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US 4,052,648 AGranted
Power factor control system for AC induction motors
AssigneeThe United States of America as represented by the Administrator of the National Aeronautics and Space Administration
InventorFrank J. Nola
Life of this patent
Estimating the term…
Abstract
A power factor control system for use with AC induction motors which samples line voltage and current through the motor and decreases power input to the motor proportional to the detected phase displacement between current and voltage to thereby provide less power to the motor, as it is less loaded.
Claims5
A power factor control system for an AC induction motor comprising:
- current sampling means including means adapted to be placed in circuit with each phase winding of a said motor for providing an AC output signal in phase with the current through said winding;
- voltage sampling means adapted to sense the voltage of an electrical input applied to said winding and for providing an output signal in phase with said voltage across said winding;
- phase detection means responsive to the outputs of said current sampling means and said voltage sampling means for providing an output which varies in accordance with the difference in phase between said current and said voltage;
- and
- a control means adapted to be electrically connected in series with each said winding of said motor, and responsive to the output of said phase detection means for varying the duration of "on" time of each cycle of input power to said winding inversely proportional to the difference in phase between said current and said voltage;
- whereby an increase in difference between the magnitude of said voltage and the magnitude of load applied to said motor is compensated for by a reduction in power to said motor, generally improving its efficiency.
3 more elements
Dependencies are inferred from the claim text.