US3887853A
Expired / Lapsed
US
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Stabilizing system for an inverter-driven induction motor
Assignee: Eaton Corp
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Filing: 1973-12-14
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Granted: 1975-06-03
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Expires: 1993-12-14
Abstract
Abstract In a motor control system in which an induction motor is driven by an inverter and the motor tends to resonate, the resonant frequency of the motor and the extent of its damping are adjusted to desirable amounts by a local feedback circuit. An output signal of the local feedback circuit is algebraically added to a speed command voltage for the motor control system. A sum signal thus produced is connected to the input of the inverter to control the motor speed. The sum signal is also employed as one of two input signals to the local feedback circuit, the second input signal being proportional to the speed of the rotor of the motor and obtained from a sensor connected with the rotor shaft. The two input signals to the local feedback circuit are subtracted and their difference signal is processed through a lag circuit and a filter network to produce the output signal of the local feedback circuit. When the inverter and motor are thus stabilized by the local feedback circuit just described, it is much easier to stabilize a larger speed-control feedback loop in which the inverter and motor may be employed.
Inventors
- 👤 Frank N Klein
- 👤 Gerald F O'callaghan
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-23 04:30
CPC Classifications
H; H02; H02P; H02P23/00; H02P23/08; H02P23/22
Claims Analysis
Total Claims: 21
Claim 1
Independent Claim
150 words
Stabilizing apparatus for use with an inverter-driven induction motor system having an inverter responsive to a principal control signal to produce ac excitation for the stator of the motor comprising sensor means for sensing the speed of the rotor of the motor and for producing a first signal dependent thereon, circuit means for producing a second signal in accordance with the frequency of power with which the stator of said motor is excited by said inverter, algebraic combining means for combining said first and second signals to produce a third signal representative of the slip frequency of said motor, frequency-dependent filter means receiving said third signal for producing a filtered fourth signal in response to said third signal at least at times when said third signal is substantially below a pull-out level, and means for controlling said inverter in accordance with both said fourth signal and said principal control signal.
Claim 2
Dependent Claim
150 words
Stabilizing apparatus for use with an inverter-driven induction motor system having an inverter responsive to a principal control signal to produce ac excitation for the stator of the motor comprising sensor means for sensing the speed of the rotor of the motor and for producing a first signal dependent thereon, circuit means for producing a second signal in accordance with the frequency of power with which the stator of said motor is excited by said inverter, algebraic combining means for combining said first and second signals to produce a third signal representative of the slip frequency of said motor, frequency-dependent filter means receiving said third signal for producing a filtered fourth signal in response to said third signal at least at times when said third signal is substantially below a pull-out level, and means for controlling said inverter in accordance with both said fourth signal and said principal control signal.
Claim 3
Dependent Claim
150 words
Stabilizing apparatus for use with an inverter-driven induction motor system having an inverter responsive to a principal control signal to produce ac excitation for the stator of the motor comprising sensor means for sensing the speed of the rotor of the motor and for producing a first signal dependent thereon, circuit means for producing a second signal in accordance with the frequency of power with which the stator of said motor is excited by said inverter, algebraic combining means for combining said first and second signals to produce a third signal representative of the slip frequency of said motor, frequency-dependent filter means receiving said third signal for producing a filtered fourth signal in response to said third signal at least at times when said third signal is substantially below a pull-out level, and means for controlling said inverter in accordance with both said fourth signal and said principal control signal.
Claim 4
Dependent Claim
150 words
Stabilizing apparatus for use with an inverter-driven induction motor system having an inverter responsive to a principal control signal to produce ac excitation for the stator of the motor comprising sensor means for sensing the speed of the rotor of the motor and for producing a first signal dependent thereon, circuit means for producing a second signal in accordance with the frequency of power with which the stator of said motor is excited by said inverter, algebraic combining means for combining said first and second signals to produce a third signal representative of the slip frequency of said motor, frequency-dependent filter means receiving said third signal for producing a filtered fourth signal in response to said third signal at least at times when said third signal is substantially below a pull-out level, and means for controlling said inverter in accordance with both said fourth signal and said principal control signal.
