Power Factor Correction
As with any equipment, an electrical system handles its job to some degree of
efficiency, ranging from poor to excellent. The measure of electrical efficiency is
known as Power Factor.
The motors and other inductive equipment in a plant require two kinds of electric
power. One type is working power, measured by the kilowatt (kW). This is what
actually powers the equipment and performs useful work. Secondly, inductive
equipment needs magnetizing power to produce the flux necessary for the
operation of inductive devices. The unit of measurement of magnetizing or
reactive power is the kilovar (kVAR). The working power (kW) and reactive
power (kVAR) together make up apparent power which is measured in kilovoltamperes (kVA).
Most AC power systems require both kW (kilowatts) and kVAR (kilovars).
Capacitors installed near the loads in a building are the most economical and efficient way of supplying these kilovars. Low voltage capacitors are traditionally a high reliability maintenance-free device.
On the spot delivery of magnetizing current provided by capacitors means that kilovars do not have to be sent all the way from the utility generator to you. This relieves both you and your utility of the cost of carrying this extra kilovar load. The utility charges you for this reactive power in the form of a direct, or indirect power factor penalty charge. In addition, you'll gain system capacity, improve voltage and reduce your power losses.
Induction motors, transformers and many other electrical loads require
magnetizing current (kVAR) as well as actual power (kW).
To reduce the kVA required for any given load, you must shorten the line that
represents the kVAR. This is precisely what capacitors do.