Determination of the Complete Penetration Magnetic Field of a HTS Pellet From the Measurements of the Magnetic Field at Its Top-Center Surface

Abstract

Abstract-In previous papers a new method to characterize HTS pellets has been presented This method is based on the measurement of their complete penetration magnetic flux density BP. It allows determining the critical current density JC and the nvalue of the classical power law model. In this paper, a method of determination of BP of a unique HTS pellet from the measurements of the magnetic field at its top-center surface is presented. This is a simpler and cheaper method than previous methods. It uses analytical calculation based on Biot and Savard law and numerical calculation based on power law. The maximum magnetic flux density produced by the SC pellet BZSCM is deduced from the measurement. BP is deduced from BZSCM multiplying it by a coefficient analytically calculated. The influence of JC(B) on this method is presented and analyzed.  Index Terms-Superconductors, magnetic field diffusion, critical current density.

2-D Numerical Modeling of a Bulk HTS Magnetization Based on <bold>H</bold> Formulation Coupled With Electrical Circuit

“…with E c = 1 µV/cm. At liquid nitrogen temperature, the parameters J c = 100 A/mm 2 and n = 21 correspond to reasonable values found in the literature [11]. When the bulk becomes fully penetrated by current and if its magnetization M = B/µ 0 −H is weak compared to the huge applied external magnetic field, it can be assumed that the superconductor behaves like air with also µ r = 1.…”

“…Surprisingly, from the point of view of the coil and the waveform of the current, modeling the bulk region with the power law (1) and J c = 100 A/mm 2 corresponds to almost the same case than air. This result can be explained since the applied field is largely greater that the penetration field B PB [11]. Finally, modeling the bulk region with copper leads to a different waveform of the current with a peak current of 4.6 kA and a time constant of 0.38 ms, between the air and diamagnetic cases.…”

“…The space between the bulk and the coil is 1 mm and marked as e. The cross-section of the coil is subdivided in three regions, further called 'rings', in order to improve the calculation of magnetic flux. The process of magnetization needs to produce a sufficient external magnetic field greater than the penetration field B PB [11], thus the magnetizing coil, also called inductor, must be coupled with a suitable magnetizer. The available capacitor bank is capable of accumulating 10 kJ of energy with a repetitive maximum current of 25 kA.…”

Characterization of High-Temperature Superconductor Bulks for Electrical Machine Application

“…In the last few l years, we proposed a new direct magnetic determination method for JC and n-value consists of the determination of the complete penetration magnetic field BP and a dedu tion of the critical current density JC. This new method is original, quick, and direct determining the critical current density Jc and n-value in bulk superconductors from ma netic field diffusion measurements [18][19][20][21]. Experimental characterization of large-s samples is a tricky issue.…”

“…where L is the length of the cylinder and R is its radius. Equation ( 2) is the equivalent of the B p formula given by different authors [18][19][20][21].…”