Moulded case circuit breaker (VCB) is widely used in low-voltage distribution industry, which is used to cut off or isolate the fault current within the normal and rated range to ensure the safety of lines and equipment. In addition, according to the requirements of China's technical code for safety of temporary electricity use on construction site, the temporary electricity circuit breaker on construction site must be transparent shell, which can clearly distinguish the on-off state of main contact, and the compliance circuit breaker must be pasted with the "AJ" sign issued by relevant safety departments.

塑殼斷路器有多種附件可以加掛，如遠程電動操作分合閘機構、分勵線圈、輔助觸點、報 警觸點等。

Moulded case circuit breaker has a variety of accessories that can be hung, such as remote electric switching mechanism, shunt coil, auxiliary contact, alarm contact, etc.

電動操作機構選型時需注意配套斷路器殼架電流，因為不同殼架電流的斷路器外形尺寸還有分合閘機構的扭矩不同。

When selecting the type of electric operating mechanism, it is necessary to pay attention to the shell frame current of the matching circuit breaker, because the external dimensions of the circuit breaker with different shell frame current and the torque of the opening and closing mechanism are different.

塑殼斷路器另一項重要性能指標是其額定短路分斷能力，此項數值的高低直接影響斷路器安全分斷故障電流的能力，一般為25/35/50/65kA。我們實際選擇過程中可以根據設計院圖紙要求選用，無要求的可以根據經驗計算回路預期短路電流值。斷路器短路分斷能力要大于回路預期短路電流。為節省成本，短路分斷能力值夠用就好。

Another important performance index of molded case circuit breaker is its rated short-circuit breaking capacity, which directly affects the safe breaking fault current capacity of the circuit breaker, generally 25 / 35 / 50 / 65ka. In the actual selection process, we can select according to the drawing requirements of the Design Institute, and if there are no requirements, we can calculate the expected short-circuit current value of the circuit according to experience. The short-circuit breaking capacity of the circuit breaker should be greater than the expected short-circuit current of the circuit. In order to save cost, the short circuit breaking capacity value is enough.

塑殼斷路器可以做成帶漏電保護功能，但是跟微型漏電斷路器一般為30mA漏電動作電流不同，塑殼漏電斷路器漏電動作電流多為100/300/500mA可調，因此可見，帶漏電保護的塑殼斷路器主要是保護下端設備或電纜漏電，而不是用來直接保護用電人員。此類斷路器實際使用過程中有一弊端，就是一般這類斷路器下端設備較多，施工人員接線過程中很容易失誤將零線和地線弄混，而導致總開關漏保跳閘，這類問題查起故障點來非常費事兒

Moulded case circuit breaker can be made with leakage protection function, but it is different from miniature leakage circuit breaker which is generally 30mA leakage action current. The leakage action current of moulded case leakage circuit breaker is mostly 100 / 300 / 500mA adjustable. Therefore, it can be seen that moulded case circuit breaker with leakage protection is mainly used to protect the lower end equipment or cable leakage, rather than directly protect the power users. There is a drawback in the actual use of this kind of circuit breaker, that is, there are many devices at the lower end of this kind of circuit breaker, and it is easy for the construction personnel to mix the zero line and ground line in the wiring process, which leads to the main switch leakage protection trip. It is very difficult to find the fault point for this kind of problem