Methods for temperature estimation and monitoring of permanent magnet: a technology review and future trends

The permanent magnet is subject to high-temperature demagnetization under high-torque or high-speed operating conditions. Accurate estimation of the temperature of the permanent magnets allows for better improvement of the cooling system, such as flow distribution and structural optimization. It is also the object of research in tracking and monitoring technology, because timely sensing of the temperature of the permanent magnet is the key to generate thermal protection mechanisms for the cooling system and active thermal protection system. In recent years, techniques for estimating and monitoring the temperature of permanent magnet have evolved, and a large body of valuable literature has been generated in the process. Therefore, this paper discusses this literature by systematically categorizing it into estimation and monitoring techniques in order to promote more researchers to understand the advantages of various methods and rationally choose the research topics they are most interested in. In addition, trends and challenges in various research directions were discussed.