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US3670235A
Expired / Lapsed
US
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Motor control system with compensation for low-frequency variations in motor energizing voltage
Assignee: Borg Warner Corp
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Filing: 1970-09-25
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Granted: 1972-06-13
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Expires: 1990-09-25
Abstract
Abstract A phase-shift stabilizer is connected in series with an inverter to provide a selective phase-shift of the individual timing pulses passed to the inverter, while maintaining a constant average frequency of these timing pulses. A rectifier circuit in a feedback line from the inverter output side provides a control voltage signal which modifies the phase-shift of each timing pulse in a direction and by an amount appropriate to offset undesired low-frequency fluctuation in the average output voltage from the inverter. The phase-shift stabilizer includes a sawtooth generator for producing a constant amplitude output signal varying in frequency as a function of a frequency regulating signal. A filter is connected to provide a signal which is a function of the undesired low-frequency modulation of the inverter output. A comparator circuit is connected to receive a composite signal formed by mixing the filter output and sawtooth generator signals, and to compare the composite signal against a reference signal. The comparator provides a phase-shifted output signal for controlling the inverter frequency to compensate for the unwanted low-frequency modulation.
Inventors
- 👤 Benton Bejach
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-23 04:58
CPC Classifications
H; H02; H02P; H02P27/00; H02P27/04; H02P27/06; H02M; H02M7/00; H02M7/42; H02M7/44; H02M7/48; H02M7/505; H02M7/515; H02M7/525
Claims Analysis
Total Claims: 11
Claim 1
Independent Claim
268 words
In a motor control system having an inverter for providing an a-c voltage, and means for supplying a frequency controlling signal including spaced timing pulses to regulate the frequency of inverter operation and correspondingly regulate the frequency of the inverter a-c output voltage, the improvement which comprises: a phase shift stabilizer, coupled in series with the inverter, including circuit means for effecting a controlled phase shift of individual timing pulses while maintaining constant the average frequency of the phase-shifted timing pulses in the output signal supplied for regulating the inverter, and circuit means, coupled to the inverter and to the phase shift stabilizer, for providing a control voltage signal which varies as a function of undesired low-frequency variations, to effect a selective phase shift of the individual timing pulses as a function of such undesired low-frequency variations, in which said phase shift stabilizer comprises a filter, connected to receive said control voltage signal and to provide a lowfrequency signal which varies with the low-frequency variations of the inverter a-c output voltage, a sawtooth generator, connected to receive the frequency-controlling signal and to provide a sawtooth voltage output signal of substantially constant amplitude and of a frequency determined by the timing pulses in the frequency-controlling signal, and a comparator stage, having a first input terminal connected to receive a reference signal, a second input terminal connected to receive a composite signal formed by mixing the low-frequency signal and the sawtooth voltage output signal, and an output terminal, connected to pass phase-shifted timing pulse signals toward the inverter to compensate for the low-frequency variations of the inverter a-c output voltage.
Claim 2
Dependent Claim
268 words
In a motor control system having an inverter for providing an a-c voltage, and means for supplying a frequency controlling signal including spaced timing pulses to regulate the frequency of inverter operation and correspondingly regulate the frequency of the inverter a-c output voltage, the improvement which comprises: a phase shift stabilizer, coupled in series with the inverter, including circuit means for effecting a controlled phase shift of individual timing pulses while maintaining constant the average frequency of the phase-shifted timing pulses in the output signal supplied for regulating the inverter, and circuit means, coupled to the inverter and to the phase shift stabilizer, for providing a control voltage signal which varies as a function of undesired low-frequency variations, to effect a selective phase shift of the individual timing pulses as a function of such undesired low-frequency variations, in which said phase shift stabilizer comprises a filter, connected to receive said control voltage signal and to provide a lowfrequency signal which varies with the low-frequency variations of the inverter a-c output voltage, a sawtooth generator, connected to receive the frequency-controlling signal and to provide a sawtooth voltage output signal of substantially constant amplitude and of a frequency determined by the timing pulses in the frequency-controlling signal, and a comparator stage, having a first input terminal connected to receive a reference signal, a second input terminal connected to receive a composite signal formed by mixing the low-frequency signal and the sawtooth voltage output signal, and an output terminal, connected to pass phase-shifted timing pulse signals toward the inverter to compensate for the low-frequency variations of the inverter a-c output voltage.
