GB1472411A - Harmonic and power factor compensation for power systems - Google Patents

Abstract

1472411 Filters INDUCTOTHERM CORP 19 Sept 1974 40836/74 Heading H3V [Also in Division H2] To reduce harmonic currents in a power supply system for a load 20 and comprising a non-linear device 22, e.g. a saturable reactor or S.C.R., a filter network 24 is provided which comprises a filter F3, &c for each harmonic to be reduced, each filter being tuned to a frequency less than its corresponding harmonic frequency and having a net inductive reactance at the corresponding harmonic frequency. The capacitors of the filter network 24 provide a leading power factor at the fundamental power supply frequency to compensate for a lagging power factor component introduced by the device 22. The load 20 may be an induction furnace corrected, e.g. by a capacitor, to have unity power factor at the fundamental frequency. Alternatively, the load may be lighting or heating generally, and static frequency multipliers may also be included. Given the line reactance X 1 and the amount of harmonic current which it is permitted to reflect back into the supply E 1 , calculations are made to determine the values of the elements in network 24 in terms of the load R. To enable the power factor at relatively high and low power levels to be corrected, the filter F 3 , may comprise two parallel branches (Fig. 6, not shown), which are selectively connectible across the load by respective switches (34, 36). A third switch (38) interconnects the two branches. Filter F 5 may be similarly sectionalized.