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An approach to model the anisotropic behaviour of core losses in grain-oriented laminations that are used in advanced electrical machines and transformers is proposed in this work. Core losses are usually split into static hysteresis loss, classical eddy current loss, and excess loss. The static hysteresis and excess loss components exhibit strongly anisotropic behaviours which at low frequencies may be modelled using the orientation distribution function (ODF) approach. However, the anisotropic behaviour of core losses at higher frequencies is rarely addressed. Therefore, this work aims to offer a method to model the anisotropy of these losses for a wide range of frequencies. This work proposes a modified approach that uses the ODF and the Kondorsky law to compute the core losses accurately in any direction for a wide range of frequencies so that the losses due to different magnetisation processes can be studied separately. The paper also highlights possible causes behind the anisotropic behaviour of the excess loss. The proposed approach is also compared with the original ODF description for modelling the loss behaviour along arbitrary directions. The computed loss-frequency behaviour at different induction levels agrees with measured ones along arbitrary directions. The proposed formulation can be used to estimate the losses of transformers and rotating machines as a function of magnetic field direction and frequency. [ABSTRACT FROM AUTHOR]

FePBNbCr amorphous soft magnetic composites (SMCs) with high compaction density (ρ c) and commendable magnetic properties were successfully fabricated via low-pressure hot-compacting at 160 MPa. Due to the thermoplastic properties of amorphous powders in supercooled liquid region (Δ T x), the hot-compacting in the Δ T x is conducive to the increase of ρ c for the amorphous SMCs, thereby improving the corresponding soft magnetic properties via reducing the number of pinning sites. Compared with these of the cold-compacted amorphous SMCs at 600 MPa, the ρ c increases by 20.3 % to 6.04 g/cm3, the effective permeability increases by 5.26 times to 95.3, while the corresponding total core loss decreases 74.5 % to 154.4 kW/m3 (100 kHz, 0.05 T) for the amorphous SMCs hot-compacted at 495 °C with a pressure holding time of 6 min. These results indicate that the low-pressure hot compacting is an effective measure to further improve soft magnetic properties of the amorphous SMCs for rapidly adapting to the development needs of high-frequency and miniaturization of electronic devices. [ABSTRACT FROM AUTHOR]

This paper focuses on two models used for the determination of power loss components in steel samples under dynamic magnetizing conditions. The considered models differ in their approach as far as the possibility of distinguishing bulk and localized eddy currents is concerned. Two samples of non-oriented electrical steel differing in silicon weight contents are the subject of experiments. A comparison of the obtained results, as well as their discussion, is given in the paper. [ABSTRACT FROM AUTHOR]

Cryogenic electric machines (CEMs) offer significant potential for highly power-dense and ultra-efficient net-zero aircraft. Aluminum (Al) displays superior conductivity to copper (Cu) at cryo-temperatures, making Al Litz wires an attractive option for CEM windings to minimize DC and eddy losses. However, accurately quantifying Al Litz wire losses remains challenging, particularly considering their unknown electromagnetic behavior at different cryo-temperatures and frequencies when embedded in iron cores. To address this, a specialized test setup was developed to measure the losses of two customized Al Litz coils, alongside a Cu Litz coil, under varying cryo-temperatures (25 to 77 K) and frequencies (50 to 1000 Hz). A numerical model was also developed using COMSOL, incorporating a temperature-dependent electrical conductivity and a homogenization model for Litz wires with rectangular cross-sections. The model was incorporated into an analytic design procedure to maximize the test-rig loss ratio within the tight space and maximum heat rejection constraints of the cryostat, to allow accurate loss separation. The experimental data aligns closely with the numerical simulations, enabling a comprehensive analysis of the loss characteristics of Al Litz wires. This study provides a detailed design methodology and serves as a valuable resource for developing CEMs for zero-emission electric aircraft.

