Magneto-thermal Model Research Articles

Integration of inter-ply electrical percolation phenomena in the multiphysics modelling of laminated composite materials

PurposeThis study aims to introduce a predictive homogenization model incorporating electrical percolation considerations to forecast the electrical characteristics of unidirectional carbon-epoxy laminate composites.Design/methodology/approachThis study presents a method for calculating the electrical conductivity tensor for various ply arrangement patterns to elucidate phenomena occurring around the interfaces between plies. These interface models are then integrated into a three-dimensional (3D) magneto-thermal model using the finite element method. A comparative study is conducted between different approaches, emphasizing the advantages of the new model through experimental measurements.FindingsThis research facilitates the innovative integration of electrical percolation considerations, resulting in substantial improvement in the prediction of electrical properties of composites. The validity of this improvement is established through comprehensive validation against existing approaches and experimentation.Research limitations/implicationsThe study primarily focuses on unidirectional carbon-epoxy laminate composites. Further research is needed to extend the model's applicability to other composite materials and configurations.Originality/valueThe proposed model offers a significant improvement in predicting the electrical properties of composite materials by incorporating electrical percolation considerations at inter-ply interfaces, which have not been addressed in previous studies. This research provides valuable information to improve the accuracy of predictions of the electrical properties of composites and offers a methodology for accounting for these properties in 3D magneto-thermal simulations.

Improved LPTN-Based Online Temperature Prediction of Permanent Magnet Machines by Global Parameter Identification

This paper presents an improved lumped parameter thermal network (LPTN) based online temperature prediction method of permanent magnet (PM) machines by global parameter identification. The proposed global parameter identification incorporates not only the loss but also the magnetic information into a fifth-order LPTN and identifies the multi-physical magneto-thermal parameters as a whole. In the identification process, the nonlinear characteristics, including the magnetic saturation, the cross-saturation, the strand skin effect, and the speed-dependent convective heat transfer, are all considered. It can eliminate the cumbersome magnetic and loss measurement efforts and improve the overall identification accuracy compared to the traditional step by step identification method. Based on the identified multi-physical magneto-thermal model, the critical temperatures of the PM machines, together with the online losses and torque, can then be predicted in real time. The experimental results show that the proposed online temperature prediction method can track the real temperature variation with errors within 5°C.

Modelling of Resistive Type Superconducting Fault Current Limiter for HVDC Grids

The protection of high voltage direct current (HVDC) grids is a challenge considering that the protection system must detect, locate, and interrupt large fault currents in a few milliseconds. Resistive type superconducting fault current limiters (R-SFCL) can help solve that difficult task, reducing the extremely demanding ratings of HVDC circuit breakers. This paper presents different approaches to model R-SFCLs in order to analyze their suitability for assessing the performance of HVDC grid protection, including the step model, the exponential model, the RQ model, and the magneto-thermal model. In the first instance, the R-SFCL models are evaluated in a test grid to analyze their parameterisation and select the most adequate model for the study of HVDC grids. The RQ model is finally chosen for its simplicity but closer behavior to the magneto thermal model in terms of fault resistance dependency and resistance evolution curve. Then, the performance of an RQ type R-SFCL model in conjunction with a mechanical circuit breaker is evaluated in a multiterminal HVDC grid with different fault cases. This way, fault currents are greatly decreased as well as circuit breaker requirements. Hence, the R-SFCL under study enables a reliable protection of the HVDC grid.

2D hybrid magneto-thermal model for PM induction heating device with rotating movement

A new 2D-hybrid model in cylindrical coordinates intended for the study of a transient magneto-thermal coupled problem is proposed. This model is used to evaluate the spatiotemporal distribution of temperature in rotating aluminum billets heated by permanent magnets induction-heating device (PMIHD). The proposed hybrid model consists of coupling an exact analytical solution of the 2D magneto-harmonic field to a 2D transient thermal analysis where the temperature dependence of electrical and thermal physical properties of the heated billet is considered. Based on the separation variables technique, the analytical solution of magneto-harmonic problem serves to evaluate the induced current and the resulting power density loss distribution in the nonmagnetic billet. Furthermore, the 2D transient thermal analysis, based on the lumped thermal network model, is developed in radial and axial directions of the heated billet. In order to validate the 2D hybrid magneto-thermal model, the performances of the studied PMIHD are compared with those obtained with Finite Element Method (FEM).

