Single-phase power supply automatic switching circuit controlled by relay

Some electrical equipment, such as lighting in important places (hospital operating rooms, etc.), important computer rooms,
mechanical equipment that must run continuously, etc., are not allowed to interrupt the power supply, otherwise it will cause heavy
losses. For these devices , a backup power supply needs to be set up . When one power
supply fails due to a fault, the backup power supply can be automatically turned on, thus improving
the reliability of power supply.