| 摘要 |
PCT No. PCT/US94/14070 Sec. 371 Date Jun. 4, 1996 Sec. 102(e) Date Jun. 4, 1996 PCT Filed Dec. 7, 1994 PCT Pub. No. WO95/16231 PCT Pub. Date Jun. 15, 1995A microprocessor (42) is coupled to sense the current and voltage in an AC line (11) at a high sampling rate and to determine the power factor. In one embodiment the primary (83) of a transformer (84) is coupled across the power lines, and at least two capacitors (86, 88), forming separate switching paths, are coupled to the secondary (85) of the transformer. High speed switching circuitry under the control of the microprocessor alternately charges and discharges the capacitors (86, 88) at varying frequencies, to alternately store energy from the power lines (11) when the variable load (32) is returning energy to the power lines, and to supply the stored energy back to the power lines when the variable load (32) is absorbing energy from the power lines (11). This corrects the power factor since the frequency of the high speed switching circuitry is varied with the varying reactance of the load. In another embodiment power factor correction is accomplished using a capacitor ladder (324), with different values of capacitance being switched into the circuit (328, 330) under microprocessor (344) control to maintain the power factor dose to unity under varying load (322) conditions.
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