Reliability and Availability Analysis of UPS

The backup battery of UPS has several kinds of physical failure modes, for example, that is caused by the loss of energy, the stress exposed from outside and the stress from inside. To find an entire failure rate, we consider this effect as a series phenomenon of each failure mode. On the assumption that backup battery of UPS has operation failure p.d.f of Erlang, we investigate the relation between system reliability of UPS and stochastic operation time of battery (for example, mean time or Erlang phase). Also as an example, we compute unavailability. Then we could get the results that its inverter availability has main effect as the important parameter for the availability measure of UPS system.