So Noguchi

A modified immune network algorithm for multimodal electromagnetic problems

Some optimization algorithms based on theories from immunology have the feature of finding an arbitrary number of optima, including the global solution. However, this advantage comes at the cost of a large number of objective function evaluations, in most cases, prohibitive in electromagnetic design. This paper proposes a modified version of the artificial immune network algorithm (opt-AINet) for electromagnetic design optimization. The objective of this modified AINet (m-AINet) is to reduce the computational effort required by the algorithm, while keeping or improving the convergence characteristics. Another improvement proposed is to make it more suitable for constrained problems through the utilization of a specific constraint-handling technique. The results obtained over an analytical problem and the design of an electromagnetic device show the applicability of the proposed algorithm

An optimal design method for superconducting magnets using HTS tape

This paper describes an optimal design method for superconducting magnets wound with high temperature superconducting (HTS) tapes (e.g. Bi2223/Ag tapes). The properties of HTS tapes have been advancing and HTS magnets have been constructed and demonstrated. However, the HTS tapes have thermally different characteristics compared with the low temperature superconducting (LTS) wires. Therefore it is necessary to consider these characteristics of HTS tapes at the magnet design stage. We propose a new configuration of the superconducting magnets using Bi2223/Ag tapes. The proposed configuration is optimized by using simulated annealing (SA), which is one of the optimization algorithms, under a lot of constraints such as B-I characteristic, central magnetic field, field homogeneity and so on. The details of the optimization method and an example of its application to a 12-Tesla superconducting magnet using Bi2223/Ag tape are shown.

Analyses of Transient Behaviors of No-Insulation REBCO Pancake Coils During Sudden Discharging and Overcurrent

Stability margin of a high-temperature superconducting (HTS) coil is two or three orders of magnitude greater than that of a low-temperature superconducting coil. In recent years, many papers have reported test results of turn-to-turn no-insulation (NI) HTS coils having extremely enhanced thermal stability, such that burnout never occurs in an NI coil, even at an operating current exceeding 2.5 times the critical current. Thus, The main goal of this paper is to clarify transient electromagnetic and thermal behaviors and mechanism of the high thermal stability in an NI REBCO coil. A partial element equivalent circuit (PEEC) model is proposed for the numerical simulation of an NI REBCO coil, which considers a local electrical contact resistance between turns, an I-V characteristic of an REBCO tape, and local self and mutual inductances of the NI REBCO coil. Using the PEEC model, we investigate the influence of the turn-to-turn contact resistance on the transient behavior of the NI REBCO coil during sudden discharging. We also perform thermal conduction analyses with the PEEC model to clarify the transient behavior of an NI REBCO coil during an overcurrent operation.

An optimal configuration design method for HTS-SMES coils

Recently, the properties of high temperature superconducting tapes have been in advance and high temperature superconducting magnets have been constructed and demonstrated. However, the high temperature superconducting tapes have different thermal characteristics compared with low temperature superconducting wires. Therefore, it is necessary to consider these characteristics of high temperature superconducting tapes at the magnet design stage. We proposed an optimal design method for superconducting coils wound with Bi2223/Ag tapes. In this paper, the configuration of 72 MJ SMES coils wound with Bi2223/Ag tapes are optimized.

Real-Time Visualization System of Magnetic Field Utilizing Augmented Reality Technology for Education

In electromagnetics education, it is important for beginners, who start to learn electromagnetics, to give an illustration of magnetic field. In this paper we propose a new real-time visualization system. It can visualize a composite image of source materials and their generated magnetic field utilizing the Augmented Reality technique to the users. With this real-time visualization system, electromagnetics learners can observe the visualized magnetic field as a realistic magnetic distribution on real-time and the visualized field changes immediately they move the objects.

An optimization method for design of SMES coils using YBCO tape

Recently, the properties of high temperature superconducting (HTS) tapes have been in advance and HTS magnets have been constructed and demonstrated. However, the HTS tapes have thermal different characteristics compared with the low temperature superconducting (LTS) wires. Moreover, Bi2223/Ag tapes and YBCO coated conductors have the different properties about the dependence on the degree of external magnetic field. Therefore it is necessary to consider these characteristics of HTS tapes at magnet design stage. We proposed an optimal design method for superconducting coils using Bi2223/Ag tapes. And the proposed configuration is optimized by using the simulated annealing (SA), which is one of the optimization algorithms, under a lot of constraints such as B-I characteristic, storage energy, and so on. The details of the optimization method and an example of its application to SMES coils (72 MJ) using YBCO coated conductors are shown.

