Design and Prototyping of a winding reconfiguration system for electric traction applications

Battery electric vehicles (BEVs) place high demands on electric drives across a wide operating range: high efficiency in customer-related driving scenarios and maximum performance in dynamic driving modes. A promising solution to this challenge is the dynamic reconfiguration of the electric machine winding configuration between series and parallel mode, enabling optimal electromagnetic properties of the drive for different operating points. This paper presents the design and prototyping of an electronic winding reconfiguration system for high-performance traction applications. Unlike mechanical switching concepts, which have long transition times and cannot switch under load, the proposed system enables fast and safe load transitions between the winding configurations. The study describes the topology and hardware of the switching unit, including the integration of power semiconductors, the required connection assemblies, cooling concept and the control of the power electronics. A novel control strategy is presented that ensures continuous current paths during switching, prevents overvoltage in the windings and minimises torque interruptions. To this end, the active short-circuit operation of the electric drive is taken into account. Simulations show that the system achieves efficiency gains of up to two percentage points in the partial load range while maintaining its full performance. The additional losses caused by the switching unit remain low in the partial load range, ensuring a net efficiency gain. The proposed concept offers a practical approach to extending the range of BEV drives by dynamically reconfiguring the windings of the electric machine, thereby improving partial load efficiency without compromising performance.