Numerical study of the flow and thermal characteristics in an internal permanent magnet synchronous motor*

Recently, internal permanent magnet synchronous motors (IPMSMs), which feature high energy density due to the incorporation of permanent magnets within the rotor, have emerged as an alternative to traditional induction motors in industrial applications. The IPMSM, consisting of a stator, a rotor with imbedded magnets, a shaft, bearings, a fan and enclosure, converts electrical energy into mechanical energy through the interaction between the magnetic fields around the stator and rotor core induced by the electric windings. The motor efficiency is determined by several losses related to electrical resistance, magnetic field change and mechanical friction. The losses act as a thermal source that increases the motor temperature, reducing its efficiency. Therefore, understanding the thermal characteristics of IPMSM is essentially important for enhancing their efficiency and ensuring stable operation. In this work, three-dimensional computations are performed to investigate the flow and thermal characteristics of IPMSM. The computations show a comprehensive temperature distribution in the motor, closely linked to both the internal and external flow characteristics of the motor. The effects of the driving conditions, such as rotational speed and load torque, on the motor's temperature distribution are investigated.