A theoretical expression for the hysteresis loss in a transverse AC magnetic field with a large amplitude of trapezoidal wave form is derived for a bronze-processed Nb3Sn multifilamentary superconducting wire with a Nb barrier protecting Cu stabilizer from Sn diffusion.
The present expression shows a quantitative agreement with our observed results over the whole range of the amplitude of the applied AC magnetic field up to near Hc2. It is to be emphasized that the values of pinning parameters adopted to estimate the values of hysteresis losses are the same as used in our previous paper to explain quantitatively the hysteresis losses when an AC magnetic field of a small amplitude is superposed to a DC bias magnetic field. Hence the hysteresis losses of a bronze-processed Nb3Sn multifilamentary superconducting wire with a Nb barrier can be described systematically over the whole range of the magnetic field by means of the modified Irie-Yamafuji model for the critical current density, if we take into account that the value of the critical current density contributing to the magnetization is usually larger than that estimated from resistive measurements.
It is also pointed out that the theoretical expressions for the hysteresis losses used frequently so far give rise to smaller values than the present expressions by a factor of more than 2, and are not adequate for a quantitative description of the hysteresis losses.
The present expressions for the hysteresis losses can also be applied to a bronze-processed Nb3Sn multifilamentary superconducting wire with a Ta barrier in which any superconducting layer is not produced.
