HV9105 Test Transformer with coupling winding for cascade connection to produce AC high voltage. The transformer consists of three windings with insulating shell and top and bottom corona free aluminium shielding electrodes. The insulation cylinder is made of epoxy resin with glass fibre reinforcement and coated with anti tracking varnish. The first exciter winding is a double winding 2x220V for connecting to approx. 220V (parallel connection) or 220 + 220V for connecting to approx. 440V (series connection) The series connection will require 50% of the parallel connection current. The second winding is the HV winding of 100 kV connected in series. The third winding, known as the “Coupler Winding” is provided for cascade connections of transformers. The coil is vacuum impregnated and insulated with high quality grade transformer oil.