The linear speed of the rotor surface of high speed permanent magnet motor (HSPMM) is as high as 100 m/s, and the air friction loss on the rotor surface is much higher than that of ordinary motors, accounting for a large proportion of the total loss, and the actual air friction loss on the rotor surface is much higher than that of ordinary motors. It is extremely difficult to directly measure and verify the size of the rotor surface. At the same time, the air friction loss on the rotor surface is related to various factors such as motor speed, air gap structure and rotor surface roughness. It is difficult to accurately calculate through theoretical analysis and analytical methods. Based on the 3D fluid field physical model, this paper analyzes the relationship between the rotor air friction loss of FeCo based HSPMM and the rotor speed, rotor geometry, surface roughness and axial wind speed. Based on HSPMM, the calculation and test method of rotor surface air friction loss are studied. Through the FeCo based HSPMM no-load test, according to the relationship between the rotor air friction loss and other losses and the motor speed, the rotor surface air friction loss can be separated from the total loss. The experimental results are consistent with the calculated values, indicating that the HSPMM rotor air friction loss calculation method based on 3D fluid field analysis is effective. [ABSTRACT FROM AUTHOR]

For the purpose of studying the influence of high frequency PWM harmonics on the losses of induction motor, this paper first introduces the latest international standard IEC/TS 60034-2-3 for the separation of the losses and the measurement of the efficiency of induction motor under PWM power supply. Then, considering that the skin effect of windings in induction motors under the condition of PWM power supply more apparent, this paper uses the stator AC resistance to replace the stator DC resistance in the IEC/TS 60034-2-3 standard to obtain more accurate separation results. On this basis, an improved method of loss separation for converter-fed induction motor is proposed by using the accurate time-step finite element method to calculate the rotor copper loss under no-load condition which cannot be considered in IEC/TS 60034-2-3 standard. Finally, this method is used to measure and separate the losses of a 5.5 kW converter-fed motor under different operating conditions. The results show that the loss of induction motor which is driven by PWM converter is obviously greater than that of sinusoidal drive, especially under light load or no load condition. The whole no-load losses of the motor driven by PWM converter increases by more than 20.0% compared with that of the sinusoidal driving condition.

As an important component of hydrogen fuel cell vehicles, the air compressor with an air foil bearing rotates at tens of thousands of revolutions per minute. The heat generation concentration problem caused by the high-speed motor loss seriously affects the safe and normal operation of the motor, so it is very important to clarify the loss distribution of the high-speed motor and adopt a targeted loss reduction design for air compressor heat dissipation. In this paper, for an air compressor with a foil bearing with a rated speed of 80,000 rpm, an empirical formula and a three-dimensional transient magnetic field finite element model are used to model and calculate the air friction loss, stator core loss, winding loss and permanent magnet eddy current loss. The accuracy of the analytical calculation method is verified by torque test experiments under different revolutions, and the average simulation accuracy can reach 91.1%. Then, the distribution of the air friction loss, stator core loss, winding loss and eddy current loss of the air compressor motor at different revolutions is obtained by using this method. The results show that the proposed method can effectively calculate the motor rotor loss of a high-speed air compressor with air foil bearing. Although the motor efficiency increases with the increase in motor speed, the absolute value of loss also increases with the increase in motor speed. Stator core loss and air friction loss are the main sources of loss, accounting for 55.64% and 29% of the total motor loss, respectively. The electromagnetic loss of winding, the eddy current and other alloys account for a relatively small proportion, which is 15% in total. The conclusions obtained in this paper can effectively guide calculations of motor loss the motor heat dissipation design of a high-speed air compressor with an air foil bearing. [ABSTRACT FROM AUTHOR]

This article presents an improved dynamic hysteresis model to predict magnetic hysteresis properties under high-frequency sinusoidal excitations. A new expression of magnetic field strength related to classical loss is derived and proposed to consider the effect of skin effect on the iron loss. The permeability related to statistical parameter is presented to establish the relationship between classical loss and excess loss. The introduction of shape factor provides a possibility for accurate prediction of dynamic loops at high frequency over a broad induction range. The accuracy of the proposed dynamic hysteresis model is verified by comparing the predicted results with the measured ones. In addition, the variation of loss components with frequency and peaked induction is analyzed. [ABSTRACT FROM AUTHOR]

The original loss separation formula introduced by Bertotti has long been utilized mainly for low-frequency sinusoidal applications. In this article, the traditional method is improved to fit into the core loss calculation under higher frequency sinusoidal and nonsinusoidal excitations, verified by the measured data of nanocrystalline material that is often used in medium-frequency transformers (MFTs). For high-frequency sinusoidal waveform, it is proposed that the exponent of the excess loss needs to be reidentified, and it is necessary to consider the skin effect for hysteresis and eddy current loss calculation under broader frequency scope. When the core is supplied with nonsinusoidal excitation (square and rectangular waveform), a new empirical method is derived based on the concept of effective frequency and the loss separation results, with which the estimation accuracy is greatly guaranteed compared to empirical methods originated from the Steinmetz equation such as improved generalized Steinmetz equation (iGSE). Due to clear separation of loss components, the new method has the potential to precisely predict losses for higher frequency applications. [ABSTRACT FROM AUTHOR]

