Measurement methods of AC losses in HTS bulk

HTS bulk can trap higher magnetic field than a permanent magnet, and non-contact magnetic bearings, electric motors and magnetic levitations are promising applications. The HTS bulks in those electric machines are exposed to magnetic field perturbations, which cause AC losses in the bulks. The AC losses deteriorate not only the efficiency of the apparatuses but also the performance by decaying trapped magnetic field. Therefore, it is important to understand the AC loss characteristics. We developed an electric method to measure the AC losses in a bulk using a double pick-up coil method. In this paper, correction factors are formulated to improve the accuracy of the method and the validity of the method is investigated by comparing the data measured by the electric and calorimetric methods.