•Magnetic characterization of Mn-Zn sintered ferrites up to 160 °C from DC to 1 GHz.•Increased doping by CaO, Nb2O5, ZrO2, and SiO2 favors loss reduction.•The temperature-dependent phenomenology has ...been assessed.•The role of eddy currents and spin damping are demonstrated.•The temperature dependent effective magnetic anisotropy < Keff > is calculated.
We investigate the effect of different doping schemes on the broadband magnetic losses and their temperature dependence in Mn-Zn ferrites. CaO, Nb2O5, ZrO2, and SiO2 are added with increasing proportions to TiO2-doped prefired powders and, after sintering at either 1275 °C or 1300 °C, the obtained ring samples are tested versus frequency f (DC-1 GHz) and peak polarization Jp (2 mT – 200 mT) up to T = 160 °C. Appropriately enhanced impurity contents are shown to induce further decrease of the energy loss in materials already prepared for best performance at high temperatures (140 – 160 °C). This behavior can be hardly ascribed to the impurity-related increase of the electrical resistivity brough about by extra-doping, being it rather connected to a corresponding monotonical decrease of the effective magnetic anisotropy < Keff > with T. The decreasing anisotropy makes the balance between the contributions of domain wall (dw) displacements and reversible rotations to the magnetization process evolving in favor of the latter. The energy loss correspondingly develops with frequency and peak polarization in a complex fashion, according to the specific dissipative mechanisms sustained by the spins precessing either inside the moving walls or in the bulk. A dividing line in the (Jp − f) plane is identified, which separates dominant dw- and rotation-generated losses. It moves downward (i.e. lower f) with increasing temperature, the higher T the lower the frequency at which the rotations, theoretically assessed via the Landau-Lifshitz equation, supersede the domain wall contribution. Once accomplished, however, the transition to rotations can lead, according to the theoretical model, to higher losses when moving to higher temperatures. Following the experimental trend of the complex resistivity versus frequency at different T values, the calculations and the experiments show that eddy currents start to contribute to the energy loss, in the 5 mm thick ring samples, around a few MHz, accounting for about 50 % of measured loss beyond some 50 MHz. The chief dissipative process at applicative frequencies and induction values is therefore identified with spin damping, to which the generalized loss decomposition method can be applied.
Accurate modeling of losses in ferrite cores is of high interest for power electronics design. Left aside the problem of modeling the constitutive law, accurate computation of losses require to model ...the 3d geometry, for instance by Finite Element (FE) analysis, which is computationally expensive. This hinders the practical usage of such models in circuit simulators which require “light” models. In this work we devise a new approximate method to take into account the microscopic structure of toroidal ferrite cores, which boils up into simple analytical formulas. The proposed method is compared to experimental measurements on a T38 ferrite core, and a FE model.
•A simplified, analytically model of losses in ferrite cores is presented.•Comparison between simplified model, Finite Element model and measurement is taken on.•The parameters of the model are not fitted, but derived from the knowledge of the structure of the core and of the material used.
•MBNenergy is a time-average variable induced from the raw Barkhausen noise signal.•The definition of MBNenergy and its link with the flux density is investigated.•The flux density is proportional to ...the square of the envelope of the MBN signal.•The absence of privileged orientation and direction of the MBN effect is verified.
Magnetic Barkhausen Noise (MBN) reflects magnetic domains’ motions during a ferromagnetic part’s magnetization process. For industrial specimens, the raw MBN signal is stochastic and not reproducible, leading to complex analyses. This issue is solved using time-average variables like the Magnetic Barkhausen Noise energy (MBNenergy).
Plotting MBNenergy as a function of the magnetic excitation gives rise to a hysteresis cycle. Recent studies have highlighted some exciting properties from this cycle, such as a way to observe the magnetic loss contribution associated with the domain wall motions. Still, questions remain, including in the basic description of MBNenergy.
This paper describes a theoretical development to understand MBNenergy further. We demonstrate that in standard characterization conditions, the magnetization variations associated with the domain wall motions are proportional to the square of the envelope of the MBN signal instead of its absolute value.
