This series air circuit breakers are suitable used in AC50/60Hz, 380V distributing systems with normal current up to 4000A for power distribution and overload, under-voltage and short-circuit protection of apparatus and circuit.Under normal conditions the breakers are used for infrequent switchover of circuits. The breakers with rated current below 1 250A used in 50/60Hz, 380V systems can protect motors form overload and short circuit, and actuate motors unfrequently under normal conditions.