Dry type transformer with improved cooling

A distribution transformer having a coil assembly mounted to a ferromagnetic core. The coil assembly includes a resin-encapsulated low voltage coil mounted to the core, a resin-encapsulated first high voltage coil disposed around the low voltage coil, and a resin encapsulated second high voltage coil disposed around the first high voltage coil. The first high voltage coil is separated from the low voltage coil by an annular first space, and the second high voltage coil is separated from the first high voltage coil by an annular second space. The low voltage coil and the first and second high voltage coils are arranged concentrically. The low voltage coil and the first and second high voltage coils have different axial lengths.