Losses in iron under the action of superposed A-C and D-C excitations

Saratoga Springs, N. Y., June 25, 1925 J. D. Ball: About ten years ago I was very much interested in investigating the amount and nature of magnetic losses in iron when subjected to a superimposed a-c. and d-c. excitation. We spent three years on this investigation and collected what we could find of the data available at that time. All the results showed quite conclusively that for a given flux change due to alternating current, there was a definite increased loss in the hysteresis if d-c. flux was superimposed upon it, and the greater the superimposed d-c. excitation, the greater the loss. The same conclusion was verified by experiments made at the United States Bureau of Standards, at the Pittsfield Laboratory of the General Electric Company, and also by tests made in the Standardizing Laboratory of the General Electric Company at Schenectady. The results from the various publications studied led us to the same conclusions.