Electricity: motive power systems – Induction motor systems – Braking
Patent
1986-07-15
1987-12-15
Smith, Jr., David
Electricity: motive power systems
Induction motor systems
Braking
187119, H02P 318, B66B 132
Patent
active
047135956
ABSTRACT:
In an elevator driven by an induction motor and having a slip control device for generating a slip frequency command signal on the basis of an error between a speed command value and a running speed value of the induction motor so as to control a VVVF type inverter which in turn provides a corresponding alternating current of variable voltage and frequency, the inverter having a smoothing capacitor on a D-C side thereof, a control apparatus for stabilizing torque of the induction motor by smoothly changing operation of the induction motor from a powering mode to a regenerative mode, the control apparatus comprising a current detector for detecting charging current of the smoothing capacitor having a portion for detecting polarity of the slip frequency command signal and a unit responsive to the charging current detected by the current detector and the slip frequency command signal generated by the slip control device for changing operation of the induction motor from the powering mode to the regenerative mode only when a voltage value based on the charging current has exceeded a preset reference voltage value after a negative sign of the slip frequency command signal is detected by the polarity detection portion.
REFERENCES:
patent: 4471419 (1984-09-01), Schneider et al.
patent: 4475631 (1984-10-01), Nomura
patent: 4503940 (1985-03-01), Watanabe
patent: 4545464 (1985-10-01), Nomura
patent: 4559549 (1986-07-01), Muton et al.
patent: 4625159 (1986-11-01), Ikejima
patent: 4667777 (1987-05-01), Nomura
Mitsubishi Denki & Kabushiki Kaisha
Smith Jr. David
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