US3564273A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Pulse width modulated control system with external feedback and mechanical memory
Assignee: General Electric Co
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Filing: 1967-11-09
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Granted: 1971-02-16
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Expires: 1987-11-09
Abstract
Abstract This invention comprises a control system for electrically controlled, mechanically actuated mechanisms of large power rating. Such mechanisms normally include mechanical actuating devices such as control valves for controlling the output operating condition of the mechanism. The control system of the invention includes electric power modulation circuit means having its input coupled to a source of electric control signals for controlling the operation of the mechanism and for producing output modulated controlled electric power signals. These output modulated controlled power signals are applied to an electromechanical positioning device such as a servomotor which has its output mechanically coupled to and controlling the position of the mechanical actuating means (valve) of the mechanism. The input of the servomotor is coupled to and controlled by the output from the electric power modulation circuit. The electric power modulation circuit preferably comprises a pulse width modulation circuit having a source of constant period pulsed clock signals supplied thereto and two output terminals. The input control signal selectively controls the width at the clock rate of the output signal pulses produced at the output of the modulation circuit as well as selects the output terminal to which the pulse width modulated pulses are supplied. As a result, the pulse width modulated output signals from one output terminal will serve to adjust the servomotor in one direction while the signals from the remaining output terminal serve to adjust the servomotor in the other direction. By reason of this arrangement, the last adjusted position of the mechanical actuating means by the servomotor serves as a memory for the overall control system until the next adjustment of the operating condition by the control system. The control system of the invention is particularly intended for use with turbinegenerator sets and for controlling the startup and initial loading of the turbine-generator set until such time that it has attained its optimum operating condition.
Inventors
- 👤 William D Cockrell
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-23 12:02
CPC Classifications
F; F01; F01D; F01D17/00; F01D17/20; F01D17/22; F01D17/24; H; H02; H02P; H02P23/00; H02P23/16
Claims Analysis
Total Claims: 28
Claim 1
Independent Claim
186 words
A control system for electrically controlled, mechanically actuated power mechanisms having mechanical actuating means for controlling the operating condition of the mechanism, means for measuring a plurality of stress margins developed during operation of said mechanisms, means for selecting the predominant one of said measured margins to provide a source of electric control signals, the control system comprising electric power modulation circuit means having its input coupled to said source of electric control signals for controlling the operation of the mechanism and for producing pulses of alternating electric power having a pulse width which is varied in accordance with an operating characteristic of said electric control signals, and an AC motor having its output mechanically coupled to and controlling the position of said mechanical actuating means and having its input coupled to and controlled by the output from the electric power modulation circuit means, said mechanical actuating means being mechanically positioned by the electromechanical positioning means and upon being so positioned thereafter serves as a memory unit for the control system until the next adjustment of the operating condition by the source of electric control signals.
Claim 2
Dependent Claim
186 words
A control system for electrically controlled, mechanically actuated power mechanisms having mechanical actuating means for controlling the operating condition of the mechanism, means for measuring a plurality of stress margins developed during operation of said mechanisms, means for selecting the predominant one of said measured margins to provide a source of electric control signals, the control system comprising electric power modulation circuit means having its input coupled to said source of electric control signals for controlling the operation of the mechanism and for producing pulses of alternating electric power having a pulse width which is varied in accordance with an operating characteristic of said electric control signals, and an AC motor having its output mechanically coupled to and controlling the position of said mechanical actuating means and having its input coupled to and controlled by the output from the electric power modulation circuit means, said mechanical actuating means being mechanically positioned by the electromechanical positioning means and upon being so positioned thereafter serves as a memory unit for the control system until the next adjustment of the operating condition by the source of electric control signals.
Claim 3
Dependent Claim
127 words
A control system according to claim 1 wherein said electric power modulation circuit means comprises a pulse width modulation circuit having a source of constant frequency AC power supplied thereto and two output terminals, the input control signal serving to selectively control the width of the pulses of electric power produced by the modulation circuit and select the output terminal to which such pulses of electric power are supplied, the pulses of electric power from one of the output terminals serving to drive the AC motor in one direction and the pulses of electric power from the remaining terminal serving to drive said motor in the other direction, and an AC power output stage selectively excited by the pulses of electric power for driving the AC motor.
Claim 4
Dependent Claim
121 words
A control system according to claim 2 wherein the AC motor comprises a servomotor having at least two actuating windings for selectively driving the motor in opposite directions and being mechanically coupled to and driving the mechanical actuating means, the said servomotor having one of its actuating windings selectively energized by the series of pulses of electric power derived from one output terminal for driving the AC motor in a first direction to an extent determined by the electric control signals, and having the remaining actuating winding selectively energized by the series of pulses of electric power derived from the remaining output terminal for driving the AC motor in the reverse direction to an extent determined by the electric control signals.
