Engineering Designer Guide

WP-3: Calculating Total Power Requirements for Data Centers Part of data center planning and design is to align the power and cooling requirements of the IT equipment with the capacity of infrastructure equipment to provide it. This paper presents methods for calculating power and cooling requirements and provides guidelines for determining the total electrical power capacity needed to support the data center, including IT equipment, cooling equipment, lighting, and power backup.
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WP-29: Rack Powering Options for High Density Alternatives for providing electrical power to high density racks in Data Centers and Network Rooms are explained and compared. Issues addressed include quantity of feeds, single-phase vs. three-phase, number and location of circuit breakers, overload, selection of plug types, selection of voltage, redundancy, and loss of redundancy. The need for the rack power system to adapt to changing requirements is identified and quantified. Guidelines are defined for rack power systems that can reliably deliver power to high density loads while adapting to changing needs.
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WP-38: Harmonic Currents in the Data Center: A Case Study This document provides an overview of how problems related to harmonic neutral currents are mitigated by load diversity, with specific focus on Information Technology data center environments. Detailed measurements of an actual operating data center are presented. This case study illustrates the way that load diversity mitigates harmonic current levels, lowers shared neutral current in multi-wire feeders and branch circuits, and improves total circuit power factor.
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WP-43: Dynamic Power Variations in Data Centers and Network Rooms The power requirement required by data centers and network rooms varies on a minute by minute basis depending on the computational load. This magnitude of this variation has grown and continues to grow dramatically with the deployment of power management technologies in servers and communication equipment. This variation gives rise to new problems relating to availability and management.
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WP-52: Four Steps to Determine When a Standby Generator is Needed for Small Data Centers and Network Rooms Small data centers and network rooms vary dramatically in regard to the amount of UPS runtime commonly deployed. This paper describes a rational framework for establishing backup time requirements. Tradeoffs between supplemental UPS batteries and standby generators are discussed, including a total cost of ownership (TCO) analysis to help identify which solution makes the most economic sense. The analysis illustrates that the runtime at which generators become more cost effective than batteries varies dramatically with kW and ranges from approximately 20 minutes to over 10 hours.
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WP-60: Avoiding AC Capacitor Failures in Large UPS Systems Most AC power capacitor failures experienced in large UPS systems are avoidable. Capacitor failures can give rise to UPS failure and can in some cases cause critical load drops on stand-alone and paralleled systems. AC capacitor failures have historically been ascribed to unavoidable random failure or supplier defect. However, recent advances in the science of capacitor reliability analysis show that capacitor failures can be controlled by system design. This paper explains AC capacitor failure mechanisms and demonstrates how UPS designers and specifiers can avoid most common AC capacitor failures and the associated consequences.
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WP-64: Alternative Power Generation Technologies for Data Centers and Network Rooms Fuel Cells and Micro Turbines are new technology alternatives for power generation for data centers and network rooms. This paper discusses the various modes of operation of these systems and examines benefits and drawbacks of the technologies when contrasted with conventional alternatives such as standby generators.
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WP-73: Reducing the Hidden Costs Associated with Upgrades of Data Center Power Capacity Scaling the power capacity of legacy UPS systems leads to hidden costs that may outweigh the very benefit that scalability intends to provide. A scalable UPS system provides a significant benefit to the Total Cost of Ownership (TCO) of data center and network room physical infrastructure. This paper describes the drawbacks of scaling legacy UPS systems and how scalable rack-based systems address these drawbacks. The cost factors of both methods are described, quantified and compared.
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WP-90: Essential Standby Generator System Requirements for Next Generation Data Centers Effective standby generator system installations must address the known problems and challenges relating to current and past designs. This paper presents a categorized and prioritized overview of generator system challenges and the requirements needed to overcome them.
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WP-93: Fundamental Principles of Generators for Information Technology Every Information Technology professional who is responsible for the operation of computing equipment needs to ensure their data center or network room is prepared for extended utility power outages. Understanding the basic functions and concepts of standby generator systems helps provide a solid foundation allowing IT professionals to successfully specify, install, and operate critical facilities. This paper is an introduction to standby generators and subsystems that power a facility’s critical electrical loads when the utility cannot.
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WP-109: Reliability Analysis of the APC Symmetra MW Power System This paper is a quantitaive reliability analysis of the APC Symmetra MW UPS performed by MTechnology, Inc. (MTech). In contrast to common MTBF calculations based on summing component failure rates, this study used techniques of Probabilistic Risk Assessment (PRA) to calculate the likelihood of over 680,000 potential failure modes. The mathematical method accounts for uncertainty in failure rates and component performance, and provides detailed guidance as to the contribution of each system component to the overall risk of failure. The study included an exhaustive analysis of the system’s architecture, component selection, control system, manufacturing practices, and response to internal and external faults. The study also included a detailed review of APC’s delta conversion online topology.
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WP-120: Guidelines for Specification of Data Center Power Density Conventional methods for specifying data center density are ambiguous and misleading. Describing data center density using Watts / ft2 or Watts / m2 is not sufficient to determine power or cooling compatibility with high density computing loads like blade servers. Historically there is no clear standard way of specifying data centers to achieve predictable behavior with high density loads. An appropriate specification for data center density should assure compatibility with anticipated high density loads, provide unambiguous instruction for design and installation of power and cooling equipment, prevent oversizing, and maximize electrical efficiency. This paper describes the science and practical application of an improved method for the specification of power and cooling infrastructure for data centers.
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