Design of transformers for resistance welding machines

A DISCUSSION OF transformer design and characteristics would have been a rather controversial subject 15 years ago, as in those days the name-plate kilovolt-ampere rating of the transformer meant little other than that it was printed in English. Oftentimes in the early years, if the power companies limited the maximum connected kilovolt-amperes for a particular installation, a machine was supplied with this name-plate kilovolt-ampere rating, regardless of the actual load drawn by the machine. It was rather common practice to use excessive amounts of copper in the secondaries and a very small amount of primary copper. There was no logical reason for this except perhaps that the secondaries could be seen while the primaries were covered. In general, confusion existed, no standard ratings were used, and it was extremely difficult for power companies or users to determine actual ratings and demand figures. This condition of course could not continue and several years ago the AIEE and the Resistance Welder Manufacturers´ Association (RWMA) drew up specifications for the standardization of welding transformer ratings.