Coil body

A coil body comprising:

• a rectangular hollow core having an outer surface and having first and second spaced axial walls projecting outwardly from the core surface around all four sides of the core substantially equidistantly from the outer surface, the projections being substantially to a first distance from the core outer surface, a first additional wall parallel to and closely spaced from the first wall projecting from the core outer surface to substantially the first distance around at least three sides of the core and substantially to at least the first distance on the fourth side of the core to create a first space between the first additional wall and the associated first wall, a second additional wall intermediate the first and second walls projecting from the core outer surface substantially equidistantly around the core to substantially the first distance to divide the area between the first and second walls and the primary and secondary winding areas, a third additional wall projecting from the outer surface parallel and closely spaced to the second additional wall to create a second space therebetween, the third additional wall projecting to substantially the first distance around three sides of the core and projecting to a second distance, greater than the first distance on the fourth side of the core, the projection on the fourth side being uninterrupted from the core's outer surface to the second distance, the second distance being greater than the first distance by an amount sufficient to establish a reverse path around the third additional wall on the fourth side at least equal to a minimum creepage between the primary and secondary winding areas, established for a transformer to be constructed from said coil body, said second distance being less than the amount necessary to establish a minimum creepage path therearound a single channel cap member having a top and two legs projecting from the top at right angles thereto with axially spaced inturned wall portions of the top and leg portions, the inturned wall portion sides being spaced from one another equal to the axial distance between the first and second spaces and having a thickness dimensioned to be received in the first and second spaces, said cap assembled onto the coil body with the inturned end wall portions received in the spaces on the three sides of the core where the third additional wall projects to substantially the first distance and with the top and two legs of the cap covering the area around the core for at least one of the primary and secondary winding areas on said three sides, the fourth side of both primary and secondary winding areas being open and not covered by a cap whereby the creepage path length on the fourth side is established solely by the projection of the third additional wall to the second distance and the coil body axis length between the primary and secondary winding areas, the top of the cap lying on the side of the coil body opposite the third wall projection to the second distance.