Abstract: A circuit breaker system for providing thermal protection to a conductor conducting current from a power source to a load. While the power source is connected to the load, a microcontroller is powered by the current passing through the conductor to thermally model the temperature of the conductor. If the microcontroller determines that the temperature of the conductor has risen to an undesirable or unsafe level, the circuit breaker disconnects the power source from the load and the current no longer passes through the conductor. With no current passing through the conductor, the microcontroller no longer receives power from the conductor. Instead, the microcontroller continues to model the temperature of the conductor as the conductor cools to an ambient temperature by receiving power from an energy storage device. Accordingly, the microcontroller continuously models the temperature of the conductor until the temperature of the conductor cools to the ambient temperature.

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.

Abstract: A circuit breaker system for providing thermal protection to a conductor conducting current from a power source to a load. While the power source is connected to the load, a microcontroller is powered by the current passing through the conductor to thermally model the temperature of the conductor. If the microcontroller determines that the temperature of the conductor has risen to an undesirable or unsafe level, the circuit breaker disconnects the power source from the load and the current no longer passes through the conductor. With no current passing through the conductor, the microcontroller no longer receives power from the conductor. Instead, the microcontroller continues to model the temperature of the conductor as the conductor cools to an ambient temperature by receiving power from an energy storage device. Accordingly, the microcontroller continuously models the temperature of the conductor until the temperature of the conductor cools to the ambient temperature.

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.

Abstract: A method and system to detect currents in the saturation region of a current transformer for a circuit breaker is disclosed. An example method is sensing a fault condition with a current transformer in a circuit breaker. The characteristic curve of the current transformer in a saturation mode is determined based on peak current. A current is received on the transformer. A secondary current is output from the transformer. It is determined whether the secondary current is indicative of a fault current in the saturation mode of the transformer. The breaker is tripped if the secondary current is indicative of a fault current.

Abstract: An automatic temperature compensation method that automatically adjusts trip point thresholds of a motor circuit protector in response to changes in temperature. The relationship between two curves is exploited to match temperature sensor readings from a temperature sensor circuit with burden resistor percentage values derived from a burden resistor circuit. A temperature inflection point is determined from the intersection of (1) the temperature sensor curve plotting the voltage output of the temperature sensor versus temperature and (2) the burden resistance curve plotting burden resistance versus temperature. A temperature value along the temperature sensor curve is transformed into the corresponding burden resistance on the burden resistance curve. The burden resistance is expressed as a percentage variance from a burden resistance at an ambient temperature.

Abstract: A method and system to calibrate a motor circuit protection device is disclosed. An example method calibrates a signal chain of a circuit breaker. The signal chain includes a current transformer, a burden resistor, a stored energy circuit and a controller. The circuit breaker includes a memory coupled to the controller. A calibration instruction routine is written in a first location of the memory. A test current is injected in the circuit breaker signal chain. The test current peak of the test current in the circuit breaker signal chain is measured. Data indicative of the test current peak is stored in a second location of the memory. The test current peak data is read from the second location of the memory. The test current peak data is compared with nominal current data related to the signal chain remotely from the circuit breaker. A calibration factor is determined based on the comparison.

Abstract: A method and system to calibrate a motor circuit protection device is disclosed. An example method calibrates a signal chain of a circuit breaker. The signal chain includes a current transformer, a burden resistor, a stored energy circuit and a controller. The circuit breaker includes a memory coupled to the controller. A calibration instruction routine is written in a first location of the memory. A test current is injected in the circuit breaker signal chain. The test current peak of the test current in the circuit breaker signal chain is measured. Data indicative of the test current peak is stored in a second location of the memory. The test current peak data is read from the second location of the memory. The test current peak data is compared with nominal current data related to the signal chain remotely from the circuit breaker. A calibration factor is determined based on the comparison.

Abstract: A method and system to detect currents in the saturation region of a current transformer for a circuit breaker is disclosed. An example method is sensing a fault condition with a current transformer in a circuit breaker. The characteristic curve of the current transformer in a saturation mode is determined based on peak current. A current is received on the transformer. A secondary current is output from the transformer. It is determined whether the secondary current is indicative of a fault current in the saturation mode of the transformer. The breaker is tripped if the secondary current is indicative of a fault current.

Abstract: An automatic temperature compensation method that automatically adjusts trip point thresholds of a motor circuit protector in response to changes in temperature. The relationship between two curves is exploited to match temperature sensor readings from a temperature sensor circuit with burden resistor percentage values derived from a burden resistor circuit. A temperature inflection point is determined from the intersection of (1) the temperature sensor curve plotting the voltage output of the temperature sensor versus temperature and (2) the burden resistance curve plotting burden resistance versus temperature. A temperature value along the temperature sensor curve is transformed into the corresponding burden resistance on the burden resistance curve. The burden resistance is expressed as a percentage variance from a burden resistance at an ambient temperature.