1,721,324 research outputs found
Analisi numerica 3D di problemi elettromagnetici e MHD tramite la minimizzazione dell'errore costitutivo
Full text linkEX-VESSEL MAGNETIC MEASUREMENTS IN JET: A CRITICAL ASSESSMENT OF THE COLLAR PROBE
No full textThe paper reviews a set of magnetic probes which was installed in JET in order to improve the field measurements
in the proximity of the iron, and focuses in particular on one of them. The set consists of six Limb probes, attached
to the upper horizontal iron yokes, and one Collar Probe, inserted in the collar region of the iron structure. The
probes include pick-up coils, flux loops, Hall sensors, and a temperature sensor.
The data provided by the system are regularly acquired and recorded within the set of JET Pulse Files. They
can be used in studies implying measurement of the stray field due to the residual magnetization, as well as for all
the modeling activities involving 3D studies, in particular resistive wall mode studies, more accurate modeling for
the vertical stabilization, interactions between NBI and magnetic field. In addition, the experience gained with
Hall transducers is considered valuable in view of their potential use in ITER.
Unlike the limb probes, the collar probe did not pass the functional commissioning, due to an unexpected
discrepancy between the signals from Hall sensors and pick-up coils. The analysis illustrated in the paper shows
that a critical assessment of the local configuration and a suitable magnetic modeling solve the issue of the
observed discordance, by putting it in relation with a local geometrical effect due to the peculiar shape of the
ferromagnetic collar teeth.
The improvement of magnetic models targeted to the prediction of signals produced by magnetic sensors
is important, also considering that a large number of magnetic probes in ITER will be located close to the
ferromagnetic inserts
Multiobjectives optimization based design of high efficiency DC/DC switching converters.
Full text linkIn this paper we explore the feasibility of applying multi objective stochastic optimization algorithms to the optimal design of switching DC-DC converters, in this way allowing the direct determination of the Pareto optimal front of the problem. This approach provides the designer, at affordable computational cost, a complete optimal set of choices, and a more general insight in the objectives and parameters space, as compared to other design procedures. As simple but significant study case we consider a low power DC-DC hybrid control buck converter. Its optimal design is fully analyzed basing on a Matlab public domain implementations for the considered algorithms, the GODLIKE package implementing Genetic Algorithm (GA), Particle Swarm Optimization (PSO) and Simulated Annealing (SA). In this way, in a unique optimization environment, three different optimization approaches are easily implemented and compared. Basic assumptions for the Matlab model of the converter are briefly discussed, and the optimal design choice is validated “a-posteriori” with SPICE simulations
Accurate computation of Magnetostatic fields in axisymmetric geometries in the presence of ferromagnetic materials
No full textIn this paper the magnetic field is computed as the superposition of two contributions: B = B0 + ΔB. The vacuum field B0 due to the coil currents can be obtained with extreme accuracy using analytical methods. The field ΔB, due to the magnetizing currents in the iron or other perturbations like eddy currents in passive conductors, is computed numerically. The splitting yields a very high accuracy in all cases in which |ΔB| ≪ |B0|. The method, based on a calibration of the numerical results, is shown to be similar, but less expensive than perturbation techniques and reduced potential approaches. The effect of the outer magnetic shield on the field produced by an air core magnet for magnetic resonance is studied and compared to the analytical solution available for a particular shield geometry. An example of application is also shown for a dynamic case in the presence of eddy currents
Numerical analysis of magnetic field diffusion in ferromagnetic laminations by minimization of constitutive error
No full textIn this article, the diffusion of electromagnetic fields into a ferromagnetic lamination is numerically studied by means of an error-based numerical method. This technique has been developed so far only for the case of nonhysteretic constitutive relations. The generalization to the hysteretic case requires a modification of the technique in order to take into account the evolution of the “magnetization state” of the media. Numerical computations obtained by using this approach are reported and discusse
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