A High-Density Single-Turn Inductor for a 6 kV SiC-based Power Electronics Building Block

This paper presents the design and optimization of a single-turn magnetic-core inductor for a 6kV, 40Hz power electronics building block (PEBB) using 10kV SiC MOSFET modules. The inductor design begins with a comprehensive comparison between air-core, single-turn and multi-turn magnetic core structures, and the single-turn magnetic core structure is concluded to be the most suitable solution for the given specifications. The design process is then followed by an optimization of geometric dimensions and magnetics by a trade-off among power loss, volume, and parasitic capacitance. To achieve high compactness by minimizing the electric field stress in the air, a grounded shielding layer is applied to surround the winding, and the high-electric-field space is filled with void-free solid insulators. Major issues resulting from the shielded winding structure include extra loss on the shield, concentrated electric field at fringes, and induced grounding current. These problems have been addressed by shield conductivity selection, a proposed field-grading termination, and a well-designed damping circuit, respectively. Finally, the fabrication process of a prototype and the experimental performance are demonstrated.