Patent ID: 7177129
Filing Date: 2007-02-13
Classification: H02H

Abstract:
1. A circuit breaker comprising: a main contactor; a current detector configured to provide test signals of a current to be monitored via the main contactor; a microprocessor-controlled tripping device including a microprocessor and a watchdog circuit configured to monitor the microprocessor, the tripping device being configured to receive energy from the current detector, to process the test signals and to activate a tripping coil so as to automatically open the main contactor when a settable limit value is exceeded; a bypass circuit configured to receive energy from the current detector and including a high pass filter connected downstream from the watchdog circuit, a first semiconductor switch connected downstream from the high pass filter, a charging capacitor dischargeable via the first semiconductor switch, and a voltage comparator having a first input, a second input and an output side, the voltage comparator being connected via the first input to the current detector and on the output side to the charging capacitor; a monitoring circuit configured to apply a first reference voltage to the second input of the comparator when a supply voltage is below a pre-defined threshold level and to apply a second reference voltage to the second input of the comparator when the supply voltage is above the pre-defined threshold level, the first reference voltage being associated with a first current limit value and the second reference voltage being associated with a second current limit value that is smaller than the first current limit value; and a actuation circuit connected on an output side thereof to the tripping coil and configured to be actuated via a first OR-input by the tripping device and via a second OR-input by the charging capacitor as a function of a state of charge of the charging capacitor.