Research on the Data Transmission Methods in the Magneto-Thermal Coupling Model for Eddy Current Braking

Research on the Data Transmission Methods in the Magneto-Thermal Coupling Model for Eddy Current Braking

The Role of Far-ultraviolet Pumping in Exciting the [O i] Lines in Protostellar Disks and Winds

Abstract We use Cloudy to re-examine excitation of [O i] 6300 Å and [O i] 5577 Å in the X-ray driven photoevaporative wind models of Owen and collaborators, and in more recent magnetothermal models by Wang et al. We find that, at the measured accretion luminosities, the far-ultraviolet (FUV) radiation would populate the upper levels of the oxygen, which would eventually contribute to the [O i] lines. FUV pumping competes with collisions as an excitation mechanism of the [O i] lines, and they each originate from a distinct region in the protostellar disk environment. Consequently, the line strengths and shapes of [O i] 6300 Å and [O i] 5577 Å would be affected by the inclusion of FUV pumping in the radiation transport simulations.

Predicting Temperature Profile on the Surface of a Switched Reluctance Motor Using a Fast and Accurate Magneto-Thermal Model

In this article, a simplified 3D magneto-thermal model to study the temperature distribution over the housing of a Switched Reluctance Machine (SRM) is proposed. The main objective of such model is to study the temperature distribution profile on the body of the machine under various working conditions in order to introduce a temperature based signature to develop condition monitoring procedures. The analysis of fluid flow and heat transfer inside the SRM supports the hypothesis that the effect of turbulent flow of the fluid and the complex heat transfer phenomenon of the rotating parts can be simplified to a heat flux boundary condition representation of the heat loss. The accuracy of the model is validated through simulation and experimental results on a prototype SRM. The developed simplified model can be used as for prediction of temperature profile on SRM surface, well suited for fault diagnosis in SRM. The proposed methodology can be modified applied in developing a thermal model for other types of electric machines.

Coupling of Magnetothermal and Mechanical Superconducting Magnet Models by Means of Mesh-Based Interpolation

In this paper we present an algorithm for the coupling of magneto-thermal and mechanical finite element models representing superconducting accelerator magnets. The mechanical models are used during the design of the mechanical structure as well as the optimization of the magnetic field quality under nominal conditions. The magneto-thermal models allow for the analysis of transient phenomena occurring during quench initiation, propagation, and protection. Mechanical analysis of quenching magnets is of high importance considering the design of new protection systems and the study of new superconductor types. We use field/circuit coupling to determine temperature and electromagnetic force evolution during the magnet discharge. These quantities are provided as a load to existing mechanical models. The models are discretized with different meshes and, therefore, we employ a mesh-based interpolation method to exchange coupled quantities. The coupling algorithm is illustrated with a simulation of a mechanical response of a standalone high-field dipole magnet protected with CLIQ (Coupling-Loss Induced Quench) technology.

A Coupling Simulation and Modeling Method for High Temperature Superconducting Magnets

Under transient operating conditions, especially in the case of alternating current or pulse current, the high temperature superconducting (HTS) magnet will suffer ac losses leading to changes in the temperature and critical current distribution throughout the magnet. A magneto-thermal model is needed to simulate this process. In fact, the state change of the magnet will lead to a nonlinear performance of the HTS magnet in the power system. This paper introduces a coupling simulation and modeling method for the HTS magnet based on a cosimulation model built in MATLAB and COMSOL. The HTS magnet element is a customized module created via the self-code S-Function in MATLAB. A magneto-thermal finite element model based on the PDE and Heat Transfer modules of COMSOL is built into the S-Function. This model allows the state of the HTS magnet to be monitored during the operating process. A small-scale HTS magnet including three single pancake coils with a dc excitation system is illustrated to verify the nonlinear characteristic of the HTS magnet and the effectiveness of this coupling simulation and modeling method.

Self-heating of bulk high temperature superconductors of finite height subjected to a largealternating magnetic field

In this work we study, both experimentally and numerically,the self-heating of a bulk, large YBCO pellet of aspect ratio (thickness/diameter) ∼ 0.4 subjected to a large AC magnetic field. To ensure accurate temperature measurements,the sample was placed in an experimental vacuum chamber to achieve a smalland reproducible heat transfer coefficient between the superconductor and thecryogenic fluid. The temperature was measured at several locations on thesample surface during the self-heating process. The experimentally determinedtemperature gradients are found to be very small in this arrangement (<0.2 K across the radius of the superconductor). The time-dependence of the average temperatureT(t) is found to agree well with a theoretical prediction based on the one-dimensional (1D) Beanmodel, assuming a uniform temperature in the sample. A 2D magneto-thermal model wasalso used to determine the space and time-dependent temperature distributionT(r, z, t) during the application of the AC field. The losses in the bulk pellet were determined usingan algorithm based on the numerical method of Brandt, which was combined with a heatdiffusion algorithm implemented using a finite-difference method. The modelis shown to be able to reproduce the main trends of the observed temperatureevolution of the bulk sample during a self-heating process. Finally, the 2D model isused to study the effect of a non-uniform distribution of critical current densityJc(r, z) on the losses within the bulk superconductor.

