US3878445A
Expired / Lapsed
US
⏱️ 0.0 years remaining
A. C. motor control apparatus and method
Assignee: Kearney and Trecker Corp
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Filing: 1972-09-01
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Granted: 1975-04-15
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Expires: 1992-09-01
Abstract
Abstract In apparatus for controlling the speed and torque of a multiphase a.c. motor in accordance with digital control signals, a first regulation circuit regulates the frequency of the a.c. electrical signal applied to the motor and another regulation circuit regulates the voltage of the a.c. signal. Both regulation circuits are controlled by digital control signals in a series of discrete steps over a range of control values and the control signals are supplied periodically to the regulation circuits. The speed and torque are controlled in accordance with an algorithm relating speed and torque to the frequency and voltage of the source of electric power which is applied to the motor, calculated by computing apparatus on a periodic basis. In one embodiment the position of the magnetic flux of the stator is controlled directly.
Inventors
- 👤 Edward E Kirkham
- 👤 Frank Zankl
- 👤 Richard E Stobbe
- 👤 John J Schachte
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-26 01:26
CPC Classifications
H; H02; H02P; H02P27/00; H02P27/04; H02P27/06; G; G05; G05B; G05B19/00; G05B19/02; G05B19/18; G05B19/19; G05B19/21; G05B19/23; G05B19/231; G05B19/237; G05D; G05D3/00; G05D3/12; G05D3/14; G05D3/1445; H02P23/00; H02P23/0077; H02P27/048; H02P2207/00; H02P2207/01; H02P27/047
Claims Analysis
Total Claims: 17
Claim 1
Independent Claim
169 words
A servo system for controlling the application of electrical power to an a.c. motor, comprising means for generating a signal representative of the speed of said motor, frequency selecting means for selecting the frequency of an a.c. voltage to be applied to said motor, means for providing an input signal representative of a selected angular position for said motor, means for deriving a control signal in response to said input signal and to said speedrepresentative signal, and amplitude selecting means responsive to said control signal for selecting an amplitude for said a.c. voltage which amplitude is determined in accordance with a predetermined relation between the torque developed by said motor and the amplitude of an a.c. voltage applied thereto at said selected frequency, whereby the torque developed by said motor has a predetermined relation to said control signal, and means for connecting a source of electrical power to said motor, said last named means being connected with, and responsive to, said frequency selecting means and said amplitude selecting means.
Claim 2
Dependent Claim
169 words
A servo system for controlling the application of electrical power to an a.c. motor, comprising means for generating a signal representative of the speed of said motor, frequency selecting means for selecting the frequency of an a.c. voltage to be applied to said motor, means for providing an input signal representative of a selected angular position for said motor, means for deriving a control signal in response to said input signal and to said speedrepresentative signal, and amplitude selecting means responsive to said control signal for selecting an amplitude for said a.c. voltage which amplitude is determined in accordance with a predetermined relation between the torque developed by said motor and the amplitude of an a.c. voltage applied thereto at said selected frequency, whereby the torque developed by said motor has a predetermined relation to said control signal, and means for connecting a source of electrical power to said motor, said last named means being connected with, and responsive to, said frequency selecting means and said amplitude selecting means.
Claim 3
Dependent Claim
62 words
Apparatus according to claim 1, wherein Said frequency selecting means comprises means for selecting one of a plurality of fixed frequencies, in accordance with the speed of said motor, such that a lower frequency is used when the motor speed is lower than a predetermined value, and a higher frequency is used when the motor speed is higher than said predetermined value.
Claim 4
Dependent Claim
81 words
Apparatus according to claim 1, wherein said amplitude selecting means comprises comparing means for comparing the value represented by said control signal with a fixed quantity, and means responsive to said comparing means for selecting an amplitude bearing one relation to said control signal when said value represented by said control signal is less than said fixed quantity, and bearing a second relation to said control signal when the value represented by said control signal is greater than said fixed quantity.
Claim 5
Dependent Claim
73 words
Apparatus according to claim 1, wherein said frequency selecting means comprises means for comparing the value of said control signal with a fixed quantity, means for selecting a frequency having a first relation to said control signal when said control signal value is less than said fixed quantity, and means for selecting a frequency having a second relation to said control signal when said control signal value is greater than said fixed quantity.
Claim 6
Dependent Claim
91 words
Apparatus according to claim 1, including switching means connected with said motor for alternately connecting said motor for operation with two different numbers of poles, and means responsive to said control signal and connected to said switching means for causing said motor to be connected for operation with a first set of poles in response to one range of values of said control signal, and for causing said motor to be connected for operation with a second set of poles in response to another range of values of said control signal.
Claim 7
Dependent Claim
37 words
Apparatus according to claim 5, including means connected with said amplitude selecting means for selecting an amplitude of zero for a predetermined time interval during switching from one set of poles to the other set of poles.
Claim 8
Dependent Claim
97 words
Apparatus according to claim 1, wherein said frequency selecting means comprises means for comparing the value of said control signal with one of first and second fixed values, means for changing the frequency selected for application to said motor from a lower frequency to a higher frequency when the value of said control signal exceeds the greater of said two values, and means for changing the frequency selected for application to said motor from said higher frequency to said lower frequency when the value of said control signal is less than the lesser of said two values.
