Reliability of uninterruptible power supply systems

After discussing basic ideas concerning the reliability of UPS (uninterruptible power supply) systems, the authors present reliability parameters and formulae, reliability formulae for down-times of short mains, reliability formulae for down-times for long mains, and reliability formulae for the entire power supply system. To give an idea of the reliability values that can be reached in uninterruptible power supply systems and of the factors by which these values are affected, a number of examples are calculated by means of the derived formulae.<>