US3593079A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Polyphase electric motor control system for speed and direction of rotation
Assignee: ZF International UK Ltd
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Filing: 1969-08-25
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Granted: 1971-07-13
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Expires: 1989-08-25
Abstract
Abstract The invention relates to a system for controlling the speed and direction of rotation of a polyphase AC motor in accordance with the magnitude and polarity respectively of an input signal. The input signal is fed to a firing circuit which is also controlled by the voltage in one of the phase lines of the motor supply. The firing circuit produces a train of square pulses of constant width and whose phase relationship with the voltages in the motor supply phase lines is dependent on the magnitude only of the input signal. The input signal is also fed to a direction sensing circuit which produces a direction signal in one of two lines depending on the polarity only of the input signal. The pulse train is gated by the presence or otherwise of the direction signal to one of two sets of semiconductor controlled rectifiers which control the current in the phase lines of the motor supply for forward and reverse rotation respectively. The speed of this rotation is dependent in a known manner on the aforesaid phase relationship.
Inventors
- 👤 Anthony Brian Plant
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-30 22:56
CPC Classifications
H; H02; H02P; H02P23/00; H02P23/24
Claims Analysis
Total Claims: 11
Claim 1
Independent Claim
156 words
An electric motor control system which comprises two sets of semiconductor controlled rectifiers, a single firing circuit adapted to produce firing pulses the phase relationship of which to the motor supply is determined by the magnitude of an input signal to the firing circuit, a pair of gate circuits associated respectively with the two sets of semiconductor controlled rectifiers a polarity detection circuit including a switching circuit which has an output signal when the said input signal is of one polarity only and electronic logic means for supplying a signal to either one of said gate circuits in accordance with the output of said switching circuit to permit the output of the firing circuit to pass to one set of semiconductor controlled rectifiers for one polarity of the input signal and to the other set of semiconductor controlled rectifiers for the opposite polarity of the input signal, for forward and reverse running of the motor respectively.
Claim 2
Dependent Claim
156 words
An electric motor control system which comprises two sets of semiconductor controlled rectifiers, a single firing circuit adapted to produce firing pulses the phase relationship of which to the motor supply is determined by the magnitude of an input signal to the firing circuit, a pair of gate circuits associated respectively with the two sets of semiconductor controlled rectifiers a polarity detection circuit including a switching circuit which has an output signal when the said input signal is of one polarity only and electronic logic means for supplying a signal to either one of said gate circuits in accordance with the output of said switching circuit to permit the output of the firing circuit to pass to one set of semiconductor controlled rectifiers for one polarity of the input signal and to the other set of semiconductor controlled rectifiers for the opposite polarity of the input signal, for forward and reverse running of the motor respectively.
Claim 3
Dependent Claim
70 words
A system as claimed in claim 1 in which the said firing circuit includes a capacitor, means for charging the capacitor at a rate variable with the magnitude of the said input signal, means for discharging the capacitor when the voltage on one phase of the motor supply is at a predetermined level, and means for converting the signal across the capacitor into a pulse train of a required form.
Claim 4
Dependent Claim
34 words
A system as claimed in claim 2 in which the means for charging the capacitor comprises a source of current which is variable in accordance with the magnitude only of the said input signal.
Claim 5
Dependent Claim
25 words
A system as claimed in claim 2 in which the said signal converting means includes a trigger circuit energized by the signal across the capacitor.
Claim 6
Dependent Claim
19 words
A system as claimed in claim 2 in which the said signal Converting means includes a pulse shaping circuit.
Claim 7
Dependent Claim
25 words
A system as claimed in claim 5 in which the output from the said pulse shaping circuit is a train of pulses of constant width.
Claim 8
Dependent Claim
79 words
A system as claimed in claim 1 in which the said logic means comprises a pair of NOR gates each having as one input a pulse train supplied from the firing circuit, one of the said NOR gates having an input from the switching circuit and the other of the NOR gates having an input formed by an output of the said one NOR gate, and a bistable circuit having as its inputs the outputs of the NOR gates.
Claim 9
Dependent Claim
26 words
A system as claimed in claim 7 in which the said pulse train from the firing circuit is obtained from the output of the trigger circuit.
Claim 10
Dependent Claim
23 words
A system as claimed in claim 7 in which the said pulse from the firing circuit is obtained from the pulse shaping circuit.
Claim 11
Dependent Claim
38 words
A system as claimed in claim 1 in which the signal supplied to the gate circuits is delayed by the electronic logic means for a period equal to the interval in the pulse train from the firing circuit.
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) | 1974-07-12 | 1975-01-11 | 1975-07-13 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1978-07-12 | 1979-01-11 | 1979-07-13 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1982-07-12 | 1983-01-11 | 1983-07-13 | $7700.00 | Window Closed / Lapsed |