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The purpose of this paper is to present a comparative analysis concerning the influence of eddy currents on the distribution of the magnetic flux density in the laminated anisotropic structures.

The influence of the magnetic flux normal to the lamination surface is particularly analysed. Several models containing internal air gaps and overlapping are tested. For every structure, the eddy currents are first taken into account and then, they are neglected. At last, the 3D simulation of the anisotropic conductivity permits to analyse separately the longitudinal and normal flux in the structure and the eddy currents induced by those fluxes.

The study leads to a more realistic numerical model with conducting laminations. The results show that the normal flux does not turn at once on lamination. The normal and longitudinal fluxes induce eddy currents which modify the flux distribution in the laminated structure.

The results of the presented simulations make it possible to elaborate a more realistic numerical model of homogenized characteristics taking into account eddy currents.

The eddy currents induced by the fluxes modifies the field distribution in the structure and should be taken into account. The internal air‐gaps higher than 0.1 mm have an influence on the field distribution; the isolation between the laminations of 0.01 mm has a smaller but not negligible effect on the magnetic flux. The direction of the normal flux from one sheet to another one does not change immediately after the entrance of the lamination, the transition is progressive.

The paper gives a new measurement method of the parameters characterising the magnetic laminations for broadband low‐level signals defined at any operational point.

High frequency phenomena machines fed by PWM inverters are related to low‐level signals corresponding to minor hysteresis loops around the instantaneous working point, which moves on the main loop at the basic frequency. The minor loops are assimilated to ellipses, which are characterised by only two parameters: the incremental magnetic permeability (μ) and the electric conductivity (σ).

For small signals high frequency field components, the laminated steel behaviour can be described by two local parameters (μ, σ) and skin effect. The values of μ and σ do not depend on frequency up to 1 MHz, but only on the operating point.

The proposed broadband characterisation should be associated with a Priesach model that defines the operating point for computer simulation of high frequency phenomena.

The broadband characterisation of magnetic laminations is useful for studying the behaviour of the windings of the PWM‐fed machines.

Broadband measurements are now possible on small magnetic steel lamination samples.

Scaled Flow Testing has been developed as a practical method to characterise the flow and thickness properties of epoxy B‐stage prepreg. This technique evolved from an analytical model of lamination flow based on parallel plate plastometer concepts modified to account for glass fabric effects. Scaled Flow Testing is designed to measure flow comparable to actual MLB lamination flow, thus it provides beneficial B‐stage theology, encapsulating, and pressed thickness data.

The purpose of this paper is to propose a transmission line model for induction machines, which serves to compute the common mode input impedance in the frequency range 10 Hz-1 MHz.

Special diligence is attributed to the modelling of eddy currents inside the core lamination. In order to determine the transmission line parameters accurately, two modelling approaches are compared. The first is a two-dimensional simulation approach where iron core lamination effects are included by means of an equivalent material approximation. The second approach consists in fully three-dimensional analysis taking into account explicitly the eddy currents induced in the laminations.

It is shown that homogenised equivalent material models may lead to large errors in the calculation of machine inductances, especially at high frequencies. However, the common mode input impedance, which is the final parameter of interest, seems to be less affected by the lamination modelling.

The paper compares different analytical and numerical approaches in the frequency range 10 Hz-1 MHz and tries to give benchmarks for errors which occur due to a number of commonly used model simplifications.

This paper aims to show a resin-flowing model based on Darcy’s law to display the flowing properties of prepreg during lamination. The conformity between the model and experimental results demonstrates that it can provide a guideline on print circuit board (PCB) lamination.

Based on the theoretical derivations of Darcy’s law, this paper made an analysis on the flow of prepreg in the pressing process, according to which a theoretical model, namely, resin-flowing model was further formulated.

This paper establishes a resin-flowing model, according to which two experiment-verified conclusions can be drawn: first, the resin-flowing properties of material A and B can be improved when the heating rate is between 1.5 and 2.5 min/°C; second, increased pressure gradient can add the amount of flowing resin, mainly featured by increasing pressure and reducing filled thickness of prepreg.

This model provides guidance on setting lamination parameters for most kinds of prepregs and decreasing starvation risk for PCB production.

This paper aims to improve the finite element modelling of transformers subjected to DC excitation, by including core joint details.

Geomagnetically induced currents (GICs) or leakage DC can cause part-cycle, half wave saturation of a power transformer’s core. Practical measurements and finite element matrix (FEM) simulation were carried out using three laboratory-scale, untanked single-phase four limb transformers resembling real power transformers in terms of the core steel and parallel winding assemblies. “Equivalent air gaps” at the joints, based on AC measurements, were applied to the FEM models for simultaneous AC and DC excitation.