Claim 5
Dependent Claim
65 words
A control system according to claim 3 wherein the power output stage comprises a pair of relays having the exciting windings thereof connected to respective ones of the output terminals for excitation by the pulses of electric power and having the contacts thereof connected to appropriate actuating windings of the servomotor motor along with a source of excitation power to control operation of the servomotor.
Claim 6
Dependent Claim
67 words
A control system according to claim 3 wherein the power output stage comprises a pair of power semiconductor devices having the control elements thereof connected to respective ones of the output terminals for excitation by the pulses of electric power and having the load terminals thereof connected to appropriate actuating windings of the servomotor along with a source of excitation power to control operation of the servomotor.
Claim 7
Dependent Claim
230 words
A control system for electrically controlled, mechanically actuated mechanisms of large power rating having mechanical actuating means for controlling the Operating condition of a mechanism, said control system comprising means for developing a plurality of externally derived electric feedback signals representative of a plurality of externally measured quantities indicative of a number of stress margin characteristics of the mechanism being controlled, main gate selection means having the plurality of externally derived feedback signals supplied thereto as inputs for selecting a desired one of the externally derived feedback signals for use in controlling operation of the mechanism, electric power modulation circuit means having its input coupled to the output from the main gate selection means for producing pulses of AC electric power, and an AC motor, means for adjusting the speed of said AC motor comprising means for applying pulses of AC electric power from said said electric power modulation circuit means to the input of said AC motor and means for varying the width of said pulses of AC electric power in accordance with the output from the main gate selection means, said mechanical actuating means being mechanically positioned by the AC motor and upon being so positioned thereafter serves as a memory unit for the control system until the next adjustment of the operating condition of the mechanism by the control signal supplied by the main gate selection means.
Claim 8
Dependent Claim
230 words
A control system for electrically controlled, mechanically actuated mechanisms of large power rating having mechanical actuating means for controlling the Operating condition of a mechanism, said control system comprising means for developing a plurality of externally derived electric feedback signals representative of a plurality of externally measured quantities indicative of a number of stress margin characteristics of the mechanism being controlled, main gate selection means having the plurality of externally derived feedback signals supplied thereto as inputs for selecting a desired one of the externally derived feedback signals for use in controlling operation of the mechanism, electric power modulation circuit means having its input coupled to the output from the main gate selection means for producing pulses of AC electric power, and an AC motor, means for adjusting the speed of said AC motor comprising means for applying pulses of AC electric power from said said electric power modulation circuit means to the input of said AC motor and means for varying the width of said pulses of AC electric power in accordance with the output from the main gate selection means, said mechanical actuating means being mechanically positioned by the AC motor and upon being so positioned thereafter serves as a memory unit for the control system until the next adjustment of the operating condition of the mechanism by the control signal supplied by the main gate selection means.
Claim 9
Dependent Claim
135 words
A control system according to claim 6 wherein said electric power modulation circuit means comprises a pulse width modulation circuit having a source of constant period, pulsed AC electric power supplied thereto and two output terminals, the input control signal serving to selectively control the width of the pulses of AC electric power produced by the modulation circuit and select the output terminal to which the pulses of AC electric power are supplied, pulses of AC electric power from one of the output terminals serving to adjust the electromechanical positioning means in one direction and the pulses of AC electric power from the remaining terminal serving to adjust the positioning means in the other direction, and a power output stage selectively excited by the pulses of AC electric power for driving the electromechanical positioning means.
Claim 10
Dependent Claim
111 words
A control system according to claim 7 further including circuit means for adjusting the zero bias level of the pulse width modulation circuit so that it responds in a different manner to incoming control signals from the main gate selection means which are over or under this zero bias level to thereby derive the pulses of AC electric power for each of the output terminals thereof, the pulses of AC electric power being applied to one output terminal in response to the incoming control signal exceeding the zero bias level and being applied to the other output terminal in response to the incoming control signal dropping below the zero bias level.
Claim 11
Dependent Claim
296 words
A control system for electrically controlled, mechanically actuated mechanisms of large power rating having mechanical actuating means for controlling the operating condition of a mechanism, said control system comprising means for developing a plurality of externally derived electric feedback signals representative of a number of stress margin characteristics of the mechanism being controlled, main gate selection means having the plurality of externally derived feedback signals supplied thereto as inputs for selecting a desired one of the externally derived feedback signals for use in controlling operation of the mechanism, electric power modulation circuit means having its input coupled to the output from the main gate selection means for modulated control electric power signals, electromechanical positioning means having its output mechanically coupled to and controlling the position of said mechanical actuating means and having its input coupled to and controlled by the output from the electric power modulation circuit means, said mechanical actuating means being mechanically positioned by the electromechanical positioning means and uPon being so positioned thereafter serves as a memory unit for the control system until the next adjustment of the operating condition of the mechanism by the control signal supplied by the main gate selection means, direct feedback means for deriving a primary feedback signal that is directly related to an operating condition of the controlled mechanism that is of primary interest in the control of the mechanism, said direct feedback means being coupled to said electric power modulation circuit means as an additional input thereto, and override control circuit means comprising a part of said electric power modulation circuit means and controlled by said primary feedback signal for overriding and taking over control of the operation of said electric power modulation circuit means in response to the primary feedback signal attaining a predetermined value.
