Power Factor Correction
| What is Power Factor Correction? Most loads on an electrical distribution system fall into one of three categories; resistive, inductive or capacitive. In a maunfacturing 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 |
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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! |
| As the power factor drops the system becomes less efficient. A drop from 1.0 to 0.9 results in 15% more current being required for the same load. A power factor of 0.7 requires approximately 43% more current; and a power factor of 0.5 requires approximately 100% (twice as much) to handle the same load. The objective, therefore, should be to reduce the reactive power drawn from the supply by improving the power factor. |  |
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If an AC motor were 100% efficient it would consume only active power but, since most motors are only 75% to 80% efficient, they operate at a low power factor. This means poor energy and cost efficiency because the Regional Electricity Companies charge you at penalty rates for a poor power factor. |