Patent US3917989A successfully refreshed from Google Patents.
US3917989A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Dual mode control of an induction electric motor
Assignee: Aerojet Rocketdyne Inc
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Filing: 1974-11-22
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Granted: 1975-11-04
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Expires: 1994-11-22
Abstract
Abstract An induction motor control circuit that includes a signal generator for providing a command signal having a frequency that represents desired motor speed, and a feedback control for providing a reference signal having a frequency determined by actual motor speed, is described herein. Control logic compares the frequencies of the command reference signals and causes the control circuit to operate in a first mode during acceleration in which the frequency of the drive signal supplied to the motor increases at a rate that depends upon actual motor speed. This controlled increase in drive signal frequency prevents changes that would be too sudden for the motor to follow immediately and that would therefore cause a torque loss. When a desired motor speed is attained, the control circuit operates in a second mode in which the frequency of the drive signal is fixed by the frequency of the command signal. The fixing of the drive signal frequency once a desired speed is attained provides good speed control.
Inventors
- 👤 Jr Jonas Bereisa
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-23 08:02
CPC Classifications
H; H02; H02P; H02P27/00; H02P27/04; H02P27/06; H02P27/045; H02P27/048; H02P2207/00; H02P2207/01; H02P27/047
Claims Analysis
Total Claims: 6
Claim 1
Independent Claim
95 words
A circuit for controlling operation of an electric induction motor, said control circuit comprising: command signal generating means for providing a cyclic command signal having a frequency representing a desired motor speed; reference signal means responsive to the induction motor for providing a cyclic reference signal having a frequency representing a speed slightly greater than the operating speed of the induction motor; drive signal means responsive to said command and reference signals for providing the induction motor with a drive signal having a frequency corresponding to the lesser of said command and reference signal frequencies.
Claim 2
Dependent Claim
95 words
A circuit for controlling operation of an electric induction motor, said control circuit comprising: command signal generating means for providing a cyclic command signal having a frequency representing a desired motor speed; reference signal means responsive to the induction motor for providing a cyclic reference signal having a frequency representing a speed slightly greater than the operating speed of the induction motor; drive signal means responsive to said command and reference signals for providing the induction motor with a drive signal having a frequency corresponding to the lesser of said command and reference signal frequencies.
Claim 3
Dependent Claim
122 words
The control circuit of claim 1 in which said drive signal means comprise: means for providing a control signal having a frequency corresponding to the lesser of said command and reference signal frequencies; signal generating means responsive to said control signal for providing a DC electric signal having a voltage level determined by the frequency of said control signal; and inverter means responsive to said control and DC signals for providing said drive signal by inverting said DC signal at a rate determined by the frequency of said control signal, said drive signal means thereby varying both the amplitude and frequency of said drive signal to permit multi-speed operation of an induction motor requiring a drive signal having a predetermined amplitude-to-frequency ratio.
Claim 4
Dependent Claim
121 words
The control circuit of claim 2 in which said control signal providing means comprise: comparator means for comparing the frequencies of said command and reference signals and providing an output signal having a first value when said reference signal has the lesser frequency and a second value when said command signal has the lesser frequency; and gating means responsive to said command, reference, and comparator means output signals for transmitting said reference signal to said signal generating means and said inverter means when the output signal from said comparator means has said first value, and for transmitting said command signal to said signal generating means and said inverter means when the output signal from said comparator means has said second value.
Claim 5
Dependent Claim
56 words
The control circuit of claim 3 in which said reference signal means comprise: means for providing a cyclic motor speed signal having a frequency representing the operating speed of the induction motor; and signal incrementing means for increasing the frequency of said motor speed signal by a pre-selected small amount to thereby provide said reference signal.
Claim 6
Dependent Claim
141 words
The control circuit of claim 4 in which: the circuit comprises a circuit for controlling operation of an induction motor having a rotatable output shaft, the torque of said shaft being a measure of motor output force; said means for providing said motor speed signal comprise tachometer means for providing an output signal having a frequency representing the rate of rotation of said motor output shaft; the output torque of said induction motor is determined at least in part by the frequency difference between said tachometer output signal and said motor drive signal; and said signal incrementing means includes means for adjusting the amount by which said tachometer output signal is incremented to thereby control the output torque generated by the induction motor upon receipt of a drive signal having a frequency corresponding to the frequency of the incremented reference signal.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1978-11-03 | 1979-05-05 | 1979-11-04 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1982-11-03 | 1983-05-05 | 1983-11-04 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1986-11-03 | 1987-05-05 | 1987-11-04 | $7700.00 | Window Closed / Lapsed |