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Journal ArticleDOI

Study of the Voltage Behavior of Jointless Superconducting 2G Loops During Pulse Magnetization

23 Jan 2020-IEEE Transactions on Applied Superconductivity (Institute of Electrical and Electronics Engineers (IEEE))-Vol. 30, Iss: 5, pp 1-6
TL;DR: In this paper, a 2G loop was magnetized with pulse magnetization from which the curves of voltage and current as functions of time were obtained, and it was possible to divide the superconductor behavior into three different stages of operation, depending on the current levels reached: for low current values, the material behaves as a perfect inductor; for current values near the critical current, it behaves as an RL circuit; and for higher values, resistance dependent on the temperature has to be taken into account.
Abstract: Low critical temperature superconducting coils can conduct persistent currents with almost no losses, as the technique to make joints is well developed and the resistive losses are negligible. The replacement of these superconductors by high-temperature superconductors may greatly reduce refrigeration costs. However, even though the technique for making these joints has greatly developed over the last years, there are still inherent difficulties associated to that process. Coils made with partially slit loops of high temperature superconducting tape have no joints, and therefore can conduct current in persistent mode. Since there are no terminals, its current must be induced through magnetization techniques, for instance, by the means of a transformer. The occurrence of persistent current is related to the voltage in the sample, making it interesting to study the voltage behavior for different regions of operation. In this work, a jointless 2G loop was magnetized with pulse magnetization from which the curves of voltage and current as functions of time were obtained. After several tests, it was possible to divide the superconductor behavior into three different stages of operation, depending on the current levels reached: for low current values, the material behaves as a perfect inductor; for current values near the critical current, it behaves as an RL circuit; and for higher values, resistance dependent on the temperature has to be taken into account. A direct relation between persistent current and the arise of a dissipative state was noted and the highest values of persistent current were observed when the pulse was intense enough to produce significant temperature variations in the sample.
Citations
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Journal ArticleDOI
TL;DR: In this paper, the first finite element analysis of quasi-static test of a superconducting machine with stacks of coated conductors arranged spirally around the rotor is presented, and the behavior of the machine as a generator is also investigated.
Abstract: This article consists on the first finite element analysis of quasi-static test of a superconducting machine with stacks of coated conductors arranged spirally around the rotor. The behavior of the machine as a generator is also investigated. Hybrid A-V-H 2D formulation and moving mesh were used as modeling framework. The stacks are represented with the homogenization technique. Quasi-static test is simulated considering a field cooling initial state and the generator simulation, a pulse field magnetization. Current density and magnetic flux density along the stack surface as well as speed and torque results are analyzed. When the machine is not moving, major current density loops are induced in the stack, following the magnetic poles. These loops are deformed by the current density induced by speed differences between stator and rotor. The quasi-static torque does not change with position. The simulation results prove the potential this topology has of operating as a generator. The quasi-static results are in agreement with measurements made with the prototype.

11 citations

Journal ArticleDOI
TL;DR: In this article, a record 4.6 T trapped field generated by high temperature superconducting (HTS) persistent current loops using a HTS ring structure was reported, where the magnetic field is in the parallel direction to the ab plane of the HTS, leading to higher critical currents in the same magnetic field.
Abstract: We report here a record 4.6 T trapped field generated by high temperature superconducting (HTS) persistent current loops using a HTS ring structure. By stacking 200 HTS rings into a compact magnet 90 mm in diameter, we performed a field cooling magnetisation at 25 K. The main advantage of the new magnet compared to existing trapped field HTS magnets is that the magnetic field is in the parallel direction to the ab plane of the HTS, leading to higher critical currents in the same magnetic field. Therefore, compact HTS magnets can be developed based on this principle to achieve high magnetic fields. Experimental results show that the final trapped field distribution depends on the ring geometry. We developed a new three dimensional model to simulate the magnetic field distribution within the HTS ring magnet and good agreement between experiments and simulation have been found. The temperature dependency and ramping rate dependency have been studied numerically as potential factors to influence the magnet field. The proposed HTS ring magnet will have promising applications in medical imaging devices, e.g. MRI, as well as electrical machines.

9 citations


Cites methods from "Study of the Voltage Behavior of Jo..."

