PURPOSE: To accelerate interrupting operation by extending the charging time of the smoothing capacitor of a power source circuit for a short time to raise the charge voltage, and enhancing the voltage to be applied to a trip electromagnetic device.
CONSTITUTION: In accordance with a rapid increase in load current IL of an AC cable run 1, a current 11 passing a smoothing capacitor (C) 72 into a detecting resistor 6 through a current transformer 4 and a rectifier 5 is increased. This is detected by a time limit circuit 8 to close a switch 9, a trigger signal S is transmitted to a one-pulse generating circuit, one pulse is generated to close a switch 75, and the output of a pulse duty modulator 74 is delivered to the (-) line of a control power source 7A. At this time, a switch 10 is opened, the direct current I1 is continuously carried to C72 during one pulse, the charge voltage is raised to make the exciting voltage to be applied to a trip coil 3 the value to which the voltage generated on both ends of the detecting resistor 6 is added, and the operating speed of a circuit breaker can be accelerated.
YAMAZAKI HARUHIKO
KASHIWABARA AKIO
KIMURA KENJI
