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Abstract Electric Circuit Element (ECE) boundary conditions (BC) defined for full-wave (FW) electromagnetic field allow a natural coupling between field devices and electric circuits. The novelty of this paper is that it shows how ECE BC can be implemented into a 3D-finite element method (FEM), when using A, a magnetic vector potential and φ, a scalar potential. Weak formulations are described and implemented in the free environment Open Numerical Engineering LABoratory (onelab). The validation is carried out on 3D examples solved both in frequency (FD) and time domain (TD), for FW formulations in potentials, as well as for corresponding Darwin approximations of Electromagneto-Quasistatic (EMQS) models. Results are compared with those obtained with a formulation in E V, where E is the electric field inside the domain and V is a scalar potential defined solely on the boundary. The results show that: 1) the use of potentials has some advantages over the EV formulation in TD only; 2) excitation type matters, the voltage excitation, here essential in FEM, proved to be the most robust one for the considered examples: a coplanar waveguide and a spiral inductor.

Electric Circuit Element (ECE) boundary conditions (BC) defined for full-wave (FW) electromagnetic field allow a natural coupling between field devices and electric circuits. The novelty of this paper is that it shows how ECE BC can be implemented into a 3D-finite element method (FEM), when using A, a magnetic vector potential and φ, a scalar potential. Weak formulations are described and implemented in the free environment Open Numerical Engineering LABoratory(onelab). The validation is carried out on 3D examples solved both in frequency (FD) and time domain (TD), for FW formulations in potentials, as well as for corresponding Darwin approximations of Electromagneto-Quasistatic (EMQS) models. Results are compared with those obtained with a formulation in EV, where E is the electric field inside the domain and V is a scalar potential defined solely on the boundary. The results show that: 1) the use of potentials has some advantages over the EV formulation in TD only; 2) excitation type matters, the voltage excitation, here essential in FEM, proved to be the most robust one for the considered examples: a coplanar waveguide and a spiral inductor. [ABSTRACT FROM AUTHOR]

The electromagnetic radiation interference mechanism from multiple noise sources on the parallel topology of SiC MOSFET and Si IGBT Inverter is blurred, which will seriously affect the high reliability application of the structure. In order to solve this problem, a topological radiation EMI prediction method is proposed, the method includes the establishment of radiation equivalent models and radiation guidelines, the proposed inverter parallel topology radiation. The modeling method of electromagnetic interference can effectively analyze the influence of radiation interference of SiC and Si devices coupled with each other, and the established PCB radiation near and far field simulation can effectively realize the accurate prediction of radiation interference of inverter parallel topology, and finally the experimental platform of the parallel SiC MOSFET and Si IGBT inverter is built and tested, the test results demonstrate the accuracy of the proposed method.

In order to improve the working efficiency of the electromagnetic heat storage device under high current and high frequency, the electromagnetic field finite element method is used to analyze and calculate the load circuit to make it in a suitable working state. Firstly, the circuit model of the energy storage device is built by using the field-circuit coupling method and the coil inductance is calculated. Secondly, the harmonic capacitor is analyzed and calculated, so that the load circuit works in a weak inductive state. On this basis, the variation law of loss on the inductor core and the distribution of water temperature rise flowing through the core at a certain water velocity are analyzed. A 50 kW prototype was built using the method proposed in this paper, and the experimental results show that the electro-thermal conversion efficiency of the electromagnetic thermal energy storage device reaches 93.39 %. The feasibility of the design method is proved by experiment and simulation, which has important guiding significance for the research and design of electromagnetic thermal energy storage device.

High temperature superconducting (HTS) cable represents a promising solution for fulfilling the power demands of cities with large loads and high density. However, due to their connection to the distribution network, HTS cables are vulnerable to fault currents exceeding ten times their rated current, which poses a serious threat to both the safety of the cable and the operation of the grid. Considering the highly nonlinear nature of superconducting conductivity, this study develops a field–circuit coupling model to investigate the transient characteristics of distribution networks incorporating superconducting cables (DNSC). Firstly, a finite element model based on the two-dimensional H formulation was built to calculate the electrical and thermal parameters of the HTS cable. Subsequently, an equivalent circuit model of the distribution network was employed to estimate the short-circuit currents. Communicating via a co-simulation server, the superconducting cable current and distribution network impedance were updated in each step. Further, based on an actual DNSC system in Shenzhen, China, the highest quenching temperature of the cable and the maximum fault current of busbars were assessed. Finally, by integrating current limiters into the system, the withstand capability of the cable and busbars was determined, which indicates that the improved protection configuration can effectively suppress fault currents and ensure safe operation. Successfully applied to an actual distribution network, the co-simulation model utilizing the field–circuit coupling method addresses the challenges of solving highly nonlinear and time-varying systems, enabling transient analysis and protection research for the integration of superconducting devices into the conventional grid. [ABSTRACT FROM AUTHOR]