We review the basic phenomenology of magnetic losses from DC to 1 GHz in commercial and laboratory-prepared soft ferrites considering recent concepts regarding their physical interpretation. This is based, on the one hand, on the identification of the contributions to the magnetization process provided by spin rotations and domain walls and, on the other hand, the concept of loss separation. It additionally contemplates a distinction between the involved microscopic dissipation mechanisms: spin damping and eddy currents. Selected experimental results on the broadband behavior of complex permeability and losses in Mn-Zn ferrites provide significant examples of their dependence on sintering methods, solute elements, and working temperature. We also highlight the peculiar frequency and temperature response of Ni-Zn ferrites, which can be heavily affected by magnetic aftereffects. The physical modeling of the losses brings to light the role of the magnetic anisotropy and the way its magnitude distribution, affected by the internal demagnetizing fields, acts upon the magnetization process and its dependence on temperature and frequency. It is shown that the effective anisotropy governs the interplay of domain wall and rotational processes and their distinctive dissipation mechanisms, whose contributions are recognized in terms of different loss components. [ABSTRACT FROM AUTHOR]

Despite the great potential and the high performance of energy-efficient line-start permanent magnet synchronous motors (LSPMSMs), their developers face a great deal of difficulties, one of which is the lack of reliable and accurate testing methods for such electrical machines. In this paper, we propose a new method for indirectly determining the efficiency of LSPMSM through the summation of individual loss components. The standard input-output method usually used for these machines is based on torque measurement, requires expensive measuring equipment, and, as a rule, has great uncertainty. Contrarily, the proposed method does not require direct measurement of torque and mechanical power on the shaft and is less sensitive to measurement uncertainties. The theoretical substantiation of the proposed method and its experimental verification using a commercially available four-pole LSPMSM with a rated power of 0.55 kW are presented. Satisfactory convergence of the experimental results obtained using the standard input-output method and using the proposed indirect method is shown. [ABSTRACT FROM AUTHOR]

[Display omitted] • The SMCs were fabricated using flaky FeSiCr modified by ZnO nanoflowers. • Stress of flake was design and analyzed by Helmholtz coils and torque model. • Nonlinear regression method was used to evaluate the loss separation. • The P cv of SMCs modified by ZnO nanoflowers is 421.29 kW/m3 at 50 mT, 100 kHz. The power loss and permeability of soft magnetic composite (SMC) might be improved by surface modification and magnetic field orientation of flake particles. The oriented ZnO-modified flaky FeSiCr SMCs were produced under the magnetic field. The orienting mechanism of flake powder under a magnetic field produced by Helmholtz coils was investigated using torque model analysis. After surface modification, the permeability and power loss of ZnO-modified flaky FeSiCr SMCs could reach 63 and 421.29 kW/m3(at 50 mT, 100 kHz), respectively. The three-dimensional loss separation results demonstrate that spin rotation mechanism, defects, and dislocations of ZnO modification from theory and experiment may be responsible for the enhanced soft magnetic characteristics. [ABSTRACT FROM AUTHOR]

The Fe-based nanocrystalline has been widely used in the innermost magnetic shielding of the spin-exchange relaxation-free (SERF) magnetometer due to its high permeability and low magnetic noise, which are significant factors limiting the sensitivity and accuracy of the measurements. However, the operating temperature of the inner shielding layer is around 80°C, and temperature has a significant impact on the magnetic noise of Fe-based nanocrystalline. To precisely analyze the magnetic noise of the Fe-based nanocrystalline in the SERF magnetometer, we first numerically simulate the 1K107 Fe-based nanocrystalline magnetic shielding barrel using the finite element method (FEM). Then, a variable-temperature dynamic Jiles-Atherton (VTDJA) model is proposed. The losses of 1K107 under various temperature are separated. The magnetic noise of 1K107 is computed using the Fluctuation-Dissipation theory. Finally, the magnetic noises of 1K107 at 25℃ and 80℃ are measured by setting up an experimental test system. Results show that the simulated deviation of the magnetic noise at 80°C and 25°C is 32 %, and the actual measured deviation is 48 %. The errors between simulated and measured magnetic noises at 25°C and 80°C are 5.29 % and 6.54 %, respectively. This study provides a novel method for the performance optimization of the SERF magnetometer. [Display omitted] • A novel method for calculating magnetic noise of Fe-based nanocrystalline based on temperature variation is proposed. • A novel variable-temperature dynamic J-A hysteresis model is proposed to separate the loss of Fe-based nanocrystalline. • The eddy current loss noise is the main magnetic noise of Fe-based nanocrystalline at 25℃-90℃ and 20–100 Hz. • The errors between simulated and measured noises at 25 °C and 80 °C are 5.29 % and 6.54 %, respectively. [ABSTRACT FROM AUTHOR]

