As society electrifies, there is a growing demand for electrical drive systems in the deployment of
renewables and electric vehicles (EVs), along with the replacement of other traditional engine and
hydraulic systems in order to reduce global emissions. For any drive system, there is a desire that
the ideal candidate would have high efficiency, high power and torque density, low cost, fault
tolerance and be relatively environmentally friendly. There are multiple electrical machine topologies in common use for these applications, such as the permanent magnet synchronous machine (PMSM), induction machine, synchronous reluctance machine and the switched reluctance machine (SRM). The SRM has received interest in recent times, especially in the electrification of passenger vehicles. It is an attractive machine topology, given it is low cost, simple design, fault tolerance, high torque density and no use of permanent magnet materials. Despite this, the SRM suffers from a lower efficiency compared to other candidate topologies and has an inherently high torque ripple (hence noise and vibration), which limits its use across a wider range of applications. In an SRM drive system, the drive converter can be a source of efficiency improvements. Dependent upon the device type used, the cost of the converter in terms of components price and volume can vary while also affecting the overall efficiency. An investigation is carried out into the power semiconductor devices used in SRM drives, where commonly used switching device types with near identical ratings are compared from a theoretical perspective, and then experimentally compared to gauge device losses. From this it is found that for the three variants (and models) of switching device, the Superjunction MOSFET outperforms both the Silicon Carbide MOSFET and Silicon IGBT in terms of losses in a limited use case scenario. Another source for efficiency improvements and the main source of the elimination of torque ripple is the control of SRMs. Using the torque ripple minimisation strategy of current profiling as a starting point, the theoretically optimal rms current for an SRM phase is established for a given
load torque. A genetic algorithm is designed which uses this rms current as a target for optimisation, which produces optimally low rms current profiles which across the full rated speed range of a four phase SRM, an increase in rms currently only 4.3% above the theoretically optimal rms current is exhibited. Along with this, the algorithm design eliminates commutation torque ripple (
| Date of Award | 19 May 2025 |
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| Original language | English |
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| Awarding Institution | - University Of Strathclyde
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| Sponsors | University of Strathclyde |
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| Supervisor | Khaled Ahmed (Supervisor) & Charles Pollock (Supervisor) |
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