The product is applicable to a line of AC 50Hz/60Hz, rated voltage 230V for 2-pole, 400V for 4-pole and rated current up to 63A. It can ensure the safety of the persons and the electric appliance. It can also be used for infrequent line conversion or/and infrequent motorstart. The product is applicable to industrial and mining enterprises,commercial districts, high-rise buildings and dwelling houses.