Soft magnetic composites (SMC) with a bionic shell structure and a delicate, regular layered arrangement were prepared via a casting process. The permeability of composite samples was 140 at 5 MHz for plane anisotropy, while that of the spherical-particle-constructed material is only 14. According to classical loss separation results, the layered bulk material without an SiO2 coating exhibited lower hysteresis loss. In contrast, the layered bulk material coated with SiO2 showed lower eddy current loss, attributed to the increase in resistivity resulting from the SiO2 coating. The magnetic loss of the layered bulk materials was 588 kW/m3 at 50 mT and 100 kHz. SMC materials with this structure are anticipated to have strong potential for magnetic cores used in high-efficiency power supplies. [ABSTRACT FROM AUTHOR]

In this paper, both nanocrystalline alloy (Fe73.5Cu1Nb3Si15.5B7) ribbon samples and toroidal samples (wound ribbon) are annealed at different temperatures in order to consider the influence of inner stress on the magnetization properties. Then the AC magnetization properties of these samples are measured. Combined with the measured results, the influence of inner stress on nanocrystalline alloy's microstructure is analyzed quantitatively based on the loss separation principle and the statistical theory of loss. By comparing measured macroscopic magnetization characteristics and excess loss, the equivalent stress state of the toroidal sample is evaluated. Furthermore, two kinds of samples' excess loss under different annealing temperatures are analyzed, and the effectiveness of stress relief at optimal annealing temperature is validated. [ABSTRACT FROM AUTHOR]

We review the basic phenomenology of magnetic losses from DC to 1 GHz in commercial and laboratory-prepared soft ferrites considering recent concepts regarding their physical interpretation. This is based, on the one hand, on the identification of the contributions to the magnetization process provided by spin rotations and domain walls and, on the other hand, the concept of loss separation. It additionally contemplates a distinction between the involved microscopic dissipation mechanisms: spin damping and eddy currents. Selected experimental results on the broadband behavior of complex permeability and losses in Mn-Zn ferrites provide significant examples of their dependence on sintering methods, solute elements, and working temperature. We also highlight the peculiar frequency and temperature response of Ni-Zn ferrites, which can be heavily affected by magnetic aftereffects. The physical modeling of the losses brings to light the role of the magnetic anisotropy and the way its magnitude distribution, affected by the internal demagnetizing fields, acts upon the magnetization process and its dependence on temperature and frequency. It is shown that the effective anisotropy governs the interplay of domain wall and rotational processes and their distinctive dissipation mechanisms, whose contributions are recognized in terms of different loss components.

Fibres-based soft magnetic composites (FSMCs) have been prepared by using Fe fibres of different diameters (65, 125, 250 and 500 μm). The Fe fibres were coated with a 3 μm thick layer of Fe 3 O 4 via the blackening process and subsequently compacted at 700 MPa. The X-ray diffraction analysis (XRD) was used to prove the formation of the Fe 3 O 4 coating on the surface of the fibres. The thickness and the uniformity of the coating were analysed via scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDX). The DC measurements performed on the composite cores revealed that the saturation induction increase from 1.36 to 1.68 T, the maximum relative permeability increase from 550 to 940, and the coercive field decrease from 796 to 454 A/m as the fibre's diameter increase from 65 to 500 μm. By using thinner fibres (65 and 125 μm), composites with low losses and stable initial relative permeability, in the frequency range 50 Hz–10 kHz, can be obtained. To distinguish between different types of losses dissipated by our compacts, and the influence of the fibre's diameter on the different components of the total losses, a numerical model for loss separation is proposed. The comparative evolution of the AC magnetic characteristics of the FSMCs and powder-based SMCs is presented. According to the presented results, this new type of composites can be successfully used to prepare magnetic cores designated to work in the medium to high-frequency range. [ABSTRACT FROM AUTHOR]

