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US 3,983,463 AGranted
Method and apparatus for controlling the speed of induction motors
AssigneeTokyo Shibaura Denki Kabushiki Kaisha
InventorsAkira Nabae, Takeo Shimamura
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AssigneeTokyo Shibaura Denki Kabushiki Kaisha
InventorsAkira Nabae, Takeo Shimamura
Estimating the term…
In a method and apparatus for controlling the speed of an induction motor energized from a source of variable frequency, e.g. a controllable inverter, a control signal which is a function of the primary current of the induction motor is produced, a predetermined slip frequency pattern signal is generated in accordance with the control signal, and the source is controlled in accordance with the slip frequency pattern signal for controlling the operating frequency. By suitably determining the shape of the slip frequency pattern signal it is possible to operate the induction motor with either one of normal induction motor characteristic, DC series motor characteristic, DC shunt motor characteristic, DC weak field motor characteristic and DC compound motor characteristic, and to operate the induction motor for smooth and continuous power regeneration.
In a method of controlling the speed of an induction motor which is energized from a source of variable frequency, the improvement which comprises the steps of producing a control signal which is a function of the primary current of said induction motor, generating a second signal having a predetermined slip frequency pattern in accordance with said control signal, generating a frequency signal proportional to the speed of said induction motor, producing a variable frequency control signal corresponding to the algebraic sum of said frequency signal and said second signal, and controlling said source in accordance with said variable frequency control siganl for controlling the operating frequency of said source thereby operating said induction motor at or near the maximum value of the torque coefficient thereof.
In apparatus for controlling the speed of an induction motor which is energized from a source of variable frequency, the improvement which comprises means for producing a control signal which is a function of the primary current of said induction motor, means responsive to said control signal for generating a second signal having a predetermined slip frequency pattern, means for generating a frequency signal proportional to the speed of said induction motor, means for producing a variable frequency control signal corresponding to the algebraic sum of said frequency signal and said second signal, and means responsive to said variable frequency control signal for controlling the operating frequency of said source thereby operating said induction motor at or near the maximum value of the torque coefficient thereof.
In apparatus for controlling the speed of an induction motor which is energized by a source of variable frequency, means for generating a frequency control signal having a predetermined slip frequency pattern and used to control said source, said means comprising a first slip frequency pattern signal generator, a second slip frequency pattern signal generator, and transfer switch means for causing said first slip frequency pattern signal generator to respond to a second control signal which is a function of the primary current of said induction motor during the powering operation of said induction motor and for causing said second slip frequency pattern signal generator to respond to said second control signal during the regeneration operation of said induction motor.
Dependencies are inferred from the claim text.