A three-phase non-linear dry-type transformer has integral molds formed of a glass fiber-reinforced polymeric material. The low voltage coil is comprised of an inner low voltage mold formed around each of the at least three core legs, a low voltage conductor winding wound upon the inner low voltage mold and an outer low voltage mold formed around the low voltage winding. The high voltage coil is comprised of an inner high voltage mold disposed around the outer low voltage mold, a high voltage conductor winding wound upon the inner high voltage mold, and an outer high voltage mold formed around the high voltage conductor winding. An annular space between the inner and outer high voltage molds and the inner and outer low voltage molds is filled by an insulating polymeric material during a casting process. The molds are bonded to the coil windings by the insulating polymeric material and remain during the operation of the non-linear transformer as integral components of the non-linear transformer.