Chapter 7 - Uninterruptible Power Supplies

Abstract

The physical size of UPS systems has decreased dramatically. As the world has switched from the mainframe to the client/server distributed networking environment, the UPS market has shifted from the large multi-module UPS systems to the small single phase UPS systems. As per U.S. industry estimates, in 1992 there was a total of US$1.225 billion worth of sales, which had a breakdown of US$ 964 million commercial, US$ 245 million industrial and US$16 million residential components. Industry estimates further indicate that over 71 percent of the UPS sales are for units less than 30 kVA ratings while 24 percent account for units of the capacity between 31 to 500 kVA ratings. Very large systems with ratings over 500kVA account for the rest. In 1992, out of total UPS market, only 37 percent was made up of large three phase systems. The 63 percent balance was made up of small single phase UPS units. It was anticipated that by 1997, the UPS market to have large three phase modules will only represent 25 percent of that total with the balance of approximately 75 percent being comprised of small single phase units. This chapter provides an overview of UPS systems with particular attention to single phase low power UPS systems used in modern information environments.