Patent ID: 8350410

Claim:
An uninterruptible power supply comprising: a rectifier for converting AC power supplied from a power source into DC power; a storage battery for storing the DC power converted; an inverter for converting the DC power into AC power; a selecting means for selecting one of an off-line operation mode and an on-line operation mode according to a detection result of detecting a condition of the AC power supplied from the power source; in the off-line operation method, AC power supplied from the power source is supplied to a load device under normal operating condition, and when any failure happens in relation to the AC power supplied from the power source, the uninterruptible power supply supplies a power output generated by the inverter to the load device; in the on-line operation method, a power output from the inverter is supplied to the load device all the time including a period of normal operating condition; and a setup means for variably setting criterion values, with which the selecting means selects an operation mode depending on the condition of the AC power supplied from the power source wherein, the uninterruptible power supply further includes a switching setup circuit for setting up operation of the selecting means by using switches; and the switching setup circuit specifies the criterion values as the setup means, and the switching setup circuit can also specify fixedly one of the off-line operation method and the on-line operation method as an operation mode of the selecting means.