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Conventional electronic article surveillance (EAS) tags are ineffective on metallic packaging. The component of the RF magnetic field perpendicular to the surface of the packaging induces eddy currents that suppress the magnetic flux, linking the inductive element of the tag. In this article, an inductive quarter-wavelength planar cavity, formed by wrapping aluminum foil around a ferrite core, was extended by wrapping additional capacitive layers of foil/dielectric around the ferrite-filled central region. This so-called wrapped tag exhibits the frequency, $Q$ -factor, and read distance characteristics of existing EAS tags, but is instead driven by the RF magnetic fields parallel to the surface of the metallic packaging. In this article, we compare the observed frequency response of the wrapped tag with a simple LC resonator model that considers the tag’s geometrical features, and use the model to describe how the design and construction of the tag can be optimized. Finite-element method (FEM) modeling is used to reveal how the current flows in the wrapped foil of the tag. Prototype tags show good reproducibility, demonstrating the potential of the design as a solution to the problem of tagging metallic packaging in the EAS industry. [ABSTRACT FROM AUTHOR]

This paper presents the design considerations in cogging torque minimization in two types of transverse flux machines. The machines have a double stator-single rotor configuration with flux concentrating ferrite magnets. One of the machines has pole windings across each leg of an E-Core stator. Another machine has quasi-U-shaped stator cores and a ring winding. The flux in the stator back iron is transverse in both machines. Different methods of cogging torque minimization are investigated. Key methods of cogging torque minimization are identified and used as design variables for optimization using a design of experiments (DOEs) based on the Taguchi method. A multilevel DOE is proposed as an optimization method to reach an optimum solution with minimum simulations. The case study is analyzed in a two-level DOE optimization. Finite element analysis (FEA) is used to study the different effects. Two prototypes are fabricated for validating the FEA results. [ABSTRACT FROM AUTHOR]

Describes a numerical approach for the analysis of microwave ferrite devices by using the finite element method. Complexity of the electromagnetic fields in ferrite components; Formulation of the mathematical model; Discussion on the numerical results.

This paper investigates the partial irreversible demagnetization characteristics of magnets in flux-switching permanent magnet (FSPM) machines. Two different partial demagnetization mechanisms in the FSPM machines are modeled and demonstrated. The 2-D finite-element analysis (FEA) results for a baseline 10 kW 15 kr/min ferrite FSPM machine verify the validity of the proposed partial demagnetization model. Performance degradation due to demagnetization is evaluated for the baseline machine based on the FEA results. This paper also proposes a novel design to enhance the demagnetization withstand capability. This research reveals the most vulnerable region of the magnet to irreversible demagnetization in the FSPM machines. It also provides a guideline for developing demagnetization withstand capability improvement techniques. [ABSTRACT FROM PUBLISHER]

In a gapped inductor, airgap fringing flux induces eddy currents in coil conductors in the vicinity of the airgap, producing unwanted power loss and heat in the coil. An open-circuit copper screen placed around the airgap of a ferrite core is shown to reduce the fringing flux around the airgap. The reduction in fringing flux is shown by experiment to reduce the power loss, in the inductor winding, associated with eddy currents induced by airgap fringing flux, and practical results compare favourably with presented finite-element results. The reduction in coil losses reduces the cooling requirement for the inductor, or alternatively, allows an increase in the thermal rating of the inductor. [ABSTRACT FROM AUTHOR]

The generalized minimal residual (GMRES) iterative method is applied to solve such sparse large non-symmetric system of linear equations resulting from the use of edge-based finite element method. In order to speed up the convergence of GMRES, the symmetric successive overrelaxation (SSOR) preconditioning scheme is applied for the analysis of millimeter wave ferrite circulator. Consequently, this preconditioned GMRES (PGMRES) approach can reach convergence ten times faster than GMRES. The reflection and insertion losses of millimeter wave waveguide circulator are compared with those obtained from literature. [ABSTRACT FROM AUTHOR]

Presents a study that examined magnetic flux distribution and iron loss distribution in ferrite cores under pulse excitation using the finite element method. Background on the use of manganese-zinc ferrite cores in the transformers of switching power supplies; Analysis of magnetic characteristics under pulse excitation; Results and implications.

Focuses on a study which proposed a microwave and thermal method to model high-power ferrite devices. Description of the microwave finite-element analysis; Discussion on the operating regions of magnetic loss that must be avoided; Investigation of the thermal characteristics of a differential phase shift ferrite-loaded waveguide; Calculations for selected bias field.

To achieve deep-induction hyperthermia, a ferrite core applicator system has been developed. The clinical goal is to produce a temperature rise of 7.5/spl deg/C at 10 cm tissue depth. Deep heating becomes possible by introducing an auxiliary electrode to control an eddy current. The auxiliary electrode has been designed to optimize the eddy current with respect to the magnetic flux density. The optimization was performed by solving the fundamental equation using the finite element method (FEM). A flexible auxiliary electrode, which can be used for clinical treatments, has been manufactured. Heating tests have been conducted with the new applicator system, which operates at 4.0 MHz. The experimental results demonstrate that the system is capable of producing a temperature rise of 7.5/spl deg/C at 10 cm depth, without heating an overlaying fat layer. [ABSTRACT FROM AUTHOR]