High Torque Density Double Stator Permanent Magnet Electric Machine

In this paper, a new configuration for high torque density electric machine is proposed. The designed electric machine houses two stators with concentrated windings on the stator poles and permanent magnet segments on the rotor. The inner airgap is adjusted to be smaller than outer airgap in this machine. As a result, the current density in inner winding can be less than that in the outer winding. Consequently, the inner winding temperature is not an issue in this machine while the average torque is not compromised. The stator is E-core type to eliminate the mutual inductance and the permanent magnets are tangentially magnetized to increase the torque density. In order to prevent local demagnetization on the corners of permanent magnets, the shape of permanent magnets and rotor segments have been modified. Moreover, 3D finite element analysis are carried out to verify 2D analysis results and to investigate the effect of end winding on motor performance. Furthermore, motor efficiency is calculated and thermal analysis have been presented.