Developing high-voltage silicon carbide (SiC) devices has enabled breakthroughs in voltage levels, power density, and efficiency in power electronic systems. Research institutions and manufacturers have recently created high-voltage SiC devices with ratings over 10 kV and 15 kV. These devices can increase the voltage level of large-capacity converters to 10 kV or higher and achieve megawatt power levels using only two- or three-level topologies. However, as voltage levels rise, the isolated power supplies for the SiC device drive circuits face greater challenges in voltage-withstand capability. These isolated power supplies draw power from the low-voltage side to supply the high-potential drive circuits. While they only need a few watts, they must withstand isolation voltages from several kilovolts to tens of kilovolts because they connect to the main circuit of the converter.

The high-frequency current transformer (HCT) is a promising isolated power supply structure known for its strong resistance to dv/dt. This advantage comes from the high integration of ultrahigh-frequency electromagnetic coupling and the low coupling capacitance of single-turn coils on the primary side. However, current research on HCT-isolated power supply mainly targets optimizing transmission efficiency, power, and coupling capacitance. There has been little systematic study of its unique insulation characteristics. As a result, the optimization design methods are unclear, and assessing insulation voltage capacity is challenging.

This paper investigates the insulation characteristics of the HCT-isolated power supply for high-voltage SiC devices. It examines six key structural factors: the inner diameter, height, and thickness of the magnetic core, as well as the winding method and wire diameter for both primary and secondary windings. This paper proposes an electric field optimization design method under compact size constraints. Additionally, a high voltage experimental platform was established to clarify the relationship between key structural parameters and the initiation voltage and discharge magnitude of partial discharges. The voltage withstand characteristics of the HCT isolated power supply were also verified. Simulation and experimental results indicate that using concentrated winding for the secondary winding results in a more uniform electric field within the structure. The inner diameter and height of the magnetic core, as well as the turns and diameter of the secondary winding, have significant effects on the electric field and partial discharge. However, the thickness of the magnetic core has a relatively weak influence on insulation capability. This study provides a theoretical basis for the design and optimization of the HCT-isolated power supply and experimentally verifies the specific effects of key structural parameters on insulation performance.