US3601689A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Thermal load indicator for electrical apparatus
Assignee: General Electric Co
•
Filing: 1969-10-24
•
Granted: 1971-08-24
•
Expires: 1989-10-24
Abstract
Abstract A thermal load indicator to show the present thermal loading of an electrical apparatus and the past maximum thermal loading. A thermal model comprising a nonlinear, temperature sensitive, resistor and a heater resistor in a thermal container is immersed in the insulation liquid of the electrical apparatus to provide a representation of the ''''hot spot'''' temperature of such apparatus. The thermal model is placed electrically in a voltage divider to provide an error signal to a servomotor circuit. The servomotor drives an indicator device to provide an indication of thermal loading. The indicator in turn is coupled to a rheostat which is driven to balance the voltage divider eliminating the error signal. A drag hand on the indicator indicates the maximum past thermal loading. Switching means are provided in the indicator device when used with a tap changing apparatus to drive such apparatus to a lower ratio when such apparatus is overheated.
Inventors
- 👤 Clarence J Kettler
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-01 08:46
CPC Classifications
H; H02; H02H; H02H11/00; H02H11/006; H02H11/007; H02H6/00
Claims Analysis
Total Claims: 12
Claim 1
Independent Claim
163 words
A thermal load indicator for electrical apparatus comprising, in combination, a. a thermal model including a nonlinear, temperature sensitive resistor and a heater resistor in a thermal container, 1. said thermal model immersed in the insulating liquid of the electrical apparatus, 2. said heater resistor thermally coupled to said nonlinear resistor and connected electrically to the current flow in the electrical apparatus, b. a voltage divider network comprising said nonlinear resistor and a rheostat, 1. a junction in said voltage divider between said nonlinear resistor and said rheostat, c. a voltage source connected across said voltage divider, d. a servomotor connected to said junction, 1. said servomotor mechanically coupled to said rheostat whereby a change in resistance in said nonlinear resistor provides a signal to said junction to actuate said servomotor to move said rheostat to eliminate said signal, and e. an indicator mechanically coupled to said rheostat to provide an indication of thermal load when said rheostat is moved by said servomotor.
Claim 2
Dependent Claim
163 words
A thermal load indicator for electrical apparatus comprising, in combination, a. a thermal model including a nonlinear, temperature sensitive resistor and a heater resistor in a thermal container, 1. said thermal model immersed in the insulating liquid of the electrical apparatus, 2. said heater resistor thermally coupled to said nonlinear resistor and connected electrically to the current flow in the electrical apparatus, b. a voltage divider network comprising said nonlinear resistor and a rheostat, 1. a junction in said voltage divider between said nonlinear resistor and said rheostat, c. a voltage source connected across said voltage divider, d. a servomotor connected to said junction, 1. said servomotor mechanically coupled to said rheostat whereby a change in resistance in said nonlinear resistor provides a signal to said junction to actuate said servomotor to move said rheostat to eliminate said signal, and e. an indicator mechanically coupled to said rheostat to provide an indication of thermal load when said rheostat is moved by said servomotor.
Claim 3
Dependent Claim
57 words
A thermal load indicator as claimed in claim 1 in which said thermal model includes a first thermal barrier within said container about said nonlinear resistor providing a first thermal time constant and a second thermal barrier about said heater resistor providing a second thermal time constant relatively short when compared to said first thermal time constant.
Claim 4
Dependent Claim
32 words
said heater resistor thermally coupled to said nonlinear resistor and connected electrically to the current flow in the electrical apparatus, b. a voltage divider network comprising said nonlinear resistor and a rheostat,
Claim 5
Dependent Claim
32 words
said heater resistor thermally coupled to said nonlinear resistor and connected electrically to the current flow in the electrical apparatus, b. a voltage divider network comprising said nonlinear resistor and a rheostat,
Claim 6
Dependent Claim
32 words
A thermal load indicator as claimed in claim 2 in which said nonlinear resistor is wound on a winding form and in which said heater resistor is mounted within said winding form.
Claim 7
Dependent Claim
76 words
A thermal load indicator as claimed in claim 1 in which said servomotor includes a servomotor driving circuit comprising a transistor connected to said junction, a silicon controlled rectifier having a gate electrically connected to said transistor and a pair of motor relays connected in circuit with said rectifier, whereby said rectifier conducts on a half cycle according to said signal to said transistor, to actuate one of said motor relays according to said half cycle.
Claim 8
Dependent Claim
44 words
A thermal load indicator as claimed in claim 1 in which said indicator includes a switching means actuated by a predetermined thermal load indication to energize an electrical motor in the electrical apparatus to run a tap switch to a lower predetermined tap setting.
Claim 9
Dependent Claim
70 words
A thermal load indicator as set forth in claim 1 in which a resistor network is provided in parallel circuit with said heater resistor, said resistor network including a fixed resistor and a variable resistor, a slider connected to said variable resistor, said slider actuated by the tap changer of said voltage regulator to include portions of said variable resistor in circuit according to the position of said tap changer.
Claim 10
Dependent Claim
116 words
A voltage regulator having a thermal load indicator comprising a thermal model of said regulator connected in a voltage divider network with a rheostat, said rheostat actuated to balance said voltage divider network to compensate for changes in said thermal model, a pointer on said indicator moved to an indication of thermal load with said rheostat, a switch member in said indicator, said switch member moved from an open to closed position when said pointer reaches a predetermined thermal indication, said switch member electrically connected to the lower control circuit of the regulator motor to actuate said lower control circuit to run back the tap changer of said regulator when said predetermined thermal load is reached.
Claim 11
Dependent Claim
116 words
A voltage regulator having a thermal load indicator comprising a thermal model of said regulator connected in a voltage divider network with a rheostat, said rheostat actuated to balance said voltage divider network to compensate for changes in said thermal model, a pointer on said indicator moved to an indication of thermal load with said rheostat, a switch member in said indicator, said switch member moved from an open to closed position when said pointer reaches a predetermined thermal indication, said switch member electrically connected to the lower control circuit of the regulator motor to actuate said lower control circuit to run back the tap changer of said regulator when said predetermined thermal load is reached.
Claim 12
Dependent Claim
65 words
A voltage regulator having a thermal load indicator as set forth in claim 7 in which a switch contact is provided between said switch member and said lower control circuit, and a switch actuator connected to said tap changer, said switch actuator closing said switch contact at high positions of said tap changer and opening said switch contact at lower positions of said tap changer.
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) | 1974-08-23 | 1975-02-22 | 1975-08-24 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1978-08-23 | 1979-02-22 | 1979-08-24 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1982-08-23 | 1983-02-22 | 1983-08-24 | $7700.00 | Window Closed / Lapsed |