Key points are not available for this paper at this time.
Wound field synchronous machines (WFSMs) are an attractive alternative to permanent magnet synchronous machines (PMSMs) given their competitive power/torque density and the controllability advantages of a direct field handle. However, these benefits can be offset by the reliability issues of carbon brushes, or the added complexity of inductive brushless exciters or rotary transformers required for the rotating field winding. Here, the design process and experimental test results for a low cost contactless capacitive power coupler (CPC) for rotor winding excitation of a WFSM are presented, using only simple printed circuit boards (PCBs). The CPC system transfers 600 W at 93% efficiency to the rotor field of a 55 kW WFSM. CPC voltages remain in the hundreds of volts and passive component sizes are minimized by switching at 2 MHz with a GaN inverter. Parasitic loss minimization design rules for trace layout in the CPC PCB structure are established for high frequency operation. A buck converter integrated into the rotating rectifier matches the load impedance of the rotor to the CPC system. A phase locked loop (PLL) tracks the resonant tank frequency of the CPC, whose saliency is spatially tied to the rotation of the machine, creating a platform for speed and position self-sensing.
Hagen et al. (Sun,) studied this question.