Abstract: A toroidal power transformer having improved insulation between the primary and secondary windings. The insulation includes an insulator sleeve fitted to the primary winding and having the primary winding lead wires positioned therein such that the lead wires extend radially outward from the primary winding. This insulator sleeve is fitted to the primary windings by way of an insulator flange formed as an integral part of the insulator sleeve which insures good insulation between the primary and secondary windings and high creepage distance.