A vacuum pressure impregnated dry type transformer has an iron core, vacuum pressure resin impregnated high voltage windings and low voltage windings. The low voltage winding is constructed with conductors. Dupond nomex insulating material includes an apparatus to secure the windings in place during a vacuum and pressure resin impregnation process. VPI transformers are used in moisture prone areas.

The primary and secondary windings are impregnated with Class H polyester resin which can withstand hot spot temperature rise upto 180 Degrees Celsius and maximum winding temperature upto 220 Degrees Celcius. The coil exhibits high short circuit protection due to the tightly bond conductors comparable to completely resin encased moulded transformers at a substantially reduced cost.