In the design of electrical machines, the increase of power density has become one of the main research themes. With most of the power loss in high power density electrical machines often being generated in the stator winding assembly, it is necessary to reduce these losses. The effects of strands and bundle positions in the slot on the AC losses in the winding are often overlooked. Taking as a case-study an existing high frequency machine, this paper analyzes and provides an in-depth insight into such effects. Exploiting the rapid advancements in precision 3D printing, it is found and experimentally verified that by controlling the position of the conductors within the top of the slot the AC losses can be markedly reduced.

This paper presents a comparison between hairpin and random distributed winding in electrical machines for automotive applications. Indeed, the overall performance of an electrical drive system is seriously affected by its winding design. The considered electrical machine has a peak power of 115kW and a maximum operating speed of 12000 rpm. Both cost and manufacturing aspects are here discussed in detail. Two different machine topologies have been investigated and Finite Element Analysis (FEA) results are presented and discussed. Then, the comparison between hairpin and random winding configuration in terms of AC copper losses are presented for the selected geometry. The accurate AC losses estimation can be done by modelling each single conductor. In order to significantly reduce the simulation time, a domain model reduction has been adopted. Based on two different driving cycles, Urban Dynamometer Driving Schedule (UDDS) and Highway Fuel Economy Test (HWFET), the AC losses have been evaluated. The main outcome of this work is the considerable reduction of AC losses by using a segmented hairpin winding.

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This paper presents an investigation into the sensitivity of high-frequency AC effects on the winding with varying number of parallel strands. Based on numerical analysis, a methodology to segregate the losses into components is presented. It is shown that the skin and proximity effect losses are not influenced by the shape and the positions of the strand bundles and these losses cannot be neglected for straight conductors even when the strand diameter is less than the skin depth.