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US 4,400,655 AGranted
Self generative variable speed induction motor drive
AssigneeImec
InventorsWilliam P. Curtiss, Gordon P. Sharp
Life of this patent
Estimating the term…
Abstract
An inverter controls an induction motor in response to signals from a power factor control circuit. The power factor control circuit receives signals related to motor terminal voltages and multiplexes them to a comparator. The inverter and multiplexor are sequenced each time the comparator input reaches a reference level. The frequency of the inverter is thus self generated. The power factor of the system can be controlled to implement a variety of control strategies.
Claims26
An induction motor drive which comprises:
- an inverter having outputs connected to the stator windings of the motor to be controlled, the inverter being operable in response to command signals to apply an alternating current to each of said motor windings;
- voltage sensing means coupled to said motor stator windings and being operable to generate quasi sinusoidal feedback signals related to the phase of the stator winding voltages;
- power factor control means connected to receive the feedback signals and being operable in response thereto to generate command signals to said inverter which control the phase of the alternating currents the inverter applies to each of said motor windings;
- means for sensing the magnitude of the stator winding current and generating a signal proportional thereto;
- means for sensing the magnitude of the magnetic flux generated by the motor stator windings and generating a signal proportional thereto;
- and
- power factor selection means connected to receive said stator winding current signal and said magnetic flux signal and being operable in response thereto to select the power factor operating point of said power factor control means such that the magnetic flux signal is controlled as a function of said stator winding current signal.
4 more elements
An induction motor drive which comprises:
- an inverter connected to receive direct current and generate alternating current waveforms for application to the stator windings of an induction motor, the frequency of the current waveforms being determined by the frequency of firing pulses applied to the inverter;
- voltage sensing means coupled to said motor stator windings and being operable to generate a cyclic feedback signal which has a frequency related to motor speed;
- and
- pulse generation means coupled to receive the cyclic feedback signal, and in response thereto, generate firing pulses to said inverter.
1 more element
An induction motor drive which comprises:
- current regulator means for providing direct current to a d.c. bus in response to a current command signal;
- a current source inverter connected to the d.c. bus and being operable to generate alternating current waveforms for application to the stator windings of an induction motor, the frequency of the current waveforms being determined by the frequency of firing pulses applied to the inverter;
- power factor control means for generating firing pulses to the current source inverter which maintain the power factor of the electric power applied to the induction motor at a determined operating level;
- and
- means for determining the power factor operating level including means for sensing the magnitude of motor flux and determining the power factor operating level in response thereto.
2 more elements
An induction motor drive which comprises:
- a current source inverter connected to receive direct current from a d.c. link and generate a balanced three phase set of tri-state alternating current waveforms for application to the stator windings of an induction motor in order to produce discrete phase advances of the stator flux field, the frequency and sequencing of the waveforms being determined by phase advance command pulses applied to the inverter;
- voltage sensing means coupled to said motor stator windings and being operable to generate substantially sinusoidal feedback signals related in both frequency and phase to the stator winding voltages;
- power factor control means connected to receive said sinusoidal feedback signals and being operable in response thereto to generate phase advance command pulses to said inverter which control the phase shift of the alternating currents applied to the motor stator windings with respect to the stator voltages, in order to maintain the power factor of the electric power applied to the induction motor at a commanded level;
- means for generating a power factor command which reflects the magnetic flux error from which the motor is to operate;
- link current regulator means for providing direct current to the d.c. link in response to a current amplitude command;
- and
- means for generating a current amplitude command for the link current regulator means which reflects the speed error from which the motor is to operate.
4 more elements
Dependencies are inferred from the claim text.