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Dynamic operational behavior (DOB) of electrical machines can cause effects that are difficult to describe and understand. The short-circuit behavior (SCB) in particular is a dangerous DOB for machine and human. It could destroy the machine itself and cause heavy damage to the power supply unit and mechanical coupling components. Analytical calculation of the SCB is simplified and thus not highly accurate. Therefore, the finite element method simulation of the SCB is an important tool for understanding these effects without the danger of damaging the machine by experiments. In this paper, a suitable field formulation, modeling details, and simulation methods for dynamic analysis of synchronous machines are presented in detail. In particular, the accuracy of 2-D and 3-D transient electromagnetic simulations is analyzed by comparison against the available measurements performed on a chosen testing salient pole synchronous machine under the conditions of three-phase, two-phase, and single-phase short circuit. [ABSTRACT FROM AUTHOR]

The Cauer ladder network (CLN) method provides an efficient representation of eddy-current fields. This paper proposes a reformulation of the CLN method that considers expansion points using the magnetic/current vector potential. To cover a wide range of frequencies, the expansion point may be changed at a later stage of the network. Only a few stages of the ladder network are required for the eddy-current field to be reconstructed accurately around the target frequency using the expansion points. [ABSTRACT FROM AUTHOR]

In this paper, one proposes a model-assisted probability of detection approach to study the reliability of detecting special defects. The approach is based on a 3-D finite-element T– $\Omega $ formulation with circuit coupling. This model is then applied to calculate performances of induction thermography method to detect thin open cracks in vessel reactor shell in nuclear installation. [ABSTRACT FROM AUTHOR]

In this paper, a stabilized reduced-order model based on the gappy proper orthogonal decomposition (POD) technique is applied to an eddy-current problem with the non-linear material property. A classical magnetodynamic finite element formulation based on the magnetic vector potential is used as reference and starting point to build up the reduced models. The computational complexity of the non-linear problem might be reduced by the discrete empirical interpolation method-POD technique, but the eddy current effects may make this method unstable. In this paper, we propose an approach which is similar to the gappy method to successfully overcome this instability problem, while keeping the computational cost (time and memory) low. [ABSTRACT FROM AUTHOR]

Transcranial magnetic stimulation (TMS) is a non-invasive, safe, effective, and food and drug administration approved treatment for major depressive disorder. TMS relies on time-varying magnetic fields to induce an electric field in the brain, resulting in depolarization or hyperpolarization of the neurons. Recently, there has been extensive research to improve the magnetic coil design, effectiveness of TMS treatment, and improvement in the computer modeling of human brains, yet little development is reported on the TMS pulse generators and coil design for small animals. TMS pulse generators, or stimulators, are the circuits which provides pulse current to drive the inductive coils (TMS coils), used to generate time-varying magnetic fields. Commercial TMS stimulators are expensive and have limitations of using standard and non-customizable coils. These stimulators do not support small inductive loads, which require high-current capabilities. Furthermore, the commercial animal coil stimulates the entire body of a mouse, as they are designed for large animals. In this paper, the authors present the design of a small sized TMS stimulator and a focused coil for the application on small animals such as mice. The proposed TMS stimulator will have the potential of handling small inductive loads enabling stimulation of specific regions within the mouse brain. [ABSTRACT FROM AUTHOR]

This paper deals with the harmonic-balance (HB) finite-element (FE) analysis of a multi-turn winding device coupled to electrical circuits comprising nonlinear components. The eddy-current effects in the windings are accounted for via a frequency-dependent reluctivity and impedance determined with a homogenization technique. The proposed multi-frequency approach is validated through a single-phase four-diode rectifier with an axisymmetric FE model of an inductor. The system of nonlinear algebraic equations is solved by means of the Newton–Raphson method. The HB results are validated with classical time-stepping simulations. The computational cost is briefly discussed. [ABSTRACT FROM AUTHOR]

