Motor drive using flux adjustment to control power factor
AssigneeRockwell Automation Technologies, Inc.
InventorsManish Pande, Yunwei Li
Life of this patent
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Abstract
The switching rectifier and switching inverter on a motor drive unit are modulated to indirectly change the magnitude of current and voltage stored in DC link by controlling the magnetic field of the motor to correct for both power factor lead and power factor lag over a wide range of motor speeds and conditions while maintaining a predetermined motor operating point.
Claims22
A motor drive system providing power factor compensation and comprising:
- a switching rectifier system receiving a source of AC power to selectively couple the AC power with an intermediate DC link to provide a DC link current or voltage;
- an inverter coupled to the DC link to receive the DC link current or voltage and to synthesize an AC output current or voltage to a motor;
- a controller coupled to the switching rectifier system and the inverter and executing a stored program to:
- (1) receive an operating command describing a desired operating point of the motor;
- (2) determine a power factor of the motor drive at the desired operating point;
- (3) determine a compensating current tending to correct the power factor to a desired value;
- (4) generate an AC output current and voltage to the motor providing the desired operating point of the motor and also producing the compensating current by changing the magnitude of the motor flux within a certain range.
A method of correcting power factor in a motor drive system having a switching rectifier system receiving a source of AC power to selectively couple the AC power with an intermediate DC link to provide a DC link current or voltage, an inverter coupled to the DC link to receive the DC link current or voltage and to synthesize an AC output current or voltage to a motor, and a controller coupled to the switching rectifier system and the inverter comprising the steps of:
- (1) receiving an operating command describing a desired operating point of the motor;
- (2) determining a power factor of the motor drive at the desired operating point;
- (3) determining a compensating current tending to correct the power factor to a desired value;
- (4) generating an AC output current or voltage to the motor providing the desired operating point of the motor and also producing the compensating current by changing the magnitude of the motor flux within a certain range.
Dependencies are inferred from the claim text.