US3737748A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Motor speed control circuit with unijunction transistor line voltage compensation
Assignee: 3M Co
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Filing: 1971-11-03
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Granted: 1973-06-05
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Expires: 1991-11-03
Abstract
Abstract An adjustable speed control circuit for a DC motor which automatically compensates for variations in both motor load and the voltage level of an AC source which supplies power for driving the motor. A command signal circuit and a reference signal circuit develop command and reference signals respectively which are applied to a solid state switch. The solid state switch operates in response to a certain differential between the command signal and the reference signal to cause current to be conducted from the AC source to the motor during the positive half-cycle of the AC voltage. The reference signal is a function of the AC line voltage and the command signal, a function of the AC line voltage, the motor armature voltage and the setting of an adjustable speed selector resistor in the command signal circuit. When the adjustable speed selector resistor is operated toward a minimum speed position, the necessary signal differential for operating the solid state switch occurs later in the positive half-cycle so that the duration of application of the positive half-cycle of AC line voltage to the motor armature is reduced; when operated toward a maximum speed position, earlier in the half-cycle so that the duration is increased. A change in motor load affects only the command signal so that the necessary differential for operating the solid state switch occurs either earlier in the positive half-cycle for an increased load or later in the positive half-cycle for a reduced load to thereby maintain the selected motor speed in spite of load changes. Any variation in AC line voltage affects both the command and reference signal circuits in offsetting fashion so that the point at which the necessary differential for operating the solid state switch occurs is at essentially the same point of the positive halfcycle.
Inventors
- 👤 P Teders
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-24 14:55
CPC Classifications
H; H02; H02P; H02P7/00; H02P7/06; H02P7/18; H02P7/24; H02P7/28; H02P7/285; H02P7/292; H02P7/293; Y; Y10; Y10S; Y10S388/00; Y10S388/907; Y10S388/917; Y10S388/918
Claims Analysis
Total Claims: 30
Claim 1
Independent Claim
359 words
In a motor speed control circuit for controlling the speed of a shunt-wound DC motor, said circuit being of the type comprising an AC voltage source and solid state switch means operable during a controlled fraction of one half-cycle of the AC source voltage to conduct half-wave rectified current from said AC source to the motor armature in response to an operating signal which is controllably phased relative to the AC source voltage, the combination comprising reference signal circuit means electrically connected to said AC voltage source and including a first RC timing circuit responsive to the AC source voltage for developig a time-varying reference signal which is a function of the AC source voltage, command signal circuit means including a second RC timing circuit electrically connected to said AC voltage source and to the motor armature for developing a timevarying command signal which is a function of the AC source voltage and the motor armature voltage, programmable switch means electrically connected to said command signal circuit means, to said reference signal circuit means and to said solid state switch means and responsive to the command signal and the reference signal for developing said controllably phased operating signal for said solid state switch means, said operating signal being of such controlled phase relationship relative to the AC source voltage that when the motor armature voltage changes thereby indicating a change in motor load, said operating signal is generated earlier in said half-cycle of the AC source voltage in response to increased motor load so that said solid state switch means is operable for an increased fraction of said half-cycle of the AC source voltage and is generated later in said half-cycle of the AC source voltage in response to reduced motor load so that said solid state switch means is operable for a reduced fraction of said half-cycle of the AC source voltage and when the peak-to-peak amplitude of the AC source voltage changes, said operating signal is substantially unchanged in phase relative to the AC source voltage, whereby compensation is provided for variations in both motor loading and the AC source voltage to maintain substantially constant motor speed.
Claim 2
Dependent Claim
359 words
In a motor speed control circuit for controlling the speed of a shunt-wound DC motor, said circuit being of the type comprising an AC voltage source and solid state switch means operable during a controlled fraction of one half-cycle of the AC source voltage to conduct half-wave rectified current from said AC source to the motor armature in response to an operating signal which is controllably phased relative to the AC source voltage, the combination comprising reference signal circuit means electrically connected to said AC voltage source and including a first RC timing circuit responsive to the AC source voltage for developig a time-varying reference signal which is a function of the AC source voltage, command signal circuit means including a second RC timing circuit electrically connected to said AC voltage source and to the motor armature for developing a timevarying command signal which is a function of the AC source voltage and the motor armature voltage, programmable switch means electrically connected to said command signal circuit means, to said reference signal circuit means and to said solid state switch means and responsive to the command signal and the reference signal for developing said controllably phased operating signal for said solid state switch means, said operating signal being of such controlled phase relationship relative to the AC source voltage that when the motor armature voltage changes thereby indicating a change in motor load, said operating signal is generated earlier in said half-cycle of the AC source voltage in response to increased motor load so that said solid state switch means is operable for an increased fraction of said half-cycle of the AC source voltage and is generated later in said half-cycle of the AC source voltage in response to reduced motor load so that said solid state switch means is operable for a reduced fraction of said half-cycle of the AC source voltage and when the peak-to-peak amplitude of the AC source voltage changes, said operating signal is substantially unchanged in phase relative to the AC source voltage, whereby compensation is provided for variations in both motor loading and the AC source voltage to maintain substantially constant motor speed.
