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In the design of compact, power dense electrical machines found in automotive and aerospace applications it may be preferable to accept a degree of eddy current loss within the winding to realise a low cost high integrity winding. Commonly adopted techniques for analysing AC effects in electrical machine windings tend only to be applicable where the conductor dimensions are smaller than the skin depth and for ideally transposed windings. Further the temperature variation of AC losses is often overlooked. In this paper a more general approach is proposed based on an established analytical model and is equally applicable to windings where the conductor size greatly exceeds the skin depth. The model is validated against test measurements and FE analysis on representative single layer winding arrangements. A case study is used to illustrate the application of the proposed analytical method to the coupled electromagnetic and thermal modelling of a typical slot winding.I.

Concentrated wound, open slot, permanent magnet electrical machines are an attractive topology for automotive and aerospace applications as they exhibit compact end-windings, resulting in high power-density, facilitate fault tolerant operation through, physical, thermal, magnetic and electrical isolation of phase windings, and the open slot structure eases manufacture. However, a significant disadvantage of this topology is the interaction between the armature reaction field and winding conductors leading to elevated AC losses. A common mitigation technique is to reduce the height of the winding in the slot to minimise this interaction, however, the conductor crosssectional area is consequently reduced which compromises lowspeed performance. This paper investigates the use of additive manufacturing to produce shaped profile windings which exhibit minimal AC loss whilst maximising the utilisation of the slot area, thereby improving low-speed performance while maintaining high-speed performance.

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This paper presents results from an investigation into the optimal design of an open-slot, modular stator winding. The impact of the stator slot shape on the winding temperature rise is explored, taking account the distribution of loss that occurs in the open slot winding, including ac effects, and the heat transfer characteristics from the winding assembly into the stator core pack. The application focus is a single-layer, concentrated wound brushless PM machine, however the work is applicable to other machine formats. Alternative stator lamination profiles are compared; the commonly used parallel sided tooth with a trapezoidal slot, and a parallel sided slot with a trapezoidal tooth. The investigation includes the development of a reduced order thermal model representation of the stator. This model is employed to undertake coupled loss and thermal analyses to provide more accurate comparisons of the designs accounting for ac and temperature effects. The experimental and theoretical findings indicate the parallel sided slot design will result in a 37 o C lower winding temperature or an 11% increase in torque at the intended machine operation point.

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