The effects of magnetic field oscillations on losses in superconducting composites

In the design of an ac generator which uses a superconducting field winding, it is essential to know the power losses likely to occur as the result of the time-varying fields produced by the loading and fault conditions during operation. The ac losses of a variety of multifilamentary wire samples have been measured under self-field conditions with no external field and under the conditions of a small alternating field superimposed on a large dc bias field. Both the isothermal calorimeter or helium boil-off method and the magnetization technique were used for the measurements. A comparison of the experimental results with the known theories is presented.