Abstract: The loss characteristics under medium frequency work conditions of two silicon steel materials were analyzed, the effect of frequency, temperature on loss property was studied, and application feasibility of two silicon steel materials in large capacity medium frequency transformers. 0.15  mm thin-gauge oriented silicon steel has lower loss below 400 Hz, while 0.08 mm ultra-thin grain-oriented silicon steel has lower loss above 400 Hz.The iron loss of both silicon steel materials under 60-130 ℃ complex conditions were decreased. The higher the temperature and the longer the heating time, the loss gradually decreases and finally reaches a stable state. Just from performance perspective, when the frequency ≤400 Hz, 0.15 mm thin-gauge grain-oriented silicon steel was more suitable for preparing large capacity medium frequency transformer cores, when the frequency ＞400 Hz, 0.08 mm ultra-thin grain-oriented silicon steel was more suitable for preparing large capacity medium frequency transformer cores.

Key words: thin-gauge grain-oriented silicon steel, ultra thin grain-oriented silicon steel, Iron loss, complex working conditions, medium frequency power transformers