Electricity: motive power systems – Induction motor systems – Power-factor control
Patent
1983-09-12
1984-07-10
Smith, Jr., David
Electricity: motive power systems
Induction motor systems
Power-factor control
318798, 318812, H02P 540
Patent
active
044595298
ABSTRACT:
A power factor control circuit is disclosed which is relatively immune to variation in the current through the winding of the motor. This is accomplished by controlling the triac firing circuits as a function of the zero crossing of motor current. For single phase motors the circuit consists of voltage and current squaring means, the outputs of which are provided through logic gates to a summing amplifier. The output of the summing amplifier is an error voltage proportional to the phase difference between the line voltage and the motor current. A control voltage, generated as a function of the zero crossing of the motor current waveform, causes firing of the triac circuit when the ramp exceeds the value of the error signal.
REFERENCES:
patent: 4052648 (1977-10-01), Nola
patent: 4249120 (1981-02-01), Earle
patent: 4266177 (1981-05-01), Nola
patent: 4297628 (1981-10-01), Hedges
patent: 4298834 (1981-11-01), Opfer
patent: 4387329 (1983-06-01), Harlow
patent: 4413217 (1983-11-01), Green et al.
patent: WO80/002895 (1980-12-01), WOX PCT Int'l Appl.
Technical Support Package Relating to Powder Factor Controller, Brief No. MFS-2380, NASA 3-79, "Energy Savings in an Induction Motor Using the 8022 Micro-Controller", Intel Applications Note AP-94, Max 80.
"Improved Power-Factor Controller", NASA Tech. Briefs, Summer 1980, vol. 5, No. 2, MFS-25323.
Nordic Controls Co.
Smith Jr. David
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