Optically-triggered half-frequency AC converter

Details Optically-triggered half-frequency AC converter Optically-triggered half-frequency AC converter

1982-05-10

1984-08-28

Wong, Peter S.

Electric power conversion systems

Frequency conversion without intermediate conversion to d.c.

By semiconductor converter

318313, 323902, H02M 5257

Patent

active

044687265

ABSTRACT:
An optically-triggered converter directly changes the frequency of an incoming voltage waveform to half frequency thereby causing an induction motor, driving a ventilation fan or the like, to operate at half speed. At this lower speed, the induction motor consumes significantly less power. A center-tapped power transformer is used to lower the magnitude of the incoming voltage waveform and a number of optically-triggered thyristor switches are connected between the transformer secondary and the induction motor. The novel trigger circuit includes a synchronous motor connected to receive the input voltage waveforms so that a cylinder attached thereto is rotated in synchronism with the input voltage waveforms. The optically-triggered thyristors are circumferentially positioned about the rotating cylinder and are triggered by a light pulse emerging through an aperture in the cylinder sidewall. The arrangement of the thyristors around the cylinder is selected so that the thyristors are enabled in a predetermined sequence forming fundamental three-phase half-frequency waveforms which are then presented to the induction motor.

REFERENCES:
patent: 3274482 (1966-09-01), Depenbrock
patent: 3479562 (1969-11-01), Cleveland
patent: 3659187 (1972-04-01), Lamorlette
patent: 3691440 (1972-09-01), Haddock
patent: 3718854 (1973-02-01), Spyron et al.

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