If the rated current, breaking capacity, and protection are met, can the plastic shell replace the frame? For example, can HCZM3 plastic-case circuit breaker be used in the main inlet line? If so, why is it common practice to use a frame instead of a much cheaper plastic case?

HCZM3 moulded case circuit breaker and HCZW3 frame circuit breaker are very common products used in circuit breaker products, but many people do not understand the difference between the two, and often appear in the choice of the situation, here first understand the concept of the two, secondly understand the difference between the two, and finally understand the choice of the two.



(1) The concept of frame and moulded case circuit breaker

1) HCZW3 frame circuit breaker

Frame circuit breakers are also commonly known as air circuit breakers or universal circuit breakers, which are mainly used for the closing of incoming lines, busbars and other large current circuits of low-voltage distribution systems. It is composed of a contact, an arc extinguishing device, an operating mechanism and a trip system, a housing and a control unit.

According to the installation method can be divided into fixed and drawer type two, fixed shell using metal materials, appearance size is large, low level of protection. Drawer type uses engineering plastic shell, compact structure, high protection level, easy maintenance. According to the protection characteristics, the frame circuit breaker can be divided into non-selective (class A) and selective (class B), class B circuit breakers mostly use electronic overcurrent release, with long delay, short delay and instantaneous action protection of three protection characteristics.

Intelligent frame circuit breaker built-in MCU, with display, alarm, self-check and communication functions, can be combined with industrial computer monitoring system. The biggest feature of the frame circuit breaker is large capacity, high limit breaking capacity and enough short-term withstand current, such as Henan Long March Electric HCZW3 circuit breaker rated current up to 6300A, rated short-term withstand current up to 85KA, which makes the frame circuit breaker has good selectivity and stability.