Transformer performs versatile functions in power system application. Low frequency transformers are heavy in weight and volume. On the contrary medium or high frequency transformers are light in weight and volume. The latest developed magnetic materials and switching devices lead to the application of medium frequency transformers in transmission networks. Transformers designed for medium frequency can also be used as an isolator between converter circuit of renewable sources and the grid connected network. In this paper, a medium frequency toroidal core multi-winding transformer (MWT) is designed and simulated in COMSOL multiphysics environment and the core loss for different amorphous materials are analyzed. Results are presented in this paper. It is recommended that the analysis of core materials for medium frequency applications will play an important role for the selection of efficient core materials for medium or high frequency transformers.