FE Modeling and Development of a High-Frequency Coreless Transformer for Impulsive Automotive Applications

Abstract:
In this research, a high-frequency coreless transformer has been designed for a low-voltage automotive application. The transformer has been designed for 1 kW absorption peaks. The power is transferred through bursts of a 6.78 MHz sine wave generated by a DC/AC resonant converter circuit. The efficiency of magnetic components at operating frequencies of the order of MHz decreases mainly due to winding and core losses. Without a magnetic core, only winding losses must be considered. However, the low reluctance materials no longer enclose the magnetic field. Thus, the coupling factor between the primary and secondary sides of the transformer becomes smaller and the EMI increases. In this work, a new toroidal geometrical arrangement of PCB as windings has been designed for a higher coupling factor. Each PCB consists of one turn for the primary winding and one turn for the secondary winding. The PCBs are connected in series or parallel to obtain the turns ratio desired. Finite Element Method simu- lations have been done on 2D and 3D models to evaluate the magnetic flux, resistance, and inductance values with different PCB sizes. Test results are shown on an early prototype of the transformer.