Applications of Reconfigurable Windings for Traction Motors and Drives

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The objective is to design a stator winding reconfiguration system which is commercially and technically attractive. The concept of reconfiguring the stator windings depending on the motor operating point is widely known to offer performance advantages in terms of motor efficiency and torque density for a given mass of rare earth magnets. From work carried out in the summer project it is also shown that there is potential to reduce the specification of power electronics. Reconfiguration of windings between star and delta modes of operation is a common practice in industrial applications for start-up of induction machines, however commercial implementation of such systems for traction applications is almost non-existent owing to cost and packaging constraints. The objective of this research is to develop and demonstrate such a system which could be commercially relevant in automotive traction motor applications, and to evaluate its efficacy.The concept which will be developed within this project is based around a mechanical switching mechanism, as we believe this offers the only realistic route to achieve the cost requirement and make this technology commercially relevant for mainstream automotive applications. Previous work details semiconductor-based switching systems but are difficult to realise for under 200 euro for the power electronics alone, not considering control circuitry or cooling. In contrast, the mechanical switching solution uses abundantly available materials and inexpensive manufacturing techniques and so has excellent potential for cost optimisation. To realise the full benefits of this concept, it is desired to be integrated into the motor packaging. This will ensure that the total package is optimised for volume and mass and is preferable to integration within the inverter because it avoids the need for 12 cables connecting the motor and inverter. Despite multiple patents in this area no commercial product has yet reached the market, highlighting the difficulty of achieving a practical solution. We believe one of the key factors in producing a practical design is reducing the number of switches, or more precisely the number of electrical contact faces, since these are ultimately what limits the package volume. A key area in which the proposed solution progresses the state-of-the-art is in reducing the number of electrical contact faces by making maximum use of double-throw switches. A full review of possible switching mechanisms will be conducted as part of the work, including electrical schematics and actuation mechanisms, with a view to minimising cost and volume. This work will ultimately analyse such systems with the aim of establishing a design methodology which can be applied to the general case, to analytically trade off volume with performance, ensuring the project outputs are widely applicable.