Then, this theoretical conclusion is confirmed experimentally. Finally, the absence of privileged orientation and direction in the MBN effect is verified in the case of unidirectional magnetization.
•Electrical steel stator sheets are cut with punching and laser methods.•According to these cutting methods were produced induction motors.•According to the 60034-2-1-1A induction motors were ...tested.•Effects of these cutting methods were investigated on induction motors.•For cutting surfaces were measured surface roughness.
In this study, M400-50A electrical steel laminations (ESLs) used in electrical machines were cut with punching and laser methods and the effect of these cutting methods on the efficiency and total losses of induction motors was investigated. ESLs were prepared by laser and punching cutting methods concerning an induction motor with a power of 5.5 kW. After the stator and rotor packages were created, processes such as winding, varnishing, and mechanical assembly were performed on the motors. It is prepared for motor efficiency (MEfficiency) and total magnetic losses (TLosses) tests according to the direct measurement method specified in the IEC 60034-2-1-1A standard. Four different frequencies (f: 50, 75, 100 and 125 Hz) and five different motor loading rates (MLoad: 25, 50, 75, 100 and 125%) were defined as independent variables in the tests. MEfficiency and TLosses values were measured as dependent variables. Plastic deformation and edge rounding were observed on the edges cut with punching and edge rounding and angled edge formation on the edges cut with the laser. The average surface roughness of the laser-cut edges was determined to be higher than the ESLs cut by punching. It was observed that TLosses increased while MEfficiency decreased with increasing frequency and MLoad value in motor tests. It was determined that the training, testing, and experimental data are quite compatible with each other and the R2 values are close to 1 in the statistical analyzes performed with ANN (Artificial neural network). In addition, it was specified that RMSE (Root mean square error) and MAPE (Mean absolute percentage error) values vary between 0.007 and 13.310% for each cutting method and mathematical models can be used to predict MEfficiency and TLosses with ANN.
This paper presents a new modeling approach capable of predicting eddy current losses in soft ferrite cores as a function of the winding current. The proposed model is formulated in the time domain, ...which defines the magnetic core as a repeated regular structure of magnetic material grains and grain boundary in space. In this way, the homogenization process of the material is avoided, intended as the definition of a set of physical parameters of a continuous material equivalent to the real structure of the material. The distribution of the current density in the core, and the core losses are computed utilizing the physical and geometric parameters of the grain of the magnetic material and of the grain boundary. To address the uncertainty in the definition of the physical and geometrical parameters of the magnetic grain and the grain boundary, a dedicated optimization procedure has been formulated, which takes into account the inaccuracy in the parameters measurement and the fact that the grain contour is an irregular surface and the boundary thickness is neither constant nor uniform. The performance assessment of the model is carried out in a broad frequency range using several experiments via a power amplifier and a DC-DC converter.
•Ferrite based soft magnetic composites developed for inroad charging application.•Good agreement with related analytic models for magnetic permeability and losses.•Magnetic permeability 2–3 times ...higher than spherical particles.•Key variables shown to be particle loading and particle aspect ratio (shape factor)
The magnetic performance of ferrite based soft magnetic composite materials (SMCs) have been investigated for inductive power transfer (IPT) applications in roads. The magnetic permeabilities and magnetic losses of SMCs were characterized for varying ferrite particle size fractions and particle loadings. The magnetic performance of the crushed ferrite powders were 2–3 times higher than expected based on magnetic particle theory for spherical magnetic particles. Findings were confirmed by comparing the magnetic performance of SMCs made from spherically ground ferrite powders. The good agreement of magnetic relative permeability measurements and related analytic models have shown that the key parameters affecting the relative permeability of SMCs are the magnetic particle loading, the magnetic particle aspect ratio and related shape factor, and interparticle alignment. Similarly, the measured magnetic power loss densities measurements in the low field limit (μr < 100) compared well with magnetic loss models where there is an inverse relationship to the magnetic relative permeability. Therefore, the best performance for ferrite SMCs is to be achieved by maximising the magnetic relative permeability which also minimises the power losses for a given B.
