The wound-core distribution transformer

A radically new form of core of simple structure and highly efficient performance has recently been developed. It is made by winding a long ribbon of magnetic steel in a tight spiral on a mandrel into the form of a heavy-walled circular cylinder. This core construction has been designated as the "wound core." It eliminates or minimizes most of the objections inherent in other types. (a) The flux runs with the grain direction throughout. All material in the core is active material. (b) There is but one effective gap in the magnetic circuit and this is of very short length and large area. (c) Only one or two pieces of strip steel are necessary to make the average small core. These are prewound and assembled on machines at high speed. (d) The waste in handling and fabrication is very small since each element is simply cut from large reels of continuous strip made to correct width at the mill. It is the purpose of this paper to describe its present application to distribution transformers.