Claim 9
Dependent Claim
154 words
A servo system for controlling an a.c. motor for constant slip operation to drive a movable member in accordance with a specified program that designates the velocity and position of the movable member comprising means responsive to command signals representative of the designated instantaneous position of the movable member and to signals representative of the actual instantaneous position of the movable member for deriving a signal proportional to the torque required of the motor to follow the program, means for supplying an a.c. voltage to said motor, means responsive to said torque-representative signal for controlling the amplitude of said a.c. voltage, means for producing a speed signal proportional to the speed of operation of said motor, means for modifying said speed signal by increasing it by an amount corresponding to a predetermined constant slip, and means for controlling the frequency of the voltage applied to said motor in accordance with said modified speed signal.
Claim 10
Dependent Claim
154 words
A servo system for controlling an a.c. motor for constant slip operation to drive a movable member in accordance with a specified program that designates the velocity and position of the movable member comprising means responsive to command signals representative of the designated instantaneous position of the movable member and to signals representative of the actual instantaneous position of the movable member for deriving a signal proportional to the torque required of the motor to follow the program, means for supplying an a.c. voltage to said motor, means responsive to said torque-representative signal for controlling the amplitude of said a.c. voltage, means for producing a speed signal proportional to the speed of operation of said motor, means for modifying said speed signal by increasing it by an amount corresponding to a predetermined constant slip, and means for controlling the frequency of the voltage applied to said motor in accordance with said modified speed signal.
Claim 11
Dependent Claim
27 words
Apparatus according to claim 8, wherein the speedresponsive signal is modified by a quantity proportional to said amplitude, to give a slip proportional to said required torque.
Claim 12
Dependent Claim
141 words
For use with a servo system for controlling the application of electrical power to an a.c. motor to regulate the movement of a movable member driven by said moTor, a method comprising the steps of generating a signal representative of the speed of the motor which will produce the desired velocity of said movable member, selecting the frequency of an a.c. voltage to be applied to said motor in response to the speed of the motor, deriving a control signal in response to a signal representative of a selected position of said movable member and to said speed signal, and selecting an amplitude for said a.c. voltage in response to said control signal which is in accordance with a predetermined relation between the torque developed by said motor and the amplitude of an a.c. voltage applied thereto at said selected frequency.
Claim 13
Dependent Claim
141 words
For use with a servo system for controlling the application of electrical power to an a.c. motor to regulate the movement of a movable member driven by said moTor, a method comprising the steps of generating a signal representative of the speed of the motor which will produce the desired velocity of said movable member, selecting the frequency of an a.c. voltage to be applied to said motor in response to the speed of the motor, deriving a control signal in response to a signal representative of a selected position of said movable member and to said speed signal, and selecting an amplitude for said a.c. voltage in response to said control signal which is in accordance with a predetermined relation between the torque developed by said motor and the amplitude of an a.c. voltage applied thereto at said selected frequency.
Claim 14
Dependent Claim
104 words
For use with a servo system for controlling the application of electrical power to an a.c. motor, a method comprising the steps of deriving a torque-representative signal proportional to the torque required of the motor to follow a predetermined program, controlling the amplitude of an a.c. voltage applied to said motor in response to said torque-representative signal, producing a speed signal proportional to the speed of operation of said motor, modifying said speed signal by increasing it by an amount corresponding to a predetermined constant slip, and controlling the frequency of the voltage applied to said motor in accordance with said modified speed signal.
Claim 15
Dependent Claim
104 words
For use with a servo system for controlling the application of electrical power to an a.c. motor, a method comprising the steps of deriving a torque-representative signal proportional to the torque required of the motor to follow a predetermined program, controlling the amplitude of an a.c. voltage applied to said motor in response to said torque-representative signal, producing a speed signal proportional to the speed of operation of said motor, modifying said speed signal by increasing it by an amount corresponding to a predetermined constant slip, and controlling the frequency of the voltage applied to said motor in accordance with said modified speed signal.
Claim 16
Independent Claim
142 words
The method of controlling the operation of an a.c. motor in accordance with signals from a record which represent a program of movements of a movable member driven by said motor, comprising the steps of generating a signal representative of the speed of the motor in response to information from said record designating the desired velocity of said movable member, selecting the frequency of an a.c. voltage to be applied to said motor in response to the speed of the motor, deriving a control signal in response to the distance of movement of said movable member during a measured period of time and to said speed signal, and selecting an amplitude for said a.c. voltage in accordance with said control signal to establish the desired operation of said motor for actuating the movable member in accordance with the program on said record.
Claim 17
Independent Claim
142 words
The method of controlling the operation of an a.c. motor in accordance with signals from a record which represent a program of movements of a movable member driven by said motor, comprising the steps of generating a signal representative of the speed of the motor in response to information from said record designating the desired velocity of said movable member, selecting the frequency of an a.c. voltage to be applied to said motor in response to the speed of the motor, deriving a control signal in response to the distance of movement of said movable member during a measured period of time and to said speed signal, and selecting an amplitude for said a.c. voltage in accordance with said control signal to establish the desired operation of said motor for actuating the movable member in accordance with the program on said record.
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) | 1978-04-14 | 1978-10-14 | 1979-04-15 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1982-04-14 | 1982-10-14 | 1983-04-15 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1986-04-14 | 1986-10-14 | 1987-04-15 | $7700.00 | Window Closed / Lapsed |