Electricity: motive power systems – Induction motor systems – Primary circuit control
Patent
1988-01-19
1988-12-13
Smith, Jr., David
Electricity: motive power systems
Induction motor systems
Primary circuit control
318345CB, 318812, A02P 540
Patent
active
047913410
ABSTRACT:
A variable speed 3-phase a-c motor is connected to a 3-phase source of alternating voltage via a plurality of controllable solid state electric valves which are so arranged and controlled that motor speed can be reduced by skipping selected cycles of the source voltage. For half speed operation 12 valves are arranged to interconnect the source and motor phases, and over two consecutive periods of the source voltage six separate, uniformly spaced "firing windows" are selected during which the conducting states of different pairs of these valves are initiated in a predetermined pattern that results, in each phase of the motor, in a double-pulse current waveform having one-half the fundamental frequency of the source voltage.
REFERENCES:
patent: 3908158 (1975-04-01), Studtmann
patent: 4176306 (1979-07-01), Asano et al.
patent: 4461985 (1984-05-01), Stitt
patent: 4524316 (1985-10-01), Brown et al.
patent: 4713744 (1987-12-01), Coston
"Low-Cost Electric Speed Controller for Small Induction Motors" by W. Matley et al., IEE Power Div. Conf. Publ. 179, pages 42-45 (Sept. 1979).
Brown Herbert J.
Stitt Thomas D.
General Electric Company
Richardson, Jr. Albert S.
Smith Jr. David
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