Data Center Journal

VOLUME 49 | APRIL 2017

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14 | THE DATA CENTER JOURNAL AC Versus DC Voltage in the Data Center By yveS Bouhadana t here has been a lot of discussion about energy savings and sustainability at a global level, in all industries. e IT community, through con- ventions, seminars and user groups, is always considering ideas on how to increase efficiency and enhance sustainability while maintaining high levels of continuity. Currently, non-IT-related functions in the data center account for more than 50% of the total power con- sumption. ese processes include environmental control; uninterruptible power supplies (UPSs), power distribution, lighting and underused IT capacity. An important topic as- sociated with increased efficiency is the use of DC power to distribute power to the loads. is article reviews the topic in detail and provides a conclusion on the basis of available technology and economics. e power provided by the utility company to an office building, then the data center in the building, is con- verted and transformed up to six times. Each time a con- version takes place, energy loss occurs in the form of heat dissipated by the components that perform the transforma- tion. e data center's HVAC system then removes that heat. Figure 1 shows an example of multiple conversions as power from the utility is distributed to the IT load. Utility power enters a building at 480 volts; it's then distributed to the UPS input. e UPS's rectifier converts that AC voltage to a DC voltage in order to charge bat- teries. e inverter then converts it back to AC voltage in order to distribute power in the data center. At that point, power to the data center is clean and continuous thanks to the UPS system. Once in distribution, the voltage is con- verted from 480 volts to 208 and 120 volts by way of trans- formers located throughout the data center. Finally, using a network of copper wires, the power reaches the IT loads at 120 volts. ose loads then convert the 120 VAC back to low DC voltage. At that point, the power has undergone four conversions. At each conversion step, the component Figure 1. converting utility voltage for distribution and use by the load.

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