The effects of modifying stator-rotor ratio and utilizing a radial and axial layout on the angular speed and torque ripple of a two-phase switched reluctance motor

Electric motors used in industrial applications have various disadvantages. Most notably, many use rare earth magnets, which are derived from rare earth metals. Rare earth metals are nonrenewable, and when mined acidifies the surrounding soil and water. Switched reluctance motors (SRM) are one potential solution to this issue, as they donʼt use rare earth magnets. However, they have one major flaw: torque ripple, the periodic change in output torque as the motor shaft rotates. Torque ripple causes instability and reduces the load-bearing performance of SRMs. The research question posed in this study was: How does modifying the stator-rotor ratio and utilizing a radial and axial layout affect the angular speed and torque ripple of a two-phase switched reluctance motor. It was hypothesized that the radial-axial stator with 8:4 pole stator-rotor ratio would produce the highest top angular speed after 60 seconds of constant operation and the lowest torque ripple because it has more stator poles and incorporates an axial layout (i.e. the conditions that would increase torque throughout a rotor revolution). The independent variables in this study were the magnetic pole number stator-rotor ratio and the inclusion of axial flux. The dependent variables were the angular speed and torque ripple of the SRM. An SRM with interchangeable stators was designed and manufactured, along with a converter circuit and converter circuit code. By modifying each stator to have either zero, one, or both of the independent variables, the dependent variables were tested. A photogate was used to generate data to derive angular speed values. To generate the data to derive torque ripple values, a wrench was attached to the rotor and pressed against a balance, and mass data was collected. The results suggested that an increased pole stator-rotor ratio increased angular speed and reduced torque ripple, while radial-axial layouts increased angular speed and torque ripple. It was concluded that the predicted hypothesis was partially correct, as the 8:4 pole stator-rotor ratio produced the highest top angular speed but not the lowest torque ripple. The 8:4 normal layout produced the second-highest top angular speed and the lowest torque ripple by a large margin, making it the best of the four proposed layouts. The results show that torque ripple can be efficiently eliminated from SRMs by increasing their pole stator-rotor ratio, making them a strong candidate for future industrial usage.