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Recently, linear generators have been widely employed to convert oceanic wave energy into electricity. Among various linear generators, linear permanent magnet generators (LPMGs) have gained attention due to their special characteristics such as high power density and simple control structure. In this paper, flat double‐sided LPMG is investigated and designed. Considering all effective design variables, a particle swarm optimization algorithm‐based optimization method is employed to maximize efficiency and minimize weight. The optimization results show an increase in efficiency and a reduction in the weight of the generator. Finally, the design results are evaluated and validated using magnetic equivalent circuit and finite element analysis methods. [ABSTRACT FROM AUTHOR]

Minimizing the material usage in thin‐film solar cells can reduce manufacturing costs and enable mechanically flexible implementations, but concomitantly diminishes optical absorption. Coherent optical effects can help alleviate this inevitable drawback at discrete frequencies. For example, coherent perfect absorption guarantees that light is fully absorbed in a thin layer regardless of material or thickness—but only on resonance. Here, it is shown that "omni‐resonance" delivers such coherent enhancement over a broad bandwidth by structuring the optical field to nullify the angular dispersion intrinsic to resonant structures. After embedding an amorphous‐silicon thin‐film photovoltaic cell in a planar cavity, pre‐conditioning the incident light using an alignment‐free optical arrangement severs the link between the resonant bandwidth and the cavity‐photon lifetime, thereby rendering the cavity omni‐resonant. Coherently enhanced near‐infrared absorption doubles the photocurrent over the targeted spectral range 660–740 nm where every wavelength resonates. These results may pave the way to transparent solar cells that optimally harvest near‐infrared light. [ABSTRACT FROM AUTHOR]

Simulation of railguns using the finite element method (FEM) is an alternative method for experiments, in the literature. Besides having many advantages, the FEM is complicated and time-consuming, especially for optimization. The circuit model method, unlike FEM, is simple, fast, and suitable for sensitivity analysis and optimization purposes. In this article, first, the circuit model is explained, and then, differential equations describing the behavior of the railgun have been derived and the equations have been solved by using the fourth-order Runge–Kutta method. The sensitivity of the railgun launching features to its parameters’ changes has been analyzed, which is an important issue that helps to design the railgun. Then, by using the particle swarm optimization (PSO) algorithm, single-objective and multiobjective optimizations have been done to maximize railgun outputs, such as velocity, efficiency, and force exerted on the armature at the moment of launching. Finally, for the validation of the proposed method, 3-D FEM has been employed. The results show the accuracy of the method. [ABSTRACT FROM AUTHOR]

The paper presents a novel technique for modeling ladder-secondary single-sided linear induction machines. Saturation effect is considered by core non-linearity characteristic for both primary and secondary. The proposed modeling method is based on magnetic equivalent circuit with adjustable accuracy. The machine parameters such as its dimensions, pole numbers, bar numbers, and also model accuracy can be chosen arbitrary in the proposed model. The end effect is considered by virtual teeth at the entry and exit ends of the machine primary. The results of the proposed method are compared with finite element method (FEM) in terms of accuracy and processing time. The results show the effectiveness of the proposed method. In addition, due to having long processing time of the FEM, the proposed method is a very suitable manner for modeling of this particular machine. Also, the accuracy of the proposed method has been confirmed by experimental results, in starting. [ABSTRACT FROM AUTHOR]

This paper presents a new method to model healthy and faulty wound-rotor induction machines (WRIMs) with and without inter-turn short circuit fault by a single set of equations. The model is presented for a machine with arbitrary pole, and rotor and stator slot numbers. A single set of equations, including both electric and magnetic parts, is solved to obtain full dynamic behavior of the machine. Therefore, the modified magnetic equivalent circuit with non-linear elements is used for modeling and a numerical technique is employed to solve the non-linear equations. The proposed modified method has a simple calculation procedure in comparison with the conventional magnetic equivalent circuit method. Solving the electric and magnetic equations by a single set of equations is the main advantage of the presented method, which is proposed for a WRIM machine, for the first time. In addition, to increase the accuracy, the saturation phenomenon is also considered in the model. Due to the saturation effect, there are some non-linear algebraic magnetic equations, which should be simultaneously solved with differential equations. A trapezoidal technique is used to convert differential equations to algebraic ones. To solve the non-linear equations, non-linear equations, Newton Newton–Raphson method is employed. Current signature analysis is used for rotor and stator inter-turn short circuit fault detection. Finally, the finite-element method is used to verify the effectiveness of the proposed modeling method. It is worth noting that the proposed method can model a healthy and faulty machine with different faults by a single model. [ABSTRACT FROM AUTHOR]

Different parts of the cylindrical coils are exposed to electromagnetic forces due to electric current flowing through it. These forces can deform the coil in axial and radial directions in abnormal operating conditions. So, in design process of cylindrical coils in many magnetic devices, mechanical stresses exerted on different parts of these kinds of coils should be determined. In this paper, analytical expressions for the forces in axial direction are derived in order to calculate the forces exerted on different parts of the cylindrical coils. In order to evaluate the precision of the method, the finite element method (FEM) is used and the results obtained by FEM are compared with the results of the analytical equations. Results obtained by finite element analysis confirm the analytical method. Due to inherent difficulties in calculation of the forces in radial direction, distribution of the latter on the coil body is calculated by FEM. The results show that the outer turns of the coil in two axial ends are exposed to the largest axial tension, while radial stresses are largest in the middle parts of the coil. In this paper, the calculations focus on the cylindrical coils; however, the method can be used for the calculation of the magnetic force distribu-tion on different parts of spiral coils, disc coils and any type of air-cored coils with different sizes. [ABSTRACT FROM AUTHOR]

