Other

Square D Company

William Davison

Steve M Meehleder

Kevin John Malo

David Joseph Dunne

Richard Allen Studer, Ii

Ryan James Moffitt

Susan Jean Walker Colsch

Paul Andrew Reid

Gary Michael Stumme

A time-synchronized trip implementation for a motor circuit protector (MCP) having a reconfigurable microcontroller. The microcontroller causes a power supply to, be charged for an initial time period during a charging mode. An onboard comparator is configured for a predetermined self-protection level of the MCP, and fault currents that exceed the comparator's threshold will directly drive a solenoid to trip the MCP. The microcontroller reconfigures the comparator's threshold to both measure and charge the power supply toward a stored energy trip voltage, which will charge quickly when high fault currents are present. As a result, self-protection is not compromised. After the trip voltage is reached, the microcontroller reconfigures the onboard comparator's threshold for self-protection trip levels. When a trip event occurs in this mode, stored energy trip activation occurs. The MCP includes user-selectable trip settings, and the microcontroller reconfigures the comparator threshold levels for user-selectable self-protection levels.

Method and system for time synchronized trip algorithms for breaker self protection

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.

Method and system of current transformer output magnitude compensation in a circuit breaker system

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. An adjusted trip point threshold is calculated from the computed burden resistor percentage, and the adjusted trip point threshold is stored in a memory.

Burden resistor temperature compensation algorithm

A redundant trip activation scheme whereby at least one pre-trip condition must be satisfied before a trip signal is sent to a trip solenoid of a motor circuit protector. To provide a layer of protection against spurious or nuisance tripping caused by software errors or external events such as EMF effects, a trip module sets a trip variable upon detection of a trip signal. Instead of tripping the MCP, the trip module requires at least an additional trip signal to be detected. The next time a trip signal is detected, the trip module checks whether the trip variable has been set, and, if so, sends a trip signal to a trip circuit, causing the solenoid to be activated. To ensure that a trip actually occurs, the solenoid can be tripped from the microcontroller via the trip circuit or from an over-voltage protection circuit in the event of a system failure, which operates independently of the trip circuit.

Redundant trip activation

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.

Method and system of calibrating sensing components in a circuit breaker system

A translation technique for translating mechanical button positions of a circuit breaker to trip point settings stored in a memory of the circuit breaker. A turn of a mechanical button turns a potentiometer button, whose output is converted to scaled voltages and converted to corresponding digital values. These digital values are checked against a range of thresholds (minimum/maximum) corresponding to mechanical orientation positions of the mechanical button. Once the mechanical orientation position is determined by scaling and converting the potentiometer output, a trip curve lookup table stored in memory is accessed to determine which trip point setting should be set for the circuit breaker based upon the button position. The circuit breaker's trip curve settings can be changed easily via the mechanical button. They can also be changed easily by modifying the trip curve lookup table without having to recalibrate the circuit breaker or the switch settings.

Switch-to-trip point translation

A motor circuit protector that trips in accordance with an instantaneous trip curve that is split into three protection regions, a self-protection region, an in-rush avoidance region, and a locked-rotor avoidance region. Software modules for detecting whether primary current exceeds each region are run in parallel or simultaneously, providing redundant instantaneous trip detection, and these redundant protection regions remain active throughout the startup and steady-state modes of operation of the motor circuit protector. This redundancy provides improved time current trip performance for a wide variety of short circuit conditions and improved system safety properties are realized. The current threshold for the self-protection region can be adjusted toward the in-rush avoidance region once steady-state operation is achieved. In startup mode, only the self-protection region may be detected, but can remain active during steady-state mode.

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Cedar Rapids, IA, United States of America

William Davison