  • ...To understand how the ramping rate affects the trapped field, according to Faraday’s Law [22], we have:...

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  • ...To understand how the ramping rate affects the trapped field, according to Faraday’s Law [22], we have: j + = -...

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Journal ArticleDOI
TL;DR: In this article, the second-generation high-temperature superconducting (2 G HTS) RE-Ba-Cu-O (REBCO, RE is rare earth) tapes have extensive applications in high magnetic flux den...
Abstract: Superconducting devices composed of the second-generation high-temperature superconducting (2 G HTS) RE-Ba-Cu-O (REBCO, RE is rare earth) tapes have extensive applications in high magnetic flux den...

1 citations

Journal ArticleDOI
12 Oct 2022-Crystals
TL;DR: In this article , the authors presented a field-circuit coupling method to study the entire magnetization process of the ring-shaped magnet, and the accumulation effect under multi-pulse magnetization was theoretically analyzed and proved by both experiments and simulation.
Abstract: The ring-shaped superconducting permanent magnet, with its great advantages in flexible sizing and trapped field, has become a potential candidate for portable medical applications. However, due to the complex geometry involved, it is difficult to predict its electromagnetic performance by traditional numerical methods. This paper presents a field-circuit coupling method to study the entire magnetization process of the ring-shaped magnet. Firstly, the principle of the numerical method is introduced and it is proved to be sufficient for a ring-shaped magnet with a large turn number. Then, the numerical model is used to discuss the relationship between pulse waveform and magnitude of trapped field. Next, the accumulation effect under multi-pulse magnetization is theoretically analyzed and proved by both experiments and simulation. Finally, based on the numerical model, a study on the decay process of ring-shaped magnets is also presented. Conclusions from this paper will be helpful for obtaining the optimization strategy of magnetization of ring-shaped magnets for practical medical applications.

1 citations

Journal ArticleDOI
TL;DR: In this article, a circuit method based on the Bean model, E-J power law and Faraday law has been built to investigate the magnetization mechanism of ring-shape magnet and the field dependent critical current of superconducting materials has been taken into consideration for further optimization.
Abstract: The so-called ring-shape superconducting trapped field magnet has been proved as a potential candidate to replace commercial permanent magnets in practical industrial applications on account of its jointless structure. In this paper, a circuit method based on Bean model, E-J power law and Faraday law has been built to investigate the magnetization mechanism of ring-shape magnet. The field dependent critical current of superconducting materials has been taken into consideration for further optimization. The numerical model was verified by both finite element method (FEM) and experiments. Compared with other methods, the circuit-based simulation method has the advantages of high efficiency, fast speed and wide applicability. On basis of this method, the paper also studied characteristics of ring-shape magnets under different working conditions to provide a guideline for the magnet design.

1 citations

References
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Journal ArticleDOI
TL;DR: In this article, the ability of 2G HTS wire to operate under high stress levels has been demonstrated in both direct sample measurement and test coils, and the high winding current density that is available with SuperPower's thin 2GHTS wire was utilized in a high field insert coil demonstration generating central fields in excess of 26.8 T.
Abstract: Recent developments in 2G HTS coil technology are presented highlighting the ability of 2G HTS wire to function under difficult operating conditions without degradation. The challenges of use in various coil constructions and applications are discussed. Several applications where the conductor is subjected to high stress levels include high field insert coils and rotating machinery. While these applications present different challenges, the ability of the conductor to operate under high stress levels has been demonstrated in both direct sample measurement and test coils. The high winding current density that is available with SuperPower's thin 2G HTS wire was utilized in a high field insert coil demonstration generating central fields in excess of 26.8 T . The ability of the wire to be tailored (stabilization, insulation, ac losses) to fit various operating parameters will also be discussed.

173 citations


"Study of the Voltage Behavior of Jo..." refers methods in this paper

  • ...During the past decade, the technique for making joints in HTS tapes has been developed significantly [3]....