Claim 3
Dependent Claim
232 words
In a control system for energizing an a-c motor from an inverter, with an oscillator circuit for supplying a frequency-regulating signal including a train of timing pulses to control the frequency of inverter operation and correspondingly regulate the frequency of the inverter a-c output voltage, the improvement which comprises a phase shift stabilizer circuit, including: circuit means, coupled to the inverter, for providing a control voltage signal including a high-frequency component related to the frequency of inverter operation, and which may include an undesired low-frequency component; a filter circuit, connected to receive the control voltage signal from the circuit means, for removing the high-frequency component and providing an output signal including only the low-frequency component; a sawtooth generator circuit, connected to receive the frequency-regulating signal and provide a sawtooth output voltage signal synchronized in frequency with the timing pulses in the frequency-regulating signal, including a feedback circuit for assisting in regulating operation of the sawtooth generator to provide a substantially constant amplitude output signal; and a comparator circuit, including a first input terminal connected to receive a reference signal, a second input terminal connected to receive a composite signal provided by mixing the sawtooth output voltage signal with the clipped low-frequency signal, and an output terminal for providing timing pulse signals of constant average frequency but which are individually phase-shifted to offset the undesired low-frequency modulation of the inverter a-c output voltage.
Claim 4
Dependent Claim
232 words
In a control system for energizing an a-c motor from an inverter, with an oscillator circuit for supplying a frequency-regulating signal including a train of timing pulses to control the frequency of inverter operation and correspondingly regulate the frequency of the inverter a-c output voltage, the improvement which comprises a phase shift stabilizer circuit, including: circuit means, coupled to the inverter, for providing a control voltage signal including a high-frequency component related to the frequency of inverter operation, and which may include an undesired low-frequency component; a filter circuit, connected to receive the control voltage signal from the circuit means, for removing the high-frequency component and providing an output signal including only the low-frequency component; a sawtooth generator circuit, connected to receive the frequency-regulating signal and provide a sawtooth output voltage signal synchronized in frequency with the timing pulses in the frequency-regulating signal, including a feedback circuit for assisting in regulating operation of the sawtooth generator to provide a substantially constant amplitude output signal; and a comparator circuit, including a first input terminal connected to receive a reference signal, a second input terminal connected to receive a composite signal provided by mixing the sawtooth output voltage signal with the clipped low-frequency signal, and an output terminal for providing timing pulse signals of constant average frequency but which are individually phase-shifted to offset the undesired low-frequency modulation of the inverter a-c output voltage.
Claim 5
Dependent Claim
36 words
A control system as claimed in claim 2 and further comprising a clipper circuit, coupled to the filter circuit, for receiving the low-frequency signal and limiting the positive-going and negative-going peak excursions of the low-frequency signal.
Claim 6
Dependent Claim
43 words
A control system as claimed in claim 3 in which said clipper circuit comprises a pair of diodes connected back-to-back between the output side of the filter circuit and a plane of potential corresponding to the design center potential for the clipper circuit.
Claim 7
Dependent Claim
65 words
A control system as claimed in claim 2 in which the filter circuit is an active filter circuit, including a first operational amplifier connected to receive the control voltage signal at its input terminals, and a second operational amplifier connected to receive a reference signal at one of its input terminals and the output signal from the first operational amplifier at its other input terminal.
Claim 8
Dependent Claim
94 words
A control system as claimed in claim 2 in which the sawtooth generator circuit includes a charging capacitor, a first operational amplifier and a transistor connected to provide a substantially constant charging current for the charging capacitor, a discharge transistor coupled in parallel with the charging capacitor for rapidly completing a discharge path in response to receipt of a timing pulse from the oscillator circuit, and at least one emitter-coupled transistor coupled between the charging capacitor and the comparator circuit to supply the sawtooth output voltage signal for mixing with the clipped low-frequency signal.
Claim 9
Dependent Claim
58 words
A control system as claimed in claim 6 and in which said sawtooth generator circuit further comprises a feedback circuit, including a feedback conductor coupled to the emitter-coupled transistor, and a second operational amplifier coupled between the feedback conductor and the first operational amplifier to assist in maintaining a substantially constant amplitude of the sawtooth output voltage signal.
Claim 10
Dependent Claim
40 words
A motor control system as claimed in claim 2, in which said circuit means comprises a rectifier circuit, coupled between the output side of the inverter and the filter circuit of the phase-shift stabilizer, for providing the control voltage signal.
Claim 11
Dependent Claim
48 words
A motor control system as claimed in claim 2, in which said circuit means includes a resistor, coupled in series with the main d-c bus supplying energy to said inverter, for providing said control voltage signal as a function of undesired low-frequency variations in the d-c bus current.
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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) | 1975-06-13 | 1975-12-13 | 1976-06-13 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1979-06-13 | 1979-12-13 | 1980-06-13 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1983-06-13 | 1983-12-13 | 1984-06-13 | $7700.00 | Window Closed / Lapsed |