UNINTERRUPTIBLE POWER-SUPPLY APPARATUS

PROBLEM TO BE SOLVED: To provide an uninterruptible power-supply apparatus in which it is possible to restrain a storage battery from becoming large-sized and which can prevent the capacity of the storage battery from being exceeded by a method, wherein the electric power is supplied reasonably to an external apparatus in a power failure. SOLUTION: An uninterruptible power-supply apparatus is constituted in such a way that it is composed of a primary-side power-supply part 1 and of a secondary-side output part 1 in which a voltage to be supplied from the primary-side power-supply part 1 is supplied to a first inverter-type device and to a second inverter-type device 5, whose degree of importance is higher than that of the first device 4, that the primary-side power-supply part 1 is provided with a commercial AC power supply 6 and with a storage battery 7, which is charged by the commercial AC power supply, 6 and that the secondary-side output part 2 is provided with a changeover means 15 by which, in a power failure, a voltage from the storage battery 7 is supplied preferentially to the second device 5 whose importance degree is high.