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Journal ArticleDOI
TL;DR: In this paper, the authors present solutions for the challenges concerning the use of the H-formulation to predict the behavior of superconducting levitators built either with YBCO bulks or stacks of 2G wires.
Abstract: Several techniques to model high temperature superconductors (HTSs) are used throughout the world. At the same time, the use of superconductors in transportation and magnetic bearings promises an increase in energy efficiency. However, the most widespread simulation technique in the literature, the H-formulation, has not yet been used to simulate superconducting levitation. The goal of this work is to present solutions for the challenges concerning the use of the H-formulation to predict the behavior of superconducting levitators built either with YBCO bulks or stacks of 2G wires. It is worth mentioning the originality of replacing bulks with HTS stacks in this application. In our simulation methodology, the movement between the HTS and the permanent magnet was avoided by restricting the simulation domain to the HTS itself, which can be done by applying appropriate boundary conditions and analytical expressions for the source field. Commercial finite element software was used for the sake of ease of implementation. Simulation results were compared with experimental data, showing good agreement. We conclude that the H-formulation is suitable for problems involving moving objects and is a good alternative to other approaches for simulating superconducting magnetic bearings.

106 citations


"Study of the Voltage Behavior of Jo..." refers methods in this paper

  • ...Our group has been investigating jointless HTS loops applied to superconducting magnetic bearings [8]– [10]....

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Journal ArticleDOI
TL;DR: In this article, a review of progress made to date on the production and characterization of persistent current joints between the five major technological superconductors (NbTi, Nb3Sn, MgB2, BiSCCO and REBCO) is presented.
Abstract: Persistent current joints are crucial components of superconducting magnets—enabling the production of the high and ultra-stable magnetic fields required, for instance, for magnetic resonance measurements. At this critical juncture when persistent mode magnets containing commercial high temperature superconductors may soon become a reality, it is of value to take stock and evaluate current challenges faced in the field of jointing. This paper provides a review of progress made to date on the production and characterization of joints between the five major technological superconductors—NbTi, Nb3Sn, MgB2, BiSCCO and REBCO, including the materials that are used to make these joints.

91 citations


"Study of the Voltage Behavior of Jo..." refers background in this paper

  • ...2968919 such as electric machines [1], since the technique for making the joints in these superconductors is already well developed [2]....

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Journal ArticleDOI
TL;DR: It is expected that the new real-time SCFCL model will provide a valuable tool not only for further protection system studies but for a wide range of RT-HIL experiments of power systems.
Abstract: A model for the SCFCL suitable for use in real time computer simulation is presented. The model accounts for the highly nonlinear quench behavior of BSCCO and includes the thermal aspects of the transient phenomena when the SCFCL is activated. Implemented in the RTDS real-time simulation tool the model has been validated against published BSCCO characteristics. As an example for an application in protection system studies, the effect of an SCFCL on a utility type impedance relay has been investigated using a real time hardware-in-the-loop (RT-HIL) experiment. The test setup is described and initial results are presented. They illustrate the effect of how the relay misinterprets the dynamically changing SCFCL impedance as an apparently more distant fault location. It is expected that the new real-time SCFCL model will provide a valuable tool not only for further protection system studies but for a wide range of RT-HIL experiments of power systems.

66 citations


"Study of the Voltage Behavior of Jo..." refers background in this paper

  • ...is equal or higher than liquid nitrogen temperature, a linear model [11], [12] is adopted...

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Journal ArticleDOI
TL;DR: In this paper, the authors simulate the behavior of resistive-type SCFCL modules based on MCP-BSCCO 2212 coils and show that short-circuit currents as high as 37 kApeak were limited to about 10% of their peak values in the first half cycle.
Abstract: Superconducting fault current limiters (SCFCLs) represent a promising solution to the problem of increasing short- circuit currents in the grid. The SCFCL is based on the fast transition from the superconducting state to the normal state, causing a sudden increase in the impedance of the network. In this paper, we simulate the behavior of resistive-type SCFCL modules. The SCFCL modules are based on MCP-BSCCO 2212 coils. The superconductor acts as a nonlinear resistance that varies with the current and the temperature. The behavior of the simulated curves is consistent with the experimental results. Short-circuit currents as high as 37 kApeak were limited to about 10% of their peak values in the first half cycle.

47 citations


"Study of the Voltage Behavior of Jo..." refers background in this paper

  • ...is equal or higher than liquid nitrogen temperature, a linear model [11], [12] is adopted...

    [...]