The primary objective in the implementation of a UPS system is to improve the reliability to the limits of technical capability, the ultimate aim being to totally eliminate the possibility of any disturbance or downtime.
The reliability of state-of-of-the-art UPS with static bypass depended on the quality of the mains (MTBF MAINS), the time to repair of the UPS (MTTR UPS) and on the reliability of the static switch. In a white paper by ABB the impact of both the (MTBF MAINS) and (MTTR UPS) on the overall UPS reliability are shown.
The everyday activities which are dependent upon computer controlled real time information systems have grown exponentially in recent years and the requirements for highest reliability UPS configurations have become every day practice. Very critical loads cannot rely on a power supply configuration of a single UPS with static bypass system; the need for (n+1) redundant parallel UPS configurations is becoming a standard.
In this paper it is shown how important the parameter MTTR is for reaching high availabilities. With ABB Modular UPS we can reach shortest MTTR and consequently highest availabilities even if we parallel bigger numbers of modules.