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AssigneeGeneral Electric Company
InventorsAllan Barr Plunkett, John Douglas D'Atre
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A new induction motor control method and system utilizes one more electric power inverters each supplying a separate induction motor with alternating current excitation power. The respective inverters preferably comprise auto-sequential commutated controlled current inverters. Direct current is supplied to each inverter in the system from a common direct current power supply preferably comprising a phase controlled rectifier circuit with individual current smoothing inductors connected in the direct current link to each power inverter for isolation purposes. A common operator controlled power level control module is provided for controlling the magnitude of the output current supplied from the common phase controlled rectifier to all of the inverters in parallel. Respective motor flux sensing means are provided for each induction motor for deriving individual feedback control signals representative of the flux developed by the respective induction motors. The flux feedback signal is summed with an input command value of a flux control signal in a suitable summing circuit, and the error signal is supplied through a suitable compensating circuit for regulating the flux level of the respective induction motors by individually controlling the frequency of the excitation current supplied to the stator windings of the motor by its associated inverter. In a preferred embodiment the actual electro-magnetic flux produced across the induction motor stator-rotor gap is sensed and fed back to the summing circuit for control purposes. This sensed actual value of motor flux signal also is utilized to derive an actual value of torque feedback control signal that is employed in controlling the magnitude of the direct current supplied by the common phase controlled rectifier to all of the inverters in parallel. It is also preferred to employ a phase lock-loop converter as the compensating circuit in the frequency control.
A new and improved induction motor control system including in combination electric power conversion apparatus having input terminals adapted to be coupled to a source of electric energy and output terminals adapted to supply alternating current excitation to an induction motor at a desired stator excitation frequency, motor flux sensing means for deriving a first feedback signal representative of the magnitude of electromagnetic flux being developed across the stator-rotor gap of the induction motor, means for providing a first control signal representative of a desired value of flux, and flux regulating means coupled to said conversion apparatus and responsive to said feedback signal and said first control signal for controlling the frequency of the stator excitation alternating current supplied to the induction motor by said apparatus as necessary to minimize the difference between the value of said feedback signal and the value of said first control signal.
A new and improved induction motor control system including in combination a plurality of alternating current induction motors, respective inverter means coupled to and supplying each of said induction motors with excitation alternating current, common direct current power supply means, direct current coupling circuit means for coupling direct current from said common direct current power supply means to the input of the respective inverter means, said direct current coupling circuit means including individual isolating choke inductors for isolating each inverter means from the others and from the common direct current power supply at alternating current frequencies, common power control means for controlling the magnitude of the direct current supplied from said common direct current power supply means to all said inverter means, respective motor flux sensing means for each of said induction motors for deriving individual feedback control signals representative of the flux developed by the respective induction motors, means for supplying an operator controlled first input control signal representative of a desired value of motor flux for each induction motor, respective flux summing circuit means responsive to the respective motor flux sensing means and respective first input control signals for deriving individual error control signals for regulating the flux level of the respective induction motors, and respective, compensating circuit means coupled to the outputs of said respective summing circuit means and to the frequency controlling inputs of the respective inverter means for individually controlling the frequency of the stator excitation alternating current supplied to the respective induction motors by their associated inverter means in a manner to minimize the individual output error control signals from the respective summing circuit means.
An improved method of controlling operation of at least one alternating current induction motor with a power converter having separate power and frequency controlling means including at least one inverter for converting direct current electric power into alternating current for exciting the induction motor, said method comprising deriving a feedback motor flux signal representative of the magnitude of motor flux produced in the induction motor and feeding back the motor flux signal thus derived to control the frequency of operation of the inverter.
Dependencies are inferred from the claim text.