Measurements confirm that introducing equivalent air gaps at the joints improves the FEM simulation of transformers carrying DC.

The FEM simulations based on the laboratory transformers are exemplary, showing the difference between modelling core joints as solid or including equivalent air gaps. They show that, for more representative results, laboratory transformers used for research should have mitred core joints (like power transformers).

This research shows why joint details are important in FEM models for analysing transformer core saturation in the presence of DC/GICs. Extending this, other core structures of power transformers with mitred joints should improve the understanding of the leakage flux during half-wave saturation.

This paper deals with a calculation method of eddy current losses and temperature rises at the stator end teeth of hydro generators. It can be used for analysing and evaluating different design variants when optimising the stator core end portion. The calculation method simulates the three‐dimensional local core end field, but uses only a two‐dimensional calculation model. Amongst all the stator teeth it treats the tooth with the highest axial and radial magnetic flux impact. The paper presents a collection of calculation algorithms of the method and provides some results gained for two different stator core end designs.

Punching of the electrical sheets impair the insulation and make random galvanic contacts between the edges of the sheets. The purpose of this paper is to model the random galvanic contacts at the stator edges of 37 kW induction machine and estimate the additional losses due to these contacts.

The presence of the surface current at the edges of sheets causes the discontinuity in the tangential component of the magnetic field. The surface boundary layer model which is based on this concept is implemented to model the galvanic contacts at the edges of the sheets. Finite element analysis based on magnetic vector potential was done and theoretical statistical study of the random conductivity at the stator edge was performed using brute force method.

Finite element analysis validates the interlaminar current when galvanic contacts are present at the edges of electrical sheets. The case studies show that the rotor and stator losses increases with the thickness of the contacts. Statistical studies show that the mean value of total electromagnetic loss was increased by 7.7 percent due to random contacts at the edges of sheets.

The novel approach for modeling the galvanic contacts at the stator edges of induction machine is discussed in this paper. The hypothesis of interlaminar current due to galvanic contacts is also validated using finite element simulation.

The purpose of this paper is to present a diffusion-controlled healing model for predicting fused deposition modeling (FDM) bond strength between layers (z-axis strength).

Diffusion across layers of an FDM part was predicted based on a one-dimensional transient heat analysis of the interlayer interface using a temperature-dependent diffusion model determined from rheological data. Integrating the diffusion coefficient across the temperature history with respect to time provided the total diffusion used to predict the bond strength, which was compared to the measured bond strength of hollow acrylonitrile butadiene styr (ABS) boxes printed at various processing conditions.

The simulated bond strengths predicted the measured bond strengths with a coefficient of determination of 0.795. The total diffusion between FDM layers was shown to be a strong determinant of bond strength and can be similarly applied for other materials.

Results and analysis from this paper should be used to accurately model and predict bond strength. Such models are useful for FDM part design and process control.

This paper is the first work that has predicted the amount of polymer diffusion that occurs across FDM layers during the printing process, using only rheological material properties and processing parameters.

The purpose of this paper is to develop a subproblem finite element method for progressive modeling of lamination stacks in magnetic cores, from homogenized solutions up to accurate eddy current distributions and losses.

The homogenization of lamination stacks, subject to both longitudinal and transversal magnetic fluxes, is first performed and is followed by local correction subproblems in certain laminations separately, surrounded by their insulating layers and the remaining laminations kept homogenized. The sources for the local corrections are originally defined via interface conditions to allow the coupling between homogenized and non-homogenized portions.

The errors proper to the homogenization model, which neglects fringing effects, can be locally corrected in some selected portions via local eddy current subproblems considering the actual geometries and properties of the related laminations. The fineness of the mesh can thus be concentrated in these portions, while keeping a coupling with the rest of the laminations kept homogenized.

The method has been tested on a 2D case having linear material properties. It is however directly applicable in 3D. Its extension to the time domain with non-linear properties will be done.

The resulting subproblem method allows accurate and efficient calculations of eddy current losses in lamination stacks, which is generally unfeasible for real applications with a single problem approach. The accuracy and efficiency are obtained thanks to a proper refined mesh for each subproblem and the reuse of previous solutions to be locally corrected only acting in interface conditions. Corrections are progressively obtained up to accurate eddy current distributions in the laminations, allowing to improve the resulting global quantities: the Joule losses in the laminations, and the resistances and inductances of the surrounding windings.