This paper presents a laboratory test procedure to determine the parameters of the inverse hysteresis model (IHM) applicable to single-phase toroidal transformer low-frequency modeling. The model parameters are obtained through a fitting procedure of the history-independent IHM of a series of open-circuit experiments and waveform recordings. These experiments can be easily executed during the transformer acceptance testing at the factory laboratory. The performance of the model is verified under various operational conditions, such as sinusoidal excitation, varied frequencies and voltages, and non-sinusoidal excitations. The results show that the model performs very well under all tested conditions giving great confidence that the proposed method can be used for parameter determination. [ABSTRACT FROM PUBLISHER]

In this paper, a new behavioral modeling approach for magneto-static hysteresis is presented. Many accurate models are currently available, but none of them seems to be able to correctly reproduce all the possible $B$ – $H$ paths with low computational cost. By contrast, the approach proposed in this paper is based on simple functions, which do not require calculus to be involved, thus assuring a very good efficiency in the algorithm. In addition, the proposed method enables initial magnetization curves, symmetric loops, minor loops, normal curves, and reversal curves of any order to be reproduced, as demonstrated through the pertinent results provided in this paper. A model example based on the proposed modeling technique is also introduced and used as inductor core, in order to simulate an $LR$ series circuit. Finally, the model ability to emulate hysteretic inductors is proved by the satisfactory agreement achieved when comparing the measured and simulated results. [ABSTRACT FROM AUTHOR]

Electrical machines with stranded random windings often suffer from considerable circulating current losses. These losses have been poorly studied because of the difficulty and computational cost of modeling stranded windings, and the stochastic nature of the problem due to the uncertain positions of the strands. This paper proposes two methods to model random stranded windings of arbitrary complexity. First, a circuit model considering the entire main flux path is presented, and some practical implementation considerations are discussed. Second, a computationally efficient finite-element approach based on non-conforming meshing is presented. Finally, a method is proposed to model the random packing process of strands within a slot, without any remeshing or inductance recalculation required. The proposed methods are then compared with special no-rotor measurement data of a large number of high-speed induction machines, and good agreement is observed. [ABSTRACT FROM PUBLISHER]

This paper presents the generation of equivalent circuits from a finite-element (FE) model of electromagnetic devices using proper orthogonal decomposition (POD). This method effectively computes the frequency response of the reduced FE model constructed by the POD-based model order reduction. Then, the circuit parameters are determined so as to minimize the error between the frequency responses of the reduced FE model and equivalent circuit. The frequency characteristics of an inductor and the induction heating machine evaluated by the equivalent circuit are shown to be in good agreement with those computed from the original FE model. [ABSTRACT FROM AUTHOR]

This paper proposes an equivalent-circuit generation from the finite-element (FE) model of electromagnetic devices using a model order reduction (MOR). In this method, an equivalent circuit is directly generated from the reduced transfer function obtained using MOR based on Padé approximation via the Lanczos process. It is shown that the generated circuit yields sufficiently accurate results in both frequency and time domains. Moreover, the computational time of the present method is much shorter than that of the circuit generation based on frequency sweep using the conventional FE analysis. [ABSTRACT FROM AUTHOR]

Superparamagnetic tunnel junctions (SMTJs) are noise powered stochastic oscillators, which can harness thermal energy through phenomena such as stochastic resonance and noise-induced synchronization. This enables them to operate with the minimal externally supplied energy, and therefore, makes them promising candidates for implementing bioinspired computing schemes. These applications require understanding how SMTJs can be integrated into CMOS circuits. In this paper, we present a compact model of SMTJ, written in the VerilogA language, that can be used within standard integrated circuit design tools. This compact model is based on the Néel–Brown model and allows for fast simulations. We show that this model can reproduce the experimental characterization of a sample subjected to different values of dc currents. Then, we definitively demonstrate the validity of the model by confronting it to the experimental results in the case of a complex phenomenon: noise-induced synchronization. [ABSTRACT FROM AUTHOR]

This paper deals with the analysis of a 1-D magneto-dynamic model (MDM) of soft magnetic steel sheets (SMSSs) under arbitrary excitation conditions. In the presented analysis, the MDM is coupled with the static hysteresis model proposed by Tellinen. The coupled model of SMSSs is evaluated using measured excitation voltages as well as measured excitation currents directly as the model input variables, where both excitation cases are compared and evaluated versus measurements. The calculated results show a good agreement with the measurements. Based on the presented analysis properties, advantages, and flexibility of the MDM model as well as the limitations of the presented coupled model are pointed out, where guidelines for an improved coupling are also given. [ABSTRACT FROM AUTHOR]

