems is the inductive load.  Typical examples include transformers, fluorescent lighting and AC induction motors.

All inductive loads require two kinds of power to function properly:

• Active power (kW) - actually performs the work
• Reactive power (kvar) - sustains the electo-magnetic field.

As an example with an unloaded AC motor, one might expect the no-load current to drop near zero.  In truth, however, the no-load current will generally show a value between 25% and 30% of full load current.  This is because of the continuous demand for magnetising current by any induction load.