Induction motor control system
AssigneeEmerson Electric Co.
InventorsVinodkumar Sadasivam, Keith Hoemann, Bret Clark
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Abstract
An induction motor control system senses the zero-cross angle of a current waveform applied to the motor's phase windings and computes the difference between the sensed current zero-cross angle and a predetermined demand voltage angle to estimate a power factor angle. The estimated power factor angle is compared to a predetermined desired power factor angle, and the voltage applied to the phase windings is adjusted in response to the difference between the estimated power factor angle and the desired power factor angle.
Claims20
A method for controlling an induction motor, the motor having a rotor and a stator including a plurality of phase windings therein to which AC voltage having a desired magnitude is applied to cause rotation of the rotor relative to the stator, the method comprising:
- sensing a zero-cross angle of a current waveform applied to the phase windings;
- computing the difference between the sensed current zero-cross angle and a predetermined demand voltage angle to estimate a power factor angle;
- comparing the estimated power factor angle to a predetermined desired power factor angle;
- and
- adjusting the magnitude of the voltage applied to the phase windings in response to the difference between the estimated power factor angle and the predetermined desired power factor angle.
An induction motor system, comprising:
- a stator;
- a rotor situated relative to the stator to rotate relative to the stator;
- a plurality of phase windings situated within the stator;
- a power source connected to the windings to output AC voltage having a desired magnitude thereto;
- a controller connected to the power source, the controller comparing a sensed current zero-cross angle to a predetermined demand voltage angle to estimate a power factor angle, and adjust the magnitude of the voltage applied to the windings in response to the difference between the estimated power factor angle and a predetermined desired power factor angle.
A control system for energizing phase windings of an induction motor with a voltage having a desired magnitude, the induction motor having a rotor and a stator, the control system comprising:
- a zero-cross angle detection circuit outputting a signal representing a zero-cross instant of a current waveform applied to the phase windings;
- and
- a processor connected to the zero-cross angle sensing circuit to receive the output therefrom, the processor storing signals representing a predetermined demand voltage angle and a predetermined power factor angle, the processor being programmed to:
- compute the difference between the current zero-cross angle and the predetermined demand voltage angle to estimate a power factor angle;
- and
- adjust the magnitude of the voltage applied to the phase windings in response to the difference between the estimated power factor angle and the desired power factor angle.
An induction motor system, comprising:
- a stator;
- a rotor situated relative to the stator to rotate relative to the stator,
- a plurality of phase windings situated within the stator;
- a power source connected to the windings to output an AC voltage having a desired magnitude thereto;
- first means for sensing a zero-cross angle of the AC voltage applied to the windings;
- and
- second means for
- comparing the sensed zero-cross angle to a predetermined demand voltage angle to estimate a power factor angle,
- comparing the estimated power factor angle to a predetermined desired power factor angle, and in response thereto,
- adjusting the magnitude of the voltage applied to the windings.
Dependencies are inferred from the claim text.