HYBRID POWER FILTERS EMPLOYING BOTH ACTIVE AND PASSIVE ELEMENTS

摘要

A hybrid power filter employing both active and passive filtering elements retaining the advantages of these elements while overcoming the main disadvantages of each when used separately. In one embodiment of the invention, the passive element comprises a capacitor and inductor in series across the power conductors connecting a source section to a load section and tuned to the frequency of the major ripple component. In shunt with the inductor, or possibly the capacitor, is an active element which generates a synthetic ripple which opposes and eliminates any residual ripple component which may pass from the source to the load section, or vice versa, due to the inherent resistance of the passive filter or to detuning of the filter formed by the passive elements. Multiple hybrid filters of this type may be connected across the power conductors, each filter being tuned to a selected frequency in a range of expected harmonic frequencies. In another embodiment of the invention, the passive element comprises a capacitor and an inductor in parallel, the parallel combination being connected in series between the source and load, together with an active element connected across the inductor of the filter.