Review and Trends in Traction Motor Design: Primary and Secondary Insulation Systems

This paper presents a review of the available insulation systems for traction motors. Two primary insulation systems used in traction applications with thermal classes of H and N are discussed. The insulation systems used in random windings are typically class H (180), and in form windings the higher temperature class N (200) is commonly used. Considering importance of resins on performance and thermal class of insulation systems, a review of different resin types is given. Additionally, secondary insulation with focus on potting is presented and trends in the insulation system development for traction motors in the coming decades are reported. The focus in insulation system development seems to be on improving the motor thermal performance to enable offering more compact designs. Additionally, further alignment with developments on semiconductor technologies in traction converters is expected.