Molded case circuit breakers, also known as device breakers, refer to housings made of plastic insulators used to isolate the conductors and grounded metal parts. All parts are sealed in a plastic housing, and auxiliary contacts, undervoltage releases, and shunt releases are modular. Molded case circuit breakers usually contain a thermal-magnetic trip unit, while large-sized molded case circuit breakers are equipped with a solid-state trip sensor.

Dean of the Shanghai Electric Apparatus Research Institute Yin Tianwen stated on June 9, 2013 that the current MCCB will take a large current at the General Electric Low Voltage Appliances General Assembly of the 2013 China Association of Electrical Equipment Association sponsored by the General Electric Low-voltage Appliances Branch of the China Electrical Equipment Industry Association. , small size direction.

At present, MCCBs are developing in the direction of large currents, and the energy storage type electric operation is interchangeable with the manual operation mechanism, which can significantly reduce the thickness of the live operation mechanism products, reduce the thickness of the distribution cabinet, increase the short-circuit breaking index, and double breakpoints. The product's high breaking index is basically matched, improving short-term resistance and selective tripping reliability.

Nowadays, on the market, there have been small-sized, cost-effective molded case circuit breakers. This type of circuit breaker has saved the production cost, reduced the thickness of the product, and expanded the range of use. In addition, the number of parts is reduced and the shape is simplified so that semi-automated mass production can be performed.

With the improvement of production techniques, the rated current of molded case circuit breakers is getting smaller and smaller, and 0.1 to 25 A of products have appeared on the market. Technical indicators have also become more and more advanced, and all kinds of performance have been improved, especially shockproof performance. In the researcher's development process, the product structure is more and more modularized, miniaturized, integrated, the structure is more and more compact, the combination scheme is flexible, and the assembly is also more convenient. In addition, the product can also be installed with soft starters, smart detectors, and more.

Similar to the universal breaker ACB, the derivative products of molded case circuit breakers, such as DC special products, distributed photovoltaic grid-connected products and reclosing leakage breakers, have also been further improved. Derivation of DC-specific products has increased the operating voltage to 1000V or even higher, can be used for photovoltaic power generation, electric vehicle charging equipment, emergency power supply and other occasions; thermal magnetic protection accuracy has also been improved; isolation switch can AC and DC common. Derived distributed photovoltaic grid-connected products tend to improve the harsh environment resistance to moisture, heat, salt spray, and ultraviolet rays, enhance the strength and corrosion resistance of key components, and improve the reliability of the mechanism and the conductive system. The minimum adjustment step can be less than Equal to 1S. The application range of derivative reclosing leakage breakers has been increased, for example, it can be used for rural network reconstruction.

Of course, these tendencies of molded case circuit breakers also need related technologies to be realized, such as contact arc extinguishing system technology; fully selective matching technology; DC critical current breaking technology; high precision and small mutual inductance technology; motor protection circuit breaker mechanism Modular technology; Industrial production technology; DC current detection and protection technology; conductive loop heating and cooling technology.

Molded case circuit breaker is one of the important products in low-voltage electrical appliances. The improvement and improvement of its performance will further protect the safety of electric power workers and help reduce electric accidents. It is hoped that the scientific and technical personnel will be able to develop molded case circuit breakers with higher safety performance in the future to eliminate the occurrence of malignant power events caused by leakage and other phenomena.