ABB miniature circuit breaker, referred to as MCB (Micro Circuit Breaker), is the most widely used terminal protection device in building electrical terminal power distribution equipment. For 125A below the single-phase, three-phase short-circuit, overload, over-voltage protection, including unipolar 1P, diode 2P, three pole 3P, quadrupole 4P and other four kinds.

　　ABB micro circuit breaker consists of operating mechanism, contact, protection device (various release device), arc extinguishing system and so on. The main contact is operated by hand or by electric closing. After the main contact is closed, the free tripping mechanism locks the main contact at the closing position. The coil of the over-current release and the thermal element of the heat release are connected in series with the main circuit, and the coil of the undervoltage release is connected in parallel with the power supply. When the circuit is short circuited or seriously overloaded, the armature of the over-current release device is pulled in, so that the free tripping mechanism is operated, and the main contact is disconnected from the main circuit. When the circuit is overloaded, the heat element of the heat release device is heated to bend the bimetallic plate, and the mechanism of the free tripping mechanism is driven. When the circuit is under voltage, the armature of the undervoltage release is released. The free tripping mechanism is also operated

　　Product selection

　　In civil building design of low-voltage circuit breaker is mainly used for line overload, short circuit, overcurrent, undervoltage, pressure loss, grounding, leakage, dual power automatic switch and motor is not frequent starting protection, operation and other purposes, the principles of selection in addition to comply with the basic principles of low-voltage electrical equipment use (environmental characteristics etc. see the Handbook of industrial and civil power distribution design) should be taken into account the following conditions:

　　1) the rated voltage of the breaker shall not be less than the rated voltage of the line;

　　2) the rated current of the rated current of the breaker and the rated current of the overcurrent release shall not be less than the calculated current of the line;

　　3) the rated short-circuit breaking capacity of the circuit breaker is not less than the maximum short-circuit current in the circuit;

　　4) the selection of distribution circuit breaker should consider short delay, short circuit breaking capacity and time delay protection stage coordination;

　　5) the undervoltage rating of the circuit breaker undervoltage release is equal to the rated voltage of the line;

　　6) when used for motor protection, the circuit breaker shall consider the starting current of the motor and do not move in the starting time; the design calculations shall be shown in the industrial and civil distribution design manual";

　　7) the circuit breaker selection shall also consider the selective cooperation of the breaker and breaker, breaker and fuse.

　　SH201-B6 SH201-B6NA SH202-B6 SH203-B6 SH203-B6NA SH204-B6 10 SH201-B10 SH201-B10NA SH202-B10 SH203-B10 SH203-B10NA SH204-B10 13 SH201-B13 SH201-B13NA SH202-B13 SH203-B13 SH203-B13NA SH204-B13 16 SH201-B16 SH201-B16NA SH202-B16 SH203-B16 SH203-B16NA SH204-B16 20 SH201-B20 SH201-B20NA SH202-B20 SH203-B20 SH203-B20NA SH204-B20 25 SH201-B25 SH201-B25NA SH202-B25 SH203-B25 SH203-B25NA SH204-B25 32 SH201-B32 SH201-B32NA SH202-B32 SH203-B32 SH203-B32NA SH204-B32 40 SH201-B40 SH201-B40NA SH202-B40 SH203-B40 SH203-B40NA SH204-B40 50 SH201-B50 SH201-B50NA SH202-B50 SH203-B50 SH203-B50NA SH204-B50 63 SH201-B63 SH201-B63NA SH202-B63 SH203-B63 SH203-B63NA SH204-B63