2003 report on developments in NEMA magnet wire dimensional and dielectric standards

During the past few years there has been a considerable amount of activity related to developing mathematical definitions of, and improving NEMA dimensional standards for round magnet wire products. Coincident with that development there was also a need to establish meaningful dielectric values for the new or revised dimensional standards. All of the dimension and dielectric test values changes discussed have been included the 2003 edition of NEMA MW 1000. Thus this paper provides a comprehensive overview of the changes and the rationale for them for users of MW 1000. The history of NEMA magnet wire dimensional standards and past efforts to harmonize NEMA dimensional standards with IEC winding wire dimensional standards are briefly reviewed with special emphasis on those dimensional changes or new dimensional specifications that have been introduced into NEMA MW 1000 over the last few years. Specific changes that will be discussed include modifications to: NEMA maximum bare dimensions from 4 AWG to 26 AWG, NEMA Heavy build dimensions from 4-13 AWG, NEMA Single, Heavy, and Triple build dimensions in the 30 to 46 AWG size range and the establishment of a Quad build specifications from 14 to 46 AWG for products other than MW 16 Polyimide. The paper then reviews the results of an industry wide study of dielectric test values of various magnet wire products in the 14-42 AWG size range and demonstrates how those results were used to develop meaningful mathematically based specified minimum test values for Single, Heavy Triple and Quadruple build round wire products in the 14 to 38 AWG size range.