초록 ▼

A 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

A 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.

대표청구항 ▼

[ What is claimed is:] [1.] A power factor correcting system, comprising:a voltage sensor having an input coupled across first and second alternating current power lines;a current sensor having an input coupled to one of said first and second power lines;a digital microprocessor;circuitry for coupli

[ What is claimed is:] [1.] A power factor correcting system, comprising:a voltage sensor having an input coupled across first and second alternating current power lines;a current sensor having an input coupled to one of said first and second power lines;a digital microprocessor;circuitry for coupling signals from said voltage sensor to said microprocessor;circuitry for coupling signals from said current sensor to said microprocessor;said microprocessor including programming means for determining a phase difference between a sensed voltage and a sensed current;incrementally adjustable power factor correction circuitry absorbing current from said power line during a portion of each cycle of the alternating current and for supplying current to said power line during another portion of said cycle of the alternating current;switching circuitry including a plurality of switching devices, coupling said power factor correction circuitry to said power line;said microprocessor being coupled to said switching circuitry to change the state of said switching devices to change the power factor of said system toward unity;said microprocessor supplying updated switching signals to said switching circuitry at least several times each second; andsaid power factor correction circuitry being a capacitive network, including a plurality of capacitors, and said switching devices selectively coupling said capacitors to the power line; andwherein said capacitive network is a binary ladder network.