Analysis of Magnet Temperature Distribution in Six-Phase Surface-Mounted Permanent Magnet Synchronous Motors

The increasing use of permanent magnet synchronous machines (PMSMs), prompted by the need for highly efficient motor drives, underscores the importance of fully exploiting machine operation. Under such operating conditions, the machine is exposed to high mechanical and electromagnetic stress. It is therefore essential to estimate stress levels on various components and focus the analysis on the most critical ones. One of the critical components is the rotor magnets of the machine. The need to monitor the state of health of the rotor magnets has led to the definition of noninvasive and sensorless algorithms to estimate their temperature. Like the performance of the machine, in particular, the magnetic properties of the rotor magnets are affected by the operating temperature. When the machine approaches its limit, accurately estimating the rotor magnet temperature is a critical task to prevent irreversible damage to the machine. In this paper, an online algorithm has been developed to monitor the magnet temperature of six-phase PMSMs, based on the analysis of the machine's back electromotive force (back-EMF). The proposed algorithm has been validated through experimental tests conducted under different thermal stress conditions.