Electromagnetic Quantities Research Articles

Study and diagnostic of electrical faults in asynchronous machines

Electric drives increasingly use asynchronous motors because of their robustness, their specific power and their cost. Their maintenance and diagnosis therefore become an economic issue.Industrial requirements in terms of maintenance direct research towards a diagnosis using electromagnetic quantities such as flux, current, voltage, and more particularly the stator current which only requires a current sensor which gives an image on the stator phase current, on the other hand this technique makes it possible to improve the reliability of the motor and to increase its service life. It is important to detect early the faults that can appear in these machines and therefore to develop operation monitoring methods has made it possible to analyze the impact of faults on the behavior of the motor. It has made it possible to obtain specific signatures for electrical failures and to predict their evolution. we studied the short-circuit fault in the three-phase asynchronous motor which is the spectral analysis of the stator currents by making a modeling by the finite element method using the FLUX 2D software.

Analytical Approach of three-dimensional Flawed Multilayered Structure for EC Inspection

This article is devoted to the development of two current source models for the analysis of 3D electromagnetic phenomena in a conductive part of spherical geometry based on the second-order magnetic vector potential method for eddy current nondestructive testing (ECNDT). The first model, for a homogeneous single-layer sphere, allows the analytical calculation of all electromagnetic quantities in the charge. The second allows to treat in addition to the three-dimensional aspect of the problem, the heterogeneity of the charge (with several layers of different conductivities). An investigations using a multifrequency system have shown better results in detection of small cracks. The observations take about the calculation of normalized impedance based on dissipate energy and Joule losses in conductive material.

A Simplified Model Predictive Current Control Strategy for Six-phase H-bridge Inverters

Background: The double-end H-bridge inverters can realize independent control of the stator voltage in each phase and have flexible advantages of modulation and fault tolerance; thus, they are more suitable for multi-phase fault-tolerant motor drives. However, due to the increase of voltage vectors and the coupling between the electromagnetic and non-electromagnetic quantities, the normal control strategies for traditional three-phase motor drives do not work anymore. Objective: This paper aimed to propose a simplified model predictive current control strategy based on the vector space decomposition (VSD) and the vectors’ gradual simplification for the three-level six-phase H-bridge inverters. Methods: Firstly, the 729 physical variables were decomposed and mapped onto the fundamental αβ subspace, harmonic xy subspace, and the zero-sequence o1o2 subspace based on the VSD. Then, to eliminate the influence of the harmonic and zero-sequence components on the control performance and make an easy digital implementation, vectors’ simplification has been proposed based on the in-depth analysis of the relationship between the voltage vectors mapped onto different subspaces and vectors’ stratification. With the simplification method, the number of voltage vectors was simplified from 729 to 12, and then the selected voltage vectors were used in the rolling optimization of the model predictive current control (MPCC) to choose the optimal one. Finally, sufficient experiments were carried out including static and dynamic conditions, different modulation index and power factor, etc., to verify the feasibility of the proposed strategy. Results: The simulation and experimental results show that with the simplified MPCC strategy, both the static and dynamic performances are relatively good, and the THDs of the phase current under different modulations and power factors are relatively low. Conclusion: The proposed MPCC algorithm for the three-level six-phase H-bridge inverters has shown obvious improvement in solving the control problems of multi-vectors and complex redundancy issues.

Point-charge models and averages for electromagnetic quantities considered in two relativistic inertial frames

Electromagnetic quantities at a spacetime point have tensor Lorentz transformations between relatively-moving inertial frames. However, since the Lorentz transformation of time between inertial frames depends upon both the time and space coordinates, averages of electrodynamic quantities at a single time will in general depend upon the inertial frame, and will differ between inertial frames. Here we illustrate how the use of continuous charge and current distributions rather than point-charge distributions can lead to physically mystifying and even inaccurate results for electromagnetic quantities and physical phenomena. The discrepancy noted between the average electric field values in different inertial frames is particularly striking because it is first order in the relatative velocity between the frames.

