US3586949A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Three-phase dc motor control system
Assignee: Pratt and Whitney Co Inc
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Filing: 1968-05-23
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Granted: 1971-06-22
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Expires: 1988-05-23
Abstract
Abstract This invention is directed to a three-phase DC motor drive for use in conjunction with machine tools for driving a spindle or a slide. In particular, the invention comprises a silicon controlled rectifier (SCR) assembly, utilized to permit threephase line voltages to be applied across the armature of a DC motor. A tachometer is utilized to generate a signal indicative of the motor speed which is combined with a command signal and a current limit signal. From the combination of these signals, a signal is generated to control the firing of the SCR assembly. This invention includes the use of saturable reactors to prevent one of the SCR''s of the assembly from firing while another is conducting. Also as an important feature of this invention, there is provided tachometer ripple cancellation in order to obtain a low noise output signal from the tachometer.
Inventors
- 👤 Kenneth D Spear
- 👤 Carles F Raber
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-25 19:37
CPC Classifications
H; H02; H02P; H02P7/00; H02P7/06; H02P7/18; H02P7/24; H02P7/28; H02P7/285; H02P7/292; H02P7/293
Claims Analysis
Total Claims: 7
Claim 1
Independent Claim
252 words
A control system for a direct current motor having an armature winding which receives electrical energy from a threephase alternating voltage source, three semiconductor controlled rectifier switching devices each having input, output and control electrodes, each of said devices having its output electrodes coupled in series with the motor armature and each of said devices having its input electrodes arranged to be coupled in series with a different one of the three-phase voltages, control means coupled to said control electrodes to control the conduction of said switching devices for controlling the speed of said motor, means providing a first signal for a motor speed reference, means for deriving a second signal indicative of the speed of the motor, means for combining said first and second signals to provide a speed error signal, means for applying said speed error signal to said control means, means responsive to the load current of said motor exceeding a predetermined value for providing a third signal proportional thereto, means for combining said third signal with said first signal to modify the reference speed of said motor and decrease the speed of said motor as the load current increases above said predetermined value, three additional semiconductor controlled rectifier devices, each of said additional devices being responsive to said control means to provide firing pulses to the control electrodes of one of said switching devices, and capacitor means coupled in circuit with said additional devices to provide fast rising gating pulses to the input electrodes of said switching devices.
Claim 2
Dependent Claim
252 words
A control system for a direct current motor having an armature winding which receives electrical energy from a threephase alternating voltage source, three semiconductor controlled rectifier switching devices each having input, output and control electrodes, each of said devices having its output electrodes coupled in series with the motor armature and each of said devices having its input electrodes arranged to be coupled in series with a different one of the three-phase voltages, control means coupled to said control electrodes to control the conduction of said switching devices for controlling the speed of said motor, means providing a first signal for a motor speed reference, means for deriving a second signal indicative of the speed of the motor, means for combining said first and second signals to provide a speed error signal, means for applying said speed error signal to said control means, means responsive to the load current of said motor exceeding a predetermined value for providing a third signal proportional thereto, means for combining said third signal with said first signal to modify the reference speed of said motor and decrease the speed of said motor as the load current increases above said predetermined value, three additional semiconductor controlled rectifier devices, each of said additional devices being responsive to said control means to provide firing pulses to the control electrodes of one of said switching devices, and capacitor means coupled in circuit with said additional devices to provide fast rising gating pulses to the input electrodes of said switching devices.
Claim 3
Dependent Claim
215 words
A cOntrol system for a direct current motor having an armature winding which receives electrical energy from a three-phase source, three pairs of controlled rectifier switching devices, each device of said pairs having gage, anode and cathode electrodes and each device of said pairs having its anode and cathode electrodes connected in parallel with the other device of the pair, each of said pairs of devices arranged to be coupled in series with a different one of the three-phase voltages, one device of each pair being connected for conduction in one direction and the other device of each pair being connected for conduction in the other direction, and control means coupled to said control electrodes for controlling the time of conduction of said devices and the speed of the motor, a saturable reactor connected in series with each pair of devices, means providing a first signal for a motor speed reference, means for deriving a second signal indicative of the speed of the motor and means for deriving a third signal indicative of the electrical load on the motor, said control means including means for combining said first, second and third signals to control the speed of said motor and decrease the speed thereof if the electrical load on said motor exceeds a predetermined value.
Claim 4
Dependent Claim
215 words
A cOntrol system for a direct current motor having an armature winding which receives electrical energy from a three-phase source, three pairs of controlled rectifier switching devices, each device of said pairs having gage, anode and cathode electrodes and each device of said pairs having its anode and cathode electrodes connected in parallel with the other device of the pair, each of said pairs of devices arranged to be coupled in series with a different one of the three-phase voltages, one device of each pair being connected for conduction in one direction and the other device of each pair being connected for conduction in the other direction, and control means coupled to said control electrodes for controlling the time of conduction of said devices and the speed of the motor, a saturable reactor connected in series with each pair of devices, means providing a first signal for a motor speed reference, means for deriving a second signal indicative of the speed of the motor and means for deriving a third signal indicative of the electrical load on the motor, said control means including means for combining said first, second and third signals to control the speed of said motor and decrease the speed thereof if the electrical load on said motor exceeds a predetermined value.
Claim 5
Dependent Claim
114 words
A motor control system in which the speed of the motor is regulated to a predetermined speed comprising a direct current motor, means providing a speed reference signal, a tachometer coupled to said motor and adapted to provide a DC signal indicative of the speed of said motor, means for combining said reference signal and said speed indicative signal to provide a speed error signal, control means responsive to said speed error signal for supplying driving energy to said motor, means for deriving an inversion of said speed indicative signal and adding said inverted signal to said speed indicative signal to cancel the AC ripple which may be present on the speed indicative signal.
Claim 6
Dependent Claim
114 words
A motor control system in which the speed of the motor is regulated to a predetermined speed comprising a direct current motor, means providing a speed reference signal, a tachometer coupled to said motor and adapted to provide a DC signal indicative of the speed of said motor, means for combining said reference signal and said speed indicative signal to provide a speed error signal, control means responsive to said speed error signal for supplying driving energy to said motor, means for deriving an inversion of said speed indicative signal and adding said inverted signal to said speed indicative signal to cancel the AC ripple which may be present on the speed indicative signal.
Claim 7
Dependent Claim
51 words
The system of claim 12 wherein said means for deriving an inversion of said speed indicative signal comprises capacitor means for coupling the AC components of the tachometer signal to an inverting circuit and thereafter the inverted AC component is summed with the tachometer signal to provide said speed error signal.
References Cited (Backward Citations)
No citation records indexed.
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1974-06-21 | 1974-12-21 | 1975-06-22 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1978-06-21 | 1978-12-21 | 1979-06-22 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1982-06-21 | 1982-12-21 | 1983-06-22 | $7700.00 | Window Closed / Lapsed |