Additive manufacturing (AM) has been undergoing dynamic development in recent years. The latest evolution of AM has been recognised as a key enabling technology in a wide range of applications, some of which include medical, aerospace and automotive industries. The use of AM opens new avenues for design solutions, otherwise challenging or impossible to realise when using more conventional techniques for manufacture. No- or low-material waste and high-flexibility are some of the attributes of modern AM. This expanded paper aims to provide an up to date overview of the existing examples of employing AM in construction of electrical machines. The paper reviews research and development work related to all integral components of an electrical machine assembly. These include active parts like coils/windings, electrical insulation, stator/rotor magnetic core packs, permanent magnets (PMs). The machine structural/mechanical and thermal management components are also discussed in the paper. Further to these, the authors make some comments/forecasts on how the AM could improve performance and manufacturability of the future electrical machines.

This paper presents a finite element investigation into the proximity losses in brushless AC permanent magnet motors used in hybrid/electric vehicle applications. The proximity effect in winding conductors is as a result of eddy-currents caused by magnetic fields generated by nearby conductors. This paper considers the influence of the conductor shape and disposition on the losses for a given stator lamination. Several structures of the winding are analysed and compared in respect to the loss and AC resistance. The analysis shows that the proximity losses can be significantly reduced through an appropriate choice of conductor shape and winding technique. The calculated results have been validated experimentally on the machine prototype for three different winding arrangements

A fast finite element (FE) based method for the calculation of eddy current losses in the stator windings of randomly wound electric machines is presented in this paper. The method is particularly suitable for implementation in large-scale design optimization algorithms where a qualitative characterization of such losses at higher speeds is most beneficial for identification of the design solutions that exhibit the lowest overall losses including the ac losses in the stator windings. Unlike the common practice of assuming a constant slot fill factor s _f for all the design variations, the maximum s _f in the developed method is determined based on the individual slot structure/dimensions and strand wire specifications. Furthermore, in lieu of detailed modeling of the conductor strands in the initial FE model, which significantly adds to the complexity of the problem, an alternative rectangular coil modeling subject to a subsequent flux mapping technique for determination of the impinging flux on each individual strand is pursued. Rather than pursuing the precise estimation of ac conductor losses, the research focus of this paper is placed on the development of a computationally efficient technique for the derivation of strand eddy current losses applicable in design optimization, especially where both the electromagnetic and thermal machine behavior are accounted for. A fractional-slot concentrated winding permanent magnet synchronous machine is used for the purpose of this study due to the higher slot leakage flux and slot opening fringing flux of such machines, which are the major contributors to strand eddy current losses in the windings. The analysis is supplemented with an investigation on the influence of the electrical loading on ac winding loss effects for this machine design, a subject that has received less attention in the literature. Experimental ac loss measurements on a 12-slot 10-pole stator assembly will be discussed to verify the existing trends in the simulation results.

This paper presents results from an analysis of thermal behavior for alternative slot liner insulation and varnish impregnation materials used in the construction of electrical machines. These materials are typically characterized by the individual material properties altered to suit a particular application. However, the manufacturer provided material data are usually inadequate when comparing the complete insulation systems. This research is focused on the conductive heat transfer from the winding body into the machine periphery in context of the complete insulation system. An experimental approach using the stator-winding segment subassembly has been adopted here, for the representative in situ heat transfer measurements. The effects of impregnation “goodness,” in volume manufacture repeatability, and individual versus in situ material physical properties on the stator-winding thermal behavior are discussed in detail. The results suggest that the use of a particular slot liner insulation and varnish impregnation has a prominent impact on the winding heat transfer, as well as appropriate manufacture and assembly processes used. The experimental work has been supplemented with theoretical analysis to provide a more comprehensive insight into the winding heat transfer phenomena; in particular the winding-to-slot contact thermal resistance.

This paper presents the results of a brushless PM starter-generator design which caters for low-cost manufacture and a highly constrained mechanical space-envelope. The startergenerator design addresses the low-cost requirement through the use of aluminium winding conductors and ferrite permanent magnets. This presents several challenges which include, but are not limited to, the selection of an appropriate machine topology to realise a high specific output with the lower performance materials, minimising the power losses associated with the higher resistivity of aluminium and the enhancement of thermal performance. The problem is further exacerbated by the demanding space-envelope, operating requirements and the necessity of design for manufacture. The selection of an appropriate machine topology is paramount in the present application as the limited mechanical space-envelope results in a pancake like geometry in which the aspect ratio of the stator outer diameter to the machine active length is high. To provide a solution satisfying all these challenging design requirements an approach combining the theoretical electromagnetic and thermal analyses together with tests on machine subassemblies has been employed here. Such a method allows for a more informed design process, where the manufacture and assembly nuances affecting the starter-generators performance are identified and accounted for prior to prototyping of the complete machine assembly. The paper discusses the employed design methodology in detail. A number of machine designs with alternative winding constructions has been considered providing an insight into challenges and limitations for the cost-effective winding construction utilising aluminium conductors. The results from analysis of the starter-generator suggest that the proposed machine design is capable of achieving the design requirements for both continuous and transient operating modes.