Copyright of Electric Machines & Control / Dianji Yu Kongzhi Xuebao is the property of Electric Machines & Control and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

In order to broaden the application of nanocrystalline soft magnetic materials in electrical engineering under extreme conditions, nanocrystalline alloys must also have good characteristics under high-frequency and nonsinusoidal excitation. In this paper, the magnetic properties of Fe-based nanocrystalline alloys excited by high repetition frequency pulses were measured. Excitation frequency and duty cycles are two important factors in the study of magnetic properties under pulse excitation. With the amplitude of the pulse remaining constant, different local hysteresis curves were obtained by changing the frequency and duty cycle. The experimental results proved that the higher the frequency is and the smaller the duty cycle is, the narrower the local hysteresis loop is. Finally, the finite element method (FEM) was used to model the magnetic core coupling with an impulse circuit based on the measured magnetic properties. Compared with the experimental results, the simulation results showed that the field-circuit coupling analysis model can effectively reflect the influence law of the frequency and duty cycle on magnetic properties. [ABSTRACT FROM AUTHOR]

Abstract We propose a method to investigate the generation mechanism of the transient vibration of a pump motor induced by electromagnetic (electromagnetic (EM)) forces. Compared with the steady vibration of a pump motor, the transient vibration characterised by a wider excitation frequency spectrum and larger instantaneous amplitude makes the vulnerable structure more easily exposed to potential damage. However, transient vibration of pump motor has not been analysed and verified before. Based on the fact that EM vibration dominates the vibration of pump motors, in this study, an approach which integrates the field‐circuit coupling method and multi‐physics finite‐element (finite‐element (FE)) simulation is proposed to estimate the structural response of pump motors under transient operating conditions. To determine the factors that determine the EM forces, an analytical model describing the transient interaction between the EM and the fluid torque is first created. It was revealed that the input voltage and slip rate are two key factors that affect the transient EM forces. Then, to quantitatively describe the transient EM forces governed by a specific control scheme during the start‐up process, a field–circuit coupling model embedding in the control scheme, electrical circuit model, motor FE model, and rotor dynamic model is established. This model allows the circuit equations, rotor dynamics equations, and magnetic field equations to be solved simultaneously. The transient EM forces obtained by the field–circuit coupling model provide excitation for the structural response calculation. Subsequently, a multi‐physics FE simulation, which takes a weak coupling strategy between the EM and structural dynamics fields, is utilised to link the different physical domains. Thus, the EM forces are transferred to a structural domain to compute the structural response by adopting a direct integration method. The integration approach developed in this study was verified on the pump motors in the main cooling units of ultra‐high voltage (UHV) converter stations. The trends of dominant components of simulated signals agree with the measured signals from the pump motors. This indicates that the proposed method can be widely applied for the transient vibration analysis and mitigation for pump motors.

Abstract A natural coupling of a circuit with an electromagnetic device is possible if special boundary conditions, called Electric Circuit Element (ECE), are used for the electromagnetic field formulation. This contribution shows how these ECE boundary conditions can be implemented into the 3D-finite element method for solving coupled full-wave electromagnetic (EM) field-circuit problems in the frequency domain. The frequency response allows the extraction of a reduced order model of the analyzed device, accounting for all the EM field effects. The implementation is based on a weak formulation that uses the electric field strength E strictly inside the domain and a scalar potential V defined solely at the boundary. Edge elements for E are used inside the three-dimensional domain and nodal elements for V are used on its two-dimensional boundary. The weak formulation is described and implemented in the free environment Open Numerical Engineering LABoratory (onelab). The validation is carried out on 3D examples.

