Origin, design and development of “K” factor transformers

K is the standard measure of the ability of a transformer to withstand nonlinear loads. Here, the author describes how dry type and liquid filled transformers can be designed to give many years of satisfactory operation even when exposed to the ever increasing nonlinear load environment. They can have all of the desirable features, like copper or aluminum windings, lower than normal full load temperature rises and indoor or outdoor enclosures. As more installations are completed and harmonic measurements taken, industry will be in a better position to specify appropriate K factor transformers for nonlinear load applications