Electricity: motive power systems – Induction motor systems – Power-factor control
Patent
1981-03-30
1983-10-25
Smith, Jr., David
Electricity: motive power systems
Induction motor systems
Power-factor control
318812, H02P 540
Patent
active
044121679
ABSTRACT:
A power factor controller for an AC induction motor which includes a control circuit adapted to be electrically connected in series with the motor for controlling the voltage applied to the motor. A sensing circuit provides phase lag signals corresponding to the difference in phase between the current through the motor and voltage across the motor. An oscillation circuit produces a cyclical output whose frequency is variable and is dependent on the value of the phase lag signal. A counter receives the cyclical output and produces a control signal corresponding to a predetermined cycle count of the cyclical output so that the duration of the control signal is dependent upon the phase difference. The control signal is applied to the control device for controlling the conduction angle of the voltage applied to the motor to thereby provide power to the motor in accordance with motor loading. Additionally, both soft start and hard start circuits are included and current limit or current trip circuits are provided for starting and running of the motor. A polyphase power factor controller is described and an additional phase loss lockout protection circuit is included.
REFERENCES:
patent: 3536957 (1970-10-01), Iverson et al.
patent: 3976919 (1976-08-01), Vandevier et al.
patent: 4007401 (1977-02-01), Kimmel et al.
patent: 4070605 (1978-01-01), Hoeppner
patent: 4355274 (1982-10-01), Bourbeau
patent: 4361792 (1982-11-01), Davis, Jr. et al.
patent: 4361793 (1982-11-01), Nordell
"Power Factor Controller", NASA Tech. Support Package Brief No. MFS-23280, G. C. Marshall Space Flight Center, Alabama 35812.
Goldner Sandor
Green Dan
Cynex Manufacturing Corporation
Smith Jr. David
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