I. Introduction
Permanent magnets (PM) based on rare earths—e.g., Neodymium-Iron-Boron—are commonly used PMs in permanent magnet synchronous machines (PMSMs) nowadays [1], [6]–[8]. The PM strength typically reduces as the PM temperature increases [1]– [5], reducing therefore the torque capability of the machine. Additionally, there is a risk of PMs permanent demagnetization if their temperature becomes too high [1]. Consequently, the knowledge of the magnet temperature in PMSMs is of great importance both for control purposes as well as to prevent PM damage.