Consulting-Specifying Engineer - March 2008 - (Page 21)

M/E Roundtable interactions between drives and to prevent disruption of the sensitive electronics in the rest of the facility. Today, 12- and 18-pulse drives, which generally do not require filtering, are relatively common and in many cases, are more economical than the six-pulse drives with the additional filters. CARR: It may be helpful to differentiate between the two principal types of harmonics and the filters used to mitigate them. Drive designers and application engineers more and more are looking to power quality standards, such as IEEE 519-1992, for guidance with respect to the need for filters on the inputs to VFDs and adjustable speed drives. The allowable harmonic limits depend on the impedance of the power source, whether it be the utility or a local generator, on most VFD applications. Significant developments and advances have been made in the area of capacitors, magnetics, fast-switching power semiconductors (such as IGBTs), micro-controllers, digital signal processors, memory devices, and chips. All of these are used in active filters, and even passive filters such as harmonic (series L-C) filters have benefited greatly from new processes in polypropylene capacitor film, powdered-iron, ferrites, grainoriented steels, etc. NASH: The majority of drives sold today employ six-pulse pulse-width modulation technology. For practical cost reasons, this is likely to remain the case into the foreseeable future. Whenever such drives represent a significant portion of the total connected load (20% or more), some form of harmonic filtering needs to be considered. Besides insuring compliance with harmonic standards, filters improve system power factor and increase available transformer capacity. Passive filters have evolved from simple trap filters to include broadband filters and hybrid filters. These provide significantly better performance than older designs. Active filters are more sophisticated. Users now have the flexibility to determine filter set-up and functional emphasis through modification of digital parameters. C S E : How does the location of filters affect how the generator reacts to VFDs in the system? PEERAN: Filters are generally located either at the VFDs or at a switchboard or switchgear that feeds a number of VFDs. VFD-Induced Shaft Current Kills Motor Bearings! BEARING PROTECTION RING Guaranteed to Protect Bearings for Life! For motors up to 100 HP / 75 kw, AEGIS SGR’s patented technology is guaranteed to protect bearings against electrical fluting damage for the life of your motor. The AEGIS Bearing Protection Ring™ extends motor life and increases system reliability. To download a free technical paper on bearing protection technologies, visit our website: 1-866-738-1857 | sales@est-aegis.com | www.est-aegis.com/cse1 Input #214 at csemag.com/quickResponse Consulting-Specifying Engineer • MARCH 2008 21 http://www.est-aegis.com/cse1 http://www.est-aegis.com/cse1 http://www.est-aegis.com/cse1 http://csemag.com/quickResponse

Table of Contents Feed for the Digital Edition of Consulting-Specifying Engineer - March 2008

Consulting-Specifying Engineer - March 2008 Contents Viewpoint Letters News M/E Roundtable Grade A HVAC When UPS and Gensets Have Issues Ignite Opportunities To Mentor Fire Protection Engineers Cooling People, Not Buildings Codes & Standards Case Study New Products Equipment Lifecycles Advertiser Index Green Space Pure Power Supplement Edison Institute Honors Recovery Efforts Canada Launches Clean Energy Software Climate Change Drives Increased Investment Critical Power for R&D Heating Calculations for Electrical Duct Bank Submetering for Energy Profiling New Products

Consulting-Specifying Engineer - March 2008

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