Design of a Race-Track Coil For Measurements of Ac Power Losses in High-Temperature Superconducting Tapes

Abstract

One of the most important parameters, crucial to applications of superconductors in cryo-electrotechnique, is power loss. Measurements of losses in superconducting long sample wires require AC magnetic fields of a special geometry and appropriate high homogeneity. In the paper part of the theoretical basis for calculations and a simple design method for a race-track coil set are presented. An example of such home-made coils, with a magnetic field uniformity of about 0.2 % over the range of about 8 cm, is given. Also a simple electronic measurement system for the determination of AC magnetization loss in samples of superconducting tapes is presented.

Theoretical analysis on ac susceptibility measurements of superconductor tapes

“…Equations ( 19) and ( 20) obtained for the case of n = 30 are also valid for n = 15; equations ( 17) and ( 18) can be used for n = 15 if numbers of 0.03, 2.5, 0.095 and 2 are replaced by 0.025, 2.1, 0.14 and 2.2, respectively, corresponding to the two dashed lines with smaller symbols in figure 4. Since the relative errors described by equations ( 17) and (18) for n = 30 are very close to those for n = 15, differing by 0.1% ∼ at a 0 /a = 3, equations ( 17)- (20) themselves will be generally used in the following sections.…”

“…However, such a technique has to be further studied experimentally. Adequate uniform high field may be produced by a set of square-cross-sectional Helmholtz or race-track coils [9,20].…”

Hysteretic Magnetization Losses of HTSC Tapes in Coaxial AC and DC Magnetic Fields

“…The two current sources possess high dynamic of the output voltages what allows obtaining reasonably high amplitudes of the output AC current without damage of the DC current source due to overvoltage in the resonance circuit. Such electric system allows to get effective magnetic field in the form B = B DC + b 0 sin 2πft within one magnet coil [15]. 1051-8223 © 2014 IEEE.…”

AC Magnetic Measurements on Superconductors

“…(Zushi, 2004) magnetic fields are applied up to 100 mT in the range 7-245 Hz but at constant temperature (77.4 K). Recently, a race-track coil system was described (Trojanowski, 2007) for generating large AC magnetic fields with excellent field-uniformity over a 80 mm length, but the system is optimized for long superconducting tapes whose size differs from cylindrical bulk superconductors that are to be characterized in this work. Finally, an iron-core electromagnet was developed in our laboratory to generate AC magnetic fields exceeding 130 mT (Lousberg, 2009) but this maximum field can be obtained in a relatively narrow frequency window (25-30 Hz).…”