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Coil pitch and the search for the perfect sine wave

Publication date: 
January 2004
Chuck Yung, EASA Senior Technical Support Specialist
Type of media: 

This started as an article to explain those cases where a 2-pole winding concentric-to-lap conversion will not run. The cause has to do with the coil pitch selected and slot spatial harmonics. These harmonics have a harmful effect on motor performance.The key is avoiding certain coil pitches, and the "problem" 2-pole pitch depends on the number of slots and the coil pitch. To make the article more useful, it includes tables to identify "preferred" coil pitches for2-pole, 3-phase windings, as well as those that should be avoided.