US4713595A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Control apparatus for elevator
Assignee: Mitsubishi Electric Corp
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Filing: 1986-07-15
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Granted: 1987-12-15
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Expires: 2006-07-15
Abstract
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.
Inventors
- 👤 Masashi Yonemoto
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-29 19:06
CPC Classifications
H; H02; H02P; H02P23/00; H02P23/08; B; B66; B66B; B66B1/00; B66B1/24; B66B1/28; B66B1/30; B66B1/308
Claims Analysis
Total Claims: 8
Claim 1
Independent Claim
203 words
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, said 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, said control apparatus comprising: a current detector for detecting charging current of the smoothing capacitor, and a switching device having a portion for detecting polarity of the slip frequency command signal and means responsive to the charging current detected by said current detector and the slip frequency command signal generated by said 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.
Claim 2
Dependent Claim
203 words
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, said 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, said control apparatus comprising: a current detector for detecting charging current of the smoothing capacitor, and a switching device having a portion for detecting polarity of the slip frequency command signal and means responsive to the charging current detected by said current detector and the slip frequency command signal generated by said 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.
Claim 3
Dependent Claim
49 words
A control apparatus for an elevator according to claim 1 wherein said polarity detection portion comprises a comparator which compares the slip frequency command signal generated by the slip control device with a predetermined reference value and generates an output expressing whether the command signal is positive or negative.
Claim 4
Dependent Claim
88 words
A control apparatus for an elevator according to claim 2 wherein said switching device further comprises an integrator for integrating the charging current detected by said current detector and for generating an integral output representative thereof, a comparator for comparing said integral output of said integrator with a predetermined reference value so as to generate an output when the integral output of said integrator exceeds the predetermined reference value, and switching means for changing the operation of the induction motor in response to the output of said comparator.
Claim 5
Dependent Claim
40 words
A control apparatus for an elevator according to claim 3 wherein the integral output of said integrator is held in a reset state when a positive sign of the slip frequency command signal is detected by said polarity detection means.
Claim 6
Dependent Claim
55 words
A control apparatus for an elevator according to claim 3 wherein said switching device further comprises gate means operable responsive to the output of said comparator and the negative sign detection of the slip frequency command signal by said polarity detection portion so as to operate and maintain the induction motor in the regenerative mode.
Claim 7
Dependent Claim
43 words
A control apparatus for an elevator according to claim 3 wherein said current detector takes the form of a current transformer supplying an output of a magnitude proportional to a magnitude of the detected charging current to said integrator of said switching device.
Claim 8
Dependent Claim
38 words
A control apparatus for an elevator according to claim 1 wherein, when the induction motor operates in the regenerative mode, the slip control device performs a slip frequency control so as to consume regenerative power within said motor.
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1990-12-14 | 1991-06-15 | 1991-12-15 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1994-12-14 | 1995-06-15 | 1995-12-15 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1998-12-14 | 1999-06-15 | 1999-12-15 | $7700.00 | Window Closed / Lapsed |