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 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. Each loop of the secondary includes a bow so that adjacent ends of each loop of the primary are sandwiched between the bows.

Abstract: A transformer system for resistance welding intended for installation on robotic devices comprises an auto transformer having a tap selection switch connected through electrical conductors to an isolation welding transformer located at the end of the robotic arm. The auto transformer is uniquely selected for the maximum efficiency thereof and the optimum reduction in the size of the conductors between the transformers. The isolation welding transformer is also optimally sized due to the reduction permissable by the previous interposition of the auto transformer in the welding system. Moreover, the isolation welding transformer comprises primary and secondary coils formed from tubular members each of which is cooled by a fluid coolant. Utilization of refrigerated coolant permits further reduction in size and mass, and increases electrical efficiency because of the unique design of the isolation welding transformer in which both primary and secondary windings are cooled by such fluid coolant.