CES-40.5F, circuit breaker for electric arc furnace, is a new-generation dedicated MV switchgear developed by Thomas Edison R&D Center of Cooper.according to the load demand characteristics of the smelting furnace group. It can be widely used in electric arc furnace smelting LF refining and many other conditions requiring frequent operation.The corresponding switchgear should act with extreme frequency during use on the basis of smelting technical requirements of high-energy arc. Fault current should also be cut off once fault occurs. With an ultra-long service life, CES-40.5F could reduce power failure time for steel users, improve their economic benefits and reduce use risks.