•Simulation method having a sound physical underpinning is used to reproduce the magnetic hysteresis loops of NOESs.•Maximum differences between the simulated and the measured magnetic loss are less ...than 1%.•New analytical simulation method in the form of a single equation to describe the magnetic behaviour of NOESs.•Method can be used to both characterize the magnetization processes and enable an energy loss prediction for NOESs.
The magnetic properties of non-oriented electrical steels (NOESs) are characterized using an analytical simulation method accounting for the microstructures in ferromagnetic materials. Complementary experimental data for thin sheet laminations, obtained using a standard single strip tester (SST), are employed with the hysteresis mechanism investigated in terms of the measurement system and Weiss Mean Field effects. It is shown that the magnetic hysteresis loops of NOESs of 3% SiFe can be generated with remarkable accuracy for a broad range of magnetization frequencies and peak flux densities. The simulation method is also suitable for performing an energy loss analysis with calculated energy losses, when compared to corresponding measured data, showing a strikingly accurate match with, in most cases, an error of less than 1%.
•According to the 60034-2-1-1A measurement standard induction motors were tested.•Effects of WEDM and AWJ cutting methods were investigated on induction motors.•The frequency and motor loading rate ...independent variables are optimized for maximum motor efficiency and minimum magnetic losses.•Cutting surfaces were analyzed and mean surface roughness values measured.
In this study, the effect of cutting electrical steel laminations using abrasive water jet (AWJ) and wire electrical discharge machining (WEDM) techniques on 5.5 kW induction motor efficiency (MEfficiency) and total magnetic losses (TLosses) was investigated. After the stator and rotor packages were formed, winding, varnishing and mechanical assembly processes were carried out and the motors were prepared for MEfficiency and TLosses tests according to the IEC 60034-2-1-1A standard. Tests were performed using different frequencies (f) and motor loading rates (MLoad). While burr formation was observed with the effect of plastic deformation on the cutting edge of electrical steels with AWJ, recast layer formation was observed with the effect of heat in WEDM. MEfficiency decreased while TLosses increased due to increasing f and MLoad in both cutting methods. Maximum MEfficiency and minimum TLosses values were measured in WEDM, it was determined that optimum results using Response Surface Methodology (RSM) were measured at f of 50 Hz and MLoad of 100% values in both cutting methods. The statistical effects of f and MLoad on MEfficiency and TLosses were revealed with ANOVA (Analysis of variance). In addition, mathematical models were developed for the prediction of MEfficiency and TLosses.
An accurate and fast transient calorimetric ferrite core-loss measurement method is proposed in this article. In contrast to electrical measurements, the accuracy of the calorimetric approach is ...largely independent of the magnetic excitation and operating frequency. However, accurate values of the thermal capacitance and the temperature of the core under test (CUT) are required. Accurate measurement of the specific heat capacity of the core material can be achieved with a differential scanning calorimeter (DSC) or by using the CUT as a dc electric conductor and measuring its thermal response for known Joule heating. Accurate temperature measurements can be realized with NTC temperature sensors. A thorough uncertainty analysis of the presented method is conducted by identifying the impact of each source of uncertainty in the course of a sensitivity analysis. For the considered reference case (R 22.1/13.7/7.9 toroidal core with N49 ferrite material by EPCOS-TDK - 500 kHz/100 mT), the method achieves a total uncertainty with a worst-case value of less than 12% or, in case of a more realistic approach considering a Gaussian distribution of each source of uncertainty, a mean value of −4.3% with a 95% confidence interval of <inline-formula><tex-math notation="LaTeX">\mathbf {\pm }</tex-math></inline-formula>3.2%. The results are verified by means of finite element method (FEM) simulations and experiments. Furthermore, a step-by-step description of the workflow for preparing and conducting the experiments is provided. The proposed method is tested experimentally and compared to a state-of-the-art electrical loss measurement method for MnZn N87 and N49 ferrite cores of EPCOS-TDK. In addition, it is used to measure the loss-map of the NiZn ferrite material 67 from Fair-Rite for very high frequencies up to 50 MHz, which enables the computation of the material's Steinmetz parameters.
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