Many electrical devices, equipments and systems needs an electromagnetic field for their standard operation. This physical necessity leads to a consumption of reactive power which is used to provide basic function but not any active power. It means that transmission and distribution system is loaded with this reactive power and that’s not an economically effective use and therefore it’s penalized by electrical utility companies.

The solution is to use local power factor compensation to provide the required rective power from power capacitors directly to the appliance to avoid undesired load of the mains network. Systems with higher harmonics content may be sensitive to create resonant circuit between power capacitors and inductance of a transformer and may cause damage of an electrical system. The solution is to use detuned PFC which combines power capacitors with detuning reactors.

This detuned system shifts the resonance frequency to lower values (below first harmonic) where no harmonics are present so the safe operation of the whole system is ensured. Besides this such circuit has a certain tuning frequency that offers a filtering effect for the harmonic currents and thanks to this reduces the distortion level in the grid system. Note that detuning reactors and their inductance must be selected to match exactly capacitor capacitance to obtain the desired tuning frequency. Also note the capacitor is exposed to increased voltage than the nominal grid voltage in detuned PFC systems because of series connection with detuning reactor.