MCCB can cut off the current automatically when the current exceeds the trip setting. Plastic shell refers to the use of plastic insulator as the shell of the device, which is used to isolate the conductor and grounding metal parts. Moulded case circuit breakers usually contain thermal magnetic trip units, while large moulded case circuit breakers are equipped with solid state trip sensors. The release unit is divided into thermal magnetic release and electronic release.

塑壳断路器也被称为装置式断路器，所有的零件都密封于塑料外壳中，辅助触点，欠电压脱扣器以及分励脱扣器等多采用模块化。由于结构非常紧凑，塑壳断路器基本无法检修。

Moulded case circuit breaker is also called device circuit breaker. All parts are sealed in plastic shell. Auxiliary contact, undervoltage release and shunt release are mostly modularized. Due to its compact structure, moulded case circuit breaker can hardly be repaired.

其多采用手动操作，大容量可选择电动分合。由于电子式过电流脱扣器的应用，塑壳断路器也可分为A类和B类两种，B类具有良好的三段保护特性，但由于因素，采用热磁式脱扣器的A类产品的市场占有率更高。

Most of them are operated by hand, and large capacity can choose electric on-off. Due to the application of electronic over-current release, moulded case circuit breaker can also be divided into class A and class B. class B has good three section protection characteristics. However, due to the price factor, the market share of class a products with thermal magnetic release is higher.

塑壳断路器是将触头、灭弧室、脱扣器和操作机构等都装在一个塑料外壳内，一般不考虑维修，适用于作支路的保护开关，过电流脱扣器有热磁式和电子式两种，一般热磁式塑壳断路器为非选择性断路器，仅有过载长延时及短路瞬时两种保护方式。

Moulded case circuit breaker (MCCB) is a kind of protective switch for branch circuit. The contact, arc extinguishing chamber, release and operating mechanism are all installed in a plastic shell. Generally, maintenance is not considered. There are two kinds of over-current release: thermal magnetic type and electronic type. Generally, thermal magnetic MCCB is a non selective circuit breaker, which only has two kinds of protection methods: overload long delay and short-circuit instantaneous.

电子式塑壳断路器有过载长延时、短路短延时、短路瞬时和接地故障四种保护功能。部分电子式塑壳断路器新推出的产品还带有区域选择性连锁功能。大多数塑壳断路器为手动操作，也有部分带电动机操作机构。

Electronic moulded case circuit breaker has four protection functions: overload long delay, short circuit short delay, short circuit instantaneous and grounding fault. Some new products of electronic moulded case circuit breaker also have regional selective interlocking function. Most moulded case circuit breakers are operated manually, and some are equipped with motor operating mechanism.