In this paper, a fast H(M) magnetostatic hysteresis model is presented, tested, and used in Simulink and partial element equivalent circuit (PEEC) environments. The model is primarily designed to achieve full compatibility with the current 3-D PEEC formalism for nonlinear isotropic magnetic materials, compatibility not met by any direct model. The capabilities of the proposed model are shown in stand-alone configuration and as a core of circuit components within the Simulink environment. Its effectiveness in the 3-D PEEC formulation is then demonstrated. [ABSTRACT FROM AUTHOR]

To achieve high-performance computing of a microwave simulation with small-size hardware and low power consumption, the authors have been working on the development of a dataflow architecture finite difference time domain (FDTD) dedicated computer. One of the biggest problems of the method of the dedicated computer for being used in practical applications is flexible design for various kinds of numerical models. The previously developed FDTD machine was designed to deal with arbitrary 3-D numerical model, any dielectric materials, and PML distributions by the same hardware circuit. This paper proposes a modified architecture of the FDTD dedicated computer for the microwave simulation in dispersive materials. [ABSTRACT FROM AUTHOR]

Among the model-order reduction techniques, the proper orthogonal decomposition (POD) has shown its efficiency to solve magnetostatic and magnetoquasistatic problems in the time domain. However, the POD is intrusive in the sense that it requires the extraction of the matrix system of the full model to build the reduced model. To avoid this extraction, nonintrusive approaches like the data-driven (DD) methods enable to approximate the reduced model without the access to the full matrix system. In this paper, the DD-POD method is applied to build a low-dimensional system to solve a magnetostatic problem coupled with electric circuit equations. [ABSTRACT FROM AUTHOR]

In this paper, a broadband equivalent node-to-node admittance functions (NAFs) model for shielded power cables are presented aiming at the direct time-domain simulation. The finite-element method is employed to obtain the frequency-dependent per-unit-length resistances, self- and mutual-inductances, and the self- and mutual-capacitances of the power cables. The matrix rational approximations are then applied to obtain the rational model (in pole-residue form) of the terminal admittance matrix of the multi-conductor transmission line (MTL) model. Next, the numerical stability of the rational model is guaranteed by the terminal (port) passivity enforcement technique. The circuit representation of the equivalent NAFs of the full cable with the length of interest can be synthesized based on the pole-residue description. It is validated by comparing the frequency response with the one computed by applying the original MTL model. [ABSTRACT FROM AUTHOR]

A novel steady-state equivalent circuit model for linear induction motors is presented in this paper. The novelty resides in classification and inclusion of end effects that are considered static and dynamic, namely as speed-independent and speed-dependent end effects. The Duncan model is used to address the dynamic end effect and appropriately modified to account for the saturation of back iron. The static end effect, which manifests itself by the alternating field component, is represented by an additional circuit branch similar to the branches of the motor with an alternating magnetic field. Each type of end effect is modeled and included separately. The results regarding determination of basic performance characteristics are compared with those obtained from finite element (FE) simulation. The procedure to identify the parameters of this circuit using a FE model is also presented. [ABSTRACT FROM PUBLISHER]

To study a multirate system, each subsystem can be solved by a dedicated software with respect to the physical problem and the time constant. Then, the problem is the coupling of the solutions of the subsystems. The waveform relaxation method (WRM) seems to be an interesting solution for the coupling, but until now, it has been mainly applied on academic examples. In this paper, the WRM is applied to perform the coupling of a controlled rectifier and a non-linear finite element model of a transformer. [ABSTRACT FROM AUTHOR]

Among the model order reduction techniques, the proper generalized decomposition (PGD) has shown its efficiency to solve static and quasistatic problems in the time domain. However, the introduction of non-linearity due to ferromagnetic materials, for example, has never been addressed. In this paper, the PGD technique combined with the discrete empirical interpolation method (DEIM) is applied to solve a non-linear magnetostatic problem coupled with the circuit equations. To evaluate the reduction technique, the transient state of a three-phase transformer at no load is studied using the full finite-element model and the PGD–DEIM model. [ABSTRACT FROM AUTHOR]

