Relation between radial stress and quench current for tightly wound dry solenoids

Urata, M.; Maeda, Hideaki

doi:10.1109/tmag.1987.1065028

Cited by 21 publications

(10 citation statements)

References 6 publications

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“…The radial stress distribution in an epoxy impregnated double pancake coil due to winding, cool down, and Lorentz force has been numerically analyzed. [9][10][11][12] Each of the coil form, conductor and insulator layers is regarded as an infinitely long thin cylinder, contacting elastically each other. Continuity of the radial-displacement and radial-stress at the interfaces gives a set of simultaneous equations, which is solved numerically.…”

Section: Structural Analysismentioning

confidence: 99%

“…A similar scenario is applicable to the Lorentz force; if the cumulative radial stress due to winding, cool down and Lorentz force exceeds the critical transverse stress, typically +10 MPa, the YBCO-coated conductor is delaminated instantly and thus the coil voltage jumps abruptly, as seen in the coil quenching of low temperature superconducting magnets. [9][10][11][12][13] In the next coil charge, the coil current for the superconducting-normal transition will be significantly reduced.…”

Section: Structural Analysismentioning

confidence: 99%

“…Arp [9], Williams and Bobrov [10], and Urata and Maeda [11] [12] demonstrated that coil winding, cool down and Lorentz force result in a radial-stress distribution in a circular coil such as a solenoid or double pancake [13]. The radial stress in a circular coil corresponds to the transverse stress applied to the YBCO-coated conductor.…”

Section: Introductionmentioning

confidence: 99%

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Degradation of the performance of a YBCO-coated conductor double pancake coil due to epoxy impregnation

Takematsu

Takao

et al. 2010

Physica C: Superconductivity and its Applications

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259

140

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Now that YBCO-coated conductors have been commercialized, a number of YBCO coils have been developed. However, their basic performances have not been systematically investigated so far. Here, we demonstrate that of a YBCO double pancake coil. The critical current of an epoxy impregnated YBCO double pancake coil was substantially degraded, i.e. the normal voltage appears above 8 A, only 18 % of that for the dry coil. It was inferred that degradation occurs if the cumulative radial stress developed during cool down exceeds the critical transverse stress for the YBCO-coated conductor (typically 10 MPa). Under these conditions, the conductor was debonded at the interface between the buffer layer and YBCO layers, or fractured in the YBCO layer itself, causing cracks on the YBCO layer, resulting in a significant decline of the critical current. These negative effects are suppressed if the coils are dry wound or impregnated with paraffin, as the bonding strengths between turns are negligible and therefore turns are separated if the cumulative radial stress tends to be tensile. For non-circular coils in which epoxy impregnation is inevitable, degradation due to cumulative tensile transverse stress is still the major problem.

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Section: Structural Analysismentioning

confidence: 99%

Section: Structural Analysismentioning

confidence: 99%

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Degradation of the performance of a YBCO-coated conductor double pancake coil due to epoxy impregnation

Takematsu

Takao

et al. 2010

Physica C: Superconductivity and its Applications

Self Cite

259

140

View full text Add to dashboard Cite

show abstract

“…The shear stress is principally responsible for premature quench, which might cause fracture of epoxy resin in the coil winding and then part of the strain energy to convert into heat [6]. Slip planes in a superconducting magnet, which allow the coil package to slide relative to the mandrel, are helpful to change the contact conditions so as to reduce the shear stress [7].…”

Section: Introductionmentioning

confidence: 99%

Effects of Slip Planes on Stresses in MICE Coupling Solenoid Coil Assembly

Wang¹,

Pan

et al. 2010

IEEE Trans. Appl. Supercond.

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Abstract-The MICE superconducting coupling solenoid magnet is made from copper matrix Nb-Ti conductors with inner radius of 750 mm, length of 285 mm and thickness of 110.4 mm at room temperature. The coil is to be wound on a mandrel made of aluminum. The peak magnetic field on the conductor is about 7.3 T when fully charged at 210 A. High magnetic field and large size make the stress inside the coupling coil assembly relatively high during cool down and full energizing. The shear stress between coil winding and aluminum casing may cause premature quench. To avoid quench potential induced by stress, slip planes were designed for the coil assembly. In this paper, FE models with and without slip planes for it have been developed to simulate the stresses during the process including winding, cooling down and charging. The stress distribution in the coil assembly with and without slip planes was investigated. The results show that slip planes with low friction coefficients can improve the stress condition in the coil, especially reduce the shear stress largely so that improve the stability.

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“…According to Burwell and Rabinowicz the descending portion of the friction-velocity curve is caused by a velocity-dependent decrease in the effective interfacial contact area. Increasing sliding speeds to the right of the friction peak reduce the corresponding asperity contact time and change the junctions' shear deformation modefrom ductile fracture to brittle failure [18].…”

mentioning

confidence: 99%

Cryotribology: Development of cryotribological theories and application to cryogenic devices

Iwasa¹,

Michael²,

Rabinowicz³

1992

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Relation between radial stress and quench current for tightly wound dry solenoids

Cited by 21 publications

References 6 publications

Degradation of the performance of a YBCO-coated conductor double pancake coil due to epoxy impregnation

Degradation of the performance of a YBCO-coated conductor double pancake coil due to epoxy impregnation

Effects of Slip Planes on Stresses in MICE Coupling Solenoid Coil Assembly

Cryotribology: Development of cryotribological theories and application to cryogenic devices

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