US3737752A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Motor control system
Assignee: Texas Instruments Inc
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Filing: 1971-04-09
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Granted: 1973-06-05
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Expires: 1991-04-09
Abstract
Abstract A system adapted for use in controlling an electric motor having a start winding, a run winding, and a capacitor connected to the start winding is disclosed in which a heat responsive current limiting device, the electrical resistance of which increases abruptly at a predetermined transition temperature, is connected in parallel relationship with the capacitor and coupled to the start winding so as to permit power to be supplied to the start winding therethrough only during starting of the motor until the predetermined transition temperature is approached whereupon power is applied to the start winding through the capacitor and the voltage established thereacross retains the heat responsive current limiting device in a heated state so that the device continues to block current flow therethrough until another starting cycle is initiated.
Inventors
- 👤 R Strachan
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-23 00:13
CPC Classifications
H; H02; H02P; H02P1/00; H02P1/16; H02P1/42; H02P1/44
Claims Analysis
Total Claims: 12
Claim 1
Independent Claim
196 words
A system adapted for use with an electric motor having a start winding, a run winding and a capacitor serially connected to the start winding, comprising a heat responsive current limiting device, said heat responsive current limiting device comprises a plurality of individual elements of preselected material each possessing a resistance characteristic having a positive temperature coefficient including a sharply defined transition temperature above which the resistance of the material increases abruptly, said individual elements being respectively mounted in adjacent facing relationship with one another and being electrically coupled and in thermal communication with one another, said heat responsive current limiting device being connected in parallel relationship with the capacitor and coupled to the start winding, and means for connecting said heat responsive current limiting means to a source of electrical power and to the start winding so as to permit power to be supplied to the start winding through said heat responsive current limiting device only during starting of the motor until the predetermined transition temperature is approached whereupon power is applied to the start winding through the capacitor and the voltage established thereacross retains said heat responsive current limiting device in a heated state.
Claim 2
Independent Claim
196 words
A system adapted for use with an electric motor having a start winding, a run winding and a capacitor serially connected to the start winding, comprising a heat responsive current limiting device, said heat responsive current limiting device comprises a plurality of individual elements of preselected material each possessing a resistance characteristic having a positive temperature coefficient including a sharply defined transition temperature above which the resistance of the material increases abruptly, said individual elements being respectively mounted in adjacent facing relationship with one another and being electrically coupled and in thermal communication with one another, said heat responsive current limiting device being connected in parallel relationship with the capacitor and coupled to the start winding, and means for connecting said heat responsive current limiting means to a source of electrical power and to the start winding so as to permit power to be supplied to the start winding through said heat responsive current limiting device only during starting of the motor until the predetermined transition temperature is approached whereupon power is applied to the start winding through the capacitor and the voltage established thereacross retains said heat responsive current limiting device in a heated state.
Claim 3
Dependent Claim
29 words
A system in accordance with claim 1 wherein a series of said elements are mounted in axially aligned contiguous relation and electrically connected in series relationship with one another.
Claim 4
Dependent Claim
69 words
A system in accordance with claim 2 wherein a housing comprising a tubular memBer of heat-resistant, refractory material is provided for supporting said elements and electrical contact members are provided extending from a point external of said housing and through the wall of said housing, said electrical contact members being in electrical contact with conductive surface portions of said individual elements disposed at opposed ends of said tubular member.
Claim 5
Dependent Claim
52 words
A system in accordance with claim 3 wherein end caps of heat-resistant refractory material are disposed at opposed end edges of said tubular member for enclosing said housing and a slot is provided in the wall of said housing defining a vent passage to permit circulation of ambient air within said housing.
Claim 6
Dependent Claim
28 words
A system in accordance with claim 4 wherein a plurality of vent slots are provided and said electrical contact members extend into said housing through said vent slots.
Claim 7
Dependent Claim
36 words
A system in accordance with claim 1 wherein said elements comprise a plurality of positive temperature coefficient of resistance thermistors electrically connected in series relationship and physically positioned in contiguous heat transfer relationship with each other.
Claim 8
Dependent Claim
147 words
A motor control system for use with an electric motor having a start winding and a run winding comprising a run capacitor connected in series relationship with said start winding, a plurality of serially connected thermistors each having a positive temperature coefficient of resistance and arranged in heat transfer relationship with one another, said plurality of serially connected thermistors being connected in shunt relationship with said run capacitor and coupled to said start winding for supplying current to said start winding for a predetermined time interval during starting of the motor while bypassing said run capacitor and substantially blocking current flow therethrough and causing current to be supplied to said start winding during running of the motor subsequent to the predetermined time interval, and means for connecting the run winding, the start winding, said run capacitor and said plurality of thermistors to a source of electrical power.
Claim 9
Dependent Claim
147 words
A motor control system for use with an electric motor having a start winding and a run winding comprising a run capacitor connected in series relationship with said start winding, a plurality of serially connected thermistors each having a positive temperature coefficient of resistance and arranged in heat transfer relationship with one another, said plurality of serially connected thermistors being connected in shunt relationship with said run capacitor and coupled to said start winding for supplying current to said start winding for a predetermined time interval during starting of the motor while bypassing said run capacitor and substantially blocking current flow therethrough and causing current to be supplied to said start winding during running of the motor subsequent to the predetermined time interval, and means for connecting the run winding, the start winding, said run capacitor and said plurality of thermistors to a source of electrical power.
Claim 10
Dependent Claim
24 words
A motor control system in accordance with claim 7 wherein said plurality of thermistors are mounted in contiguous heat transfer relationship with each other.
Claim 11
Dependent Claim
60 words
A motor control system in accordance with claim 7 wherein a start capacitor is provided connected in series relationship with said plurality of serially connected thermistors and in series relationship with the start winding for shifting the phase of current being supplied to the start winding while current is being supplied thereto through said thermistors during starting of the motor.
Claim 12
Dependent Claim
35 words
A motor control system in accordance with claim 9 wherein said plurality of thermistors are respectively mounted in abutting physical relationship with each other and maintained in closely coupled heat transfer relationship with each other.
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 |