Iron loss will be rapidly increased when the permanent magnet iron core synchronous motor runs at a high speed, which makes the motor produce so much heat that causes low efficiency of the motor and even burns out the motor. The iron-core-free permanent magnet synchronous motor remedies this defect and has a high efficiency at high speed. This article makes a comparative analysis on the iron-core-free permanent magnet synchronous motor torque density with different slot engagement classifications. The paper puts forward an optimized model of permanent magnet synchronous motor without the iron core. The technology of the permanent magnet synchronous motor without iron core is studied based on this model which provides a method to design and manufacture the iron-core-free permanent magnet synchronous motor.

The irreversible demagnetization of Nd-Fe-B permanent magnet (PM) material appears during the use of Nd-Fe-B permanent magnet synchronous motor (PMSM) has been blocking this kind of motor towards the direction of large-scale. Demagnetization of PM is mainly affected by the working temperature and the reverse magnetic field of stator armature, and the accurate calculation for the demagnetization characteristics of PMSM is usually difficult by using the analytical method. In this paper, we derive the calculation formula of the knee point under a working temperature for permanent magnets in PMSM firstly, then calculate and analyze the demagnetization characteristics of PMSM under different working temperatures and loads by using the Finite Element Method (FEM), Thereby more accurately reflect the working characteristics of PM and the overload capability of motor. This paper provides theoretical basis for the selection of PM materials and the calculation of PM thickness in the PMSM design.