Refurbishing electrical machines to have a higher performance and/or reliability is a clear trend in the circular economy. This paper investigates the gain in efficiency, torque density and reliability with replacing the windings and the iron of the stator of existing three-phase synchronous reluctance machines (SynRMs), resulting in a multiphase machine. The stator housing, shaft, bearings and the rotor are not changed, to keep the cost of refurbishing low. As the housing and rotor are kept, logical constraints are to have the same inner and/or outer stator diameters, air gap length and axial length. In the new windings, an identical copper volume is considered as a constraint. An optimization technique is coupled to 2D finite element method to select the optimal slot dimensions. Case studies showed that it is possible to replace the stator of existing three-phase SynRMs with a better performance multiphase one. It is found that the average torque, efficiency and power factor of the five-phase SynRM are increased by 11.78%, 0.72% and 5.54%, respectively, compared to a three-phase SynRM at rated conditions. At higher speeds (three times rated value), the efficiency and average torque are greatly improved by about 3.64% and 33.67%, respectively, compared to the three-phase SynRM. Moreover, a faulty case of one phase opened is also investigated. The five-phase SynRM works at 75.45% of the healthy rated torque of the three-phase SynRM, whereas the three-phase SynRM works at only 43%. Measurements on an existing 5.5-kW, three-phase SynRM confirm the observed results.

中文翻译：

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将三相同步磁阻电机改造为多相电机

翻新电机以具有更高的性能和/或可靠性是循环经济的明显趋势。本文研究了通过更换现有三相同步磁阻电机 (SynRM) 的定子绕组和铁芯来获得多相电机的效率、转矩密度和可靠性增益。定子外壳、轴、轴承和转子都没有改变，以保持低翻新成本。由于外壳和转子保持不变，因此逻辑约束应具有相同的定子内径和/或外径、气隙长度和轴向长度。在新绕组中，相同的铜体积被视为约束。优化技术与二维有限元方法相结合，以选择最佳槽尺寸。案例研究表明，可以用性能更好的多相定子代替现有三相 SynRM 的定子。结果表明，在额定条件下，与三相 SynRM 相比，五相 SynRM 的平均扭矩、效率和功率因数分别提高了 11.78%、0.72% 和 5.54%。在更高的速度下（额定值的三倍），与三相 SynRM 相比，效率和平均扭矩分别大大提高了约 3.64% 和 33.67%。此外，还调查了一相开路的故障情况。五相 SynRM 以三相 SynRM 正常额定扭矩的 75.45% 工作，而三相 SynRM 仅以 43% 工作。对现有 5.5 kW 三相 SynRM 的测量证实了观察到的结果。