1. The rated voltage of ABB miniature circuit breaker must be greater than or equal to the voltage of the line.

2，ABB微型斷路器熱脫扣器額定電流要稍大線路中的負載電流，（如果保護對象是導線，則斷路器額定電流稍小于導體的安全載流量。）

2. The rated current of ABB miniature circuit breaker thermal release shall be slightly larger than the load current in the line. (if the protection object is a conductor, the rated current of the circuit breaker shall be slightly smaller than the safe current carrying capacity of the conductor.)

3，ABB微型斷路器的極限分斷電流要大于電路可能出現的最大短路電流。

3. The limit breaking current of ABB miniature circuit breaker shall be greater than the maximum short-circuit current that may occur in the circuit.

4，如果保護對象線路里沖擊電流比較大要考慮斷路器瞬時脫扣值的大小和動作時間，例如電動機回路，一般啟動電流是額定電流的4一7倍，如果是重載時啟動電流會更大，選擇ABB微型斷路器作侏護時，應選擇額定電流稍大于電動機額定電流（是電機額定電流的1.2倍一1.5倍）而瞬時動作值大于電動機最大啟動電流的ABB微型斷路器。

4. If the impulse current in the line of the protection object is relatively large, the instantaneous tripping value and action time of the circuit breaker shall be considered. For example, the starting current of the motor circuit is generally 4-7 times of the rated current. If it is heavy load, the starting current will be greater. When ABB miniature circuit breaker is selected as low protection, ABB miniature circuit breaker with rated current slightly greater than the rated current of the motor (1.2-1.5 times of the rated current of the motor) and instantaneous action value greater than the maximum starting current of the motor shall be selected.

5，極數的選擇，根據需要控制的相線和零線數量合理選擇ABB微型斷路器極數，單相電用1P或2P的，三相電用3P或4P的。

5. Selection of the number of poles: the number of poles of ABB miniature circuit breaker shall be reasonably selected according to the number of phase lines and zero lines to be controlled. 1p or 2p for single-phase power supply and 3P or 4P for three-phase power supply.