Claim 5
Dependent Claim
46 words
Stabilizing apparatus as defined in claim 1 and wherein said means for controlling said inverter in accordance with said fourth signal comprises algebraic summation means receiving said fourth signal and said principal control signal and producing a sum signal in response thereto for controlling said inverter.
Claim 6
Dependent Claim
24 words
Stabilizing apparatus as defined in claim 2 and wherein said second signal is obtained from the sum signal output of said algebraic summation means.
Claim 7
Dependent Claim
18 words
Stabilizing apparatus as defined in claim 1 and wherein said frequency-dependent filter means comprises electric lead/lag filter means.
Claim 8
Dependent Claim
32 words
Stabilizing apparatus as defined in claim 4 and wherein said lead/lag filter means comprises a lag filter having lag characteristics matched to the lag of said motor between slip and air-gap torque.
Claim 9
Dependent Claim
21 words
Stabilizing apparatus as defined in claim 4 and wherein said lead/lag filter means comprises means for critically damping said induction motor.
Claim 10
Dependent Claim
52 words
Stabilizing apparatus as defined in claim 1 and wherein said sensor means comprises means for producing successive pulses upon rotation of said rotor anD frequency-to-voltage converter means for converting said successive pulses to said first signal, said first signal comprising a dc signal varying in accordance with the frequency of said pulses.
Claim 11
Dependent Claim
127 words
Stabilizing apparatus as defined in claim 1 and further comprising speed feedback means for controlling rotor speed, said speed feedback means including command signal means for producing a command signal specifying a desired speed of said rotor, rotation sensing means for producing a feedback signal in dependence upon the rotation of said rotor, comparator means for comparing said command signal with said feedback signal and for producing a position error signal in accordance with an accumulated difference between said command and feedback signals, said comparator means including means for producing an offsetting signal corresponding to the slip of said motor, and combining circuit means for combining said command signal and said position error signal and said offsetting signal to produce said principal control signal for said inverter.
Claim 12
Independent Claim
179 words
A system for controlling an induction motor comprising means for producing a principal control signal, inverter means responsive to said principal control signal to produce an ac voltage for energizing the stator windings of said motor, sensor means responsive to incremental changes in the angular position of the rotor of said motor for producing feedback frequency signals in respsonse to said incremental changes of position, conversion means for converting said feedback frequency signals to current feedback signals responsive to the feedback frequency, circuit means for providing a signal representing the frequency of ac voltage produced by said inverter, means for producing a slip signal having a magnitude which represents the slip frequency of said motor including means for subtracting said signal representing the inverter frequency from said current feedback signal to produce said slip signal, filter means for attenuating and phase-shifting said slip signal including at least slip signal values substantially below a pull-out level, and means for connecting the output signal of said filter means with said inverter to combine with said command signal in controlling said inverter.
Claim 13
Independent Claim
179 words
A system for controlling an induction motor comprising means for producing a principal control signal, inverter means responsive to said principal control signal to produce an ac voltage for energizing the stator windings of said motor, sensor means responsive to incremental changes in the angular position of the rotor of said motor for producing feedback frequency signals in respsonse to said incremental changes of position, conversion means for converting said feedback frequency signals to current feedback signals responsive to the feedback frequency, circuit means for providing a signal representing the frequency of ac voltage produced by said inverter, means for producing a slip signal having a magnitude which represents the slip frequency of said motor including means for subtracting said signal representing the inverter frequency from said current feedback signal to produce said slip signal, filter means for attenuating and phase-shifting said slip signal including at least slip signal values substantially below a pull-out level, and means for connecting the output signal of said filter means with said inverter to combine with said command signal in controlling said inverter.
Claim 14
Dependent Claim
46 words
Stabilizing apparatus as defined in claim 9 and wherein said filter means comprises lag filter means simulating an internal lag in said motor between slip and air-gap torque, and further comprises lead network filter means for simulating feedback around said internal lag, to damp said motor.
Claim 15
Dependent Claim
94 words
Stabilizing apparatus for an inverter-driven induction motor system having a principal control signal controlling said inverter comprising circuit means for producing a signal representing the slip of said motor, filter means receiving said slip signal and attenuating and shifting the phase thereof differently for different frequencies of variation of said slip signal and operative at least for slip signal values substantially below a pull-out level, and means for combining the attenuated phase-shifted signals from said filter means with the principal control signal to control the resonant frequency and damping of said inverter-driven motor system.