Internal capacitive compensation of the reactive power of the screw electromechanical converter

Introduction. A special category among induction machines with a massive rotor is occupied by the class of multifunctional electromechanical energy converters, which are integrated with the links of technological processes Problem. The exchange of reactive energy between the source and the electromechanical converter during periods of operation with a low load leads to a significant decrease in its efficiency and power factor. With the use of non-linear loads and taking into account possible resonance, it has become more difficult to improve the power factor by installing capacitor banks. Goal. Increasing the energy indicators of the electromechanical converter by spatial displacement of the main and additional stator windings and internal capacitive compensation. Methodology. Comparative analysis of connection schemes and spatial arrangement of stator windings when using internal capacitive compensation. Modeling and experimental studies of electromagnetic and electromechanical characteristics of a screw electromechanical converter. Results. The distribution of electromagnetic quantities was established and the choice of the angle of spatial displacement of the main and additional windings of the stator phases of the modified converter, which ensure an increase in the value of the electromagnetic torque and power factor, was justified. The results of experimental studies of the screw electromechanical converter are presented. Originality. For the first time, a method of internal capacitive compensation of reactive power is proposed for multifunctional electromechanical converters of technological purpose. Practical value. The use of the proposed method of spatial displacement of the main and additional stator windings and internal capacitive compensation will ensure an increase in the energy performance of the screw electromechanical converter. References 23, tables 3, figures 15.

Semianalytical modeling of squirrel-cage induction machines with consideration of iron permeability and eddy-currents using elementary subdomain technique

PurposeThis paper aims to propose a semianalytical model of a squirrel-cage induction machine (SCIM), considering local magnetic saturation and eddy-currents induced in the rotor bars.Design/methodology/approachThe regions of the rotor and stator are divided into elementary subdomains (E-SDs) characterized by general solutions at the first harmonic of the magneto-harmonic Maxwell’s equations. These E-SDs are connected in both directions (i.e., along the r- and θ-edges).FindingsThe calculation of the magnetic field has been validated for various values of slip and iron permeability. All electromagnetic quantities were compared with those obtained using a two-dimensional finite-element method. The semianalytical results are satisfactory compared with the numerical results, considering both the amplitude and waveform.Originality/valueExpansion of the recent analytical model (E-SD technique) for the full prediction of the magnetic field in SCIMs, considering the local saturation effect and the eddy-currents induced in the rotor bars.

On the Magnetic Charge of an Electron and the Generalized Electrodynamic Forces

In the late 90s of XX century the author proposed a concept describing an electric charge as a rotating mass. Such a description makes it possible to exclude the Coulomb quantity from the system SI and to describe all electrodynamic quantities in mechanical dimensions. According to the dimensionality, a magnetic charge is an electric charge divided by the speed of light. In the 10s of the 21st century, the authors of this article proposed a generalization of the traditional system of Maxwell’s equations in the context of a mechanical description of electromagnetic quantities. The generalized system has a solution for single charges. From these solutions, one can construct the energy and momentum of the interaction of two electrons. In this case, the electron is the unit of two principles: the electric and the magnetic. The gradient of the interaction energy gives the interaction force of the electric charges of the electrons, and the time derivative of the interaction momentum gives the interaction force of the magnetic charges of two electrons. A formal description of these forces completes the article.

An SIE Formulation With Triangular Discretization and Loop Analysis for Parameter Extraction of Arbitrarily Shaped Interconnects

A surface integral equation (SIE) formulation under the magneto-quasi-static assumption is proposed to efficiently and accurately model arbitrarily shaped interconnects in packages. Through decently transferring all electromagnetic quantities into circuit elements, the loop analysis is used to carefully construct matrix equations with an independent and complete set of unknowns based on graph theory. In addition, an efficient preconditioner is developed, and the proposed formulation is accelerated by the pre-corrected fast Fourier transform (pFFT). Four practical examples, including a rectangular metallic interconnect, bonding wire arrays, interconnects in a real-life circuit, and the power distribution network (PDN) used in packages, are carried out to validate its accuracy, efficiency, and scalability. Results show that the proposed formulation is accurate, efficient, and flexible to model complex interconnects in packages.