Based on the previous research on electromagnetic pulse coupling, which pays more attention to the front-door coupling or the back-door coupling alone, this paper analyzes the influence of an electromagnetic pulse on electronic devices and systems through the joint analysis of front-door and back-door couplings using the finite-difference time-domain method (FDTD). This specific measure is used to simplify the front-door coupling to the voltage source injection, which occurs simultaneously with plane wave irradiation. This coupling scheme of the front door and back door with the voltage source and plane wave acting simultaneously is rarely seen in previous analyses, which also gives consideration to the working state of the circuit. Although the equivalent circuit model is widely used, it cannot effectively reflect the working state of the diode circuit under the conditions of large injection and high frequency. In view of the limited application scenarios of the traditional equivalent circuit model, which cannot accurately describe the internal response characteristics of the diode under different electromagnetic pulse coupling, this paper introduces an improved equivalent circuit model based on the physical model. Taking the Positive Intrinsic-Negative (PIN) limiter as the target, this paper analyzes the influence of the front-door and back-door joint coupling on its performance under different electromagnetic pulses and then gives protection suggestions. [ABSTRACT FROM AUTHOR]

One of the primary causes of additional losses in dry-type distribution transformers is harmonic disturbances in the distribution network. It is critical to investigate the change law of trans-former losses under harmonic conditions. The effect of harmonics on transformer core losses and winding losses is first investigated in this paper. The field-circuit coupling method is then used to create a finite element model of a three-phase phase dry type distribution transformer. Finally, the relationship between core loss and harmonic voltage, winding loss and harmonic current is calculated and analyzed for each harmonic frequency. The AC resistance factor model is found to be more accurate than the conventional model in calculating transformer harmonic winding losses. This paper's findings have significant theoretical implications for the analysis of harmonic losses and loss reduction in distribution networks. [ABSTRACT FROM AUTHOR]

With the rapid development of UHV power transmission and transformation project in our country, the gradually increasing electromagnetic capacity and electromagnetic loads of power transformers causes serious heating of the transformers. Therefore, it is particularly important to accurately calculate its temperature rise. Based on field-circuit coupling method, this paper took a 240000 KVA, 330 KV power transformer as the research object to calculate the whole temperature rise and heat transfer characteristics. Firstly, the average velocity of fluid was gotten by three-dimensional flow field of transformer which is calculated by establishing thermal network model of the transformer, phase winding and related structures. And then substitute it into thermal network model. The whole average temperature and temperature rise was gotten by using first law of thermodinamics and after the iteration. And according to the temperature rise test, this paper comprised and analyzed the computed results of thermal network and numerical analysis. Results showed that the error of the thermal network model was within the scope of the permit, and it was simple and quick. The method can provide basis for the future heat transfer research and temperature rise prediction of transformer. [ABSTRACT FROM AUTHOR]

In order to study the influence of harmonics on the vibration and noise of permanent magnet synchronous motor, this paper introduces an analysis method based on field-circuit coupling, and establishes a complete analysis process from the control strategy to the vibration and noise response of the motor. Firstly, the coupling model including control strategy, main circuit model and electromagnetic field model is established. Secondly, the finite element model of the permanent magnet synchronous motor under the influence of coupling is established to analyze and compare the electromagnetic force wave characteristics of the coupling excitation and the sinusoidal excitation. Then, the coupled electromagnetic force is loaded into the structural field to simulate and calculate the vibration and noise. Finally, the effectiveness of the model is verified through experimental sound pressure level comparison under steady-state and speed-up conditions, and it provides a reference for vibration and noise prediction of the motor system. [ABSTRACT FROM AUTHOR]

We propose a method to investigate the generation mechanism of the transient vibration of a pump motor induced by electromagnetic (electromagnetic (EM)) forces. Compared with the steady vibration of a pump motor, the transient vibration characterised by a wider excitation frequency spectrum and larger instantaneous amplitude makes the vulnerable structure more easily exposed to potential damage. However, transient vibration of pump motor has not been analysed and verified before. Based on the fact that EM vibration dominates the vibration of pump motors, in this study, an approach which integrates the field‐circuit coupling method and multi‐physics finite‐element (finite‐element (FE)) simulation is proposed to estimate the structural response of pump motors under transient operating conditions. To determine the factors that determine the EM forces, an analytical model describing the transient interaction between the EM and the fluid torque is first created. It was revealed that the input voltage and slip rate are two key factors that affect the transient EM forces. Then, to quantitatively describe the transient EM forces governed by a specific control scheme during the start‐up process, a field–circuit coupling model embedding in the control scheme, electrical circuit model, motor FE model, and rotor dynamic model is established. This model allows the circuit equations, rotor dynamics equations, and magnetic field equations to be solved simultaneously. The transient EM forces obtained by the field–circuit coupling model provide excitation for the structural response calculation. Subsequently, a multi‐physics FE simulation, which takes a weak coupling strategy between the EM and structural dynamics fields, is utilised to link the different physical domains. Thus, the EM forces are transferred to a structural domain to compute the structural response by adopting a direct integration method. The integration approach developed in this study was verified on the pump motors in the main cooling units of ultra‐high voltage (UHV) converter stations. The trends of dominant components of simulated signals agree with the measured signals from the pump motors. This indicates that the proposed method can be widely applied for the transient vibration analysis and mitigation for pump motors. [ABSTRACT FROM AUTHOR]

