Theoretical and experimental study of AC loss in high temperature superconductor single pancake coils

Abstract

The electromagnetic properties of a pancake coil in AC regime as a function of the number of turns is studied theoretically and experimentally. Specifically, the AC loss, the coil critical current and the voltage signal are discussed. The coils are made of Bi 2 Sr 2 Ca 2 Cu 3 O 10 /Ag (BiSCCO) tape, although the main qualitative results are also applicable to other kinds of superconducting tapes, such as coated conductors. The AC loss and the voltage signal are electrically measured using different pick up coils with the help of a transformer. One of them avoids dealing with the huge coil inductance. Besides, the critical current of the coils is experimentally determined by conventional DC measurements. Furthermore, the critical current, the AC loss and the voltage signal are simulated, showing a good agreement with the experiments. For all simulations, the field dependent critical current density inferred from DC measurements on a short tape sample is taken into account. 1 In fact, this condition is not strictly sufficient. The external field must be much larger than the self field of a stack made of as many tapes as those in the radial direction when the radial field dominates the AC loss (and equivalent with the axial direction when the dominant is the axial field).

Modeling and comparison of superconducting linear actuators for highly dynamic motion

“…It should be noted that these parameters can all vary with the operating temperature. The obtained parameter values are similar to those found in the literature [19] In this study, only the losses in the superconducting layer are considered. The instantaneous power loss P, in the volume of the superconducting tapes, is calculated as…”

Magnetic Field in the Winding of an YBCO Pancake Coil: Experiments and Calculations

“…We calculated the current distribution and the AC loss in the coil by means of the Minimum Magnetic Energy Variation (MMEV) method, as we did in [9], [10]. This method takes into account the hysteresis of the current distribution, the actual aspect ratio of the superconducting layer, non-uniform critical current density, , a depending on the magnetic field and the orientation angle , , and any combination of DC or AC applied magnetic field and transport current in each superconducting tape.…”

“…We extract from measurements of the critical current in an applied magnetic field. For this, we adjust a realistic formula for in such a way that the difference between the calculated in-field critical current and the measured one is minimum for a set of measured B and , as we did in [10]. For the simulation in this article, we take the measured data for a 4 mm wide tape with similar properties as the 12 mm wide tape of the coil.…”

Power Losses of 2G HTS Coils Measured in External Magnetic DC and Ripple Fields

“…Other researchers are focused on AC losses in racetrack or pancake coils e.g. [15][16][17] or in HTS generators as a whole 18 . The most important factor for superconducting generator or motor applications is to know AC losses (stator) and power losses in the rotor.…”