Claim 12
Dependent Claim
296 words
A control system for electrically controlled, mechanically actuated mechanisms of large power rating having mechanical actuating means for controlling the operating condition of a mechanism, said control system comprising means for developing a plurality of externally derived electric feedback signals representative of a number of stress margin characteristics of the mechanism being controlled, main gate selection means having the plurality of externally derived feedback signals supplied thereto as inputs for selecting a desired one of the externally derived feedback signals for use in controlling operation of the mechanism, electric power modulation circuit means having its input coupled to the output from the main gate selection means for modulated control electric power signals, electromechanical positioning means having its output mechanically coupled to and controlling the position of said mechanical actuating means and having its input coupled to and controlled by the output from the electric power modulation circuit means, said mechanical actuating means being mechanically positioned by the electromechanical positioning means and uPon being so positioned thereafter serves as a memory unit for the control system until the next adjustment of the operating condition of the mechanism by the control signal supplied by the main gate selection means, direct feedback means for deriving a primary feedback signal that is directly related to an operating condition of the controlled mechanism that is of primary interest in the control of the mechanism, said direct feedback means being coupled to said electric power modulation circuit means as an additional input thereto, and override control circuit means comprising a part of said electric power modulation circuit means and controlled by said primary feedback signal for overriding and taking over control of the operation of said electric power modulation circuit means in response to the primary feedback signal attaining a predetermined value.
Claim 13
Dependent Claim
63 words
A control system according to claim 9 wherein the override control circuit means comprises a terminal load set potentiometer connected in opposition to the direct feedback connection to the pulse width modulation circuit whereby upon the primary feedback signal exceeding the terminal load value set into the potentiometer, further production of pulse width modulated output signals in the increasing load direction is prevented.
Claim 14
Dependent Claim
89 words
A control system according to claim 10 wherein the override control circuit means further includes a minimum load potentiometer and comparison circuit means for comparing the primary feedback signal to the minimum load value set on the minimum load potentiometer and for overriding control of the pulse width modulation circuit upon the primary feedback signal dropping below the preset minimum load value to thereby cause the pulse width modulation circuit to produce output pulse width modulated signals at the output terminal thereof which will cause the load to increase.
Claim 15
Dependent Claim
223 words
A control system according to claim 11 wherein the mechanism being controlled comprises a steam turbine-generator set, the mechanical actuating means comprises the main steam supply valve from the boiler to the turbine and its associated bypass and control valves and electrohydraulic actuating mechanism, the means for developing a plurality of externally derived electric feedback signals comprises a plurality of sensing instruments for sensing turbine casing temperature, pressure, turbine speed, expansion, vibration, eccentricity, elongation, etc., together with computation circuits which derive predicted future values of such operating conditions from the existing instantaneous measured values, and the electromechanical positioning means comprises a constant speed servomotor mechanically driving a reference potentiometer that in turn controls the electrohydraulic valve actuating mechanism of the steam turbine, the said servomotor having one of its actuating windings selectively energized by the series of pulse width modulated control signals derived from one of the output terminals of the pulse width modulation circuit to cause the servomotor to drive the reference potentiometer in a direction to increase loading on the turbine-generator and having the other of its actuating windings selectively energized by the series of pulse width modulated control signals derived from the other output terminal of the pulse width modulation circuit to cause the servomotor to drive the reference potentiometer in a direction to decrease loading on the turbine-generator set.
Claim 16
Dependent Claim
45 words
A control system according to claim 12 further characterized in that the direct feedback means comprises a load feedback signal from the generator to the pulse width modulation circuit and constitutes primary feedback signal that is directly related to the loading on the turbine-generator set.
Claim 17
Dependent Claim
50 words
A control system according to claim 13 wherein the mechanical connection of the servomotor to the reference potentiometer is through a suitable gear assembly that is also geared to and selectively driven by a manual reference adjustment knob for manually overriding aNd additionally controlling the operation of the turbine-generator set.
Claim 18
Dependent Claim
81 words
A control system according to claim 14 wherein the power output stage of the pulse width modulation circuit comprises a pair of relays having the exciting windings thereof connected to respective ones of the output terminals of the pulse width modulation circuit for excitation by the pulse width modulated clock pulses and having the contacts thereof connected through a source of energizing power to appropriate actuating windings of the servomotor to control the direction and extent of movement of the servomotor.
