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IAEI Magazine | Author: Michael Z. Lowenstein
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Michael Z. Lowenstein

Dr. Lowenstein holds an A.B. in chemistry from Oberlin College, and an M.S. and Ph.D. in physical and analytical chemistry and physics from Arizona State University. He spent 13 years as a college chemistry professor and 8 years as a national program manager for the Solar Energy Research Institute. His experience with harmonics includes 15 years designing filters for 3-phase industrial drives. In 1989 he founded Harmonics Limited, a company devoted to solving harmonic problems caused by multiple computer loads. He has served as a lecturer at the University of Wisconsin, Milwaukee, teaching courses in power quality and non-linear loads. He has presented invited lectures and seminars at national meetings for numerous organizations with concerns about power quality and harmonics. Dr. Lowenstein is a member of The IEEE Industrial Applications Society, The Power Engineering Society, and the Standards Society. He serves on SCC 22, the power quality Standards Coordination Committee, the body with coordination responsibility for all IEEE power quality standards, and is involved in the revision of IEE519 currently underway.


The 3rd Harmonic Blocking Filter: A Well Established Approach to Harmonic Current Mitigation

It has long been recognized that harmonic currents, particularly the 3rd harmonic, flowing in a wye distribution system serving multiple computer loads, are detrimental to system operation. Problems caused by these harmonic currents include overheated transformers, switchgear and wiring; random circuit breaker tripping; and reduced useable system capacity. Conventional methods used to mitigate the harmful effects of these harmonic currents include k-rated or de-rated transformers, harmonic mitigating transformers (zig-zag and phase shifting,) oversized switchgear, double or triple neutrals, and other "accommodation” techniques. However, it is easier to prevent the flow of harmonic currents than to treat them after they are flowing in the system. The 3rd-harmonic blocking filter is a well-established device that prevents harmonic current flow.