Thermal Modeling and Limitations for Power Electronics Embedded in Medium-Voltage Cables

As next-generation energy technologies gain traction and power demand increases, the existing electrical infrastructure faces significant stress, prompting innovative solutions to enhance the grid's capacity and lifespan. This work explores the possibility of embedding medium-voltage power electronics directly inline with the cable, and the resulting thermal challenges. Since the majority of power distribution cables installed in the U.S. are passively cooled, the work focuses primarily on passive cooling, with an emphasis on the limitations of axial heat spreading within the cable. To date, literature on axial spreading of high incident heat loads on cables and cable environments is limited, typically reporting cases with $< $10 W of incident heat load. This work will explore the considerations, limits, and trade-offs of cable-embedded heat loads significantly larger than the cable losses. Both external and internal effects are modeled analytically in non-dimensional terms via a Biot number analysis, allowing fundamental limits and trade-offs to be derived. The work culminates in the design and experimental validation of a cable-embedded thermal system capable of passively dissipating 300 W of heat from a coaxial SiC MOSFET switch module over a length of 20 cm, thus validating the possibility of medium-voltage cable-embedded power electronics from a thermal standpoint.