Man tank of the transformer is welded by high tensile strength steel plates and is divided into upper and lower parts. Shell-type transformers have coils that are completely sealed with insulating material and are in turn surrounded by wire cores, so there is no fear of damage due to external influences, and there is no need to provide an insulating space. Based on this, there is only a little assembly space between the iron core of the shell-type transformer and the inner wall of the oil tank. The oil tank is closely matched with the iron core and windings. The oil tank is a completely welded structure without bolts, which is very different from traditional transformers. The body is installed in a fuel tank, which is filled with transformer oil.