AC loss measurements of a high critical temperature superconductor transporting sinusoidal or non-sinusoidal current

In electrical engineering, static converters generate harmonics; consequent ly the losses in the conductors increase. To use High-Tc superconductors fo r current transportation, it is important to evaluate and to measure their losses. Under the assumption that the superconductor is only exposed to its self-field, Bean's model is used to compute these losses. This work deals with the losses in a cylindrical High-Tc superconductor current-lead. It is made of compacted composite of Bi-Pb-Sr-Ca-Cu-O-2223, the value of its cri tical current is about 100 A (measured with 1 mu V/cm criteria). Two types of measuring methods are used. The first of them uses a differential amplif ier associated with a computer, which calculate the instantaneous power by numerical integration. The second series of experiments, valid only with si nusoidal current, are made using a lock-in amplifier measuring the R,M,S, v oltage. The value of transport current is high enough to be compatible with applications, Both methods give nearly the same results for sinusoidal sig nal. Measurements are made with non-sinusoidal current, to do that the supe rconductor sample is fed by a dimmer switch, The experiments show that the losses are essentially a function of the maximum value of the current, not of the firing angle, We conclude that the shape of the current is not impor tant compared to its peak value.