Single transistor power control circuit for a DC motor washing m

Details Single transistor power control circuit for a DC motor washing m Single transistor power control circuit for a DC motor washing m

1980-01-04

1982-05-11

Smith, Jr., David

Electricity: motive power systems

Plural diverse motor controls

Motor-reversing

318269, 318293, H02P 540, H02P 312

Patent

active

043296300

ABSTRACT:
A low cost power control circuit which achieves variable speed, quasi four-quadrant motor control well suited to the requirements of a direct drive clothes washing machine. For handling relatively low frequency motor direction control signals (one or two Hertz), four relatively inexpensive, low frequency thyristors are employed in a four-leg bridge circuit arrangement. For handling relatively high frequency chopper duty cycle control signals (10 kHz), a single high frequency power transistor is employed. To provide quasi four-quadrant control entirely suitable for clothes washing, a fifth thyristor and a series dissipation resistor are connected across the motor terminals and switched ON during agitation just prior to each motor reversal when motor velocity is decreasing and motor back emf exceeds applied emf. A feedback servomechanism is employed to control motor rotational velocity via chopper pulse width modulation. In the feedback loop, the means for generating a signal representative of actual motor velocity preferably comprises a negative impedance converter circuit responsive both to overall voltage across the input terminals of the thyristor bridge and to current through the bridge and operable to minimize the effect of motor internal impedance to derive a signal representative of motor induced emf, and therefore representative of motor velocity, with improved accuracy.

REFERENCES:
patent: 3152462 (1964-10-01), Elliott et al.
patent: 3152463 (1964-10-01), Sones et al.
patent: 3279223 (1966-10-01), Severance et al.
patent: 3369381 (1968-02-01), Crane et al.
patent: 3982161 (1976-09-01), Grace
patent: 4114074 (1978-09-01), Stewart et al.
patent: 4118658 (1978-10-01), Salva et al.
patent: 4215303 (1980-07-01), Brimer
patent: 4234834 (1980-11-01), Jennings

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