American Power Conversion White Paper Sample

In order to meet today’s efficiency and environmental demands, UPS manufacturers can utilize three factors to improve the efficiency of large UPS: technology, topology, and modularity. Together these factors can reduce the electrical UPS losses in the form of heat energy (kW). This paper explains the efficiency curve and will discuss common errors made in evaluating UPS efficiency. It will show how technology, topology, and modularity allow manufacturers to improve UPS efficiency. For a discussion on full data center efficiency see APC White Paper #113, “Electrical Efficiency Modeling for Data Centers”.

UPS Efficiency Curve
If there is only one UPS efficiency number listed on a UPS data sheet, it is almost certainly quoted at 100% load (rated load) and at various other favorable system states such as fully charged batteries, nominal UPS input voltage, and optional input transformers and filters disconnected or not installed. The fact is that most UPS manufacturers quote UPS efficiency at 100% load because it represents the very best efficiency the UPS will attain. Unfortunately, very few customers will ever reap the benefits of this efficiency because they will never reach 100% load. Specifying a UPS based on its nameplate efficiency is like buying a car that gets maximum fuel efficiency on the highway and using it for city driving. A better way to specify a UPS is to use the efficiency at approximately 30% load which tends to be the average load most medium to large scale data centers operate at. To do this one must first understand what a UPS efficiency curve is and how it is created.