Claim 16
Dependent Claim
94 words
Stabilizing apparatus for an inverter-driven induction motor system having a principal control signal controlling said inverter comprising circuit means for producing a signal representing the slip of said motor, filter means receiving said slip signal and attenuating and shifting the phase thereof differently for different frequencies of variation of said slip signal and operative at least for slip signal values substantially below a pull-out level, and means for combining the attenuated phase-shifted signals from said filter means with the principal control signal to control the resonant frequency and damping of said inverter-driven motor system.
Claim 17
Independent Claim
98 words
A method of stabilizing an induction motor that is energized by an inverter having a principal inverter input signal comprising the steps of providing a first signal proportional to the slip, passing said first signal through a lag circuit to produce a second signal proportional to air-gap torque, passing said second signal through a stabilizing filter to produce a third signal, utilizing said third signal as a feedback signal by combining said third signal with the principal inverter input signal to produce a fourth signal, and controlling said inverter with said fourth signal and the principal input signal.
Claim 18
Independent Claim
98 words
A method of stabilizing an induction motor that is energized by an inverter having a principal inverter input signal comprising the steps of providing a first signal proportional to the slip, passing said first signal through a lag circuit to produce a second signal proportional to air-gap torque, passing said second signal through a stabilizing filter to produce a third signal, utilizing said third signal as a feedback signal by combining said third signal with the principal inverter input signal to produce a fourth signal, and controlling said inverter with said fourth signal and the principal input signal.
Claim 19
Dependent Claim
50 words
A method as defined in claim 12 and wherein said step of providing a first signal proportional to the slip comprises sensing the rotor speed of said mOtor and producing a fifth signal in response thereto, and subtracting said fifth signal from said fourth signal to produce said first signal.
Claim 20
Dependent Claim
203 words
Stabilizing apparatus for use with an inverter-driven induction motor system having an inverter responsive to a principal control signal to produce ac excitation for the stator of the motor comprising sensor means for sensing the speed of the rotor of the motor and for producing a first signal dependent thereon, circuit means for producing a second signal in accordance with the frequency of power with which the stator of said motor is excited by said inverter, algebraic combining means for combining said first and second signals to produce a third signal representative of the slip frequency of said motor, frequency-dependent filter means for producing a filtered fourth signal in response to said third signal, and means for controlling said inverter in accordance with both said fourth signal and said principal control signal, and wherein said frequency-dependent filter means comprises lead/lag filter means including resistance and reactance means for retarding the phase angle of said fourth signal with respect to said third signal in a first frequency range and for advancing the phase angle of said fourth signal with respect to said third signal in a second frequency range and further comprises means for manually adjusting the phase-changing characteristics of said lead/lag filter means.
Claim 21
Dependent Claim
203 words
Stabilizing apparatus for use with an inverter-driven induction motor system having an inverter responsive to a principal control signal to produce ac excitation for the stator of the motor comprising sensor means for sensing the speed of the rotor of the motor and for producing a first signal dependent thereon, circuit means for producing a second signal in accordance with the frequency of power with which the stator of said motor is excited by said inverter, algebraic combining means for combining said first and second signals to produce a third signal representative of the slip frequency of said motor, frequency-dependent filter means for producing a filtered fourth signal in response to said third signal, and means for controlling said inverter in accordance with both said fourth signal and said principal control signal, and wherein said frequency-dependent filter means comprises lead/lag filter means including resistance and reactance means for retarding the phase angle of said fourth signal with respect to said third signal in a first frequency range and for advancing the phase angle of said fourth signal with respect to said third signal in a second frequency range and further comprises means for manually adjusting the phase-changing characteristics of said lead/lag filter means.
References Cited (Backward Citations)
US3512067A
Cited
US3372323A
Cited
US3743906A
Cited
US3700986A
Cited
US3671831A
Cited
US3753064A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1978-06-02 | 1978-12-02 | 1979-06-03 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1982-06-02 | 1982-12-02 | 1983-06-03 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1986-06-02 | 1986-12-02 | 1987-06-03 | $7700.00 | Window Closed / Lapsed |