YCM3 series moulded case circuit breaker (herein after called circuit breaker) which adopts international advanced design and manufactural technology, small and compact, modularization, high breaking capacity, short arcing over distance, environment protecting etc. They are applied for the power distribution network of AC 50Hz，rated working voltage 690V and below, rated current from 12.5A to 1600A, it can be used to distribute electric power and protect power equipment against overload, short circuit, undervoltage etc. The circuit breaker can change the circuit and start motor infrequently. YCM3 series circuit breaker is equiped with intelligent controllers, with the increasing selection range of setting current,power supply is more reliable, successive and safe. The YCM3 complies with standard of IEC60947-2.