Control scheme of a novel permanent-magnet-assisted switched reluctance machine

In this paper, two types of permanent-magnet-assisted switched reluctance motors (SRMs) characterized by placing permanent magnets in either common or excitation poles are comparatively investigated in terms of performance such as torque production and efficiency improvement with respect to switch-on and switch-off angles through dynamic performance estimation. Four conditions for angle control are employed to predict dynamic performance in the two proposed permanent-magnet-assisted SRMs compared to the design of no permanent magnets, and the conditions are the increase of advance angle with a fixed turn-off angle (Condition A), the increase of advance angle with a fixed dwell angle (Condition B), the increase of dwell angle with a fixed advance angle (Condition C), and finally, the decrease of advance angle with a fixed dwell angle (Condition D). The permanent-magnet-assisted SRMs are always superior to the no-permanent-magnet design in terms of efficiency regardless of the condition of switching angles, and torque performance is overall in the same situation except for condition C due to a gradual boost in the negative torque of the permanent-magnet-assisted SRMs. Also, the placement of permanent magnets in either common or excitation poles is critical in condition C, and regarding the increase of power density, condition A is the best. The permanent-magnet-assisted SRMs are higher than the no-permanent-magnet structure by approximately 30% in power density under the condition of the same efficiency. The prototype of two permanent-magnet-assisted SRMs and their drive system have been built up.