HP ProLiant DL380p ISS Technology Focus, Number 14 - Page 3

Table 1-1. The application recommendations in the table are based on the differences in the performance, cost, and endurance of the HP solid-state solutions. Follow these recommendations to ensure that you choose the correct product. Table 1-1: Enterprise solid-state storage device classes Efficiency of DC vs. AC power supplies HP offers 1200 W -48 V DC Common Slot Power Supplies with 90% efficiency for our ProLiant DL360 G7, DL380 G6 and G7, and DL385 G6 and G7 servers. We also offer selfcooled 2250 W -48 V DC power supplies with 90% efficiency specifically designed for the HP BladeSystem c7000 Enclosure. Each c7000 enclosure can contain up to six 2250 W 48 V DC power supplies for a maximum of 13500 W output capacity. This article will answer some frequently asked questions from our customers about the origin of -48 V DC power supplies and about their efficiency compared with that of today‟s AC power supplies. Origins of the -48 V standard The -48 V DC standard has existed for many years in the telecommunications industry because the telecoms use large banks of -48 V DC batteries as their primary power source (Figure 2-1). They continually charge these batteries using either AC power from the grid or from generators if the grid fails. If the generators fail, the batteries allow the telephone system to run until power returns. Figure 2-1: -480 V AC to -48 V DC power distribution The advantages of -48 V power Interest has increased in distributing DC power in the data center because of power losses that occur whenever conventional UPS and server power supplies convert incoming AC