Vehicle Design

This paper presents a fast and accurate state-space model for synchronous machines taking into consideration the machine geometry, material non-linearities and core losses. The model is first constructed by storing the solutions of multiple static finite element (FE) simulations into lookup-tables (LUTs) to express the stator flux linkages as functions of the state variables, i.e., the winding currents and the rotor position. Different approaches are discussed to include the core loss into the model. A novel approach is presented for constructing a pre-computed LUT for the core loss as a function of the state variables and their time derivatives so that the loss can be directly interpolated when time-stepping the state-space model. The Simulink implementation of the proposed core-loss model shows a good match with time-stepping FE results with a 120-fold speedup in computation. In addition, comparison against calorimetric loss measurements for a 150-kVA machine operating under both sinusoidal and pulse-width modulated voltage supplies is presented to validate the model accuracy.

As the growth in electric vehicle (EV) chargers continues to push research towards compact and efficient power converters, high-frequency magnetic designs become pivotal. However, they introduce new challenges related to excessive magnetic losses and adverse parasitic components. Using planar transformers with PCB windings can address these by offering good heat dissipation, low losses, and controlled parasitics. Furthermore, interleaved winding configurations can circumvent traditional design trade-offs. Therefore, this paper presents a planar transformer design using PCB windings with novel interleaving and design aspects to minimise the losses and parasitic components of the high-frequency transformer. It aims to achieve an optimal balance between the trade-offs whilst ensuring compatibility with the target converter’s requirements and cooling system. The proposed anti-symmetrical interleaving achieves a drastic reduction of factor 8.6 in interwinding capacitance compared to conventional full-interleaving combined with low winding losses. The paper provides extensive comparison studies of different interleaving types, supported by thorough finite element simulations. The resulting design approach is applied to a 4 kW isolated dc-dc converter for level-1 EV charging. Finally, different prototypes are built and extensively characterised and validated for implementation in the EV charger. The resulting transformer features a gravimetric and volumetric power density of 15.1 kW/kg and 76.4 kW/l, respectively