A new algorithm for numerical identification of the static Preisach hysteresis model is proposed for more accurate estimation of dc-biasing hysteresis curves and hysteresis loss of the grain-oriented silicon steel sheet. Based on the experimental asymmetric major hysteresis loop under dc-biased magnetization, two sets of first-order reversal curves corresponding to ascending and descending branches, respectively, are numerically generated for construction of the Everett function. According to the equivalent field separation technique, a dynamic hysteresis model is established by parameter extraction of excess loss, and then used for simulation of dc-biasing dynamic hysteretic behaviors. The consistency between the simulated results and the measured ones demonstrates the effectiveness of the proposed method. The effect of dc bias on iron loss is analyzed as well. [ABSTRACT FROM AUTHOR]

Gas-atomized Fe-Si-Al soft magnetic powder cores with different fine powder mass ratios were prepared by the epoxy/silica composite insulation method in this paper. High-quality insulation layer based on silica was found to form on the surface of Fe-Si-Al magnetic particles. It limited the eddy current within the core ef-fectively and thus resulted in good frequency stability of the core's effective permeability. The influence of the fine powder on the core's magnetic properties was investigated in detail. It was found that adding appropriate amount of fine powder helped the increase of the density of the powder core and the reduction of the core's effective demagnetizing field. As the consequence, both the effective permeability and the core loss were improved at the expense of the DC-Bias performance. However, the excessive addition of fine powder was found to be harmful for the core's magnetic properties. It reduced the core's density and enhanced the core's effective demagnetizing field, which resulted in the decrease of the effective permeability and the increase of the core loss. A preliminary study on the magnetic mechanism of the powder core prepared with fine powder was performed through separating the core loss at different frequencies for all the samples into the hysteresis loss and the eddy-current loss based on the Bertotti model. It was found that at frequencies below 120 kHz for the powder core, with the amount of fine powder increasing, the hysteresis loss, same as the total core loss, exhibited an increasing tendency after the initial decrease, while the eddy-current loss kept decreasing. This indicated that the eddy-current loss could be effectively restrained by the addition of the powder with a small size and the loss in the common frequency range below 100 kHz for powder core was mainly determined by the hysteresis mechanism based on the effective demagnetizing field. [ABSTRACT FROM AUTHOR]

This paper presents the design characterization, optimization, and experimental validation of a multilayer ac winding that provides a high quality rotating MMF with reduced end-turn length. Harmonics in the airgap MMF have been characterized with standard winding functions and verified using finite element analysis (FEA). The multilayer winding design is optimized for a commercial premium efficiency/IE3 benchmark machine using grid multiobjective genetic algorithm (GMGA) and a prototype has been built. Performance of the designed motor has been verified with both FEA and experiments. Evaluation under IEEE 112 test standard demonstrates that by only updating its stator winding design, the designed motor can achieve IE4 class efficiency under the same frame size and cooling type as its IE3 class benchmark. [ABSTRACT FROM AUTHOR]

Abstract Bioinspired Soft Magnetic Composites (SMCs) with nacre-like structure were fabricated using highly planar arranged flaky-Sendust. These SMCs show particularly high permeability and low loss, thus exhibiting great potential for high frequency magnetic components. Due to the high saturation magnetization and permeability of metal soft magnetic materials, it is possible to miniaturize magnetic devices by reducing the total loss, especially the eddy current loss at high frequency. The new SMCs with nacre-like structure exhibited a high permeability of up to 600 at 1 MHz, which was ten times that of common Sendust composites. The total loss decreased to 470.82 and 1162.60 kW/m3 at 100 and 200 kHz, respectively (stimulated at 100 mT), and the maximum magnetic induction increased to 714 mT at 8000 A/m, which was superior to that of ferrites. This outstanding comprehensive property is a result of the anisotropic demagnetizing factor of the flaky particles in a planar arrangement, which can be derived from the Aharoni's formula. The minimum total loss is a result of the balance of hysteresis and eddy current loss for the small thickness, which is below skin depth. In addition, the three-dimensional loss separation characteristic was analyzed using the nonlinear regression method to theoretically evaluate the influencing factors related to the morphology of the materials. This approach provides small, high frequency, and high saturation magnetic devices for switching regulators, photovoltaic inverter boost inductors, and noise filters. Graphical abstract Image 1 [ABSTRACT FROM AUTHOR]