In this paper, a novel massively space-time parallel finite element (FE) transformer model is proposed for power system electromagnetic transient simulations. The method utilizes the reduced magnetic vector potential (RMVP) formulation to solve the electromagnetic field in the transformer, and the 3-D tetrahedral edge element is applied to discretize the RMVP formulation. The discretized nonlinear system is solved by adaptive transmission line modeling (TLM) and matrix-free conjugate gradient iterator, which allows parallelism at the elemental-level and eliminates the need for Newton-Raphson (NR) iterations over the large-scale global matrix. The paper also integrates the parallel-in-time method with the finite element solver to further parallelize the model at space-time level, and the GPU implementation of the model realized a speedup of over 55 and high accuracy, compared with a commercial FE software.

Permanent magnet synchronous motors with the formed winding can not only improve the slot fill factor and heat dissipation capacity but also effectively reduce the additional loss in the winding. Formed winding permanent magnet synchronous motors will become the future development tendency. Due to inherent features of the formed winding, the circulating current loss is a non-negligible issue. This paper proposes using the formed winding in permanent magnet synchronous motors and analyzes the circulating current loss in the formed winding. First, the finite element models of integer slot and fractional slot motors are established, and the magnetic field analysis are carried out. Then two commonly used methods of calculating circulating current loss are introduced in detail, and their calculation results are compared. Moreover, the high-precision field-circuit coupled finite element method is used to calculate the circulating current loss of integer and fractional motors. And circulating currents of the hairpin winding and the formed winding are compared. The analysis indicates that the circulating current in the formed winding cannot be ignored. Finally, comprehensive and in-depth research on the influencing factors of circulating current loss in the formed winding has been conducted. The results clarify that the number of parallel strands, the width of the slot opening, and the stator current have a considerable influence on the circulating current loss.

In this paper, a large oil-immersed self-cooling power transformer with a capacity of 180 MVA and a voltage grade of 220 kV is taken as the research object, and the global fluid network model of the transformer is established according to the oil circuit structure of the transformer and the circulation path of the cooling medium. Based on the decoupling method of fluid network, a three-dimensional finite element calculation model of local fluid field and temperature field is established at the decoupled location. Finally, the hot spot temperature of the winding appears at the 5th layer of the high-voltage winding, which is 89.2 °C, and the lowest temperature appears at the bottom of the low-voltage winding, which is 55.1 °C. The top oil temperature is 69.2 °C, and the bottom oil temperature is 47.6 °C. The temperature experiment of the prototype shows that the relative error of the calculation result of the hot spot temperature of the high voltage winding is 4.45%, the relative error of the calculation result of the hot spot temperature of the medium voltage winding is 4.43%, and the relative error of the calculation result of the hot spot temperature of the low voltage winding is 3.58%. It proves the accuracy of the global fluid network decoupling method to calculate the global temperature of the transformer, which provides a reference for the prediction of the global temperature of the transformer. [ABSTRACT FROM AUTHOR]

Copyright of Electric Machines & Control / Dianji Yu Kongzhi Xuebao is the property of Electric Machines & Control and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

A natural coupling of a circuit with an electromagnetic device is possible if special boundary conditions, called Electric Circuit Element (ECE), are used for the electromagnetic field formulation. This contribution shows how these ECE boundary conditions can be implemented into the 3D-finite element method for solving coupled full-wave electromagnetic (EM) field-circuit problems in the frequency domain. The frequency response allows the extraction of a reduced order model of the analyzed device, accounting for all the EM field effects. The implementation is based on a weak formulation that uses the electric field strength E strictly inside the domain and a scalar potential V defined solely at the boundary. Edge elements for E are used inside the three-dimensional domain and nodal elements for V are used on its two-dimensional boundary. The weak formulation is described and implemented in the free environment Open Numerical Engineering LABoratory (onelab). The validation is carried out on 3D examples. [ABSTRACT FROM AUTHOR]

