ABSTRACT
A dry-type transformer is one in which the insulating medium surrounding the winding assembly is a gas or dry compound. Many perceptions of dry-type transformers are associated with the class of design by virtue of the range of ratings or end-use applications commonly associated with that form of construction. The history of dry-type transformers can be traced to demonstration of the principle of electromagnetic induction and development of ac lighting systems. In 1885, Stanley designed closed-core transformers subsequently modified by Oliver Shallenberger and Albert Schmid making manufacturing of transformers easier and inexpensive, defining the basic principles for transformer design. General practice is to seal or coat dry-type transformer windings with resin or varnish to provide protection against adverse environmental conditions that can cause degradation of transformer windings. Winding-temperature rise in dry-type transformers is more sensitive to the magnitude and distribution of eddy current loss within the winding.
