Low-power superconducting motors

Granados, X.; López, Javier E.; Bosch, R.; Bartolomé, Elena; Lloberas, J.; Maynou, R; Puig, T.; Obradors, X.

doi:10.1088/0953-2048/21/3/034010

Cited by 22 publications

(16 citation statements)

References 18 publications

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“…6. It is shown that the mitigation effect during the applied timevarying field stage (second stage) contributed by the ferromagnetic surface shield is relatively large when B ex = 0.1 T, compared with the case where B ex = 0.3 T. The mitigation performance of the ferromagnetic surface shield is a passive effect, which means if the magnitude of applied field is below the saturation field and the final trapped field near the ferromagnetic surface is relatively high, the enhancement performance will be also high as shown in equation (5):…”

Section: B Surface Shieldingmentioning

confidence: 99%

“…arge, single-grain (RE)BCO high-temperature superconducting (HTS) bulk materials have great potential to trap high magnetic fields of over 17 T below 30 K [1], [2] and up to3 T at 77 K [3]. More compact and high-performance applications can be realized by using HTS bulks [4][5][6][7][8][9][10][11], but in practical applications these can be exposed to time-varying magnetic field perturbations. Since this phenomenon affects the magnetic field trapped in the bulks to a large extent, the overall efficiency and performance can be limited.…”

Section: Introductionmentioning

confidence: 99%

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Mitigation of Demagnetization of Bulk Superconductors by Time-Varying External Magnetic Fields

Zeng

Ainslie

et al. 2016

IEEE Trans. Appl. Supercond.

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Large, single-grain high-temperature superconducting (HTS) bulks have significant potential to replace permanent magnets in various engineering applications. However, based on our previous research, the trapped field in a bulk superconductor can be attenuated or even erased when a bulk is subjected to a time-varying, external magnetic field. Therefore, it is important to develop a method to protect bulks from demagnetization by (a) improving the thermal conduction of the bulk and/or (b) reducing AC losses. Improvement in the thermal conduction of bulks involves modification of the material fabrication process, which may have a detrimental effect on its superconducting properties. Employing shielding materials around a bulk helps to decrease the AC losses, but also provides a durable way to maintain the original material properties. In this paper, two shielding cases are proposed and evaluated numerically: ringshaped shielding with a copper coil, and surface shielding with a ferromagnetic material. Based on the numerical modelling results, the ring-shaped coil works well for externally applied AC fields of larger magnitude and higher frequency. However, the ferromagnetic material was preferable for surface shielding for relatively lower fields. Finally, an optimal shield design is presented.

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Section: B Surface Shieldingmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Mitigation of Demagnetization of Bulk Superconductors by Time-Varying External Magnetic Fields

Zeng

Ainslie

et al. 2016

IEEE Trans. Appl. Supercond.

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“…The common point of the investigations mentioned above is that they refer usually to a relatively "low" number of transverse ac cycles (typically up to 100-1000) with a "large" amplitude (typically from 0.1 Hp to several times Hp, where Hp denotes the full-penetration field). In applications such as magnetic bearings and brushless ac machines [46][47][48][49][50][51][52], however, the transverse fields of small amplitude are applied repeatedly for a long time. This is precisely the regime studied in the present work.…”

Section: Introductionmentioning

confidence: 99%

Measurements on magnetized GdBCO pellets subjected to small transverse ac magnetic fields at very low frequency: Evidence for a slowdown of the magnetization decay

Fagnard

Kirsch

Morita

et al. 2015

Physica C: Superconductivity and its Applications

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Due to their ability to trap large magnetic inductions, superconducting bulk materials can be used as powerful permanent magnets. The permanent magnetization of such materials, however, can be significantly affected by the application of several cycles of a transverse variable magnetic field. In this work, we study, at T = 77 K, the long term influence of transverse ac magnetic fields of small amplitudes (i.e. much smaller than the full penetration field) on the axial magnetization of a bulk single grain superconducting GdBCO pellet over a wide range of low frequencies (1 mHz -20 Hz). Thermocouples are placed against the pellet surface to probe possible self-heating of the material during the experiments. A high sensitivity cryogenic Hall probe is placed close to the surface to record the local magnetic induction normal to the surface. The results show first that, for a given number of applied triangular transverse cycles, higher values of dBapp/dt induce smaller magnetization decays. An important feature of practical interest is that, after a very large number of cycles which cause the loss of a substantial amount of magnetization (depending on the amplitude and the frequency of the field), the rate of the magnetization decay goes back to its initial value, corresponding to the relaxation of the superconducting currents due to flux creep only. In the amplitude and frequency range investigated, the thermocouples measurements and a 2D magneto-thermal modelling show no evidence of sufficient self-heating to affect the magnetization so that the effect of the transverse magnetic field cycles on the trapped magnetic moment is only attributed to a redistribution of superconducting currents in the volume of the sample and not to a thermal effect.

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“…Highly sensitive magnetic measurement systems, such as in a biomagnetic imaging device, need efficient magnetic shields for reducing the effects of the external magnetic disturbances [4,5,6]. Powerful magnets are required in magnetic bearing systems, where they produce large levitation forces [7,8], or in rotating machines, where they produce a large torque on the shaft [9,10,11].…”

Section: Introductionmentioning

confidence: 99%

Numerical simulation of the magnetization of high-temperature superconductors: a 3D finite element method using a single time-step iteration

Lousberg

Ausloos

Geuzaine

et al. 2009

Supercond. Sci. Technol.

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Abstract.We make progress towards a 3D finite-element model for the magnetization of a high temperature superconductor (HTS): We suggest a method that takes into account demagnetisation effects and flux creep, while it neglects the effects associated with currents that are not perpendicular to the local magnetic induction. We consider samples that are subjected to a uniform magnetic field varying linearly with time.

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Low-power superconducting motors

Cited by 22 publications

References 18 publications

Mitigation of Demagnetization of Bulk Superconductors by Time-Varying External Magnetic Fields

Mitigation of Demagnetization of Bulk Superconductors by Time-Varying External Magnetic Fields

Measurements on magnetized GdBCO pellets subjected to small transverse ac magnetic fields at very low frequency: Evidence for a slowdown of the magnetization decay

Numerical simulation of the magnetization of high-temperature superconductors: a 3D finite element method using a single time-step iteration

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