The four-stage fast linear transformer driver (FLTD) with sharing cavity shell, gas insulation, and pluggable main bricks is the fundamental building block of the next-generation China Z-pinch driver CZ34. This contribution presents the self-consistent electromagnetic (EM) field distributions of the four-stage FLTD using the field-circuit coupled time-domain finite integration technique. Principles and methods on establishing the 3-D EM numerical model are discussed. The first analysis on equivalent inductances of the 92 main discharging bricks in the induction cavity and bricks’ EM characteristics is implemented. Simulated and experimental results demonstrate good consistency in the electrical performance of the four-stage FLTD with sharing cavity shell. Comparisons between the sharing cavity shell and independent cavity shell structures are performed in terms of load current and voltage and EM field distributions. Thus, applicability of the newly developed sharing cavity configuration is confirmed. The EM-interference (EMI) inside the induction cavity of the two kinds of FLTDs is also expounded and compared for the first time. This article offers a novel viewpoint on the related problems and supports the subsequent research activity and efforts to improve the performance of FLTD and Z-pinch machine. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Harbin University of Science & Technology is the property of Journal of Harbin University of Science & Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The aim of this contribution is the first numerical investigation on the electromagnetic (EM), thermal, and mechanical coupled fields of a newly developed single-stage fast linear transformer driver (FLTD) with 24-separate columns in the China Z-pinch driver CZ34. Considering the mutual influences of the EM, thermal, and mechanical fields during a pulsed current discharging process of the FLTD, the proposed numerical model is calculated using the field-circuit coupled time-domain finite integration technique (TD-FIT). By making reference to Tonti’s classification diagram, integral form state variables in the transient thermal field and mechanical field can be defined similar to those of the EM field. With appropriate time integration schemes, governing equations of different physical fields can be transformed to corresponding algebraic time-updating equations. The two-way interplays of the EM, thermal, and mechanical fields are performed with predefined coupling terms and time steps. The simulated results indicate that during one current discharging process, the temperature rise is less than 1 K and the maximum deformation generated by the Lorentz force is less than 0.1 mm. [ABSTRACT FROM AUTHOR]

In order to accurately obtain the temperature field of permanent magnet synchronous motor, we propose a field-circuit coupling method. This study takes a permanent magnet synchronous motor as the research object, uses MATLAB/Simulink to build the control strategy of the motor, and then deploys the finite element analysis software ANSYS Maxwell and ANSYS Simplorer to build the two-dimensional electromagnetic field model and control circuit model of the motor to form the field-circuit coupling model. The field-circuit coupling model calculates the loss of the motor, and imports the loss into the threedimensional magneto-thermal coupling model of the motor. Thus, the change of the temperature field of the motor can be observed in the base speed and weak field. The prototype test verifies the accuracy of the method. This method provides a basis for accurate calculation of the temperature field for motors. [ABSTRACT FROM AUTHOR]

We present a comprehensive and variational approach to the coupling of electromagnetic field models with circuit‐type models. That coupling relies on integral nonlocal quantities like voltage and current for electric ports, magnetomotive force, and magnetic flux for magnetic ports, and linked currents and fluxes for "tunnels" in the field domain. These quantities are closely linked to nonbounding cycles studied in algebraic topology and they respect electromagnetic power balance laws. We obtain two dual variational formulations, called E‐based and H‐based, which provide a foundation for finite‐element Galerkin discretization. [ABSTRACT FROM AUTHOR]

The safety and reliable operation of power grid is directly related to the ability of power transformer to withstand short-circuit, therefore, it is a problem to be solved to improve the ability of large power transformer windings to withstand short-circuit. Taking a three-phase five-limb power transformer as an example, the transient electromagnetic field, short-circuit electrodynamics force of windings and mechanical strength of coils are analyzed in depth. Firstly, the three-dimensional finite element model of the prototype is established, and the magnetic flux density distribution of the three-dimensional transient electromagnetic field of transformer under short-circuit operation and the axial and radial static force magnitude of the winding are calculated by using the field-circuit coupling method, and the distribution law can be obtained. At the same time, the mechanical strength of power transformer winding in its height direction is discussed, and the modal vibration mathematical model of transformer low-voltage winding in Z-axis direction is established. The displacement change and resonance frequency of the winding wire cake in the axial direction caused by short-circuit are calculated, and the short-circuit electrodynamics force of the winding is also checked. The research in this paper provides a theoretical basis for strengthening the design of short-circuit withstanding capacity of windings, and has a certain theoretical and engineering application value. [ABSTRACT FROM AUTHOR]

