Losses in Iron Under the Action of Superposed Alternating- and Direct-Current Excitations

The paper presents the results of wattmeter measurements of iron loss in a small experimental reactor designed for a-c. and d-c. excitations. All the resistances were measured by the d-c. voltmeter-ammeter method, and the I² R losses were subtracted from the total wattmeter readings. A-c. core losses are plotted against d-c. excitation for various a-c. flux densities. These curves were checked qualitatively by means of hysteresis loops taken with a special bilateral oscillograph. All results show a comparatively small change in core loss as d-c. excitation is added, the core loss even showing a decrease when the a-c. saturation is high. The core loss proper is distinguished from the double frequency circulating current copper loss, and means are given for decreasing this I² R loss.