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A procedure for determining the electrical resistivity of anisotropic materials is presented. It offers several improvements to the well-known Montgomery method. One improvement, in particular, is the ability to obtain the electrical resistivity for all three axes of an orthorhombic crystal analytically, rather than using the iterative approach suggested by Montgomery for the third axis. All necessary equations are derived and their application in determining the tensor components of the electrical resistivity is explained in detail. Measurements on isotropic specimens were executed in order to test the foundations of the method. Measurements on anisotropic samples are compared with measurements obtained by using the standard four-probe method, revealing good agreement. [ABSTRACT FROM AUTHOR]

This paper presents the design, manufacturing and test results of HTS coils for single-phase resistive current limiters using two different Bi-2223/Ag tapes. Two coils were separately wound on cylindrical G-10 tubes with helical path. One of the coil was wound in a bifilar conductor arrangement aiming at reducing the self-inductance. The maximum flux density is 40 mT on the HTS tape for both coils and the calculated inductance is 5.76 μH for the noninductively wound coil and 28.3 μH for the conventional one. The two coils were individually tested under DC and AC currents. The DC power loss was calculated from the measured voltage-current values product and the AC power loss was determined by the liquid nitrogen mass boil-off measurement. The acquired voltage AC waveforms were analyzed through the separation of distinct contributions due to magnetic flux and to a resistive component in-phase with the current. It was observed an inflection point common to the DC and AC power losses curves close to Ic attributed to the AC transition current. [ABSTRACT FROM AUTHOR]

This paper presents a mathematical method to quickly calculate the flux density vector B produced by the current circulating in a resistive single-phase superconducting electrical current limiter (RSCL), at any point of its whole space, using the Biot-Savart's Law. As the calculation using the exact form of the turns of each coil (single layer cylindrical coil with helicoidal form presenting voids (free space) between neighbor turns) is computationally very cumbersome to be used in a RSCL dynamic simulator, it is proposed in this paper to substitute the real coil, only for the subject of the calculation, by an imaginary coil formed by plane closed circular turns with the same number of turns, the same height and radius as the real coil. Each turn of the imaginary coil is placed exactly in the medium position between successive turns of the actual coil and will carry the same current. The coil self-inductance is also calculated to verify the accuracy of the proposed method. [ABSTRACT FROM AUTHOR]

A very accurate mathematical method, named Helicoidal Method, to calculate the flux density vector B produced by the current circulating in the resistive single-phase superconductor electrical current limiter (RSCL) coils, at any point of the its whole space, using the Biot-Savart's Law is presented in this paper. It is very important to remember that these coils are single layer concentric cylindrical coils with voids (free space) between its neighbor turns which turns present helicoidal form. The calculation of the vector B, at any point of the space of the coils, is used in the dynamic simulation of the RSCL for design and operation purposes, but it is also used to calculate the self-inductance of each electrical current limiter coil and the mutual inductance between each pair of coils, which are necessary to determine the equivalent impedance of the RSCL. To verify the proposed method accuracy the self-inductance of three different coils, made with copper wire, are calculated, measured and the results are compared. [ABSTRACT FROM AUTHOR]