The incorporation of hysteresis models in the finite element method is important for the accurate predictions of the performance of low-frequency electromagnetic devices. The Jiles-Atherton and Preisach models are frequently used for this purpose. The classical Preisach model is more accurate and can represent a broad range of magnetic materials. However, it is computationally very expensive and therefore hysteresis coupled finite element (FE) simulations take too much time to solve. In this work, a computationally efficient method of implementing the Preisach model is presented using the closed form expression for modeling the Everett function which not only reduces the total execution time of the model but also simplifies its implementation. The incorporation of the proposed implementation into FE simulations shows faster computation times and better numerical convergence when compared to the conventional implementation. The proposed approach is only valid for the H-based Preisach models.

Two dual-band terahertz metamaterials based on nested split ring resonators (SRRs) were designed and fabricated on a flexible plastic substrate. Each nested SRR structure composed of two electric field coupled resonators exhibited two transmission minimums, which inherently come from the LC resonances of the respective SRRs. The primary and secondary resonance frequencies can be individually fine-tuned by adjusting the geometry of the respective resonator. The fabricated devices exhibited very low insertion loss of 3 dB in the transmission band and the high attenuation of 27 dB in the stop band.

The effects of temperature-dependent material properties, including those of silicon steel and permanent magnet (PM) materials, on the design process of inverter-fed PM motors are investigated in this paper. The magnetization curves of these materials are measured experimentally at different temperatures and are imported into a finite-element package. Then, a statistical study of an integrated motor-drive system consisting of an interior PM motor connected to a space vector modulated inverter is performed by assigning four different temperatures and building a design space of various objectives including the integrated system efficiency, speed limits, motor startup quality, torque ripple, total harmonic distortion, and power factor as the geometrical dimensions are varied. The results reveal that incorporating the realistic material properties into the design process is essential. Moreover, different motor-drive performances have totally different variation rates as the material properties are changed. Finally, a set of optimal designs at different temperatures is proposed to show the effect of changing material properties.

A terahertz (THz) in-line polarization converter that yields a polarization conversion ratio as high as 99.9% is demonstrated at 1 THz. It has double-layer slot structures oriented in orthogonal directions that are electrically connected by 1/8-wavelngth-long through-via holes beside the slot structures. The slots on the front metal-plane respond to the incident THz wave with polarization orthogonal to the slots and generates a circulating surface current around the slots. The surface current propagates along a pair of through-via holes that function as a two-wire transmission line. The propagating current generates a surface current around the backside slot structures oriented orthogonal to the slot structures on the front metal layer. The circulating current generates a terahertz wave polarized orthogonal to the backside slot structures and the 90° polarization conversion is completed. The re-radiating THz wave with 90° converted polarization propagates in the same direction as the incident THz wave.

The Jiles-Atherton (JA) model explains hysteresis phenomenon in a ferromagnetic material through domain wall transitions with five material constants called the JA parameters. These parameters describe the magnetic characteristics of a ferromagnetic material and are identified from the measured saturated B-H loop. However, the JA parameters cannot predict the inner loops accurately and this presents a serious problem for the JA model to be used in finite element based computer-aided design simulations. In this paper, we have proposed a new approach which assumes one of the JA parameters to be a function of magnetic field intensity H, or magnetic flux density B, and requires knowledge of the inner loops. The improvement in the accuracy of the modified JA model has been demonstrated by comparing its predictions with measurements and one of the already published works.

High operating temperatures modify the magnetic behavior of ferromagnetic cores which may affect the performance of electrical machines. Therefore, a temperature-dependent material model is necessary to model the electrical machine behavior more accurately during the design process. Physics-inspired hysteresis models, such as the Jiles-Atherton (JA) model, seem to be promising candidates to incorporate temperature effects and can be embedded in finite element simulations. In this paper, we have identified the JA model parameters from measurements for a temperature range experienced by non-oriented electrical steels in electrical machines during their operation. Based on the analysis, a parameter reduction has been performed. The proposed approach simplifies the identification procedures by reducing the number of model parameters and does not require any additional material information, such as the Curie temperature. The resulting temperature-dependent JA model is validated against measurements, and the results are in good agreement.