Distribution transformer having static shield

Claim 2

In an electrical distribution transformer having primary and secondary windings wherein said primary winding includes a plurality of superimposed helical layers of electrical wire turns, a static shield comprising an elongated strip of thin insulating material positioned contiguous an exterior layer of said wire turns and having a conductive coating on the surface thereof disposed away from said exterior layer and having both longitudinal side edges folded over and flattened so that said insulating material is exposed on the outer surface of said shield, a thin strip of conductive material electrically connected to said conductive coating and also electrically connected adjacent the line end wire turn of said exterior layer, and an envelope of insulation wrapped around said elongated static shield so that it is disposed between said conductive coating and said exterior layer of wire turns.

Claim 3

In the combination of claim 1 wherein said strip of conductive material is cold welded to said conductive coating.

Claim 4

In the combination of claim 1 wherein said static shield comprises aluminum backed crepe paper.

Claim 5

In the combination of claim 1 wherein said static shield comprises aluminum-backed paper and said strip of conductive material is cold welded to said aluminum and said envelope of insulating material comprises a plurality of superimposed elongated strips of insulation having their longitudinal side edges folded over said aluminum backed paper shield and flattened so that they surround said shield and insulate it from said exterior layer of wire turns.

Claim 6

In the combination of claim 1 wherein said exterior layer is the radially outermost layer of wire turns, said static shield overlays said outermost layer, and said thin strip of conductive material is electrically connected adjacent the finish wire turn of said outermost layer.

Claim 7

In the combination of claim 1 wherein said exterior layer is the radially innermost layer of wire turns, said static shield underlays said innermost layer, and said thin strip of conductive material is electrically connected adjacent the start wire turn of said innermost layer.

Claim 8

In an electrical distribution transformer having primary and secondary windings wherein said primary winding includes a plurality of adjacent primary winding sections each of which includes a plurality of radially superimposed helical layers of electrical wire turns, a static shield for each primary winding section comprising an elongated first strip of thin insulating material wound in overlaying relation to the outer layer of wire turns of said primary winding section and having a conductive coating on the surface thereof away from said outer layer and having both longitudinal edges folded over and flattened so that said insulating material is exposed on the outer surface of said shield, an insulation envelope wrapped around said first insulating strip carrying said conductive coating, a thin conductive lead strip electrically connected to said conductive coating and also electrically connected adjacent finish wire turn of said outer layer of said section, and a second elongated strip of insulating material disposed between each said static shield and the corresponding outer layer of wire turns and having its longitudinal side edges folded over a short distance in the lateral direction to provide a long creep path between static shields of adjacent primary winding sections.

Claim 9

In an electrical distribution transformer having primary and secondary windings wherein said primary winding includes a plurality of adjacent primary winding sections each of which includes a plurality of radially superimposed helical layers of electrical wire turns, a static shield for each primary winding section comprising an elongated first strip of thin insulating material wound in overlaying relation to the outer layer of wire turns of said primary winding section and having a conductive coating on the surface thereof away from said outer layer and having both longitudinal edges folded over and flattened so that said insulating material is exposed on the outer surface of said shield, an insulation envelope wrapped around said first insulating strip carrying said conductive coating, a thin conductive lead strip electrically connected to said conductive coating and also electrically connected adjacent finish wire turn of said outer layer of said section, and a second elongated strip of insulating material disposed between each said static shield and the corresponding outer layer of wire turns and having its longitudinal side edges folded over a short distance in the lateral direction to provide a long creep path between static shields of adjacent primary winding sections.

Claim 10

In the combination of claim 7 wherein said static shield comprises aluminum-backed crepe paper and said insulation envelope and said second insulating strip are of kraft paper.

Claim 11

In the combination of claim 8 wherein said thin conductive lead strip is cold welded to said aluminum coating of said static shield.

Claim 12

In an electrical distribution transformer having primary and secondary windings wherein said primary winding includes a plurality of adjacent primary winding sections each of which has a plurality of radially superimposed helical layers of electrical wire turns, first and second static shields for each said primary winding section wound in overlaying and underlaying relation respectively to the outermost and innermost layers of wire turns of said primary winding section, each said static shield comprising an elongated first strip of thin insulating material having a conductive coating on the surface thereof away from the adjacent layer of wire turns and having both longitudinal edges folded over and flattened so that said insulating material is exposed on the outer surface of said shield, an insulation envelope wrapped around said first insulating strip, a second elongated strip of insulating material disposed between said static shield and the adjacent layer of wire turns and having the longitudinal side edges folded over a short distance in the lateral direction to provide a long creep path between static shields of adjacent primary winding sections, and a thin conductive lead strip connected to said conductive coating, said lead strips of said first and second shields being electrically connected to the finish and start wire turns of the associated primary winding section respectively.

Claim 13

In an electrical distribution transformer having primary and secondary windings wherein said primary winding includes a plurality of adjacent primary winding sections each of which has a plurality of radially superimposed helical layers of electrical wire turns, first and second static shields for each said primary winding section wound in overlaying and underlaying relation respectively to the outermost and innermost layers of wire turns of said primary winding section, each said static shield comprising an elongated first strip of thin insulating material having a conductive coating on the surface thereof away from the adjacent layer of wire turns and having both longitudinal edges folded over and flattened so that said insulating material is exposed on the outer surface of said shield, an insulation envelope wrapped around said first insulating strip, a second elongated strip of insulating material disposed between said static shield and the adjacent layer of wire turns and having the longitudinal side edges folded over a short distance in the lateral direction to provide a long creep path between static shields of adjacent primary winding sections, and a thin conductive lead strip connected to said conductive coating, said lead strips of said first and second shields being electrically connected to the finish and start wire turns of the associated primary winding section respectively.