Electromagnetic Performance Analysis of a Field-Modulated Permanent Magnet Motor Using Improved Hybrid Subdomain Method

The hybrid subdomain method (HSDM) combining conventional SDM with equivalent magnetic network has been proved to be a qualified approach to field prediction. However, this method still suffers two issues: first, the saturation effect of stator core is considered but that of rotor core is ignored, thus causing no-accuracy calculation; second, the mathematical complexity is inevitable due to adoption of virtual line-current density as extra interface conditions. This work is to develop an improved HSDM (IHSDM) for accurately and efficiently predicting the electromagnetic performance of a field-modulated permanent-magnet motor. The key of the proposed IHSDM is to fully consider magnetic saturation inside both stator and rotor cores. More importantly, the replacement of virtual-line current density by virtual-surface magnetization and current density makes interface conditions as simple as the SDM. The quantitative comparisons with conventional HSDM and FEA are conducted and the prototyping tests are also performed. It shows that the proposed IHSDM has lower time consumption and occupied memory, and electromagnetic quantities have about two times more accuracy than conventional HSDM. Additionally, a dynamic calculation is achieved by the IHSDM and verified by FEA.

Sensitivity Analysis Using the Virtual Work Principle for 2-D Magnetostatic Problems

The sensitivity analysis of electromagnetic quantities such as the magnetic force and torque is a crucial step when optimizing electromagnetic devices with gradient-based optimizers. This paper provides an analytical derivation of those two quantities using the virtual work principle in a finite element package. It is suitable for any kind of optimization. A focus on the particular use of this sensitivity on shape optimization is presented. The development and validation of the method is detailed in this case. Finally, it is applied to the shape optimization of a switch reluctance motor (SRM) to improve its performances.

A New Transmitting Coil for Powering Endoscopic Capsules Using Wireless Power Transfer

This study focuses on using wireless power transfer (WPT) technology based on magnetic resonant coupling (MRC) to supply electric power to an endoscopic capsule to be used for the direct feeding of specific functions or for battery charging. One of the main limitations of the diffusion of endoscopic capsules is the limited autonomy of the internal battery. The aim of the paper is to present an innovative system to wirelessly power capsules using inductive coupling. Here, a new transmitting coil architecture is proposed to allow the wireless charging of the capsule equipped with a monoaxial receiving coil for any possible geometric position and orientation. The new wearable transmitting coil consists of four rectangular coils with independent excitations, and it is capable of producing a magnetic field in any direction. The obtained results in terms of electrical performance of the proposed WPT system and in terms of in situ electromagnetic physical quantities are compared with the basic restrictions of electromagnetic field (EMF) safety guidelines. The results obtained are very promising, as the proposed WPT configuration can transfer at least 250 mW in a capsule that travels along the entire gastrointestinal tract.

Simulation of the Electromagnetic Waves Propagation in Conductive Media Using Analytical Formulae

Abstract The paper aims to investigate the electromagnetic waves behavior in conductive media using analytical formulae. An example of a very long vertical conductive wall of given thickness placed in front of a vertically polarized electromagnetic wave is considered. The variation of the electromagnetic field quantities inside the conductive wall are detailed using analytic formulae. The numerical example considered was aimed to easily understand the important properties of the field behavior inside the conductive wall. The main conclusions end the paper.

