Miniature circuit breaker
A miniature circuit breaker(mcb) is a small-capacity plastic case circuit breaker with a very compact structure. It is generally composed of an operating mechanism, contacts, protection devices (various trip units), and an arc extinguishing system. It is mainly used for overload and short circuit protection in the line with rated voltage of 400V and below and rated current of 125A, as well as infrequent operation of motor and infrequent conversion of line.
Miniature circuit breakers are one of the most widely used terminal protection devices in building electrical terminal distribution devices. Although miniature circuit breaker is a terminal electrical equipment, it is widely used in many applications such as construction engineering, civil lighting and so on because of its superior performance, convenient use and reasonable price.
Residual current circuit breaker
Residual current circuit breaker (RCCB) is mainly used in the equipment leakage fault and the life-threatening personal electric shock protection, with overload and short-circuit protection function, can be used to protect the overload and short-circuit of the line or motor, and can also be used as the non frequent switching start-up of the line under normal conditions. The common residual current circuit breakers are divided into voltage type and current type, and current type is divided into electromagnetic type and electronic type.
What are the similarities and differences between miniature circuit breaker and residual current circuit breaker?
Both miniature circuit breaker and residual current circuit breaker play the role of line overload protection. The miniature circuit breaker is the opening and closing switch for controlling the electrical circuit. If air is used as the arc extinguishing medium, it is called air switch. Miniature circuit breakers are generally selected according to the rated current (load) and used as the main switch of the electrical circuit. Residual current circuit breaker includes overload, short circuit and leakage protection functions, and can be installed independently, which is equivalent to leakage protector plus miniature circuit breaker or leakage accessory plus miniature circuit breaker. When a miniature circuit breaker with leakage protection function, called residual current circuit breaker. If it is an electrical device only used for leakage protection, it is called leakage protector. In addition, leakage accessories must be used together with miniature circuit breakers.
Why is it necessary to install leakage protector after the protection is connected to zero (ground)?
No matter whether the protection is connected to neutral or grounded, the protection range is limited. For example, "protective connect to neutral", is to connect the metal shell of electrical equipment with the zero line of the power grid, and install fuses at the power supply side. When the electric equipment is in contact with the shell, a single-phase short circuit of the relative zero line will be formed. Due to the large short-circuit current, the fuse will be quickly fused and the power supply will be disconnected for protection. Its working principle is to change the "the power supply has leakage to the shell" into "single-phase short-circuit fault", so as to obtain large short-circuit current cut-off insurance. However, the electrical shell collision fault is not frequent in the construction site, and the leakage fault often occurs, such as the leakage caused by damp equipment, excessive load, long circuit, aging insulation, etc. These leakage current values are small and can not quickly cut off the insurance. Therefore, the fault will not automatically eliminate and exist for a long time. But this leakage current has posed a serious threat to personal safety. Therefore, it is necessary to install a leakage protector with higher sensitivity for supplementary protection.
How to use leakage protector?
After installing the wiring, press the leakage test button of the leakage protector to create a short-term artificial leakage situation to check whether the leakage protector can operate. The test button should be tested once a month to check the function of leakage protector. In case of earth leakage, the leakage protector will trip automatically. Before the fault is cleared, even if the handle is pushed to the "on" position again, the circuit can not be re connected, which avoids connecting the fault circuit by mistake.
How to use leakage accessories?
Leakage accessories need to be used together with miniature circuit breakers. After installation and wiring, press the leakage test button of leakage accessories to create a short-term artificial leakage situation to check whether the leakage accessories can act. The test button should be tested once a month to check the function of leakage accessories. In case of overload or short circuit, the handle of miniature circuit breaker will act and the handle of leakage accessory will not act. When a leakage trigger occurs, both handles act. When resetting, the handle of leakage accessory must be reset first. Before the cause of leakage is eliminated, the handle of miniature circuit breaker and the handle of leakage accessory cannot be reset.