An optimal design method for highly homogeneous and high-field superconducting magnets

Highly homogeneous and high-field superconducting magnets are difficult to design for optimal configuration, which has the minimum winding volume. In this paper, we propose an optimal design method utilizing a modified genetic algorithm to realize the minimum winding volume design for multi-section superconducting magnets. The detail of the algorithm and two examples of its application to three-section superconducting magnets are shown.

An optimal design method for SMES coils using HTS tapes

This paper describes an optimal design method for SMES coils wound with high temperature superconducting (HTS) tapes (e.g., Bi2223/Ag tapes). Recently, the properties of HTS tapes have advanced and HTS magnets have been constructed and demonstrated. However, the HTS tapes have different thermal characteristics compared with the low temperature superconducting (LTS) wires. Therefore, it is necessary to consider these characteristics of HTS tapes at magnet design stage. We propose an optimal design method for SMES coils using Bi2223/Ag tapes. And the proposed configuration is optimized by using the simulated annealing, which is one of the optimization algorithms, under a lot of constraints such as B-I characteristic, storage energy, and so on. The details of the optimization method and examples of its application to small SMES coils (0.5 MJ) using Bi2223/Ag tape are shown.

Measurement and Simulation of Magnetic Field Generated by Screening Currents in HTS Coil

In coils wound with high-temperature superconducting (HTS) tapes, large screening currents are induced in the tape by the radial component of the magnetic field. Furthermore, when a transport current is supplied to the HTS tape under a magnetic field, the total current (which consists of the transport and screening currents) flows inhomogeneously. The magnetic field generated by the screening currents affects the magnetic field distribution in cyclotron applications. Investigating the effects of the screening currents on the reduction, hysteresis, and drift of the magnetic field in the HTS coil is therefore necessary. In our previous studies, we have developed a novel simulation code for a three-dimensional electromagnetic field with the aim of clarifying these effects. In the present study, we measured the reduction and hysteresis of the magnetic field generated by the screening currents for a small model of HTS pancake coil. Additionally, we numerically investigated the influence of the screening current in the HTS coil on the spatial and temporal behavior of the magnetic field using our developed simulation code, which considers the nonlinear voltage-current characteristics.

`Electromaglev' (`active-maglev') - magnetic levitation of a superconducting disk with a DC field generated by electromagnets. Part 4: Theoretical and experimental results on supercurrent distributions in field-cooled YBCO disks

We present Part 4 results of a comprehensive theoretical study of an ‘‘electromaglev’’ system, in which a high-temperature superconducting bulk YBCO sample is levitated stably in a DC magnetic field generated by magnet system underneath the floating object. An electromagnetic analysis, based on a three-dimensional finite element technique (FEM) applied to the current vector potential method, has been developed to determine the supercurrent distribution in a field-cooled (and hence trapped-flux) YBCO disk that levitates stably in a magnetic field generated by the magnet system. The supercurrent distribution thus determined was in turn used to compute trapped-flux-induced field profiles of the disk and predict a ‘‘levitation current’’ in the magnet system at which the disk, initially resting on a support plate, begins to levitate. Agreement between computed field profiles and levitation currents and those measured in the experiment was excellent, validating the analysis itself and the method used to derive solutions. The analysis demonstrates that the supercurrent distribution within a trapped-flux disk is far more complicated than that derived from the Bean model for a long cylinder under a uniform axial magnetic field. It is used for a parametric study of the eAects of disk dimensions (radius, thickness, radius/thickness ratio) and trapped-flux strength on supercurrent distribution and lift-to-weight ratio. The magnitude of the Br component generated by the magnet system is very important for lift and it is shown that thinner disks rather than thicker disks can improve lift-to-weight ratio. Because accuracy of the analysis is disk-size independent, small disks are time-eAcient for performing the analysis. ” 2000 Elsevier Science Ltd. All rights reserved.