A transformer and a method of manufacturing the same are provided. The transformer includes a coil assembly mounted to a leg of a core. The coil assembly includes a low voltage coil and an insulation spool disposed over the low voltage coil. The insulation spool is composed of an insulating material and includes a plurality of guide strips defining a plurality of series of aligned notches. A high voltage coil is mounted to the insulation spool and includes a plurality of disc windings disposed in the series of aligned notches, respectively. Each of the disc windings comprises alternating concentric conductor layers and insulating layers. The conductor layers each have a width to thickness ratio of greater than 20:1.