Comparative Reliability of Uninterruptible Power Supply Configurations

Abstract

This paper compares the reliability of four uninterruptible power supply (UPS) configurations; single module, parallel redundant, static bypass, and static bypass redundant. Equations for calculating the MTBF's of these configurations are presented along with component reliability estimates. Effects of failure rates of associated circuitry are included. System MTBF's of 200,000 hours for redundant and 150,000 hours for static bypass systems are now achievable. Guidelines for system type selection are included as performance curves. Effects of aging and appropriate corrective action are discussed.