The three-phase uninterruptible power supply is mainly used as a backup power supply for ship power. When the ship power is normally supplied, the three-phase uninterruptible power supply performs floating charge on the battery pack and supplies power to the load at the same time; when the ship power is lost, the battery pack converts the DC power into ship AC power through the three-phase uninterruptible power supply to supply power to important loads. The three-phase uninterruptible power supply has functions such as input overvoltage alarm, input low voltage alarm, output overvoltage alarm, output low voltage alarm, and overcurrent alarm.