Copyright of Electric Machines & Control / Dianji Yu Kongzhi Xuebao is the property of Electric Machines & Control and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Limitation in manufacturing tolerances and assembly imperfections are the source of asymmetrical stator axes (ASA) defect, in particular, in a vacuum dry pumps (VDP) where the canned permanent magnet machines (CPMMs) are with fractional slot concentrated winding (FSCW). The performance and multi-physical field of CPMM in the vacuum environment is vulnerable to ASA. This work provides comprehensive research on the influence of ASA on the performance and multi-physical field of CPMM for VDP. This article establishes a mathematical model and Park transformation of a 1.6kW 6-pole/9-slot CPMM under the ASA condition. With the universality of ASA and not so strictly symmetrical stator axes as commonly expected, the experimental results demonstrated the significant impacts of ASA on the drive performance and multi-physical field, especially the inductance characteristics, the symmetry degree of stator current and flux linkage, rotor electromagnetic force and stator electromagnetic vibration of CPMM. The obtained conclusions can act as a significant reference for robust design and analysis of electric machines and drives. [ABSTRACT FROM AUTHOR]

The focus of this paper is numerical analysis on the performance of a newly designed mega-ampere (MA) class single-stage fast linear transformer driver (FLTD) with 24 separate columns in the China Z-pinch driver CZ34. However, the internal structure and media distribution of the FLTD induction cavity is very complicated and the short rise time of the bricks' discharge current will make spatial discretization much denser, resulting in a dramatic increase in the computational complexity of a 3-D model. In this paper, the electromagnetic (EM) characteristics of the single-stage FLTD with 24-separate columns are investigated based on the time-domain finite integration theory (TD-FIT). The discharge currents of brick capacitors in the circuit model are coupled to the field model as excitations. The grid size of the key components in FLTD cavity are refined by nonuniform grids. To further reduce the number of degrees of freedom (DoFs), the surface impedance boundary condition (SIBC) is used to model good conductors. Measurements and simulation results demonstrate that TD-FIT is effective and accurate in analyzing the EM transients of FLTD. Equivalent inductance of the discharging brick will increase by ~35 nH due to the mutual flux linkage among neighboring bricks when all the 23-bricks are triggered synchronously. [ABSTRACT FROM AUTHOR]

In this article, a novel edge-domain decomposition (EDD) method is proposed to solve 3-D nonlinear finite element (FE) problems of electromagnetic devices and transient field circuit co-simulation. The method applies reduced magnetic vector potential formulation to discretize the physical problem based on 3-D edge elements, and the solution region is divided into many sub-domains that only contain one edge unknown. The solution of lightweight nonlinear sub-domain systems can be massively parallelized, and the neighbor-to-neighbor communication scheme eliminates the need to assemble the global FE matrix. This article also introduces an indirect coupling scheme to handle large eddy currents to interface the EDD FE system with external circuits. The abovementioned algorithms are then implemented on a many-core GPU for transient field circuit co-simulation. The result shows an auto-gauging property, and the comparison with a commercial FE software indicates a speedup of over 43 times with relative error less than 2%. [ABSTRACT FROM AUTHOR]

A field-circuit coupled algorithm was developed to model the circuit behaviors and electromagnetic-field details of electromagnetic railguns. The railgun launcher was described by a 3-D transient eddy current field model with the electric current as the exciting source. The launcher was also treated as an RL series load of an external circuit composed of capacitor-based pulse forming networks. The variable resistance and inductance of the launcher were calculated by the electromagnetic field results, and the field-circuit coupling was achieved by matching the current, resistance, and inductance in both the external circuit and the launcher. The algorithm was partly verified by experiments of a two-turn series-augmented railgun system. The full dynamic numerical results, such as the current and voltage histories, transient load characteristics, and time evolution of electromagnetic field, provided a deep insight on the launching process of the augmented railgun. [ABSTRACT FROM AUTHOR]

This paper proposes an efficiency optimization method for the permanent magnet synchronous motor (PMSM) based powertrain by using field-circuit coupled finite-element method (FEM) for electric vehicle or hybrid electric vehicle applications. In this paper, an alterable flux-weakening (FW) angle is employed in the armature current control strategy for the FW operation. The optimal FW angle for each certain operating condition can be obtained through the pre-selection, which improves the system efficiency compared to conventional FW methods. Then, the lookup table (LUT) for optimal armature current control commands is obtained. Through using this optimal LUT in the drive system, the system efficiency can be significantly improved for the entire operation range. The time-stepping FEM is used to simulate the PMSM system, which integrates the electromagnetic field analysis of the motor prototype and the control algorithm of the drive system. A 2-D transient FEM model is built for a 15 kW PMSM in ANSYS Maxwell, and a vector control circuit model is set up in ANSYS Simplorer. Experiments are carried out on the 15 kW PMSM prototype to verify the accuracy of the simulation results and the effectiveness of the proposed design method.

