Cross undervoltage protection switch from double entry

The utility model relates to a cross undervoltage protection switch from double entry. It includes power supply circuit, voltage sampling circuit, microprocessor, silicon controlled rectifier, electromagnetic switch unit and drive circuit, microprocessor carries out whether excessive pressure or under -voltage judgement to grid voltage and according to the judged result to drive circuit output actuation signal or release signal, when grid voltage is in excessive pressure or undervoltage state, microprocessor output actuation signal, drive circuit control silicon controlled rectifier switches on, the tripping operation of electromagnetic switch unit, when grid voltage was in normal condition, microprocessor exported the release signal, and drive circuit control silicon controlled rectifier ends, and the electromagnetic switch unit closes a floodgate, microprocessor sets for has a delay time T, and normal condition is resumeed at grid voltage in electromagnetic switch unit tripping operation back, and normal condition maintains T after the time, and microprocessor just exports the release signal. The utility model discloses simple structure, work more reliably, more stable.