Uninterruptible Power Solutions are often solved at the facility level with unnecessarily large, inefficient, expensive and complex AC UPS systems. While this provides an easy demarcation line between the facility and end equipment, with each focusing on a different part of the problem, it also results in overall operating efficiency and total cost of ownership being difficult to ascertain and optimize.
OPTIMIZINGUNINTERRUPTIBLEPOWER
FORMODERNDATAPROCESSING
New Methods to Address
Compelling Needs
By: Gary Mulcahy
June 28, 2005
White Paper: TW0051GARY MULCAHY
Gary Mulcahy is Executive Vice President of the CommercialProducts Division of Transistor Devices, Inc. (TDI). He receivedhis BE-EE from New York University followed by graduate studyat the Polytechnic Institute of New York. Mr. Mulcahy is arecognized authority in power conversion technology and thedesign, development and production of power systems formaximum performance and reliability with minimal life cyclecost of ownership.EXECUTIVE SUMMARY
Uninterruptible Power Solutions are often solvedat the facility level with unnecessarily large,inefficient, expensive and complex AC UPSsystems. While this provides an easy demarcationline between the facility and end equipment, witheach focusing on a different part of the problem,it also results in overall operating efficiency andtotal cost of ownership being difficult to ascertainand optimize. Initial and operating costs cangenerally be reduced and system reliabilityincreased by incorporating a relatively simple DCUPS as an integral part of the data processing orcommunication equipment.
1THE CHALLENGES OF NEW-GENERATION DATA PROCESSING EQUIPMENT
New generation data processing equipment provides ever-increasing speed and bandwidthutilization benefits, while Internet based communication and commerce activities continually fuelthe need for more performance. One result of this self-reinforcing spiral is the amount andconcentration of electrical energy being ported toward core data processing infrastructure. This hasbrought forth new challenges regarding energy and resources wasted on inefficient power systems.
Data processing equipment is generally segregated into channels built around microprocessorcores. In the past these microprocessors would typically utilize less than 100W of energy perchannel. However, modern equipment quite often sees this power requirement exceed 200W perchannel, with future equipment forecasted to go well in excess of this value. As these channelsare paralleled together into clusters, the total energy being utilized presents unique challenges.
With current industry practices, AC power distribution systems are typically employed to powerdata processing equipment clusters. In addition, critical infrastructure installations generallyemploy power systems with an uninterruptible source of electrical power. Uninterruptible poweris generally viewed at the facility level, as opposed to the equipment level. While this provides aneasy demarcation line between the facility and data processing equipment, with each focusing ona different part of the problem, it also results in overall operating efficiency and total cost ofownership being difficult to ascertain and optimize.
Facility-level AC UPS systems are quite often constructed around a model similar to the oneportrayed in the following diagram.
Figure 1: Facility Level AC UPS
2The central AC UPS generally involves conversion from incoming raw AC power to DC, and thenreconverting from DC back to AC. Moreover, since data processing equipment generally operatesfrom 208/220VAC line voltage, facility-level entry power usually must be transformed from 480VACdown to 208VAC either before or after the UPS. A battery is then connected as an alternate inputto the DC-AC converter so that if incoming raw AC power is interrupted, the system automaticallyswitches over to battery power. Alternately, a rotating flywheel may be used to store energy andprovide uninterruptible AC power. Uninterruptible AC power is then passed through an AC powerdistribution grid and fanned out to individual data processing apparatus.
Once inside DP equipment, AC power is once again converted into DC power. Off-line power suppliesprovide power factor correction as well as load isolation from the incoming power line. This generallyinvolves at least two stages of power conversion. In addition, most modern microprocessors requirevery low voltages at fairly high currents, such as 1.1V at 100A. Moreover, the precision of the voltagerequired is such that voltage regulation circuitry must be located directly next to the microprocessor. Inorder to eff... [download for more]
