Quantitative Analysis of Hybrid-Excited Doubly Salient Machine With Subslot Bottom PMs and Its Comparative Study

This article proposes a doubly salient machine (DSM) with subslot bottom permanent magnets (PMs) to enhance the torque production. The key is that with auxiliary slot-PM excitation, the stator yoke dc saturation can be mitigated to enhance the torque production capability of dc field excitation, meanwhile additional slot-PM flux can be pushed into the airgap, which can build a parallel excitation and generate additional effective torque. Comparing dc-excited DSM and subslot bottom represents PM DSM (SBPM-DSM), the steady torque can be enhanced by 12.8% with the use of subslot bottom PMs. In this article, torque separation effects due to dc field excitation and slot-bottom PMs are quantitatively analyzed with frozen permeability method. By using time-stepping finite-element analysis, the electromagnetic performances of two machines are evaluated. Experimental results verify validity of the proposed design.