Conductor Material Properties Research Articles

90-mm/18.8-T All-HTS Insert Magnet for 1.3 GHz LTS/HTS NMR Application: Magnet Design and Double-Pancake Coil Fabrication.

This paper deals with the latest design of an all High Temperature Superconductor (HTS) insert for our 1.3 GHz NMR program. Due to a loss of our original 600 MHz HTS insert, the entire program was revised, and upon further examination of the options available for the HTS insert, which included not only conductor material properties, but also new winding technologies recently developed here at the FBML, it has finally been decided to build an 800 MHz (H800) insert purely based in SuperPower YBCO conductor. The new H800 will still be comprised of nested stacks of double-pancake coils and will run in the background of a 500 MHz LTS NMR magnet already available at FBML. We present here electromagnetic and mechanical details of the H800 design, winding technique employed, and testing of individual coils.

A proposed algorithm for an overhead transmission line conductor temperature rise calculation

SUMMARY The work carried out in this paper is to deal with a proposed conductor temperature rise computation algorithm. This simple algorithm gives more accurate calculation, making use of the load current and the weather data parameters, particularly the amount of solar incidental radiation upon the conductor and the conductor material properties. The calculation is based on the heat transfer mechanisms occurring in the stranded exposed overhead transmission lines (OHTL) conductors in a natural environment. In this paper, the mathematical models for the use of the natural and forced convections are presented by using Numbers of Grashof and Reynolds, respectively, in the determination of the temperature rise of the OHTLs. Skin effect and iron losses are also taken into account in order to determine the alternating current resistance of an Aluminium Conductor Steel Reinforced in the process of iteration's heat balance equation. The surface area factor of the stranded conductors that increases the loss by radiation from the conductor surface is also used to calculate the temperature rise of the stranded OHTL. Copyright © 2012 John Wiley & Sons, Ltd.

Testing of NCSX Composite Coil Material Properties

The National Compact Stellarator Experiment (NCSX) is now in design and requires 18 modular coils that are constructed to a highly complex geometry. The modular coil conductors are designed as a composite of a fine gauge stranded copper cable shaped to the required geometry and vacuum impregnated with a resin. These composite conductors exhibit unique material properties that must be determined and verified through testing. The conductor material properties are necessary for design modeling and performance validation. This paper will present the methods used to test and measure the coil conductor material properties, the unique challenges in measuring these complex materials at both room and liquid nitrogen temperatures and the results of those tests.

Stability of a poloidal field coil in rapidly changing magnetic fields

A poloidal field model coil of 3 m in diameter was designed and built according to the following specifications: stability was required during an exponential field variation of /spl Delta/=0.4 T with a time constant of 5 ms, corresponding to a maximum field change of 80 T/s. The superconducting cable developed for this purpose was tested in a short sample experiment, yielding a stability limit beyond this requirement. The test results of the model coil are in good agreement with the stability limit expected from the cable experiment. They can be explained in terms of a simple stability model which compares the energy input due to coupling losses with the transient heat removal capability of supercritical helium. A more detailed stability calculation was performed with a computer code taking into account the temperature dependence of helium and conductor material properties. The coil reached the stability limit expected from the measured cable parameters and showed no unexpected ramp rate limitations.