Abstract: Linear induction motors have been widely employed in industry because of their simple structure and low construction cost. However, they suffer from low efficiency and power factor. In addition, existence of so called end effect influences their performance especially in high speeds. The end effect deteriorates the performance of the motor by producing braking force. So, in this paper, by using Duncan equivalent circuit model, a new analytical equation is proposed to model end effect braking force. Employing the proposed equation and considering all phenomena involved in the single-sided linear induction motor, a simple design procedure is presented and the effect of different design variables on the performance of the motor is analyzed. A multi-objective optimization method based on genetic algorithm is introduced to maximize efficiency and power factor, as well as to minimize the end effect braking force, simultaneously. Finally, to validate the optimization results, 2D finite element method is employed. [Copyright &y& Elsevier]

Single-sided linear induction motors (SLIMs) have been widely used in industry, especially in high-speed transportation systems. The performance of the SLIMs is considerably affected by the characteristics of its secondary back-iron. The conductivity of the iron used as well as its magnetic permeability influence the performance of the machine, while the magnetic permeability itself is affected by the input frequency of the SLIM. In this paper, using Dancan equivalent circuit model and considering all phenomena involved in the single-sided linear induction motor, the outputs of the motor such as efficiency, power factor, normal force and output thrust are analytically derived. Then, the effects of the input frequency on depth of the field penetr-ation and saturation level of the secondary back-iron as well as the SLIM outputs are analyzed. To confirm the analytical results, 2D time-stepping finite element method is employed. The results are in good agreement with each other confirming the analytical analysis. [ABSTRACT FROM AUTHOR]

The insulation hot spot temperature (HST) represents the most important limiting factor of a transformer insulation life. Ambient temperature involved in the HST computations in all transformer thermal models affects insulation life-time directly or indirectly. Regarding the importance of the ambient temperature in transformer's insulation life, in this paper a new thermal model for the estimation of HST in transformers has been proposed and using this thermal model, the effect of the ambient temperature on HST and transformer insulation life is investigated. The proposed model has been validated using real data gathered from a 180 MVA transformer. [ABSTRACT FROM AUTHOR]

The authors realize this effect in the near-infrared in a hydrogenated amorphous silicon (a-Si:H) PIN-diode solar cell incorporated into an unpatterned asymmetric planar Fabry-Pérot cavity. Keywords: coherent perfect absorption; omniresonance; solar cells EN coherent perfect absorption omniresonance solar cells 1 1 1 04/22/21 20210420 NES 210420 In article number 2001107, Ayman F. Abouraddy and co-workers demonstrate that an omni-resonance scheme can extend coherent perfect absorption continuously over a broad spectral bandwidth, thereby rendering this coherent-enhancement arrangement relevant for solar conversion applications. Doubling the Near-Infrared Photocurrent in a Solar Cell via Omni-Resonant Coherent Perfect Absorption (Advanced Optical Materials 8/2021). [Extracted from the article]

This paper develops a new model with adjustable accuracy to evaluate performance of permanent magnet Vernier machine (PMVM) based on flexible magnetic equivalent circuit (MEC) method. The desired machine parameters such as number of flux modulation poles (FMPs), winding pole‐pairs, and geometrical dimensions can be chosen in the presented model. By utilizing nonlinear core magnetization curve, saturation effect is taken into account. There are two main contributions in this study. First, the flexible MEC model is developed to predict the machine performance accurately. The second contribution is that the developed model can be used to evaluate the performance of the machine under no‐load and loading conditions at the same time. The results of MEC model under no‐load and loading conditions are compared with 2D‐finite element method (FEM) and 3D‐FEM in terms of accuracy and simulation time. The results indicate acceptable accuracy and suitable processing time of the proposed MEC model. [ABSTRACT FROM AUTHOR]

This paper presents an improved magnetic equivalent circuit (MEC) method for modeling linear permanent-magnet synchronous motors (LPMSMs) with adjustable accuracy. The performance of machine with different dimensions, poles and slot numbers can be studied by the proposed flexible MEC, where the core nonlinearity is fitted on the material B–H curve. End effect is modeled by considering two virtual zones with desired accuracy at both entrance and exit ends of the primary. A new structure based on magnets segmentation is also proposed to investigate its effect on the motor performance. Finally, the results of the proposed method are compared with 3D-FEM to show the effectiveness of the presented model. The results show improvement in processing time with good accuracy compared to previous classic methods. In general, introducing a new model based on an improved MEC approach for modeling LPMSMs considering slot effect, iron core saturation and segmented PMs with flexible accuracy by adjusting the number of flux tubes is the paper novelty which is studied in this work. [ABSTRACT FROM AUTHOR]

Summary: Growing the industry and population in a region leads to the growth of required amount of electrical energy. Electrical companies should provide high quality energy according to the demand of customers. Load is an effective parameter of any system, and the network programmers should consider the annual load growth of the system and predict the required energy for each region by investigating previously recorded data of consumed electrical energy and stochastic analysis. In this paper, a new combined method for long‐term energy forecasting is proposed. This method, which combines the land‐consumption method and curve fitting based on generalization method, in addition to having simple calculations, takes into account the saturation. Moreover, loads from detailed formal program provided by the relevant institutes have been used, which results in better coordination between all organizations in charge of energy predictions and development of the countries. A suitable filtering method is also employed for input data to improve the method accuracy. To show the effectiveness of the proposed method, the results of different methods have been compared with those of the proposed method as well as real data. Then, real data of former 11 years of consumed energy gathered from Shiraz Electrical Distribution Company subscribers are employed and the energy for future 11 years is forecasted. [ABSTRACT FROM AUTHOR]