Geometry analysis and optimization of PM-assisted reluctance motors

In this paper, a detailed geometry analysis of the rotor structure is presented, for both synchronous reluctance and PM-assisted reluctance motor, in order to suggest an automatic procedure to draw the rotor structure. The shape of flux barriers is selected to achieve both high d-axis inductance and low q-axis inductance, in order to obtain high output torque. Methods to properly design the geometry of the end of each barrier and PMs are adopted. In order to draw a rotor with proper shape, different modifications are discussed. After that, such a drawing procedure is used to rapidly analyze the impact of some geometry changes on the machine performance. The analyzing process starts from a reluctance motor, considering the number of barriers, insulation ratio, split ratio and slots per pole per phase. Then, the PMs are inset into flux barriers and the effect of PM width on torque, power factor and flux weakening capability is investigated. At last, the demagnetization limit under overload operations is analyzed.