Selection of breaker:

The breaker with low rated voltage shall be in accordance with circuit voltage. 

The rated current of breaker with low voltage shall be no less than the calculated current passing it (calculated according to 1.25 times). 

The type of breaker with low voltage shall accord with requirements of installation condition, protective performance and operating mode. 

The interruption capacity of breaker with low voltage is verified according to short circuit current. 

The selection of breaker with low voltage releaser:

The rated current of thermal releaser shall be in accordance with its controlled motor or other loaded rated current. 

The setting current in instantaneous release of magnetic releaser shall be more than the peak current when load circuit is in normal operation. When the load is motor, the setting current Iz in instantaneous movement of magnetic releaser is: Iz≥KIs (K: safety factor, as for DW series of frame type of breaker, K=1.35; as for DZ series of plastic shell type of breaker, K=1.7, Is: starting current of motor). 

Precautions for installation and use of breaker with low voltage:

The breaker with low voltage shall be in vertical installation as stipulation, and its upper and lower connecting wires shall use the wires (or busbar) with specified section, which shall not be too small. 

The setting current of releaser of breaker with low voltage and its other parameters and selection parameters with characteristics are not allowed to change at will once they have been adjusted. After using for a long time, inspect whether its spring is locked by rusting, in order to avoid affecting correct motion. 

After examination and repairing, switch on and off for several times under the situation without electricity, and put into use after the inspection motion is accurate and reliable.