FE Modeling of Superconducting EDS System Employing Mixed Formulations and Field-Circuit Coupling Method

Superconducting (SC) electrodynamic suspension (EDS) technology utilizes the electromagnetic force generated by the interaction between the onboard SC magnets and ground figure-8-shaped coils. In this article, a transient 3-D finite-element (FE) model using a suspension unit with cross-connected null-flux coils is established. First, mixed <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$A$ </tex-math></inline-formula> – <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$V$ </tex-math></inline-formula> formulations are adopted to solve different domains. The field-circuit coupling method is introduced to connect the 8-shaped coils on two sides of the track and realize the simulation of the operation of lateral offset. Second, the periodic linear extrusion operator solves the continuity of electromagnetic quantities across the common boundaries of the moving and fixed domains and avoids mesh reconstruction and distortion. The computational efficiency of the model is significantly improved. The custom boundary conditions are demonstrated in detail. The dynamic circuit analytical model is used to verify the correctness of the model. Finally, high-speed operations of a vertical or lateral offset of the EDS system are simulated. The transient electromagnetic force and force density acting on the figure-8-shaped coils are analyzed. This article provides a more efficient and general analysis approach for the long-term operation of EDS trains with cross-connected figure-8-shaped null-flux coils, especially with lateral offset.

Development of a mathematical model of a frequency-controlled electromagnetic vibration motor taking into account the nonlinear dependences of the characteristics of the elements

The wider application of vibration machines (VM) with electromagnetic motors (EMVM) in various industries, including in vibration test benches for telecommunication devices and equipment has been studied in the paper. Difficulties associated with maintaining their productivity and efficiency at a given level are largely hindered. These factors mainly depend on the determination of the degree of influence of the nonlinearities of the input-output characteristics on the output values of the VM, the possibilities of tuning into the resonance mode, and the control of the output values while ensuring the energy-saving mode of operation of the EMVM. The mathematical model has been developed for a frequency-controlled EMVM taking into account the nonlinear dependencies of the characteristics of the elements, which makes it possible to determine the most accurate amplitude of oscillations of the EMVM working body when passing through resonance, observed with changes in the voltage frequency. The analysis of the physical processes of the influence of nonlinear elements of the electric circuit of the EMVM on the electromagnetic quantities and the derived analytical expressions of these nonlinearities, which make it possible to determine the harmonic composition of the current of the EMVM winding, are made. The system of vector control of the EMVM and the inclusion of a mathematical model of the engine into the control system have been developed, which will allow calculating the frequencies of free oscillations of the working body for tuning into the resonance mode.

On the similarity of electromagnetic and gravitational fields

It is well known that gravitational quantities are in many ways similar to electromagnetic quantities. The masses that create a gravitational field are similar in this to electric charges. A gravitational static field, like an electrostatic field, is characterized by potential and intensity. Vortex and rotational movements of masses are often and quite justifiably compared with a magnetic field. According to existing concepts, there are four types of different fundamental physical interactions: strong, weak, electromagnetic and gravitational. Strong and weak interactions are manifested inside atomic nuclei and between elementary particles, electromagnetic – between charges, and gravitational acts between massive bodies, becoming the main one in the case of astronomical objects. The article presents a comparison of mechanical and gravitational quantities from the condition of their similarity to electromagnetic quantities. Visual systemically possible patterns involving field gravitational quantities similar to electromagnetic ones are given.

Implantation of Coated Superconducting Materials in the Synchronous Machine for Superconducting Energy Storage

Numerical tools appear to be essential for modeling and designing devices based on superconducting materials. In this article different simulation results are presented, using a computer code based on the finite element method adopted for the resolution of the electromagnetic equations, in the case of an axisymmetric two-dimensional problem, with this code we study the variations of the different electromagnetic quantities. The second generation superconductor has been modeled as an interesting diamagnetic material as inductive pulse sources. The performance in magnetic field resistance, energy storage and thermal stability of the ribbon, known as YBCO, makes it possible to broaden its field of application. Two categories of machines have been proposed and analyzed, the first is classic and the second uses a superconducting ribbon. In addition, a comparative study between the two proposed models is carried out and the results are analyzed and discussed.