When the electromagnetic transients occur in a power transformer, an inrush current is generated in its winding. The inrush current not only affects the performance of the transformer windings, but also affects the lifetime of the transformer. Many factors affect the inrush current, the most influential ones among which are the closing phase angle and the residual flux. In this paper, a dry-type transformer simulation model is built to analyze the influence of the inrush current on the performance of transformer windings during no-load reclosing conditions. Firstly, the inrush current was generated in the transformer windings during the no-load reclosing operation under different residual fluxes. Secondly, the field-circuit coupling 3d finite element method is used to analyze the electromagnetic force at different locations of the transformer windings under the influence of different inrush currents. The results of winding structural parameter variations are obtained through electromagnetic-structural coupling simulation, and the electromagnetic forces are used as the input parameter for the structural analysis. Finally, the residual flux is generated by controlling the opening and closing angle of the transformer through the phase-controlled switch, and the winding electromechanical characteristics are tested under different residual fluxes. Finally, comparisons of the test and simulation results are drawn to verify the impact of the closing angle and residual flux on inrush current and the winding deformation during the no-load reclosing conditions.

In this paper, a symmetric field-circuit coupled finite element method for low-frequency full-wave Maxwell problems using a magnetic vector potential formulation is proposed. The resultant fully discrete coefficient matrix is made symmetric for the first time by introducing the so-called source electric scalar potential for solid conductors, where the terminal currents are converted from the surface integrations of the current density vectors to volumetric integrations. The numerical examples, including a benchmark capacitor charging problem with external circuit connections, are solved, and the numerical results match well with the reference solutions. The proposed formulation is useful when analyzing electromagnetic fields with coupled inductive–capacitive effects and external circuit connections. [ABSTRACT FROM AUTHOR]

The focus of this paper is numerical analysis on the performance of a newly designed mega-ampere (MA) class single-stage fast linear transformer driver (FLTD) with 24 separate columns in the China Z-pinch driver CZ34. However, the internal structure and media distribution of the FLTD induction cavity is very complicated and the short rise time of the bricks’ discharge current will make spatial discretization much denser, resulting in a dramatic increase in the computational complexity of a 3-D model. In this paper, the electromagnetic (EM) characteristics of the single-stage FLTD with 24-separate columns are investigated based on the time-domain finite integration theory (TD-FIT). The discharge currents of brick capacitors in the circuit model are coupled to the field model as excitations. The grid size of the key components in FLTD cavity are refined by nonuniform grids. To further reduce the number of degrees of freedom (DoFs), the surface impedance boundary condition (SIBC) is used to model good conductors. Measurements and simulation results demonstrate that TD-FIT is effective and accurate in analyzing the EM transients of FLTD. Equivalent inductance of the discharging brick will increase by ~35 nH due to the mutual flux linkage among neighboring bricks when all the 23-bricks are triggered synchronously.

The computation of the electromagnetic transients in a power transformer with nonlinear material using the finite element method (FEM) is so dense that the traditional nonlinear solver employing the Newton–Raphson method can hardly execute in real time. In this paper, we emulate the finite-element computation of electromagnetic transients of a transformer in real time for the first time. The transmission line modeling (TLM) method employed in the FEM successfully decoupled the nonlinear elements from the linear network so the nonlinearities could be solved individually, which is perfect for parallel processing. The parallelism of the TLM-FE solution is sufficiently explored and realized on a field-programmable gate array with deep data pipelining, and the implementation can execute in real time and provide detailed field information of the transformer during the transients. The proposed noniterative field–circuit coupling enabled the transformer to interface with an external network and the comparison with commercial FEM software proved the accuracy and computational efficiency of the real-time FE model. [ABSTRACT FROM PUBLISHER]