Claim 3
Dependent Claim
56 words
The combination of claim 1 wherein said circuit further includes speed adjustment means for varying the command signal relative to the reference signal to thereby vary the phase of said operating signal relative to the AC source voltage and cause the motor to operate at a speed correlated to the setting of said speed adjustment means.
Claim 4
Dependent Claim
22 words
The combination of claim 2 wherein said speed adjustment means is in said command signal circuit means and varies said command signal.
Claim 5
Dependent Claim
14 words
The combination of claim 3 wherein said speed adjustment means comprises adjustable resistance means.
Claim 6
Dependent Claim
57 words
The combination of claim 1 wherein said command signal circuit means is responsive to the voltage differential between the peak amplitude of the AC source voltage and the motor armature voltage such that the command signal is a function of the voltage differential between the peak amplitude of the AC source voltage and the motor armature voltage.
Claim 7
Dependent Claim
62 words
The combination of claim 5 wherein for a constant peak-to-peak amplitude of the AC source voltage said command signal circuit means causes said programmable switch means to generate said operating signal earlier in said half-cycle of the AC source voltage in response to increased differential between the AC source and armature voltages and later in said half-cycle in response to reduced differential.
Claim 8
Dependent Claim
78 words
The combination of claim 5 wherein for a constant motor load said command signal circuit means and said reference signal circuit means are responsive to a change in the peak-to-peak amplitude of the AC source voltage such that the changes in the command signal and the reference signal have substantially offsetting effects relative to said programmable switch means so as to cause the phase of said operating signal relative to the AC source voltage to remain substantially unchanged.
Claim 9
Dependent Claim
129 words
The combination of claim 1 wherein said programmable switch means comprises a programmable unijunction transistor having an anode terminal, an anode gate terminal and a cathode terminal and electrically connected to said reference signal circuit means and to said command signal circuit means such that the reference signal is applied as a reference voltage signal at the anode gate terminal relative to the cathode terminal and the command signal is applied as a command voltage signal at the anode terminal relative to the cathode terminal to thereby develop a control voltage signal between the anode gate t1rminal and the anode terminal, said programmable unijunction transistor being operable in response to a certain magnitude of the control voltage signal for generating said operating signal for said solid state switch means.
Claim 10
Dependent Claim
69 words
The combination of claim 8 wherein said command signal circuit means is constructed to develop the command signal such that the magnitude thereof increases from an initial signal level during said half-cycle of the AC source voltage and said reference signal circuit means is constructed to develop the reference signal such that the magnitude thereof increases from an initial signal level during said half-cycle of the AC source voltage.
Claim 11
Dependent Claim
40 words
The combination of claim 9 wherein the initial signal level of said command signal relative to the initial signal level of said reference signal is less than the certain magnitude of the control voltage signal for generating said operating signal.
Claim 12
Dependent Claim
54 words
The combination of claim 10 wherein said command signal circuit means develops said command signal at a rate greater than that at which said reference signal circuit means develops said reference signal after the magnitude of said command signal and the magnitude of said reference signal begin increasing from their respective initial signal levels.
Claim 13
Dependent Claim
114 words
The combination of claim 8 wherein said command signal circuit means is constructed to develop the command signal such that the magnitude thereof increases in the positive direction from an initial signal level during the initial portion of said half-cycle of the AC source voltage and said reference signal circuit means is constructed to develop the reference signal such that the magnitude thereof increases from an initial signal level during said initial portion of said half-cycle of the AC source voltage, the initial signal level of the command signal relative to the initial signal of the rEference signal being less than the certain magnitude of the control voltage signal for generating said operating signal.
Claim 14
Dependent Claim
46 words
The combination of claim 12 wherein said command signal circuit means is constructed to develop the command signal at a rate greater than that at which the reference signal circuit means develops the reference signal once said signals begin increasing from their respective initial signal levels.
Claim 15
Dependent Claim
106 words
The combination of claim 12 wherein said command signal circuit means is constructed to develop the command signal such that the time rate of change of the command signal magnitude increases with increasing motor load to thereby cause the certain magnitude of the control voltage signal for generating said operating signal to be developed earlier in said half-cycle of the AC source voltage and decreases with decreasing motor load to thereby cause the certain magnitude of the control voltage signal for generating said operating signal to be developed later in said half-cycle of the AC source voltage, whereby compensation is provided for variations in motor loading.
Claim 16
Dependent Claim
128 words
The combination of claim 12 wherein said command signal circuit means and said reference signal circuit means are constructed to develop the command and reference signals respectively such that the time rate of change of the magnitude of the command signal and the time rate of change of magnitude of the reference signal are functions of the peak amplitude of the AC source voltage which so change relative to each other in response to a change in the peak amplitude of the AC source voltage that the certain magnitude of control voltage signal for generating said operating signal is developed at a relatively unchanged point in said half-cycle of the AC source voltage whereby compensation is provided for variations in the peak-to-peak amplitude of the AC source voltage.
