US3908158A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Control system for adjusting a-c motor speed at line frequency or a subharmonic of the line frequency
Assignee: Borg Warner Corp
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Filing: 1974-09-16
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Granted: 1975-09-23
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Expires: 1994-09-16
Abstract
Abstract Speed control of an a-c motor is accomplished with back-to-back thyristors coupled between the power line and the motor. A gate circuit (1) selects which of the thyristors can be gated on, and (2) determines the actual time of thyristor conduction in each half-cycle. In turn the gate circuit is regulated, as to thyristor selection, by a countdown arrangement including frequency control and multivibrator circuits. The gate circuit is also regulated, to determine the actual conduction time, by a voltage control circuit coupled to the frequency control circuit. Thus the frequency control circuit regulates motor speed as a function either of the fundamental power line frequency, or a subharmonic of the line frequency.
Inventors
- 👤 George H Studtmann
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-27 06:25
CPC Classifications
H; H02; H02P; H02P25/00; H02P25/02; H02P25/10; H02P25/14
Claims Analysis
Total Claims: 11
Claim 1
Independent Claim
138 words
AN A-C MOTOR SPEED CONTROL SYSTEM FOR AN A-C MOTOR CONNECTED FOR ENERGIZATION FROM AN A-C POWER LINE SUPPLYING POWER AT A FUNDAMENTAL LINE FREQUENCY, COMPRISING: A BIDIRECTIONAL SWITCH COUPLED BETWEEN THE POWER LINE AND THE MOTOR, AND CONTROL MEANS COUPLED BOTH TO THE POWEER LINE AND TO THE BIDIRECTIONAL SWITCH, WHICH CONTROL MEANS INCLUDES A COUNTDOWN CIRCUIT COUPLED TO AND SYNCHRONIZED WITH THE POWER LINE, CONNECTED TO CONTROL THE GATING OF THE BIDIRECTIONAL SWITCH AT A GATING FREQUENCY THAT IS EQUAL TO, OR A SUBHARMONIC OF, THE FUNDAMENTAL LINE FREQUENCY, AND A VOLTAGE CONTROL CIRCUIT, ALSO COUPLED TO AND SYNCHRONIZED WITH THE POWER LINE TO CONTROL THE GATING OF THE BIDIRECTIONAL SWITCH FOR ALL, OR A VARIABLE AMOUNT LESS THAN ALL, OF EACH INDIVIDUAL HALF CYCLE OF ENERGY AT THE GATING FREQUENCY DETERMINED BY THE BIDIRECTIONAL SWITCH.
Claim 2
Dependent Claim
138 words
AN A-C MOTOR SPEED CONTROL SYSTEM FOR AN A-C MOTOR CONNECTED FOR ENERGIZATION FROM AN A-C POWER LINE SUPPLYING POWER AT A FUNDAMENTAL LINE FREQUENCY, COMPRISING: A BIDIRECTIONAL SWITCH COUPLED BETWEEN THE POWER LINE AND THE MOTOR, AND CONTROL MEANS COUPLED BOTH TO THE POWEER LINE AND TO THE BIDIRECTIONAL SWITCH, WHICH CONTROL MEANS INCLUDES A COUNTDOWN CIRCUIT COUPLED TO AND SYNCHRONIZED WITH THE POWER LINE, CONNECTED TO CONTROL THE GATING OF THE BIDIRECTIONAL SWITCH AT A GATING FREQUENCY THAT IS EQUAL TO, OR A SUBHARMONIC OF, THE FUNDAMENTAL LINE FREQUENCY, AND A VOLTAGE CONTROL CIRCUIT, ALSO COUPLED TO AND SYNCHRONIZED WITH THE POWER LINE TO CONTROL THE GATING OF THE BIDIRECTIONAL SWITCH FOR ALL, OR A VARIABLE AMOUNT LESS THAN ALL, OF EACH INDIVIDUAL HALF CYCLE OF ENERGY AT THE GATING FREQUENCY DETERMINED BY THE BIDIRECTIONAL SWITCH.
Claim 3
Dependent Claim
155 words
An a-c motor speed control system as claimed in claim 1, in which said bidirectional switch includes first and second unidirectional switches, each of which has a control terminal and operates responsive to receipt of a signal at such terminal to pass only positive or only negative portions of the a-c energy on the power line, and in which the countdown circuit includes a multivibrator having two output connections, one of which is coupled to the control terminal of the first unidirectional switch and the other of which is coupled to the control terminal of the second unidirectional switch, and the countdown circuit further includes a frequency control circuit, coupled both to the multivibrator and to the a-c power line, connectd to sequentially set and reset said multivibrator to produce at the multivibrator output connections changes in state for successive periods corresponding to a whole number of half cycles equal to or greater than two.
Claim 4
Dependent Claim
53 words
An a-c motor speed control system as claimed in claim 2, in which the control means includes a full wave rectifier, coupled to the a-c power line and having its output coupled both to the multivibrator and to the frequency control circuit, for providing both supply power and synchronization to said countdown unit.
Claim 5
Dependent Claim
32 words
An a-c motor speed control system as claimed in claim 2, in which the bidirectional switch comprises a pair of thyristors connected in parallel with one anode connected to the others cathode.