As a portable high-performance computing technology for electromagnetic wave simulations, several kinds of dedicated computers for the finite-difference time-domain (FDTD) method have been considered. We previously proposed a dataflow architecture FDTD dedicated computer and showed that the estimated performance of the FDTD dataflow machine could exceed those of the high-end PC and GPU computers. On the other hand, the digital circuit of our previously proposed FDTD dataflow machine was inefficiently implemented in the field-programmable gate array (FPGA) owing to dual-mode operations of the normal grids and the perfectly matched layer (PML) grids, that is, almost half parts of the FPGA hardware resources were not used in our previously proposed machine. This paper proposes a modified architecture of the 3-D FDTD dedicated computer to improve the inefficient use of the FPGA hardware resources. The modified digital circuit of the FDTD scheme is designed to execute the FDTD calculation for eight normal grids or four PML grids. In the modified machine, there are almost no unused parts of hardware resources, and double size of FDTD scheme circuits can be implemented in the same size FPGA compared with the previously proposed machine. [ABSTRACT FROM AUTHOR]

This paper deals with a new analytical parametric magneto-dynamic model of a thin soft magnetic steel sheet (SMSS). The interdependence of the magnetic field and eddy currents inside such an SMSS is calculated by dividing the sheets into an arbitrary number of slices. Using an adequate number of slices, the magnetic field and eddy currents are described piece-wise uniformly across the SMSS for a given excitation dynamics. Dynamic hysteresis loops for arbitrary excitations can be calculated using the proposed model. The calculated results are validated by the measurements on a non-oriented SMSS. [ABSTRACT FROM AUTHOR]

The Proper Orthogonal Decomposition (POD) combined with the (Discrete) Empirical Interpolation Method (DEIM) can be used to reduce the computation time of the solution of a Finite Element (FE) model. However, it can lead to numerical instabilities. To increase the robustness, the POD_DEIM model must be constructed by preserving the structure of the full FE model. In this paper, the structure preserving is applied for different potential formulations used to solve electromagnetic problems. [ABSTRACT FROM AUTHOR]

The multi-slice method allows approximation of the 3-D phenomena without carrying out a full 3-D analysis, e.g., in skewed radial flux electrical machines. The idea is to divide a 3-D machine into several 2-D finite-element models along the axis, connected by electrical circuits. Here we show how the multi-slice method is perfect for parallel computation; the computation efficiency is close to that of 2-D models in modern parallel hardware. The results are shown to agree with 3-D computation and experimental results. [ABSTRACT FROM AUTHOR]

Multidisciplinary optimization strategies are widely used in the static case and can be extended to a problem with a time-domain model in order to reduce optimization time. The waveform relaxation method is a fixed-point approach applied to waveforms, which allows the coupling of dynamic models. Using the individual discipline feasibility strategy, the coupling is transferred to the optimization problem and leads to a high decrease of the number of model evaluations compared with the multidisciplinary feasibility strategy. The drawback of this approach might be the increased number of optimization variables, but it is coped through an efficient way to compute the derivatives of time-dependent variables. [ABSTRACT FROM AUTHOR]

A volume integral formulation using facet elements to compute eddy currents in thin conductive shells is presented. The formulation is general and considers the field variation through the depth due to the skin effect. The formulation leads to an equivalent lumped elements circuit that can be coupled with an external circuit. The resolution of the circuit is achieved by the independent loops method. The formulation has been validated because of two numerical examples. Results are compared with an axisymmetric finite-element method (FEM) and another shell formulation implemented in a 3-D FEM. [ABSTRACT FROM PUBLISHER]

After its recent improvements described here, open source finite element software Elmer is shown to be a highly efficient option for electrical machine modeling. The parallelization of computational burden is shown to be a necessity. The methods implemented enable applying fully parallel computation to electrical machine models, including rotation and electrical circuits. Computational experiments performed demonstrate that Elmer can effectively utilize several hundreds of computational cores in parallel, making it an attractive alternative when computational speed is of high importance. [ABSTRACT FROM PUBLISHER]

