Abstract: A transformer comprising a core, a primary winding and a secondary winding in which one of the windings, preferably the winding with the least coils, is formed from a tubular member formed in a plurality of coils in the preferred embodiment of a step down transformer, the secondary winding is formed from a tubular member. A connector block at each end of the secondary winding includes an appropriate fluid passage and means for connecting a fluid coupling to the block so that the inlet and outlet of the fluid circulation system can be secured to the tubular member forming the secondary winding. The connector blocks also include threaded apertures adapted to receive the bolt for providing an electrical connection to an electrical apparatus such as a welding gun. The loops of the primary coil are interdigitally arranged with the loops of the secondary coil so that the fluid in the secondary coil absorbs heat from both the primary and secondary windings.

Abstract: A transformer for electric welders, especially welders having a welding gun secured to a robot arm, comprises a small lightweight loop core having first and second substantially C-shaped sections abutted together at their free ends with primary and secondary windings coaxially wrapped about one pair of abutting shanks. The secondary winding comprises an elongated flat sheet wrapped around abutting shanks of the core and has projecting tabs extending from opposite sides of the sheet. A primary winding comprising a plurality of coil sections is coaxially wrapped about the secondary winding whereby the secondary winding is substantially entirely coupled to the primary winding. The windings are encapsulated in a dielectric material such as a synthetic polymer resin. The transformer is preferably connected to a high frequency electrical power source.