The role of test methods and specifications in coil winding

This paper's intent is to offer a comprehensive overview of the fundamental factors that affect the reliability and quality of coil wound bobbins, with emphasis on ultrafine magnet wire. It starts by introducing some well known concepts of dielectrics, that are further expanded by examples of insulation (enamels) behavior under conditions that play a fundamental role in premature failures. It then introduces the findings of research done on defects in the raw materials that are used to manufacture magnet wire. It discusses the role that microdefects in the copper precursor rods, magnet wire manufacturing, coil winding process and the effect of the bobbin operating conditions on those microdefects. It examines the role of different manufacturing quality tests methods and coil winding specifications, their value and limitations as a tool to measure and specify the quality of a bobbin. Finally it presents an innovative way of testing bobbins that data shows is significantly more sensitive in detecting microdefects on the finished coil.