US3671832A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Suppression of torque modulation in electric motor drive systems by frequency control
Assignee: Motors Liquidation Co
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Filing: 1971-05-06
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Granted: 1972-06-20
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Expires: 1991-05-06
Abstract
Abstract An electric motor is supplied voltage having a continually varying frequency to obviate cyclic torque pulsations or torque modulation observed to cause vibrations in the motor and load. An AC alternator is connected through a frequency changer with an induction motor in a controlled slip motor drive system including a continually varying slip frequency signal to shift the slip frequency in relation to a nominal value to prevent cyclic torque pulsations. The slip frequency is varied at a rate such that the rotor and load operate at the nominal slip, being incapable of following the changes in input frequency.
Inventors
- 👤 Jalal T Salihi
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-02 15:00
CPC Classifications
H; H02; H02P; H02P23/00; H02P23/08
Claims Analysis
Total Claims: 4
Claim 1
Independent Claim
137 words
An AC induction motor control, comprising: an AC induction motor, a source of power, a frequency changer interconnecting said motor and said source of power for controlling the frequency of an alternating voltage applied to said motor, slip frequency control means coupled with said frequency changer and said motor for controlling the output frequency of said frequency changer and motor slip frequency, and means connected with said slip frequency control means to continually vary the slip frequency in relation to a nominal slip frequency value at a rate of variance in excess of the mechanical time constant of the motor such that the motor operates at a constant speed though the frequency of input power cyclically varies, whereby torque pulsations associated with energization of the motor are obviated as a source of mechanical vibration during motor operation.
Claim 2
Dependent Claim
137 words
An AC induction motor control, comprising: an AC induction motor, a source of power, a frequency changer interconnecting said motor and said source of power for controlling the frequency of an alternating voltage applied to said motor, slip frequency control means coupled with said frequency changer and said motor for controlling the output frequency of said frequency changer and motor slip frequency, and means connected with said slip frequency control means to continually vary the slip frequency in relation to a nominal slip frequency value at a rate of variance in excess of the mechanical time constant of the motor such that the motor operates at a constant speed though the frequency of input power cyclically varies, whereby torque pulsations associated with energization of the motor are obviated as a source of mechanical vibration during motor operation.
Claim 3
Dependent Claim
153 words
An AC induction motor control, comprising: an AC induction motor, a source of AC power, a controlled rectifier converter interconnecting said motor and said source of AC power, slip frequency control means coupled with said converter and said motor to sequentially and periodically gate the controlled rectifiers of said converter to control converter operating frequency and motor slip frequency, and means connected with said slip frequency control means to continually vary the slip frequency in relation to a nominal slip frequency value at a rate of variance in excess of the mechanical time constant of the motor such that the motor operates at a constant speed though the frequency of input power cyclically varies, said last named means causing excursions of the slip frequency exceeding the width of frequency bands defining torque modulation, whereby torque modulation associated with energization of the motor is obviated as a source of mechanical vibration during motor operation.
Claim 4
Dependent Claim
153 words
An AC induction motor control, comprising: an AC induction motor, a source of AC power, a controlled rectifier converter interconnecting said motor and said source of AC power, slip frequency control means coupled with said converter and said motor to sequentially and periodically gate the controlled rectifiers of said converter to control converter operating frequency and motor slip frequency, and means connected with said slip frequency control means to continually vary the slip frequency in relation to a nominal slip frequency value at a rate of variance in excess of the mechanical time constant of the motor such that the motor operates at a constant speed though the frequency of input power cyclically varies, said last named means causing excursions of the slip frequency exceeding the width of frequency bands defining torque modulation, whereby torque modulation associated with energization of the motor is obviated as a source of mechanical vibration during motor operation.
References Cited (Backward Citations)
US3323032A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1975-06-20 | 1975-12-20 | 1976-06-20 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1979-06-20 | 1979-12-20 | 1980-06-20 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1983-06-20 | 1983-12-20 | 1984-06-20 | $7700.00 | Window Closed / Lapsed |