Review of fusion system magnet problems

Montgomery, D.B.

doi:10.1109/fusion.1989.102164

Cited by 6 publications

(2 citation statements)

References 12 publications

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“…In fact, early statistics has shown that most magnet failures are related to insulation problems [1]. Compared with insulation for low temperature superconductor (LTS), the insulation on coated conductor for high field magnet applications has special challenges.…”

Section: Introductionmentioning

confidence: 99%

Insulation of Coated Conductors for High Field Magnet Applications

Lü

Kandel

Han

et al. 2012

IEEE Trans. Appl. Supercond.

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Insulation in a high field superconducting magnet plays a critical role. For high field magnets using coated conductor, insulation faces a few special challenges. In order to maximize the engineering current density, the conductor insulation has to be very thin (e.g.). In addition to required mechanical and dielectric integrity under high stresses at cryogenic temperatures, the temperature during insulation process needs to be significantly lower than 200where degradation of coated conductor may occur.In this paper, we will first review the options for coated conductor insulation. Then we present our UV cured epoxy insulation system developed for insulating coated conductors. This reel-toreel system is able to coat YBCO tapes or co-winding steel tapes with 10 UV cured epoxy. The coating has good dielectric property and shows no cracking or de-bonding in liquid nitrogen under up to 0.75% of applied bending or tensile strains. In addition, a silica sol gel based ceramic coating system has been developed for coating oxides on steel co-winding tapes, taking advantage of excellent thermal properties of the oxides. Some issues of both UV cured epoxy and the sol gel insulation coatings will be discussed.

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Section: Introductionmentioning

confidence: 99%

Insulation of Coated Conductors for High Field Magnet Applications

Lü

Kandel

Han

et al. 2012

IEEE Trans. Appl. Supercond.

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“…where L is the inductance (H) and dI/dt is the charging rate in Ampers per second [11]. The induced voltage can lead to electric short circuits within the windings of the magnet coil that can be prevented by applying turn-to-turn electrical insulation in the magnet coil.…”

Section: Introductionmentioning

confidence: 99%

Development of TiO₂electrical insulation coating on Ag-alloy sheathed Bi₂Sr₂CaCu₂O_8−xround-wire

Kandel¹,

Lü²,

Jiang³

et al. 2015

Supercond. Sci. Technol.

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We have developed TiO2 coating on Ag-alloy sheathed Bi2Sr2CaCu2O8−x (Bi-2212) round-wire conductor for electrical insulation in Bi-2212 magnets. The green coating has a base layer comprised of TiO2, polyvinyl butyral (PVB) and a small amount of polysilicate and a top layer made of polyacrylic. The coating was applied on the conductor using a continuous reel-to-reel dip coating process and showed very good adherence and flexibility that is suitable for magnet coil winding. The thickness of the coating is a function of slurry viscosity, wire withdrawal speed and wire radius. Small test coils were built with the coated Bi-2212 round-wires and were heat treated at 100 atm pressure. During the heat treatment, the PVB and polyacrylic were removed from the green coating and the polysilicate decomposed to SiO2 that served as a sintering aid for TiO2. After the heat treatment, the coating remained strongly adhered to the conductor and did not have a detrimental effect on the critical current (Ic) values. The breakdown voltage was about 150 V across a 7 μm thick heat treated coating on Bi-22112 round-wire conductor, corresponding to a dc dielectric strength of about 21 MV m−1.

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