Electricity: motive power systems – Induction motor systems – Power-factor control
Patent
1986-06-06
1989-01-24
Smith, Jr., David
Electricity: motive power systems
Induction motor systems
Power-factor control
318778, 318798, 318812, H02P 540
Patent
active
048003263
ABSTRACT:
When induction motors are lightly loaded their power factors and efficiency are poor but in the present invention power factor is controlled regardless of load. An induction motor is connected by way of a triac to a supply. The voltage across the triac is monitored by a comparator for voltage steps which correspond to current turn-off and a signal is developed at the output of an amplifier which represents error from required phase lag. A further comparator and a trigger pulse generator trigger the triac in accordance with the error. An override circuit overrides the control system during starting. A number of further induction motors may be connected in parallel with the motor. Additional circuits deal with problems arising when a three-phase induction motor is connected by three wires only.
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National Research Development Corporation
Smith Jr. David
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