A Comprehensive Review of Thermal Conductivity of Stator Windings in Electric Machines

Electric machines are crucial in modern industries, playing a substantial role in power generation, manufacturing, transportation, and renewable energy. Consequently, extensive research is focused on enhancing their performance, making it essential to understand their thermal behavior for effective modifications and improvements. While existing literature covers thermal effects in electric machines, the specific analysis of thermal conductivity in stator windings, a major contributor to energy losses, has remained significantly underexplored due to the complicated geometrical, material, and manufacturing factors. This paper presents a comprehensive review of methods and challenges related to characterizing the equivalent thermal conductivity of stator windings, categorizing them into analytical, numerical, and experimental approaches, with three sample levels (domain, motorette, and prototype). Furthermore, the paper introduces concepts of anisotropy, components, and available winding technologies to establish a solid foundation before discussing these methods. This review highlights the strengths and limitations of each method, emphasizing their needs and constraints to advance high-performance electric machines, and ultimately contributing to the evolution of more reliable and efficient electric machines.