Abstract—this paper presents a complete methodology for the design of AC permanent magnet motors for electric vehicle traction. Electromagnetic, thermal and mechanical performance aspects are considered and modern CAD tools are utilised throughout the methodology. A 36 slot 10 pole interior permanent magnet design example is used throughout the analysis. Index Terms— Design Methodology, Permanent Magnet Motor, Traction, Computer-Aided Design I. INTRODUCTION For an engineer using computer aided design (CAD) tools to design a permanent magnet (PM) motor for a traction application there is little guidance available. A small amount of academic literature exists discussing design methodologies, these are typically incomplete and generally take the form of either an objective analytical calculation or an optimisation problem, describing the derivation of some motor parameters for a well-defined problem that is difficult to generalise to different design tasks [1], [2],[3], [4]. In this literature CAD tools are typically primarily used either to validate the result of analytical sizing exercises or as a black box optimisation engine. Alternatively some literature exists relating to the use of CAD tools [5] in a design process, this advocates an unstructured trial and error approach. This is clearly at odds with the structured deductive design philosophy proposed in academic literature and is likely to result in a satisfactory rather than optimal design. Here a methodology is presented that attempts to reconcile these approaches, adopting the structured scientific approach to design found in academia while utilising a number of CAD tools and remaining flexible enough to be used across a variety of design projects. The aim of this paper is to present a complete methodology that provides a simple, rigorous and scientific approach to the design of AC PM electric motors for traction applications utilising a number of modern CAD design tools where electromagnetic, thermal and mechanical performance aspects are taken into account. The methodology aims to optimise performance across the entire operational envelope and the techniques detailed in [6] are used throughout to achieve this. This work was supported by the Bristol University EPSRC funded Industrial Doctorate Centre in Systems (Grant EP/G037353/1) and Motor Design Ltd. J.Goss and D.Staton are with Motor Design Ltd, UK, (e-mail j.goss@motor- design.com and d.staton@motor-design.com ) R.Wrobel and P.Mellor are with The University of Bristol, Electronic and Electrical Engineering Department, UK, (e-mail r.wrobel@bristol.ac.uk and p.h.mellor@bristol.ac.uk ) It is understood that electric motor design is not simply an objective calculation and as such the methodology allows flexibility to accommodate for the intuition and experience of the design engineer, as well as constraints or goals that cannot simply be expressed within the technical specification. Throughout this paper the methodology is illustrated using examples from the design of a 36 slot 10 pole interior permanent magnet motor for a small electric vehicle application. The software tools utilised throughout this procedure are SPEED PC-BDC and PC-FEA [7] for electromagnetic modelling, Motor-CAD [8] for thermal modelling, Autodesk inventor [9] for mechanical modelling and Motor-LAB [10] to analyse the thermal and electromagnetic performance of the design across the full operating envelope. II. OVERVIEW OF THE DESIGN METHODOLOGY Fig. 1 shows a basic outline of the methodology, no iterative loops are shown as these are dependent on the specific design, however some iteration will be required and it should be minimised where possible. Figure 1- Overview of the design methodology The Design of AC Permanent Magnet Motors for Electric Vehicles: A Design Methodology James Goss, Rafal Wrobel, Phil Mellor, Dave Staton