A High-Performance Phase-Shift Full-Bridge Converter with 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 power converter and rotary transformer (RT) is a promising solution. The RT is normally implemented by a pot core that accommodates a stationary and rotating winding separated by a large air gap, so it has a relatively large leakage inductance. In this case, the phase-shift full-bridge (PSFB) converter is a suitable topology as the leakage inductance can be utilized to achieve soft-switching. Due to the loosely coupled RT and the small resistance of the field winding, the behavior of the PSFB converter is slightly different from the traditional case that incorporates a resonant inductor and a tightly coupled transformer. In this paper, the characteristics of the PSFB converter with the RT are investigated by considering the critical parasitics of the RT, and the maximum load current value is derived for the converter design. The design optimization is carried out to provide 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 72-A output current with 88.53% efficiency.