Abstract: A method of constructing a distribution transformer of the type having a magnetic circuit in the form of one or more hollow coils and having primary and secondary windings by coiling an electrically insulated wire. The wires are then juxtaposed to form primary and secondary windings while interposing a flat insulating sheet material between adjacent coils. A cooling liquid is associated with the primary and the secondary coil windings and a rigid support frame is formed above these windings. A ferro-magnetic steel ribbon is coiled about at least one leg of the support frame containing the primary and secondary windings whereby to form a magnetic circuit.

Abstract: A distribution transformer and a method of making same. The transformer has at least one closed magnetic circuit in the form of a hollow toroidal coil made from ferro-magnetic steel ribbon. An electric circuit is formed by a primary winding and a secondary winding each constituted by one or more sub-assemblies in the form of a double pancake. These double pancakes are juxtaposed and molded together in a solid insulating material to form a rigid insulating frame on which the magnetic circuit is wound to form one or more magnetic coils. The rigid insulating frame, which is constituted by the primary and secondary windings and the insulating material, also includes therein conduits capable of circulating a cooling fluid through the windings whereby to provide heat exchange to cool the assembly of the electrical and magnetic circuits.