The proper orthogonal decomposition combined with the discrete empirical interpolation method is investigated in order to reduce a finite-element model of a multiple-input non-linear device. The non-linear reduced problem is solved using the Newton–Raphson method. The transient state of a three-phase transformer with a variable load is studied with the proposed reduction method for different supply voltage conditions. [ABSTRACT FROM PUBLISHER]

We propose a model of an equivalent electrical circuit specifically designed for a ferrite inductor excited by a nonsinusoidal waveform valid for use in an electronic circuit simulator. We estimate the model parameters by means of Finite Elements in 2-D which leads to significant computational advantages over the 3-D model. We carry out the validation of the procedure for an RM14/I core by comparing the experimental and simulated output waveforms obtained at different frequencies and levels of excitation from the linear to the saturation regions. In addition, we consider the effect of power losses in the core. [ABSTRACT FROM AUTHOR]

Non-invasive repetitive transcranial magnetic stimulation (TMS) is a neuromodulation technique in which time-varying magnetic fields induce electric fields on the patient’s brain, thus stimulating neurons in the targeted cortical region. We have created a new model of the basal ganglia motor pathway in the human brain, using the Python package called NEST. We simulated healthy nuclei with random noise and connection weights optimized to mimic established background neuronal activity noise in the connecting nuclei. We then simulated Parkinsonism by removing dopaminergic (DAergic) input from the substantia nigra pars compacta to the striatum. The results showed the production of characteristic Parkinsonian neuronal features, ranging from pathological highly irregular to burst signals matching those found during in vivo animal and human microelectrode recording studies. With the model thus validated, we modeled deep brain stimulation (DBS) current delivery to the globus pallidus internus (GPi) in a Parkinsonian brain and simulated neuron firing as an effect of DBS. Finally, repetitive TMS at various frequencies was simulated at the level of the motor cortex, which produced predicted downstream firing rate effects and intra-neuronal synchrony at the level of the GPi. Although typical clinical TMS at 10 pulses/s was suggested to offer some beneficial effects, firing rates and patterns and desynchronous firing were most effectively normalized to match those seen in a healthy GPi upon stimulation at 50 pulses/s. Thus, our modeling suggests that cortical, non-invasive TMS may be a viable alternative to DBS surgery for patients with Parkinson’s disease (PD). [ABSTRACT FROM AUTHOR]

To eliminate the inefficiencies of the existing physics-based planar-gate insulated gate bipolar transistor (IGBT) model without considering an arbitrary free-carrier injection condition and 2-D effects at the MOS end of the drift region in the transient performance simulations, a coupled circuit-ambipolar diffusion equation model and its numerical solution methodology is proposed. Moreover, the proposed model treads the nonlinearity in a complete transient manner. The accuracy of the proposed model is validated by comparing the computed results with both experimental ones and those of an existing model. [ABSTRACT FROM AUTHOR]

A consistent and computationally efficient finite-element model for the simulation of the steady-state operation of surface-mounted permanent magnet brushless dc motors driven from quasi-square wave inverters is presented. The methodology combines the magnetostatic finite-element and the steady-state time-periodic circuit models with time averaging. A weak field-circuit coupling is established through the effective constant current and lumped parameters estimated at various loading conditions. The performance characteristics, determined via the proposed model for two different motors, are comparable with those obtained from the comprehensive time-stepping finite-element model, with the execution time being approximately a hundred times shorter for the former. [ABSTRACT FROM AUTHOR]

For the time domain simulation of coupled systems, co-simulation is a prominent approach. The contraction and the speed of convergence of corresponding schemes depend on the design of the coupling interface and the computational order among others. Here, the field/circuit coupling is investigated, where the standard approach of decoupling is to separate the field and the circuit part. In this context, we introduce a new decoupling approach: $LR$ -coupling. For this coupling type, general stability and contraction are directly influenced by the coupling interface. Thus, these properties are independent of embedded electric networks or embedded electromagnetic devices. Furthermore, first investigations demonstrate that the use of a dedicated coupling interface may enhance the convergence properties, i.e., it may reduce the computational effort for prescribed tolerances. [ABSTRACT FROM AUTHOR]