What is a Miniature Circuit Breaker?

Figure 1: Different types of miniature circuit breakers.

The miniature circuit breaker (MCB) is suitable for overload and short-circuit protection of AC 50/60Hz rated voltage 230/400V, rated current up to 63A, and can also be used for infrequent operation conversion of the line under normal conditions. Miniature circuit breakers are mainly used in various places such as industrial, commercial, high-rise and residential buildings.

The Constitution of the Miniature Circuit Breaker

The miniature circuit breaker consists of the following main parts:
1. Disconnectable contact connector. It consists of fixed contacts and movable contacts.
2. Devices consisting of metal cylinders or insulating cylinders, in which disconnectable contact couplers and arc extinguishing equipment and transmissions are installed.
3. The transmission device that drives the contact.
4. Arc extinguishing equipment.

When the commonly used small circuit breaker breaks the circuit, its moving contacts and fixed contacts are mechanically separated. When closing, the moving contact and the fixed contact are closed by the opposite mechanical movement. During the operation of making and breaking the load circuit, arcing will be generated between the fixed contact and the moving contact. The arc generated during the opening process is much more severe than the closing process. When the current at the breaking is very large, especially when breaking a short circuit, the arc is very large, and it is often very difficult to disconnect the circuit.

Characteristics of the Miniature Circuit Breaker

Figure 2: Structure of a miniature breaker.

1. The rated short-circuit breaking capacity is high, and some rated current levels can reach more than 10KA.
2. Double wiring function, easily connect standard bus bar and flexible wire.
3. Combination terminal with finger touch protection, higher safety.
4. It is operated by an energy storage mechanism, and the contacts are quickly closed, which overcomes the adverse effects caused by the speed of manual operation of the handle and improves the service life of the product.
5. A variety of accessories are available, and the modular and flexible combination is very convenient for users to install.
6. The shell and some functional parts are made of high flame retardant, high temperature and impact resistant plastics.
7. The current limiting coefficient is high, and the cost efficiency is superior.

Applications of the Miniature Circuit Breaker

The miniature circuit breaker has the characteristics of advanced structure, reliable performance, high breaking capacity, beautiful appearance and small size. It is mainly used in places with AC 50HZ or 60HZ, rated voltage below 400V, and rated working current below 63A.
It is used for overload and short-circuit protection of lighting, distribution lines and equipment in office buildings, residences and similar buildings, and can also be used for infrequent on-off operation and conversion of lines. It is mainly used in various places such as industrial, commercial, high-rise and residential buildings.

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