Method of manufacturing a transformer coil having cooling ducts

1. A method of manufacturing an electrical transformer coil comprising:

providing a mandrel;

providing a plurality of pre-formed plastic cooling ducts;

providing conductive material;

winding the conductive material around the mandrel to form a plurality of layers;

during the winding, positioning the pre-formed plastic cooling ducts so as to be disposed between the layers;

encapsulating the layers with the pre-formed plastic cooling ducts disposed in-between in a resin;

placing plugs in opposing open ends of each of the pre-formed plastic cooling ducts before the layers and the pre-formed plastic cooling ducts are encapsulated in the resin;

removing the plugs after the layers and the pre-formed plastic cooling ducts are encapsulated in the resin; and

allowing the resin to cure while the cooling ducts remain disposed between the layers, thereby permanently incorporating the cooling ducts into the electrical transformer coil.

2. The method of claim 1 , wherein the electrical transformer coil is formed so as to be cylindrical, and wherein the pre-formed plastic cooling ducts are positioned so as to be radially spaced apart.

3. The method of claim 1 , wherein each of the pre-formed plastic cooling ducts is formed by pultrusion from a second resin.

4. The method of claim 3 , wherein the resin used to encapsulate the layers and the pre-formed plastic cooling ducts is an epoxy resin, and wherein the second resin is a polyester resin.

5. The method of claim 1 , further comprising placing a mold over the mandrel, and wherein the conductive material is wound over the mold.

6. The method of claim 5 , further comprising removing the mold after the layers and the pre-formed plastic cooling ducts are encapsulated in the resin.

7. The method of claim 1 , wherein each pre-formed plastic cooling duct has an enclosed periphery with open ends and an interior passage extending between the open ends.

8. The method of claim 1 , wherein each of the pre-formed plastic cooling ducts comprises polyester resin reinforced with fiberglass filaments.

9. The method of claim 1 , wherein the conductive material comprises conductor sheeting.

10. The method of claim 9 , wherein the pre-formed plastic cooling ducts are disposed around the circumference of the electrical transformer coil.

11. The method of claim 10 , wherein the pre-formed plastic cooling ducts are disposed between successive layers of the conductor sheeting.

12. A method of manufacturing an electrical transformer coil comprising:

providing a mandrel;

providing a plurality of pre-formed plastic cooling ducts;

providing conductive sheet material;

winding the conductive sheet material around the mandrel to form a plurality of conductive layers;

during the winding, positioning the pre-formed plastic cooling ducts so as to be disposed between successive conductive layers;

encapsulating the conductive layers with the pre-formed plastic cooling ducts disposed in-between in a resin; and

allowing the resin to cure while the pre-formed plastic cooling ducts remain disposed between the layers, thereby permanently incorporating the pre-formed plastic cooling ducts into the electrical transformer coil.

13. The method of claim 12 , wherein the method further comprises:

providing insulating sheet material; and

winding the insulating sheet material to form a plurality of insulating layers, the winding of the insulating sheet material being performed during the winding of the conductive sheet material such that the insulating layers and the conductive layers are alternating.

14. The method of claim 13 , wherein the pre-formed plastic cooling ducts are disposed around the circumference of the electrical transformer coil.

15. The method of claim 14 , wherein the conductive sheet material has a width equal to the axial length of the electrical transformer coil.