Claim 17
Dependent Claim
44 words
The combination of claim 8 wherein said second timing circuit comprises a command capacitor and means for developing the command voltage signal as a time-varying voltage across said capacitor, which voltage is a function of the AC source voltage and the motor armature voltage.
Claim 18
Dependent Claim
37 words
The combination of claim 16 wherein said capacitor is electrically connected in parallel with the anode-cathode circuit of said programmable unijunction transistor to cause the time-varying command voltage signal to be applied across the anode-cathode circuit thereof.
Claim 19
Dependent Claim
59 words
The combination of claim 17 wherein said means for developing the time-varying command voltage signal comprises means for developing the command voltage signal at the anode of said programmable unijunction transistor relative to the cathode thereof such that the magnitude of the command voltage signal increases from an initial voltage level during said half-cycle of the AC source voltage.
Claim 20
Dependent Claim
32 words
The combination of claim 18 wherein said reference signal circuit means is constructed to develop said reference voltage signal as a time-varying voltage which is a function of the AC source voltage.
Claim 21
Dependent Claim
37 words
The combination of claim 19 wherein said reference signal circuit means comprises means for developing the reference voltage signal such that the magnitude thereof increases from an initial voltage level during said half-cycle of the AC source.
Claim 22
Dependent Claim
76 words
The combination of claim 20 wherein said command signal circuit means and said reference signal circuit means are constructed such that the differential between the initial levels of said reference voltage signal and of said command voltage signal is less than the certain magnitude of the control voltage signal for generating said operating signal and the differential between the reference voltage signal and the command voltage signal increases during said half-cycle of the AC source voltage.
Claim 23
Dependent Claim
41 words
The combination of claim 21 wherein the increasing differential between the reference voltage signal and the command voltage signal reaches the certain magnitude of the control voltage signal for generating sAid operating signal during said half-cycle of the AC source voltage.
Claim 24
Dependent Claim
99 words
The combination of claim 22 wherein the point in said half-cycle at which the differential between the reference signal voltage and the command signal voltage reaches the certain magnitude of the control voltage signal for generating the operating signal is such that for a selected motor speed and a selected motor load the controlled fraction of said half-cycle of the AC voltage during which said AC source is electrically connected to the motor armature is of such duration that energy delivered from said AC source to the motor powers the selected motor load while maintaining the selected motor speed.
Claim 25
Dependent Claim
114 words
The combination of claim 23 further including speed adjustment means for controlling the rate of increase of said command voltage signal such that the rate of increase is reduced in response to adjustment of said speed adjustment means toward a minimum speed position to thereby develop the certain magnitude of the control voltage signal for generating said operating signal later in said half-cycle of the AC source voltage and the rate of increase is increased in response to adjustment of said speed adjustment means toward a maximum speed position to thereby generate the certain magnitude of the control voltage signal for generating said operating signal earlier in said half-cycle of the AC source voltage.
Claim 26
Dependent Claim
31 words
The combination of claim 24 wherein said first RC timing circuit comprises a reference capacitor and means for developing the reference voltage signal as a time-varying voltage across said reference capacitor.
Claim 27
Dependent Claim
66 words
The combination of claim 25 wherein said means for developing the reference voltage signal is constructed such that the reference voltage signal increases from an initial signal level during substantially said half-cycle of the AC source voltage to a maximum signal level and decreases from the maximum signal level to the initial signal level during the remaining portion of the cycle of the AC source voltage.
Claim 28
Dependent Claim
52 words
The combination of claim 25 wherein said reference capacitor is electrically connected in parallel with the anode gate -cathode circuit of said programmable unijunction transistor and the electrical connection of said two capacitors to the cathode of said programmable unijunction transistor is electrically connected to the positive terminal of the motor armature.
Claim 29
Dependent Claim
35 words
The combination of claim 25 wherein said reference signal circuit further comprises a stepdown transformer connected to said AC source for reducing the magnitude of the AC source voltage applied to said first timing circuit.
Claim 30
Dependent Claim
141 words
The combination of claim 17 wherein the electrical connection between said command capacitor and the cathode of said programmable unijunction transistor is electrically connected to one terminal of the motor armature, the other terminal of the motor armature is electrically connected to one terminal of the AC voltage source and said command signal circuit means is electrically connected to the other terminal of said AC voltage source and said means for developing the command voltage signal includes means for restricting current flow from said AC source to unidirectional flow from said other terminal of said AC source through said capacitor and through the motor armature to said one terminal of the AC source to develop said increasing command voltage signal across the anode-cathode circuit of said programmable unijunction transistor during an initial fraction of said half-cycle of the AC source voltage.
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) | 1976-06-04 | 1976-12-04 | 1977-06-05 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1980-06-04 | 1980-12-04 | 1981-06-05 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1984-06-04 | 1984-12-04 | 1985-06-05 | $7700.00 | Window Closed / Lapsed |