With the proliferation of electronic loads such as computers, the incidence of power quality-related problems is growing. As a result, the uninterruptible power supply (UPS) market has grown significantly in the last few years. What follows is an overview of UPS functions and descriptions of common types of UPSs and backup power sources. 16.1 UPS Functions The primary purpose of a UPS is to provide conditioned, continuous power to its load. Another UPS function that is of growing importance in to