Small circuit breakers are mainly suitable for overload and short circuit protection in power lines with a rated voltage of 400V and below and a rated current of generally 125A or below. They can also be used for infrequent operation of motors and infrequent switching of power lines.
Miniature circuit breakers are widely used in industrial, commercial, high-rise buildings, and residential areas due to their characteristics of track installation, modular size, diversified functions, artistic design, and safe use. The plastic casing of a miniature circuit breaker consists of a base and a cover, and all components are installed in the plastic base. When overload and short circuit faults occur in the circuit, the delay release and instantaneous release will open the operating mechanism through the transmission rod, thereby driving the rapid disconnection of the contacts. The base and cover of the plastic casing of the miniature circuit breaker can be produced and manufactured using BMC molding method.
BMC molding compound is an abbreviation for Bulk (Dough) molding compound, which stands for bulk molding compound. It is commonly referred to as unsaturated polyester bulk molding compound in China. Its main raw materials are GF (short cut glass fiber), UP (unsaturated resin), MD (filler), and various additives mixed thoroughly to form a pre impregnated material in the form of a cluster.
BMC materials were first applied in West Germany and the United Kingdom in the 1960s, and then developed significantly in the United States and Japan in the 1970s and 1980s, respectively. BMC molded plastic shell circuit breaker shell products can accurately control the size, have good flame retardancy and resistance to electric traces, have high dielectric strength, corrosion resistance and pollution resistance, excellent mechanical properties, low shrinkage and stable color.
The flow characteristics of BMC molded plastic are excellent, making it very suitable for molded case circuit breaker shell products with detailed and dimensional requirements. BMC molded plastic can be used to produce molded case circuit breaker shells through compression molding and injection molding processes. Especially, the BMC injection molding process for producing molded case circuit breaker casings has improved production efficiency, ensuring that the finished products are environmentally friendly and aesthetically pleasing; Significantly reducing the labor intensity of operators is more suitable for the production of small molded case circuit breaker casings, but large molded case circuit breaker casings are generally produced through BMC molding technology. When the shell of a large BMC molded circuit breaker is pressed and formed, a certain amount of prepared BMC molding material is placed into a preheated mold, and then the mold is closed at a certain speed; BMC molding compound flows under pressure and fills the entire mold cavity; Maintain the required temperature and pressure for a certain period of time, and when it has completed the physical and chemical processes and solidified, shaped, and achieved optimal performance, open the mold and remove the BMC plastic shell circuit breaker housing product.