Claim 19
Dependent Claim
78 words
A control system according to claim 14 wherein the power output stage of the pulse width modulation circuit comprises a pair of power semiconductor devices having the control elements thereof connected to respective ones of the output terminals of the pulse width modulation circuit for excitation by the pulse width modulated clock pulses and having the load terminals thereof connected to appropriate actuating windings of the servomotor to control the direction and extent of movement of the servomotor.
Claim 20
Dependent Claim
171 words
In an operating system which produces differently measurable quantities representing the operating conditions of said system, means for controlling said operating system comprising means for providing first signals representative of stress margins developed by said operating system, means for selecting and processing desired ones of said first signals to produce a plurality of different control signals, said means for selecting and processing desired ones of said control signals comprising a source of reference signals and means for comparing given ones of said first signals with corresponding ones of said reference signals to produce said control signals, a source of clock signals having a given recurrence rate, means for producing output signals, means responsive to said given recurrence rate clock signals to control the recurrence rate of said output signals, means responsive to selected ones of said control signals to control the number of time recurrences of said output signals at said recurrence rate, a motor, and means for controlling motor action comprising means for applying said output signals to said motor.
Claim 21
Dependent Claim
171 words
In an operating system which produces differently measurable quantities representing the operating conditions of said system, means for controlling said operating system comprising means for providing first signals representative of stress margins developed by said operating system, means for selecting and processing desired ones of said first signals to produce a plurality of different control signals, said means for selecting and processing desired ones of said control signals comprising a source of reference signals and means for comparing given ones of said first signals with corresponding ones of said reference signals to produce said control signals, a source of clock signals having a given recurrence rate, means for producing output signals, means responsive to said given recurrence rate clock signals to control the recurrence rate of said output signals, means responsive to selected ones of said control signals to control the number of time recurrences of said output signals at said recurrence rate, a motor, and means for controlling motor action comprising means for applying said output signals to said motor.
Claim 22
Dependent Claim
46 words
An arrangement according to claim 17 further comprising a source of additional control signals, and means responsive to said additional control signals and said motor action to produce a resultant output control signal, and means for controlling said operating system with said resultant output control signal.
Claim 23
Dependent Claim
45 words
An arrangement according to claim 17 further comprising a signal divider for producing resultant signal s signals having a signal characteristic adjustable between a maximum and a minimum value, and means for controlling the value of said signal characteristic in response to said motor action.
Claim 24
Dependent Claim
83 words
A turbine loading control closed cycle system comprising a constant speed servomotor, a source of clock pulses, a source of first control signals representing stress margins developed by said turbine during operation, means responsive to said clock pulses for providing pulsed AC power of given frequency for controlling motor operation, means for controlling the duration of said power pulses of given frequency as a function of said first signals, and means responsive to said motor operation to provide control without overcontrol or hunting.
Claim 25
Dependent Claim
83 words
A turbine loading control closed cycle system comprising a constant speed servomotor, a source of clock pulses, a source of first control signals representing stress margins developed by said turbine during operation, means responsive to said clock pulses for providing pulsed AC power of given frequency for controlling motor operation, means for controlling the duration of said power pulses of given frequency as a function of said first signals, and means responsive to said motor operation to provide control without overcontrol or hunting.
Claim 26
Dependent Claim
96 words
A turbine loading control comprising a source of analogue signals representing a plurality of stress margins developed during operation of said turbine, means for selecting the most critical of said signals and converting said selected signals to pulses of AC power of given frequency whose pulse width varies as a function of the magnitude of said most critical of said signals, a constant speed AC servomotor, a controllable system, means for adjusting the average speed of said AC motor comprising said motor responsive to said pulses of electric power to provide proportional control of said system.
Claim 27
Dependent Claim
96 words
A turbine loading control comprising a source of analogue signals representing a plurality of stress margins developed during operation of said turbine, means for selecting the most critical of said signals and converting said selected signals to pulses of AC power of given frequency whose pulse width varies as a function of the magnitude of said most critical of said signals, a constant speed AC servomotor, a controllable system, means for adjusting the average speed of said AC motor comprising said motor responsive to said pulses of electric power to provide proportional control of said system.
Claim 28
Dependent Claim
32 words
An arrangement according to claim 21 further comprising means for constraining motor speed between given values, system output between given values and the balance level between directions of rotation of said servomotor.
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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) | 1974-02-15 | 1974-08-17 | 1975-02-16 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1978-02-15 | 1978-08-17 | 1979-02-16 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1982-02-15 | 1982-08-17 | 1983-02-16 | $7700.00 | Window Closed / Lapsed |