Performance and Quench Characteristics of a Pancake Coil Wound With the 2G YBCO Roebel Cable

Abstract

Abstract-The YBCO Roebel cable is a promising option for the high-energy accelerator magnets and tokamak devices with high-current carrying capability and compactness. Referring to the complex current sharing and normal zone propagation, it is difficult to apply the traditional superconductor quench measurement methodology to such a long Roebel cable (2 m) in an adiabatic condition. An alternative method for the quench measurement is to make a Roebel pancake coil cowound with ribbon fiberglass. This paper starts reporting the methodology to wind the coil with impregnation process and the wire installment for the quench measurement. Some initial performance measurements and a first trial of the quench measurement were processed in LN2 at 77 K to show the robust performance of this Roebel cable at all the current contacts while maintaining the cable effectively adiabatic or similar to real magnets.Index Terms-Roebel cable, pancake coil, high temperature superconductors, quench measurement.

Characterization of HTS Coils for Superconducting Rotating Electric Machine Applications: Challenges, Material Selection, Winding Process, and Testing

“…Weak and damaged points that can occur along the tape length during the coil assembling process trigger a partial quench or lead to a full coil quench. In addition, usually hotspots initiate in such weak points over time and could burn the insulation or cause some other electro-thermal stresses [33,34]. These rapid electro-thermal transients lead to a quench due to low heat transfer in the internal turns which are unable to dissipate the amount of heat accumulated [2,25].…”

“…To distinguish one coil from another, each coil is identified by a three-point code indicator, respectively: HTS tape manufacturer (Su, SP, Am); core configuration (F, M) and material (G, S); turns number (26,34). After the winding process, to suppress mechanical vibration, all coils were fixed by cryogenic tape symmetrically distributed over the perimeter of the coil.…”

“…Considering instead the I op /I c = 0.4 parameter, at the same turns number (34), configuration (Fixed) and core material, SP coils show slightly lower losses than Su coils: SP_FG = 0.25 W and SP_FS = 1.2 W; Su_FG = 0.4 W and Su_FS = 1.5 W (see Fig. 5).…”

Quench in a pancake coil wound with REBCO Roebel cable: model and validation

“…The model was configured to represent the REBCO Roebel coil used in the experimental study [18,19] for comparison and validation.…”

“…However, quench measurements at liquid nitrogen temperature have not extensively been performed and require further investigations, given the considerably different working conditions, in terms of material properties (specific heat, thermal and electrical conductivities of the materials) and temperature margin with respect to the current sharing temperature. To this purpose, a dedicated experiment was performed at the University of Southampton with a heavily instrumented Roebel cable [18,19].…”