US3794950A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Overcurrent protection system and sensor used therewith
Assignee: Texas Instruments Inc
•
Filing: 1972-03-13
•
Granted: 1974-02-26
•
Expires: 1992-03-13
Abstract
Abstract An overcurrent sensor adapted to cooperate with a controller to control the power to a load is shown. In the embodiment illustrated, the controller is an electrical switching means to which the overcurrent sensor furnishes a passive signal in the form of circuit resistance to cause the controller to operate to decrease or increase electrical power to the load circuit at desired current values. The overcurrent sensor comprises a PTC (Positive Temperature Coefficient) thermistor or an NTC (Negative Temperature Coefficient) thermistor mounted in heat transfer relation, through a layer of electrical insulation, with a first heater which is electrically connected in series with an electrical load, and a heat sink member mounted in heat transfer relation through a layer of electrical insulation with the series heater to provide means for changing the transient response time of the thermistor to the series heater current. A second heater is optionally mounted in shunt relation to the first heater to provide a means of increasing the steady state current at which the controller operates, above that obtained solely with the first heater while maintaining approximately unchanged the transient response time of the thermistor assembly for corresponding overload currents.
Inventors
- 👤 O Kilner
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-28 06:54
CPC Classifications
H; H02; H02H; H02H3/00; H02H3/08; H02H3/085; H01; H01C; H01C7/00; H01C7/02; H01C7/022; H01C7/04
Claims Analysis
Total Claims: 16
Claim 1
Independent Claim
155 words
An overcurrent sensor assembly to control the operation of an electrical load having a selected ultimate trip current level and a selected short trip time at corresponding values of overload current comprising a temperature dependent thermistor having an outer peripheral surface, electrical leads connected to spaced portions of the thermistor, an elongated heater element having an inner and outer surface, a portion of the inner surface thereof wrapped around a substantial portion of the peripheral surface of the thermistor in close heat transfer relation theRewith, the heater is formed with a loop and has first and second legs having free distal end portions extending outwardly from the loop, the thermistor is received in the loop, and two terminal pads are provided, the free distal end portions disposed on respective terminal pads, a thin layer of electrically insulative material intermediate the thermistor and the heater element, and means to electrically connect the heater to the load.
Claim 2
Dependent Claim
155 words
An overcurrent sensor assembly to control the operation of an electrical load having a selected ultimate trip current level and a selected short trip time at corresponding values of overload current comprising a temperature dependent thermistor having an outer peripheral surface, electrical leads connected to spaced portions of the thermistor, an elongated heater element having an inner and outer surface, a portion of the inner surface thereof wrapped around a substantial portion of the peripheral surface of the thermistor in close heat transfer relation theRewith, the heater is formed with a loop and has first and second legs having free distal end portions extending outwardly from the loop, the thermistor is received in the loop, and two terminal pads are provided, the free distal end portions disposed on respective terminal pads, a thin layer of electrically insulative material intermediate the thermistor and the heater element, and means to electrically connect the heater to the load.
Claim 3
Dependent Claim
14 words
An assembly according to claim 1 in which the heater physically supports the thermistor.
Claim 4
Dependent Claim
17 words
An assembly according to claim 1 in which the thermistor has a positive temperature coefficient of resistance.
Claim 5
Dependent Claim
17 words
An assembly according to claim 1 in which the thermistor has a negative temperature coefficient of resistance.
Claim 6
Dependent Claim
117 words
An overcurrent sensor assembly to control the operation of an electrical load having a selected ultimate trip current level and a selected short trip time at corresponding values of overload current comprising a temperature dependent thermistor having an outer peripheral surface, electrical leads connected to spaced portions of the thermistor, an elongated heater element having an inner and outer surface, a portion of the inner surface thereof wrapped around a substantial portion of the peripheral surface of the thermistor in close heat transfer relation therewith, a thin layer of electrically insulative material intermediate the thermistor and the heater element, means to limit temperature overshoot of the thermistor, and means to electrically connect the heater to the load.
Claim 7
Dependent Claim
117 words
An overcurrent sensor assembly to control the operation of an electrical load having a selected ultimate trip current level and a selected short trip time at corresponding values of overload current comprising a temperature dependent thermistor having an outer peripheral surface, electrical leads connected to spaced portions of the thermistor, an elongated heater element having an inner and outer surface, a portion of the inner surface thereof wrapped around a substantial portion of the peripheral surface of the thermistor in close heat transfer relation therewith, a thin layer of electrically insulative material intermediate the thermistor and the heater element, means to limit temperature overshoot of the thermistor, and means to electrically connect the heater to the load.
Claim 8
Dependent Claim
46 words
An assembly according to claim 5 in which the means to limit temperature overshoot comprises an elongated heat sink wrapped around a portion of the outer surface of heater element and a thin layer of electrically insulative material intermediate the heat sink and the heater element.
Claim 9
Dependent Claim
110 words
An overcurrent sensor assembly to control the operation of an electrical load having a selected ultimate trip current level and a selected short trip time at corresponding values of overload current comprising a temperature dependent thermistor, electrical leads connected to spaced portions of the thermistor, a first heater element having a portion thereof in intimate heat transfer relation with the thermistor, a thin layer of electrically insulative material intermediate the thermistor and the heater element, means to electrically connect the heater to the load, and means to adjust ultimate trip time of the assembly while having essentially no effect on the short trip time at corresponding values of overload current.
Claim 10
Dependent Claim
110 words
An overcurrent sensor assembly to control the operation of an electrical load having a selected ultimate trip current level and a selected short trip time at corresponding values of overload current comprising a temperature dependent thermistor, electrical leads connected to spaced portions of the thermistor, a first heater element having a portion thereof in intimate heat transfer relation with the thermistor, a thin layer of electrically insulative material intermediate the thermistor and the heater element, means to electrically connect the heater to the load, and means to adjust ultimate trip time of the assembly while having essentially no effect on the short trip time at corresponding values of overload current.
Claim 11
Dependent Claim
29 words
An assembly according to claim 7 in which the means to adjust the ultimate trip time is a second elongated heater element electrically connected across the first heater element.
Claim 12
Dependent Claim
25 words
An assembly according to claim 8 including two terminal pads, the first and second heater elements electrically connected to and physically supported on respective pads.
Claim 13
Dependent Claim
65 words
An assembly according to claim 7 in which the first heater element has a first and second surface, the thermistor is disposed contiguous to the first surface, electrically insulative material is disposed intermediate the first heater element and the thermistor, a heat sink is disposed contiguous to the second surface and electrically insulative material is disposed intermediate the heat sink and the first heater element.
Claim 14
Dependent Claim
30 words
An assembly according to claim 10 including a second elongated heater element physically spaced from the heat sink and electrically connected in parallel circuit relation with the first heater element.
Claim 15
Dependent Claim
30 words
An assembly according to claim 11 in which the second heater element is in the form of a spiral disposed about the thermistor, first heater element and the heat sink.
Claim 16
Dependent Claim
15 words
An assembly according to claim 11 in which the second heater element is generally U-shaped.
References Cited (Backward Citations)
US2253577A
Cited
US2375497A
Cited
US3028473A
Cited
US3243572A
Cited
US3444399A
Cited
US3426441A
Cited
US3614345A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1977-02-25 | 1977-08-27 | 1978-02-26 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1981-02-25 | 1981-08-27 | 1982-02-26 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1985-02-25 | 1985-08-27 | 1986-02-26 | $7700.00 | Window Closed / Lapsed |