Hi

How can I solve the harmonic and resonance problems when I am dealing with the power factor correction?
Could anyone tell me the principle and steps of switching the capacitor to correct the power factor precisely?

Thanks a lot.
Lewis

Hello Lewis

The harmonic currents in the capaciotrs can be reduced by using detuning capacitors.
The automatic selection of capacitors is achieved by the use of a power factor control relay. This measures the power factor. If the power factor is less than a preset level, (typically 0.95) it connects another bank and continues to add banks until the power factor is high enough. If the power factor becomes capacitive, the relay begins to shed banks until the measured power factor is in a suitable band.
Best regards,

Hello Marke

Sorry, could you explain more about the detuning inductors?
Any other methods or techniques can improve the power factor, harmonics and the effect of resonating at the same time?
Active filters or passive filters can improve it?

Thanks
Lewis

Detuning reactors are just inductors added in series with the capacitors to provide a series tuned circuit of somewhere between 100 and 250 Hz. Typically 189Hz on a 50Hz system for a 7% reactor. This results in an inductive system above resonance and thereby reduces harmonic current flow.

The alternative is an active compensator which is essentially an inverter either using series or shunt injection to correct the harmonic currents. This can also provide reactive currents and result in an overall power factor improvment. These systems are expensive at the moment.
Best regards,