Power Factor Correction

Power factor correction is the term for a technology that has been used since the early 20th century to restore power factor to unit as close as economically feasible. This is usually accomplished by adding capacitors to the power grid, which balance the reactive power demand of the inductive load, thus reducing the loading on the supply. There should be no effect on equipment operation. To reduce losses in the distribution system and electricity bills, power factor correction is added, usually in the form of capacitors to neutralize as much of the magnetizing current as possible. The capacitors included in most power factor corrected devices draw a current that leads the voltage, creating a leading power factor. When the capacitors are connected to a circuit operating with a nominal lagging power factor, the degree of lag of the circuit is proportionally reduced. Typically the corrected power factor is 0.92 to 0.95. Some power distributors offer incentives to operate at a power factor better than 0.9, for example, and some penalize low power factor consumers. There are many ways to measure this, but the bottom line is that the consumer is encouraged to apply power factor correction to reduce wasted energy in the distribution system. Most grid operators now penalize power factors below 0.95 or 0.9.

Advantages of power factor correction

The benefits that can be achieved by applying the correct power factor correction are:

Power Factor Improvement

Power factor correction is achieved by adding capacitors in parallel with connected motor or lighting circuits and can be applied at the equipment, switchgear or at the source of the installation. Static power factor correction can be applied to each individual motor by connecting correction capacitors to the motor starter. Disadvantages can occur when the load on the motor changes and can result in under or over correction. Static Power Factor Correction should not be applied to the output of a variable frequency drive, solid state soft starter or inverter as capacitors can cause serious damage to electronic components. Overcorrection should not occur if the power factor correction is the correct size. Typically, the power factor correction for a single motor is based on the no-load power (magnetizing power) because the reactive load of a motor is comparatively constant compared to the actual load in kW. Overcompensation should be avoided.

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