A 3-D vector magnetization model with interaction field

This paper presents a vector model of magnetization based on the three-dimensional (3-D) Stoner-Wohlfarth elemental operator. To account for the magnetic interactions between particles, a phenomenological mean-field approximation is employed. The paper also illustrates the numerical simulation results of the magnetization in 3-D. This model will be useful to simulate the magnetization process of complicated topology flux electromagnetic devices. © 2005 IEEE

A general electromagnetic field-circuit coupling method based on time-stepping finite element analysis for performance analysis of pulse-width modulated switching converters considering hysteresis effects

Considering the special characteristics existing in the pulse-width modulated (PWM) switching converter, a general method for the time-stepping finite element analysis based electromagnetic field coupling with its feeding circuit used in the analysis of PWM switching converter considering hysteresis effects is introduced in this paper. Comparing with the electromagnetic field-circuit indirect coupling method (ICM), the proposed method has overcome the drawback that the ICM cannot take the hysteresis effects into account. Compared with the electromagnetic field-circuit direct coupling method (DCM), the proposed method has the similar accuracy but higher efficiency. Furthermore, like the ICM, the proposed method also divides the system with higher state dimensions produced by the DCM into two subsystems with lower state dimensions; this may reduce the algorithm convergence problem which often happens in high dimensional systems. © 2008 American Institute of Physics

Magnetic flux penetration in polycrystalline SmFeO0.75F0.2As

The recently discovered Fe-As superconducting materials which show high potential ability to carry current due to their low anisotropy have attracted a great number of attentions to understand their superconductivity mechanism and explore their applications. This paper presents a method to synthesis SmFeO0.75F0.20As polycrystalline by hot press in detail. The magnetization at different temperatures and applied fields obtained by a superconducting quantum interference device are also discussed. In addition, the local magnetization process is presented by magneto-optical imaging technique at the conditions of zero-field-cooling and field-cooling. It is found that the collective magnetization process of the newly discovered Fe-As superconductors is very similar to that of high-Tc cuprates. For instance, the Fe-As superconductors and high-Tc cuprates have the same magnetization features due to strong pining and intergrain weak link. The global supercurrent is significantly lower than local grain supercurrent due to the weak line between the grains

Study on rotational hysteresis and core loss under three-dimensional magnetization

In this paper, magnetic properties of soft magnetic composite (SMC) materials under alternating and various rotational magnetizations have been properly measured, modeled, and analyzed at typical frequencies of 5, 50, and 500 Hz. The relationship between the magnetic flux density vector B and magnetic field strength vector H has been systemically studied when the B loci are well controlled to be circles and ellipses in three orthogonal planes of the three-dimensional (3-D) tester. The core loss features against magnetic flux densities with alternating and rotational magnetizations are also compared and analyzed. It is found that the rotational core losses are nearly twice of the alternating core losses at the same magnitude of flux density. Experimental results show that SMC materials have good 3-D features, and great potential for application in rotational magnetic flux machines. © 2011 IEEE

Robust optimization in HTS cable based on design for six sigma

The nonuniform ac current distribution among the multilayer conductors in a high-temperature superconducting (HTS) cable reduces the current capacity and increases the ac loss. Various numerical simulation techniques and optimization methods have been applied in structural optimization of HTS cables. While the existence of fluctuation in design variables or operation conditions has a great influence on the cable quality, in order to eliminate the effects of parameter perturbations in design and to improve the design efficiency, a robust optimization method based on design for six sigma (DFSS) is presented in this paper. The optimization results show that the proposed optimization procedure can not only achieve a uniform current distribution, but also improve significantly the reliability and robustness of the HTS cable quality, comparing with those by using the particle swarm optimization. © 2008 IEEE

Measurement of soft magnetic composite material using an improved 3-D tester with flexible excitation coils and novel sensing coils

In this paper, accurate measurement of three dimensional (3-D) magnetic properties of soft magnetic composite (SMC) material is carried out by using an improved 3-D tester with adjustable excitation coils and novel sensing coils attached upon the surface of the SMC specimen. Comparing with the conventional 3-D tester operating at 50 Hz, the improved 3-D tester enables measurements over wide frequency range from 2 Hz to 1000 Hz. The relationships between the B vector and H vector are measured under both alternating and rotating flux conditions, and the core loss features are analyzed. These experimental results are crucial for designing new SMC electrical machines, which are expected to operate at 200 Hz or above. © 2006 IEEE

Robust optimization of multilayer conductors of HTS AC cable using PSO and perturbation analysis

For a High Temperature Superconducting (HTS) cable, a non-uniform AC current distribution among the multilayer conductors gives rise to increased AC losses. To get a uniform current distribution among the multilayer conductors, a constrained optimization model is constructed with continuous and discrete variables, such as the winding angle, radius and the winding direction of each layer. Under the constraints of the mechanical properties and critical current of the tape, the Particle Swarm Optimization (PSO) algorithm is employed for structural parameter optimization in both warm and cold dielectric type HTS cables. A uniform current distribution among layers is realized by optimizing the structural parameters. The perturbation analysis is employed to evaluate the parameters after optimization. It is found that the robust stabilizations are different among the various optimal results. The PSO is proved to be a more powerful tool than the Genetic Algorithm (GA) for structural parameter optimization. © 2006 IEEE

Current distribution analysis for high temperature superconducting cable considering hysteresis characteristics

This paper presents a hysteresis model for Type-II high temperature superconductor (HTS) by using simplified Preisach Model, in which the Preisach distribution function μ-kα, β) is determined only based on the B-H limiting loop. The nonlinear dynamic circuit model of the superconductor is established. In the circuit model, the hysteresis inductance and hysteresis loss described by using simplified Preisach Model are deduced. Applying the hysteresis circuit model, the currents flowing in different superconductor layers of high temperature superconducting cable are simulated, as well as the hysteresis loss of the superconducting cable. The simulation results are verified by comparison with the data recorded in literatures. Finally, the influences of hysteresis on superconducting cable are analyzed and discussed. © 2010 - IOS Press and the authors. All rights reserved

Near-Infrared Super Resolution Imaging with Metallic Nanoshell Particle Chain Array

We propose a near-infrared super resolution imaging system without a lens or a mirror but with an array of metallic nanoshell particle chain. The imaging array can plasmonically transfer the near-field components of dipole sources in the incoherent and coherent manners and the super resolution images can be reconstructed in the output plane. By tunning the parameters of the metallic nanoshell particle, the plasmon resonance band of the isolate nanoshell particle red-shifts to the near-infrared region. The near-infrared super resolution images are obtained subsequently. We calculate the field intensity distribution at the different planes of imaging process using the finite element method and find that the array has super resolution imaging capability at near-infrared wavelengths. We also show that the image formation highly depends on the coherence of the dipole sources and the image-array distance.Comment: 15 pages, 6 figure

Visualization of vortex motion in FeAs-based BaFe<inf>1.9</inf>Ni <inf>0.1</inf>As<inf>2</inf> single crystal by means of magneto-optical imaging

Superconductivity has been found in newly discovered iron-based compounds. This paper studies the motion of magnetic vortices in BaFe1.9Ni 0.1As2 single crystal by means of the magneto-optical imaging technique. A series of magneto-optical images reflecting magnetic flux distribution at the crystal surface were taken when the crystal was zero-field cooled to 10 K. The behavior of the vortices, including penetration into and expulsion from the single crystal with increasing and decreasing external fields, respectively, is discussed. The motion behavior is similar to that observed in high-Tc superconducting cuprates with strong vortex pinning; however, the flux-front is irregular due to randomly distributed defects in the crystal. © 2011 American Institute of Physics