Patent US4745991A successfully refreshed from Google Patents.
US4745991A
Expired / Lapsed
US
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Speed control apparatus for A.C. elevator
Assignee: Mitsubishi Electric Corp
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Filing: 1987-04-01
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Granted: 1988-05-24
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Expires: 2007-04-01
Abstract
Abstract A speed control apparatus for an A.C. elevator according to this invention comprises integration circuits which integrate outputs of current detectors for detecting primary currents of an induction motor and which are reset at fixed periods, and holding circuits which hold outputs of the integration circuits for a predetermined time. Thus, the influences of the ripples of the currents by pulse width modulation are eliminated, and the digital conversions of the three-phase currents can be performed by a single analog-to-digital converter.
Inventors
- 👤 Tooru Tanahashi
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-31 10:41
CPC Classifications
B; B66; B66B; B66B1/00; B66B1/24; B66B1/28; B66B1/30; H; H02; H02P; H02P21/00; Y; Y02; Y02B; Y02B50/00
Claims Analysis
Total Claims: 12
Claim 1
Independent Claim
152 words
A speed control apparatus for an A.C. elevator, comprising: an inverter which inverts D.C. power into A.C. power of variable voltage and variable frequency, a cage driving motor which is supplied with the A.C. power from said inverter and which drives a cage of the elevator, a speed detector which detects a speed of said motor, a current detector which detects a primary current of said motor, an integration circuit which integrates an output of said current detector and which is reset at every fixed period, a holding circuit which holds an output of said integration circuit for a predetermined time, and control means for controlling the primary current and a frequency of said motor with an output of said speed detector and an output of said holding circuit, thereby to control said inverter so as to control a torque current and an exciting current of said motor independently of each other.
Claim 2
Dependent Claim
152 words
A speed control apparatus for an A.C. elevator, comprising: an inverter which inverts D.C. power into A.C. power of variable voltage and variable frequency, a cage driving motor which is supplied with the A.C. power from said inverter and which drives a cage of the elevator, a speed detector which detects a speed of said motor, a current detector which detects a primary current of said motor, an integration circuit which integrates an output of said current detector and which is reset at every fixed period, a holding circuit which holds an output of said integration circuit for a predetermined time, and control means for controlling the primary current and a frequency of said motor with an output of said speed detector and an output of said holding circuit, thereby to control said inverter so as to control a torque current and an exciting current of said motor independently of each other.
Claim 3
Dependent Claim
21 words
A speed control apparatus for an A.C. elevator as defined in claim 1, wherein said motor is a three-phase induction motor.
Claim 4
Dependent Claim
24 words
A speed control apparatus for an A.C. elevator as defined in claim 1, wherein said inverter is an inverter of pulse width modulation system.
Claim 5
Dependent Claim
21 words
A speed control apparatus for an A.C. elevator as defined in claim 1, wherein said current detector is a current transformer.
Claim 6
Dependent Claim
30 words
A speed control apparatus for an A.C. elevator as defined in claim 1, wherein said integration circuit is a parallel circuit which consists of an operational amplifier and a capacitor.
Claim 7
Dependent Claim
26 words
A speed control apparatus for an A.C. elevator as defined in claim 1, wherein said holding circuit is configured of a capacitor and an operational amplifier.
Claim 8
Dependent Claim
29 words
A speed control apparatus for an A.C. elevator as defined in claim 1, wherein said control means, said integration circuit and said holding circuit are configured of a microcomputer.
Claim 9
Dependent Claim
36 words
A speed control apparatus for an A.C. elevator as defined in claim 7, wherein said control means receives an input obtained by subjecting the output of said holding circuit to analog-to-digital conversion by an analog-to-digital converter.
Claim 10
Dependent Claim
39 words
A speed control apparatus for an A.C. elevator as defined in claim 8, wherein the single analog-to-digital converter is comprised, and it delivers the held outputs of three respective phases to said control means by changing-over them in succession.
Claim 11
Dependent Claim
35 words
A speed control apparatus for an A.C. elevator as defined in claim 7, wherein said control means includes input means for converting a speed command value into a digital value and delivering the digital value.
Claim 12
Dependent Claim
37 words
A speed control apparatus for an A.C. elevator as defined in claim 7, wherein said control means includes input means for converting the output of said speed detector into a digital value and delivering the digital value.
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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) | 1991-05-24 | 1991-11-23 | 1992-05-24 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1995-05-24 | 1995-11-23 | 1996-05-24 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1999-05-24 | 1999-11-23 | 2000-05-24 | $7700.00 | Window Closed / Lapsed |