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Co-authored technical paper discusses meeting code requirements, managing faults,
optimizing design and understanding issues with 30-cycle transfer switches
Florham Park, N.J. — Emerson Network Power, a business of Emerson (NYSE: EMR) and a global leader in maximizing availability, capacity and efficiency of critical infrastructure has published a white paper titled “Effective Selective Coordination Design.”
The document, co-authored by Dan Caron, principle of Bard, Rao + Athanas Consulting Engineers, and Ron Schroeder, director of applications engineering and product management, for Emerson Network Power’s ASCO Power business, shares current, unbiased perspectives of selective coordination. The paper addresses code requirements and the importance of selective coordination to a power distribution system. Ultimately, the white paper explains how to determine and achieve effective selective coordination and properly describes the roles of power transfer switches and specifying cycle times. Also watch a video on selective coordination.
Design Engineers need to balance the importance of business continuity, equipment protection, personnel safety and cost management rather than assume 30-cycle transfer switches are the best solution for every selective coordination application.
Typically, a 3- or 18-cycle transfer switch will perform just as well as the 30-cycle switch at a fraction of the cost. A survey of engineers showed more than 88 percent of respondents believe that effective selective coordination requires the proper cycle time, not a cookie cutter approach for all applications.
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asco selective coordination news release – 2
Specifying Cycle Times
The approach used by Bard, Rao + Athanas Consulting Engineers for specifying transfer switch cycle times recognizes that projects are custom designed and built because one size doesn’t necessarily fit all applications..
The majority of transfer switches that BR+A engineers specify are 3-cycle switches. They have specified 30-cycle switches where one or more of the following conditions exist:
1. Larger projects, where the fault current on the emergency system is high.
2. Where the instantaneous is defeated in order to selectively coordinate (note that this may change with the acceptance of the new NFPA 99).
3. Where transfer switches are served by ANSI Switchgear, which also has 30-cycle withstand ratings.
“Selective coordination requirements for emergency and legally required standby systems are challenging electrical engineers to consider how systems respond to short circuits,” Jim Degnan, principal of Sparling, a consulting engineering firm based in Seattle, said.
For more information on selective coordination, call (800) 800 ASCO (2726), email CustomerCare@ASCO.com or visit www.EmersonNetworkPower.com/ASCO and www.Ascoapu.com. Download the white paper, “Effective Selective Coordination Design.”
About Emerson Network Power
Emerson Network Power, a business of Emerson (NYSE:EMR), delivers software, hardware and services that maximize availability, capacity and efficiency for data centers, healthcare and industrial facilities. A trusted industry leader in smart infrastructure technologies, Emerson Network Power provides innovative data center infrastructure management solutions that bridge the gap between IT and facility management and deliver efficiency and uncompromised availability regardless of capacity demands. Our solutions are supported globally by local Emerson Network Power service technicians. Learn more about Emerson Network Power products and services at www.EmersonNetworkPower.com.
About Emerson
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 around the world. The company is comprised of five business segments: Process Management, Industrial Automation, Network Power, Climate Technologies, and Commercial & Residential Solutions. Sales in fiscal 2012 were $24.4 billion. For more information, visit www.Emerson.com.
