SECONDARY THERMAL SENSOR FOR PRIMARY CONDUCTORS
First Claim
1. A circuit breaker having a thermal sensor coupled to a secondary winding of a current transformer for modeling a temperature of a primary conductor carrying primary current to the circuit breaker, the circuit breaker comprising:
- a electrically conductive element at least a part of which is coupled to an electrical conductor carrying secondary current from the secondary winding of a current transformer in the circuit breaker, the conductive element being dimensioned such that a thermal mass of the conductive element, determined according to a function that includes a ratio of the primary current to the secondary current and a heat capacity of the conductive material, models a rate of heating or cooling in the primary conductor; and
a semiconductor element connected to at least part of the conductive element and providing a voltage across a p-n junction of the semiconductor element, the voltage varying as a function of a temperature of the conductive element.
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Accused Products
Abstract
A thermal sensing system for providing thermal protection to an electronic circuit breaker that does not require any additional components. The layout of the conductive traces on the printed circuit board are dimensioned and configured so that the ratio of primary current to primary conductor thermal mass heating is correlated with the ratio of secondary current to secondary thermal mass heating. A voltage at a semiconductor junction in the rectifier behind the secondary transformer is measured, and a temperature or heat is calculated based on the voltage. Because this temperature or heat calculation is correlated with the temperature or heat of the primary conductor, a trip routine can be added based on the measured voltage for thermal protection of the primary conductors. A thermal history of the ‘primary thermal mass’ is also provided for robust thermal protection of the circuit breaker load and primary conductors.
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Citations
19 Claims
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1. A circuit breaker having a thermal sensor coupled to a secondary winding of a current transformer for modeling a temperature of a primary conductor carrying primary current to the circuit breaker, the circuit breaker comprising:
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a electrically conductive element at least a part of which is coupled to an electrical conductor carrying secondary current from the secondary winding of a current transformer in the circuit breaker, the conductive element being dimensioned such that a thermal mass of the conductive element, determined according to a function that includes a ratio of the primary current to the secondary current and a heat capacity of the conductive material, models a rate of heating or cooling in the primary conductor; and a semiconductor element connected to at least part of the conductive element and providing a voltage across a p-n junction of the semiconductor element, the voltage varying as a function of a temperature of the conductive element. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18)
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19. An electronic circuit breaker having a thermal sensor coupled to a secondary winding of a current transformer for modeling a temperature of a primary conductor carrying primary current to the circuit breaker, the electronic circuit breaker comprising:
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an electrically conductive element at least a part of which is coupled to an electrical conductor carrying secondary current from the secondary winding of a current transformer in the circuit breaker, the conductive element having a thermal mass proportional to a thermal mass of the primary conductor, wherein a ratio of the primary current to the thermal mass of the primary conductor is correlated with a ratio of the secondary current to the thermal mass of at least the conductive element; a semiconductor element connected to at least part of the conductive element and providing a voltage across a p-n junction of the semiconductor element, the voltage varying as a function of a temperature of the conductive element; and a controller that receives the voltage, calculates a temperature based on the voltage, and causes the circuit breaker to trip responsive to the temperature calculation.
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Specification