A White Paper from the Experts in Business-Critical Continuity™ Evaluating the Opportunity for DC Power in the Data Center by Mark Murrill and B.J.
Summary With data center managers struggling to increase efficiency while maintaining or improving availability, every system in the data center is being evaluated in terms of its impact on these two critical requirements. The power system has proven to be one of the more difficult systems to optimize because efficiency and availability are often in conflict; the most efficient approach to critical power is rarely the most reliable.
Introduction The first decade of the twenty-first century was one of incredible growth and change for data centers. The demand for computing and storage capacity exploded, and many IT organizations struggled to deploy servers fast enough to meet the needs of their businesses. At the same time, the trend to consolidate data centers and centralize computing resources resulted in fewer opportunities for planned downtime while also increasing the cost of unplanned outages.
In recent years, manufacturers have increased component efficiencies and developed new operating modes, such as the “eco-mode” available on some UPS systems, to improve efficiency. Figure 2 shows AC UPS operation when in eco-mode. Efficiency is improved by bypassing the conversion in the inverter; however, this introduces the potential for reduced system reliability.
480V AC Rectifier Rectifier Inverter Inverter 480V AC Transformer Transformer 208V AC AC DC DC DC DC DC 12V DC Load Load Battery Battery Figure 1. Typical 480V AC to 208V AC data center power system configuration. Figure 1. Typical 480V AC to 208V AC data center power system configuration. Double Conversion UPS Server Server Double UPSData Center A Practical Approach toConversion DC in the Bypass Bypass PDU PSU -48V power supplies at the point of use.
Factors Affecting Power Distribution Selection When selecting an optimal power architecture for a particular facility, the number of factors data center designers and managers have to consider is substantial. Understanding the impact of each factor is essential to making an informed choice for your data center.
In the white paper “Phase Balancing: The Last Few Inches of a HighEfficiency Power System”4, Server Technology analyzes the impact of unbalanced loads on a 30A, 240/415V 3-phase circuit loaded in a Wye configuration. If the load is balanced, the current through each input phase is 8A, and losses can be calculated at 19 watts per 100 feet of cable. In the most unbalanced case, current through one phase is 24A and losses escalate to 115 watts per 100 feet of cable.
NetSure™ ITM Row-Based DC UPS The NetSure™ ITM is a data center-optimized row-based 48V DC UPS from Emerson Network Power. It is designed to support the move to higher efficiency, density and flexibility enabled by row-based power and cooling. Instead of deploying one large DC power plant, which would require DC power to be distributed across the facility, 480V AC power is delivered directly to the NetSure™ ITM, which then provides protected power to racks of 48V equipment in close proximity [Figure 6].
by keeping a minimum number of PCUs near full load and putting the rest on standby with the ability to respond quickly to changing load conditions.
Emerson (NYSE:EMR), based in St. Louis, Missouri (USA), is a global leader in bringing technology and engineering together to provide innovative solutions for customers in industrial, commercial, and consumer markets through its network power, process management, industrial automation, climate technologies, and appliance and tools businesses. For more information, visit: Emerson.com.
