Characterization of YBCO bulk superconductors for 100 kWh flywheel

Matsunaga, Kentaro; Yamachi, N.; Tomita, Masaru; Murakami, Masato; Koshizuka, N.

doi:10.1016/s0921-4534(03)01014-1

Cited by 10 publications

(6 citation statements)

References 6 publications

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“…In some applications, however, the bulk superconductor may experience periodic variations of the applied magnetic field that are caused, for example, by vibrations or irregular magnetization by a permanent magnet interacting with the sample [15,16]. The resulting hysteresis losses caused by the associated vortex motion may induce a temperature increase of the superconductor [17,18], which, in turn, reduces the critical current density and has a detrimental effect on the flux trapped in the material [19][20][21][22][23][24][25][26][27][28].…”

Section: Introductionmentioning

confidence: 99%

“…Bulk melt-processed Y-Ba-Cu-O (YBCO), high temperature superconductors (HTS) are usually fabricated in disc or cylindrical geometries for various permanent magnet-like applications [1,2], such as rotating machines [3][4][5][6] or magnetic bearings [7][8][9][10], due to their ability to trap large magnetic inductions [11][12][13][14]. In some applications, however, the bulk superconductor may experience periodic variations of the applied magnetic field that are caused, for example, by vibrations or irregular magnetization by a permanent magnet interacting with the sample [15,16]. The resulting hysteresis losses caused by the associated vortex motion may induce a temperature increase of the superconductor [17,18], which, in turn, reduces the critical current density and has a detrimental effect on the flux trapped in the material [19][20][21][22][23][24][25][26][27][28].…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Self-heating of bulk high temperature superconductors of finite height subjected to a large alternating magnetic field

Laurent¹,

Fagnard²,

Babu³

et al. 2010

Supercond. Sci. Technol.

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Abstract. In this work we study, both experimentally and numerically, the self-heating of a bulk, large YBCO pellet of aspect ratio (thickness / diameter) ~ 0.4 subjected to a large AC magnetic field. To ensure accurate temperature measurements, the sample was placed in an experimental vacuum chamber to achieve a small and reproducible heat transfer coefficient between the superconductor and the cryogenic fluid. The temperature was measured at several locations on the sample surface during the self-heating process. The experimentally determined temperature gradients are found to be very small in this arrangement (< 0.2 K across the radius of the superconductor). The time-dependence of the average temperature T(t) is found to agree well with a theoretical prediction based on the one-dimensional (1-D) Bean model, assuming a uniform temperature in the sample. A 2-D magneto-thermal model was also used to determine the space and time-dependent temperature distribution T (r, z, t) during the application of the AC field. The losses in the bulk pellet were determined using an algorithm based on the numerical method of Brandt, which was combined with a heat diffusion algorithm implemented using a finite-difference method. The model is shown to be able to reproduce the main trends of the observed temperature evolution of the bulk sample during a self-heating process. Finally, the 2-D model is used to study the effect of a non-uniform distribution of critical current density J c (r, z) on the losses within the bulk superconductor.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Self-heating of bulk high temperature superconductors of finite height subjected to a large alternating magnetic field

Laurent¹,

Fagnard²,

Babu³

et al. 2010

Supercond. Sci. Technol.

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“…These materials are extremely promising as a competing technology for permanent magnets in several engineering applications including magnetic bearings and brushless ac machines [4]- [7]. In many topologies envisaged for designing an efficient electrical motor based on bulk superconductors, the YBCO sample is permanently magnetized parallel to its -axis and placed in the machine rotor [8], [9].…”

mentioning

confidence: 99%

“…In this configuration, the sample is likely to experience transient variations of the applied magnetic field caused by modifications of the applied torque on the shaft. In a similar way, when bulk superconductors are used in magnetic bearings, the vibration or the irregular magnetization of the permanent magnet can result in a time-varying magnetic induction [4]. The resulting vortex motion may cause large hysteresis losses and a significant temperature increase which, in turn, has a detrimental effect on the initial trapped flux [10], [11].…”

mentioning

confidence: 99%

Measurements of Thermal Effects in a Bulk YBCO Single Domain Superconductor Submitted to a Variable Magnetic Field

Laurent

Vanderbemden

Meslin

et al. 2007

IEEE Trans. Appl. Supercond.

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Abstract-When YBCO single domains are subjected to a variable magnetic field, the motion of vortices may give rise to a significant temperature increase and a degradation of the superconducting properties. We have experimentally investigated such effects in bulk melt-processed YBCO single domains. Several temperature sensors, a pick-up coil and two Hall probes were placed against the surface of a monolithic bulk YBCO pellet. Data were simultaneously recorded during the application of ac magnetic fields of various amplitudes, either with or without a pre-existing dc trapped flux. The measurement results agree well with to those obtained by numerical modeling. It was also found that a superimposed dc magnetic moment reduces the temperature increase caused by the ac magnetic field.Index Terms-High-temperature superconductors, magnetic variables measurement, thermal variables measurement.

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“…Textured Y-Ba-Cu-O bulk superconductors continue to hold promise for important new technological applications including high power density motors/generators, levitators, flywheels and fault current limiters [1][2][3]. In order to increase the performance of these devices, further improvements of both the critical current density and the size of the single domain Y-Ba-Cu-O superconductors are necessary.…”

Section: Introductionmentioning

confidence: 99%