Switching Transient Regime of Shunts Release from a Low Voltage Circuit Breaker Commanded by a PLC

Modern automatic circuit breakers are provided with electronic modules, special coils and geared motors. These components allow remote reading and remote control of the devices that are included in local or national power distribution systems. The data transfer is made via industrial protocols. This work proposes the operation of the automatic circuit breaker with a PLC. The charging of the spring, the closing and the opening of the main contacts are accomplished by means of electromagnetic relays controlled by the PLC under certain conditions and at certain times. The relays control a DC motor and respectively the corresponding DC coils of shunt opening release and shunt closing release. Communication of the PLC with a PC is made via the RS232 serial port, which allows viewing on PC screen the status of the main contacts and of the charging spring. The paper presents both the operating mode of the software implemented on the PLC and the transient regimes of the coils for each individual operation of the automatic circuit breaker.