A study on magneto-thermal analysis of IPMSM for electrical vehicle with water-cooling system

In this paper, we present a magneto-thermal model of an interior-permanent magnet synchronous machine (IPMSM) for electrical vehicle. Both magnetic and thermal field aspects are described based on 2-D finite element method (FEM). For accurate estimation of heat sources in the machine, we analyzed harmonic iron loss using variable loss coefficients and magnet loss in the electromagnetic field. In addition, we estimated convective exchange coefficient considering water-cooling system of the machine. Finally, experimental results on 60 kW, 3600 rpm are reported and compared with the simulation results.

2D finite element method study of the stimulation induction heating in synchronic thermography NDT

This paper describes the induction-lockin-thermography (ILT) in non-destructive testing (NDT). The defect can be localised and its depth estimated by the phase and the module of the temperature in synchronic regime. Various sources of external energy can be used to excite the heat flux in examined object. In this work the electromagnetic induction is employed to heat the specimen. The interaction of the specimen with the induction stimulation is studied by using the axisymmetric magnetothermal model, which is solved by the finite element method (FEM). This study aims to detect the eventual defect by choosing both parameters, electromagnetic and thermal frequencies.

A magneto-thermal study of a high-speed synchronous reluctance machine

The paper presents a magneto-thermal model of a high-speed synchronous reluctance machine (SRM). Both magnetic and thermal aspects are described using two-dimensional and three-dimensional finite-element method for machine modeling. Additional current harmonics losses, friction losses, and convective exchange coefficients at high speed are estimated. Finally, test results on a 20kW, 20 000rpm SRM are reported and compared with the simulation results.

A simplified FEM based calculation model for 3-D induction heating problems using surface impedance formulations

A simplified FEM based combined magneto-thermal calculation model for nonlinear 3-D induction heating problems is described. The model is based on the combination of linear and nonlinear surface impedances evaluated using transient magnetic field calculation. The power dissipated in surface impedances is calculated and transferred to the thermal model as heat fluxes. After the temperature distribution is calculated the surface impedances are updated to correspond to the present electromagnetic and thermal states of the work piece. The performance of the model was verified with comparison to the measurements.

3D numerical study of the annular induction plasma installation

In order to know the behavior of the annular induction plasma device and to define its operating conditions at atmospheric pressure, a three-dimensional numerical magneto-thermal model based on the nodal finite element method is presented. The calculation has been done to evaluate the influence of the number of the transformer arms on the field distribution and on the total power of the plasma. The ( A , V) magnetic formulation is applied to multiply connected regions and it is coupled to the thermal one to evaluate the temperature profile.

Modeling of 3D electromagnetic and heat transfer phenomena for materials with poor conductivity

A coupled three-dimensional magneto-thermal model for the materials with poor conductivity is presented. The magnetic (A,V-A) formulation with nodal finite element method, is applied to a multiply connected region. In the presence of high permeability materials the addition of the penalty coefficient is discussed. The electromagnetic equation is coupled with the thermal equation to evaluate the temperature field and the total power in the thermal device.

Fully coupled 'quasi-axisymmetric' magneto-thermal model for skin effects analysis in resistive Tokamak coils

A two-dimensional quasi-axisymmetric time-varying finite-element code that discretizes the magnetic and thermal equations, solving them simultaneously, is presented. Some results obtained in realistic test cases of practical interest are displayed and discussed. The code has been used for the analysis of thermoelectromagnetic stresses in the resistive toroidal field coils of fusion machines under design and development. The code computes the magnetic and thermal fields at each time instant of the time integration domain. The quasi-axisymmetric formulation makes it possible to analyze realistic coil geometries with reasonable computer resources and makes the use of the code feasible also for a preliminary analysis of tentative designs.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

The use of a generator system to solve magnetothermodynamic problems by the finite element method

Increasingly, we find that coupled physical phenomena (e.g. magnetothermal ones) must be solved in numerical simulation. Real and complex variables mathematicaly coupled and an asymetrical finite element matrix are used in the magnetothermal model. Magnetic and heat transfer phenomena are not studied on the same domain. A generator, Flux-Expert, has been used in order to describe the magnetothermal coupled problem. An induction heating problem has been solved with this method.