Fractional slot concentrated winding (FSCW) is a kind of winding structure with few-slots/coils multi-poles. FSCW has the potential value of high torque density due to its short end-winding and high slot fill ratio and is widely used in low-speed direct-drive application situations. However, compared with integral slot winding (ISW), the back EMF coefficient of FSCW is smaller, which leads to smaller output torque under the same condition. To improve the back EMF coefficient of FSCW, equidirectional toroidal winding (ETW) is proposed and applied to the dual rotor slotless axial flux permanent magnet motor (AFPM), in which the unit structure is three slots/coils two poles, and the ideal back EMF coefficient is the same as that of ISW. In this paper, firstly, the structure of ETW is introduced and its operating principle is analyzed. Then, compared with the AFPM with ISW, the open circuit and load characteristics of the AFPM with ETW under two conditions of the same wire gauge and the same coil width are analyzed respectively. The back EMF coefficient and output torque of ETW-AFPM are similar to that of ISW-AFPM under the same coil width. The back EMF coefficient and output torque of ETW-AFPM are a little lower than that of ISW-AFPM under the same wire gauge. Finally, the experimental results also validate the feasibility of AFPM with ETW and the correctness of the analysis results. © 2022 Institute of Electrical Engineers of Japan. Published by Wiley Periodicals LLC.

中文翻译：

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等向环形绕组与整体槽绕组无槽轴向磁通永磁电机对比分析

分数槽集中绕组（FSCW）是一种少槽/线圈多极的绕组结构。FSCW由于其端部绕组短、槽填充率高而具有高扭矩密度的潜在价值，被广泛应用于低速直驱应用场合。但与积分槽绕组（ISW）相比，FSCW的反电动势系数更小，导致相同条件下的输出转矩更小。为提高FSCW的反电动势系数，提出了等向环形绕组（ETW）并应用于双转子无槽轴向磁通永磁电机（AFPM），其单元结构为三槽/线圈两极，理想的反EMF 系数与 ISW 相同。本文首先介绍了ETW的结构，分析了其工作原理。然后，与带ISW的AFPM相比，分别分析了带ETW的AFPM在相同线规和相同线圈宽度两种情况下的开路和负载特性。在相同线圈宽度下，ETW-AFPM的反电动势系数和输出转矩与ISW-AFPM相似。在相同线规下，ETW-AFPM的反电动势系数和输出扭矩略低于ISW-AFPM。最后，实验结果也验证了 AFPM 与 ETW 的可行性以及分析结果的正确性。© 2022 日本电气工程师学会。由 Wiley Periodicals LLC 出版。在相同线圈宽度下，ETW-AFPM的反电动势系数和输出转矩与ISW-AFPM相似。在相同线规下，ETW-AFPM的反电动势系数和输出扭矩略低于ISW-AFPM。最后，实验结果也验证了 AFPM 与 ETW 的可行性以及分析结果的正确性。© 2022 日本电气工程师学会。由 Wiley Periodicals LLC 出版。在相同线圈宽度下，ETW-AFPM的反电动势系数和输出转矩与ISW-AFPM相似。在相同线规下，ETW-AFPM的反电动势系数和输出扭矩略低于ISW-AFPM。最后，实验结果也验证了 AFPM 与 ETW 的可行性以及分析结果的正确性。© 2022 日本电气工程师学会。由 Wiley Periodicals LLC 出版。