Simulating the transient effects occurring in superconducting accelerator magnet circuits requires including the mutual electro-thermo-dynamic interaction amongthe circuit elements, such as power converters, magnets, and protection systems. Nevertheless, the numerical analysis is traditionally done separately for each element in the circuit, leading to possible inconsistent results. We present STEAM, a hierarchical cosimulation framework featuring the waveform relaxationmethod. The framework simulates a complex system as a composition of simpler, independent models that exchange information. The convergence of the coupling algorithm ensures the consistency of the solution. The modularity of the framework allows integrating models developed with both proprietary and in-house tools. The framework implements a user-customizable hierarchical algorithm to schedule how models participate to the cosimulation, for the purpose of using computational resources efficiently. As a case study, a quench scenario is cosimulated for the inner triplet circuit for the high luminosity upgrade of the Large Hadron Collider at CERN. [ABSTRACT FROM AUTHOR]

Accurate measurement of overvoltage in power grids is of great significance to study the characteristics of overvoltage and design of insulation coordination. Based on the research of D-dot voltage sensor, we designed a Dual-Differential D-dot overvoltage sensor. In order to quantify the structural parameters of the sensor, improve the performance and measurement accuracy of the sensor. The Field-Circuit Coupling method was proposed to be used in the parameter design of D-dot overvoltage sensor. The joint simulation of space electromagnetic field model and equivalent circuit model of the Dual-Differential D-dot overvoltage sensor was established with the finite element simulation software Ansoft Maxwell and circuit simulation software Simplorer. Finally, the actual sensor was manufactured. A test platform was built to verify the steady-state and transient performance of the sensor. The results show that the Dual-Differential D-dot sensor has excellent steady-state and transient performance, the error of phase and amplitude are small, and the sensor can achieve the non-contact measurement of power transmission line. Simultaneously, the rationality of the Field-Circuit Coupling method was further verified.

Transient effects occurring in a superconducting accelerator circuit can be correctly simulated only if the models consistently account for the electrothermodynamic coupling between the magnets, the protection systems, and the remaining network. We present a framework based on the idea of cosimulation. The core component is a coupling interface exchanging information between the independent models. Within the framework, we simulate selected parts of a magnet and the electrical network, combining appropriately different commercial tools. This modularity gives the possibility of integrating new tools in the framework, to provide further insights on different physical domains as mechanics or fluid dynamics. The workflow is applied to the field-circuit coupling of an LHC main dipole magnet. [ABSTRACT FROM PUBLISHER]

Magnetic vector potential (MVP) formulation combined with finite edge elements has gained substantial application in 3-D eddy-current field computation. Compared with its magnetic scalar potential counterpart, the MVP formulation is much easier to treat multiply-connected conductors. With the availability of advanced direct linear solvers with high performance on parallel or multi-core platforms, it becomes more and more important to develop gauged MVP formulations. To this end, the gauging technique is essential to ensure that the MVP formulation is uniquely solvable by direct solvers. In this paper, a novel method for imposing Coulomb gauge to transient eddy-current problems using edge elements for approximating the MVP is proposed. The resultant linear matrix equation is symmetric and uniquely solvable. Current excitations and voltage excitations for stranded conductors and solid conductors are formulated, respectively. Field-circuit coupled scheme for solid conductors is also presented. Extensive numerical examples are computed using the proposed formulation, which has proved to be promising in further engineering applications. [ABSTRACT FROM AUTHOR]

The simultaneous solution of circuit and field equations is often required in the analysis of magnetic devices. Although schemes for the solution of this coupled problem have been proposed, the existing formulations are usually tied to specific time discretization or nonlinear iteration expressions and therefore lack generality. In this paper, a highly systematized approach is proposed for strong circuit-field coupling in a transient finite element context, by identifying primitive stamps for field elements, circuit elements, and circuit-field couplings. The filamentary and solid conductors of the field model are the key elements for systematic interconnection using generalized stamps and modified nodal analysis. As a result, the coupling equations are treated just as any other circuit element, simplifying the implementation and providing a unified framework for circuit-field analysis. Both circuit and field stamps are independent of the time discretization and nonlinear solving procedure. With the proposed scheme, the finite element equations can be linked to circuits of arbitrary topology. The theory is developed for the axisymmetric and Cartesian 2-D cases and several examples are then solved to show the effectiveness of our new approach. Solutions are compared with those produced by well-known and validated commercial software packages which implement different, proprietary, and/or undisclosed circuit-field coupling methods. [ABSTRACT FROM AUTHOR]