rwwengheaderPower Factor Correction

Reactive Power Compensation

Power factor is the ratio between the kW and the kVA drawn by an electrical load where the kW is the actual load power and the kVA is the apparent load power

For a machine to perform work it must be supplied with energy. In the case of electric motors, more electricity must be supplied than actually appears as useful work at the motor shaft. A certain amount of electricity is required just to maintain the necessary magnetic field and does not produce any useful work. This component is known as reactive power.

The reactive power used by electrical equipment like transformers, electric motors, welding units, server banks, lighting systems and static converters adds additional load to generators, transmission lines, transformers, switchgear and cables.

Benefits & Disadvantages


  • Cheap to implement
  • Quick to implement
  • Small space requirements
  • Can be implemented at load or motor terminals
  • Flexibility on sizes and number of steps depending on plant requirements


  • Limited protection
  • Not suitable for changing loads
  • Always on when connected
  • No control
  • Risk of harmonic resonance


  • Little to no risk of resonance if designed correctly
  • Reduction of individual harmonics
  • Easy to install
  • Can control according to load
  • Avoid resonance
  • Suitable for medium to high harmonic environments (2%> = <6% VTHD)


  • More space needed than plain compensation
  • More expensive than plain PFC
  • Reduced flexibility when plant load changes


  • Very fast switching (20-40ms)
  • Can control according to load
  • Low discharge time
  • Suitable for medium to high harmonic environments (2%> = <6% VTHD)
  • Eliminate switching transients


  • 35% more expensive than contactor switched PFC
  • Limited reduction of harmonics
Reactive Power Compensation

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