A power transformer manufacturer which was located in economical boycotted country met some problems in material provision. The core material and some other things shall be supplied by a foreign company that they work under its license. While boycotting duration they got to use inferior material in core transformer construction. Whereas they didn't have adequate base knowledge of transformer design, they followed all construction algorithms that were dictated by foreign company. They thought this instruction deviation only influenced the power losses of transformers, but in practice they found other important problem about short circuit withstand of transformers. The power transformers windings sometimes were damaged mechanically due to a sever short circuit fault current. What is your opinion? How core material selection influenced the transformer withstand against short circuit current?