Influence of Conduction Angles on Single-Layer Switched Reluctance Machines

This paper investigates the influence of conduction angles on the performances of two 3-phase 12-slot/8-pole short-pitched switched reluctance machines (SRMs): single-layer SRM with conventional winding (SL-CSRM) and single-layer SRM with mutually coupled winding (SL-MCSRM). Both unipolar and bipolar excitations are employed for the SRMs with different conduction angles such as unipolar 120° elec., unipolar 180° elec., bipolar 180° elec., bipolar 240° elec., and bipolar 360° elec. Their flux distributions, self- and mutual-flux linkages, and inductances are analyzed, and followed by a performance comparison in terms of on-load torque, average torque, torque ripple, using 2-D finite-element method. Copper loss, iron loss, and machine efficiency have also been investigated with different phase currents and rotor speeds. The predicted results show that the conduction angle of unipolar 120° elec. is the best excitation approach for the SL-CSRM at low current and also modest speed, as its double-layer (DL) counterpart. However, at high current, the higher average torque is achieved by a conduction angle of unipolar 180° elec. For the SL-MCSRM, bipolar 180° elec. conduction is the most appropriate excitation method to generate a higher average torque but lower torque ripple than others. The lower iron loss is achieved by unipolar excitation, and the SL-CSRM with unipolar 120° elec. conduction produces the highest efficiency than others at 10 Arms. In addition, the performances of single-layer machines have been compared with those of the established DL-SRMs with conventional and mutually coupled windings. The prototype SRMs for both SL-CSRM and SL-MCSRM have been built and tested to validate the predictions.