ZW5 series intelligent air circuit breaker is mounted in the distribution network of AC50Hz, 400V or 690V for the electric energy distribution, line protection and protecting the power equipment against the danger caused by the failure of overload, short-circuit, under-voltage, or single-phase grounding with great and selective intelligent protective functions so as to avoid unnecessary power-cut and raise both the safety and reliability of the electricity network in running. It is suitable for the non-frequent conversion in the circuit or for the non-frequent start-up to protect the electromotor.