Induction Motors Technical Condition In-Service Testing Methods

The article describes methods for in-service diagnostics of the technical condition of induction motors, which are the most widely used type of electromechanical systems. By now, a large number of various studies on this matter have been published. It is stated that the accomplished studies implement an "external" approach to solving the problem, which consists in deriving a diagnostic conclusion based on an analysis of changes in the electric motor external characteristics in one of its operation modes. In addition, these studies are based on two-dimensional models of the classical theory of electrical machines, which does not allow them to adequately reflect situations of multidimensional distribution of electromagnetic quantities in a vector space. These circumstances generated the need to develop more advanced diagnostic methods, called topological ones. Topological diagnostics methods are theoretically substantiated based on the ideas about the IM multidimensional vector space. It is shown that the parametric properties of the vector space and first of all of its working area, have a key influence on the electromechanical energy conversion efficiency. Two methods for testing different areas of the vector space are outlined. In the first case, the space working area is tested for parametric uniformity and operational stability. The results of three experiments provide unbiased and sufficient information about the degree of its homogeneity, about the changes that have occurred during the operation, and about their rates. The testing makes it possible to draw well-grounded conclusions about the electric motor active part technical condition and the degree of its criticality. In the second case, the vector space phase coordinates are tested for parametric uniformity and operational stability. The results presented testify that the proposed testing scheme is sensitive to phase parameter deviations. This is facilitated by the differential principle of its construction. The signal in a short-circuited phase, which appears in the case of a parametric phase imbalance, serves as its clear indicator. The presented mathematical modeling data confirm the efficiency of the proposed testing methods.

Artificial intelligence-based models for reconstructing the critical current and index-value surfaces of HTS tapes

For modelling superconductors, interpolation and analytical formulas are commonly used to consider the relationship between the critical current density and other electromagnetic and physical quantities. However, look-up tables are not available in all modelling and coding environments, and interpolation methods must be manually implemented. Moreover, analytical formulas only approximate real physics of superconductors and, in many cases, lack a high level of accuracy. In this paper, we propose a new approach for addressing this problem involving artificial intelligence (AI) techniques for reconstructing the critical surface of high temperature superconducting (HTS) tapes and predicting their index value known as n-value. Different AI models were proposed and implemented, relying on a public experimental database for electromagnetic specifications of HTS tapes, including artificial neural networks (ANN), eXtreme Gradient Boosting (XGBoost), and kernel ridge regressor (KRR). The ANN model was the most accurate in predicting the critical current of HTS materials, performing goodness of fit very close to 1 and extremely low root mean squared error. The XGBoost model proved to be the fastest method, with training computational times under 1 s; whilst KRR could be used as an alternative solution with intermediate performance.

Mathematical modeling of typical electrical circuits, oscillators and pendulums

The work is devoted to mathematical and simulation modeling of electromechanical systems, in which oscillations in electrical circuits, oscillators and pendulums are studied under the action of forces of various physical nature. To compile the equations of electromechanical systems, the apparatus of analytical mechanics was used, in which the electromagnetic and mechanical quantities characterizing the system appear as formally equal. The equations of motion are based on the Lagrange-Maxwell equations. The simulation was performed using computer algebra programs.

Evaluation of Convolution Integrals at Late-Times Revisited

The late-time evaluation of electromagnetic (EM) field quantities yielded by convolution integrals that combine Green’s functions available at discrete time samples and strictly causal excitations is critically revisited. A typical situation is used for tracing the causes of the divergent late-time behavior that is often experienced. A framework combining a suitable integral partitioning with a polynomial approximation is shown to effectively guarantee the integrals’ convergence. The formulation is validated via numerical experiments evidencing its accuracy and computational efficacy. The method is amenable to be used in a wide range of problems requiring the late-time evaluation of convolution integrals of the indicated type.