Specifying dry-type distribution transformers for solid-state applications

Existing theories, specification, and standards relating to the application of dry-type distribution transformers for solid-state applications are discussed. The criteria for selecting the proper transformer for several types of solid-state loads, such as UPSs, rectifiers, variable-speed drive systems, etc. are discussed. A significant set of computer-generated calculations that show the behavior of dry-type distribution transformers of various sizes and conductor configurations under both sinusoidal and nonsinusoidal conditions is presented. It is readily seen that improper selection of a transformer for a solid-state application may result in a serious reduction in efficiency as well as a large increase in temperature rises with detrimental effect on the expected life span of the transformer. A few experimental results from tests carried out on several transformers are presented