Claim 6
Dependent Claim
163 words
An a-c motor speed control system for an a-c motor connected for energization from an a-c power line supplying power at a fundamental line frequency, comprising: a single bidirectional switch between the power line and the motor, a gate circuit, coupled to the bidirectional switch, operable to regulate the bidirectional switch both as to the direction and the amount of power transfer between the a-c power line and the motor, a countdown circuit, coupled to and synchronized with the power line, connected to control the gate circuit to regulate the direction of power transfer at a gating frequency that is equal to, or a subharmonic of, the fundamental line frequency, and a voltage control circuit, also coupled to and synchronized with the power line, connected to control the gate circuit to regulate the amount of power transfer by passing all, or a variable amount less than all, of each individual half cycle of power of the gating frequency determined by the countdown circuit.
Claim 7
Dependent Claim
163 words
An a-c motor speed control system for an a-c motor connected for energization from an a-c power line supplying power at a fundamental line frequency, comprising: a single bidirectional switch between the power line and the motor, a gate circuit, coupled to the bidirectional switch, operable to regulate the bidirectional switch both as to the direction and the amount of power transfer between the a-c power line and the motor, a countdown circuit, coupled to and synchronized with the power line, connected to control the gate circuit to regulate the direction of power transfer at a gating frequency that is equal to, or a subharmonic of, the fundamental line frequency, and a voltage control circuit, also coupled to and synchronized with the power line, connected to control the gate circuit to regulate the amount of power transfer by passing all, or a variable amount less than all, of each individual half cycle of power of the gating frequency determined by the countdown circuit.
Claim 8
Dependent Claim
181 words
An a-c motor speed control system as claimed in claim 5, in which the single bidirectional switch includes a pair of thyristors connected back to back, such that conduction of one thyristor passes power in one direction to the motor and conduction of the other thyristor passes power in the other direction to the motor, and the time of conduction of each thyristor in each half-cycle of energy at the power line frequency determines the amount of power transferred to the motor during that respective half-cycle, and in which the countdown circuit comprises a multivibrator circuit having its output connections coupled to the gate circuit, such that the state of the multivibrator determines which of the two thyristors can be gated on and thus determines the direction of power transfer to the motor at any given time, and the countdown circuit further comprises a frequency control circuit, having its output connections coupled to the multivibrator circuit to regulate the timing of the multivibrator, which frequency control circuit has at least one adjustable component to determine the periodicity of the multivibrator circuit.
Claim 9
Dependent Claim
55 words
An a-c motor speed control system as claimed in claim 6 and further comprising a rectifier bridge circuit, coupled between the a-c power line and each of the voltage control, multivibrator, and frequency control circuits, to insure synchronization of said circuits with the fundamental line frequency of the power supplied over the a-C power line.
Claim 10
Independent Claim
217 words
The method of controlling the speed of an a-c motor energized from a power line providing single-phase a-c electrical power alternating at a substantially constant fundamental frequency, which method employs only a single bidirectional switch connected to operate the motor either at a reference speed related to the fundamental line frequency or at a lower speed than would result from supplying power at said fundamental line frequency, comprising the steps of: gating to the motor through the single bidirectional switch at least part of a number of the positive fundamental frequency half-cyles, but none of the negative half-cycles, of the single-phase a-c power, which number is a whole number equal to or greater than one; and thereafter gating to the motor through the single bidirectional switch at least part of a number of the negative frequency half-cyles, but none of the positive half-cycles, of the single-phase a-c power, which number is a whole number equal to or greater than one, said gating of at least part of the half-cycles supplying the only a-c power gated from the power line to the motor, thus delivering to the motor a resultant alternating power at a frequency either equal to the fundamental frequency or equal to a subharmonic frequency of the fundamental frequency, and thus correspondingly regulating the motor speed.
Claim 11
Independent Claim
217 words
The method of controlling the speed of an a-c motor energized from a power line providing single-phase a-c electrical power alternating at a substantially constant fundamental frequency, which method employs only a single bidirectional switch connected to operate the motor either at a reference speed related to the fundamental line frequency or at a lower speed than would result from supplying power at said fundamental line frequency, comprising the steps of: gating to the motor through the single bidirectional switch at least part of a number of the positive fundamental frequency half-cyles, but none of the negative half-cycles, of the single-phase a-c power, which number is a whole number equal to or greater than one; and thereafter gating to the motor through the single bidirectional switch at least part of a number of the negative frequency half-cyles, but none of the positive half-cycles, of the single-phase a-c power, which number is a whole number equal to or greater than one, said gating of at least part of the half-cycles supplying the only a-c power gated from the power line to the motor, thus delivering to the motor a resultant alternating power at a frequency either equal to the fundamental frequency or equal to a subharmonic frequency of the fundamental frequency, and thus correspondingly regulating the motor speed.
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) | 1978-09-22 | 1979-03-24 | 1979-09-23 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1982-09-22 | 1983-03-24 | 1983-09-23 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1986-09-22 | 1987-03-24 | 1987-09-23 | $7700.00 | Window Closed / Lapsed |