A High-Performance Phase-Shift Full-Bridge Converter with a Rotary Transformer for the Field Excitation of Electric Machines

For energizing the rotating field winding of electric machines without mechanical contact, the contactless energy transfer (CET) with a rotary transformer (RT) and a power converter is a promising solution. The RT is a special transformer that allows the rotation of windings by separating the stationary and rotary windings, and the power converter utilizes the RT as an interface for energy transfer. Due to the large air gap and non-interleaved winding structure, the parasitics of the RT are pronounced, where the leakage inductance and ac resistance of the windings are relatively larger, and the magnetizing inductance is relatively smaller. In this article, the phase-shift full-bridge (PSFB) converter is adopted as the power converter, as the leakage inductance of the RT can help achieve soft-switching, and high switching frequency can be achieved for high power density. By considering the parasitics of the RT, the operation principle, total power losses and maximum output current of the PSFB converter with the RT are investigated, and the design optimization is carried out to design a high-performance PSFB converter with the RT. Finally, a PSFB converter with the RT is built in the lab, which works at 240-kHz switching frequency and can achieve 73.67-A output current with 88.53% efficiency.