Method of construction of a distribution transformer having a coiled magnetic circuit

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 extending through the interior of the magnetic circuit, said method comprising the steps of:

• (i) forming primary and secondary windings by winding a flat electrically insulated conductor to form a pair of single flat coils each in the form of a pancake, said pancakes being wound in opposed directions to one another and forming a cross-over junction at the interior of the windings so that the terminal end of each winding lies on the outer periphery of the pancakes and the two windings lie in parallel planes and form a double pancake;
• (ii) interposing flat insulating sheet material between and to each side of adjacent coils;
• (iii) inserting cooling means in association with the primary and secondary coil windings and molding a solid insulating material about said windings, said cooling means and said sheet material to form a rigid support frame thereabout;
• and
• (iv) coiling a ferro-magnetic steel ribbon about at least one leg of said support containing the primary and secondary windings to thereby form said magnetic circuit.