Power Factor...
In electrical engineering, the
power factor of an AC electrical power system is defined as the ratio of the
real power flowing to the load, to the apparent power in the circuit, and is a
dimensionless number between -1 and 1. Real power is the capacity of the
circuit for performing work in a particular time. Apparent power is the product
of the current and voltage of the circuit. Due to energy stored in the load and
returned to the source, or due to a non-linear load that distorts the wave
shape of the current drawn from the source, the apparent power will be greater
than the real power. A negative power factor occurs when the device which is
normally the load generates power which then flows back towards the device
which is normally considered the generator.
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 transferred. The higher currents
increase the energy lost in the distribution system, and require larger wires
and other equipment. Because of the costs of larger equipment and wasted
energy, electrical utilities will usually charge a higher cost to industrial or
commercial customers where there is a low power factor.
Linear loads with low power
factor (such as induction motors) can be corrected with a passive network of
capacitors or inductors. Non-linear loads, such as rectifiers, distort the
current drawn from the system. In such cases, active or passive power factor
correction may be used to counteract the distortion and raise the power factor.
The devices for correction of the power factor may be at a central substation,
spread out over a distribution system, or built into power-consuming equipment.