Loss Characterization of Soft Magnetic Core Materials from Room to Cryogenic Temperatures: A Comparative Study for Cryogenic Power Electronic Applications

This paper presents a comprehensive experimental study addressing the lack of consistent low-temperature data on magnetic materials for high-efficiency cryogenic power electronics. A unified dataset is provided for the first time, covering temperatures from room temperature down to −194 °C, excitation frequencies between 25 kHz and 400 kHz, and technologically relevant flux densities. The investigated materials include MnZn- and NiZn-ferrites, nanocrystalline alloys (Vitroperm, Finemet), and various classes of alloyed powder cores. The characterization comprises magnetic hysteresis behavior, saturation flux density, temperature- and frequency-dependent core losses, permeability, and DC bias performance under cryogenic conditions. The results demonstrate that nanocrystalline materials and selected powder cores (MPP, Edge) exhibit superior cryogenic performance, while ferrites and low-cost powder cores suffer from significant loss increases or magnetic instability at low temperatures. These findings provide a solid basis for the selection and design of magnetic components in next-generation cryogenic power-electronic systems.