The molded case circuit breaker can automatically cut off the current when the current exceeds the trip setting. Plastic casing refers to the use of plastic insulators as the outer shell of a device, used to isolate conductors and grounded metal parts. Molded case circuit breakers typically contain thermal magnetic trip units, while larger models of molded case circuit breakers are equipped with solid-state trip sensors. Its release unit is divided into: thermal magnetic release and electronic release. The commonly used rated currents are as follows: 15 25 30 40 50 60 75 80 100 125 160 200 225 250 315 350 400 500 630 A.