Comparative study of electromagnetic performance of switched reluctance machines under different excitation techniques

This paper analyses and compares the electromagnetic performance of switched reluctance (SR) machines having three different excitations, i.e. conventional unipolar, AC sinusoidal bipolar with/without DC bias. Under the AC sinusoidal bipolar excitation, the SR machine becomes synchronous reluctant (SynR) machines having concentrated winding. On the other hand, in principle the SR machine under sinusoidal and excitation with DC bias is similar to the switched flux permanent magnet (SFPM) machine. During the finite element investigation, the torque capability and torque-speed characteristics are particularly investigated, whilst the losses and efficiency are also highlighted. In conclusion, the SR machines having AC sinusoidal bipolar excitations with DC bias exhibits relatively smooth output torque, widest torque-speed characteristics, lowest iron loss as well as relatively high efficiency. Furthermore, comparing with the conventional unipolar excitation, both AC sinusoidal bipolar excitations can result in much lower torque ripple percentage and same or even higher average output torque, as well as lower iron loss and higher efficiency. A prototype is constructed and experimental results are presented to verify the predictions and analyses.