Electricity: motive power systems – Induction motor systems – Primary circuit control
Patent
1984-04-30
1985-01-01
Smith, Jr., David
Electricity: motive power systems
Induction motor systems
Primary circuit control
318811, H02P 540
Patent
active
044917783
ABSTRACT:
A speed control for an AC motor varies the frequency and amplitude. The speed control includes a rectifier which converts the AC power supplied to negative and positive DC. A switch connects each power conductor leading to the motor with one of the DC voltages. The switches are switched on and off to provide alternately positive and negative voltage. Controls for the switches include an oscillator which provides pulses of frequency that can be varied. A binary counter counts the pulses from the oscillator and provides binary outputs. A memory unit provides a programmed output to the switches for each binary output received. In one embodiment, the amplitude is varied by comparing a triangular wave from the oscillator with the DC input level. Enabling pulses equal to the excess of the triangular wave over the DC input enable the memory unit. In another embodiment, the enabling pulses are provided to an amplitude switch which is cycled to vary the DC rail voltage.
REFERENCES:
patent: 4099109 (1978-02-01), Abbondanti
patent: 4123692 (1978-10-01), Gilmore
patent: 4290108 (1981-09-01), Woehrle et al.
patent: 4292577 (1981-09-01), Ceaser et al.
patent: 4348734 (1982-09-01), Dougherty
Mazur, T., "A ROM-Digital Approach to PWM-Type Speed Control of AC Motors", AN-733, Motorola 1974.
Knox Dick L.
Leuthen John M.
Lockyear Kevin W.
Bradley James E.
Felsman Robert A.
Hughes Tool Company
Smith Jr. David
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