Abstract Iron-based soft magnetic composites (SMCs) coated with the ferrimagnetic Fe 3 O 4 layer have been fabricated by in-situ oxidation and hydrogen reduction methods, and then the effects of annealing process on the soft magnetic properties were investigated. It showed that the Fe 3 O 4 insulating layer was coated on the surface of the iron powders, which effectively reduced the magnetic dilution and decreased the core loss of the composites. In addition, the Fe/Fe 3 O 4 core-shell composites exhibited high permeability and frequency stability of permeability after annealing. The real part of permeability of the soft magnetic composites could reach a maximal value of 142.9 and a rather low core loss of 274.9 W/kg (measured at 50 mT and 100 kHz). Based on the magnetic loss separation model, the hysteresis loss and eddy current loss coefficient was obtained. It was indicated that the annealing process enhanced the eddy current loss coefficient while the hysteresis loss coefficient is close to each other for all the samples. Therefore, this work can provide a method to prepare soft magnetic composites with excellent magnetic properties and low core loss. Highlights • The Fe/Fe 3 O 4 core-shell SMCs were successfully prepared by in-situ oxidation and hydrogen reduction methods. • The Fe 3 O 4 insulting shell layer could reduce the magnetic dilution effect in the SMCs. • The real part permeability of the SMCs maintains the high value of 142.9. • The annealing enhanced the permeability and the eddy current loss coefficient of the SMCs. [ABSTRACT FROM AUTHOR]

[Display omitted] • APTES-involved insulating technique was used to coat nano kaolin on FeNi particels. • Magnetic properties of FeNi@kaolin SMCs were regulated by adjusting kaolin dosage. • Loss mechanisms for FeNi@kaolin SMCs were clarified based on loss separation model. • Proper kaolin contents were determined to endow FeNi SMCs with low core loss. • Magnetization state can reasonably explain core loss under large DC bias excitations. Constructing the high-quality insulating layer and verifying the effects of DC bias field on magnetic properties is crucial in optimizing magnetic components based on soft magnetic composites. In this paper, a novel APTES-involved insulation technique has been developed to successfully coat kaolin on FeNi particles. Additionally, magnetic properties can be effectively regulated by changing the dosage of kaolin. The results show that anti-magnetization capacity and resistivity are improved by increasing kaolin content. Loss separation model and magnetic field simulation were used to investigate how the coating layer and DC bias field influence core loss for FeNi@kaolin SMCs. It can be found that structural demagnetizing field and eddy current were believed to be the main determinants of core loss variation in ideal sinusoidal waves, while the degree of magnetization state away from saturation plays a leading role in core loss under larger DC bias fields. Therefore, FeNi SMCs insulated with 1 wt% and 7 wt% kaolin exhibit the lowest core loss at DC bias field of 0 Oe and above 100 Oe, respectively. This work not only provides an effective insulating technique, but also supplies deeper insights into optimizing SMC-based magnetic components under larger DC bias fields. [ABSTRACT FROM AUTHOR]

• In this paper, we propose a new parameter identification method of inverted Preisach model, which uses the measured quasi-static concentric hysteresis loops to simulate the static DC hysteresis behavior of grain-oriented silicon steel sheets. • Then, the dynamic magnetic field intensity related to excess loss is improved by considering the nonlinear relationship between statistical parameter of excess loss V 0 and AC peaked magnetic flux density B acm , DC magnetic field intensity H dc and frequency f. • Finally, a dynamic hysteresis model in the form of field separation is proposed to predict the asymmetric hysteresis curve under AC-DC hybrid magnetization. The simulation hysteresis curve and loss under different AC-DC hybrid magnetization are compared with the measured ones, which verifies the accuracy and effectiveness of this method. Firstly, a new method for parameter identification of inverted Preisach model is proposed to simulate static DC-biasing hysteresis behavior of the grain-oriented (GO) silicon steel sheet by using the measured quasi-static concentric hysteresis loops under DC-biasing magnetization. Then, the dynamic magnetic field intensity related to excess loss is improved by considering the nonlinear relationship between the statistical parameter V 0 and the AC peaked magnetic flux density, DC magnetic field intensity as well as frequency. Finally, a dynamic hysteresis model in form of field separation is presented to predict asymmetric hysteresis curves under multi-harmonic and DC-biasing hybrid magnetization. The simulated hysteresis curves as well as losses under different AC-DC hybrid magnetizations are compared with the measured ones, which verifies the accuracy and effectiveness of the proposed method. [ABSTRACT FROM AUTHOR]

Abstract The effect second milling time on the electromagnetic properties of MnZn ferrites has been studied up to MHz range. The average particle sizes of powder ranging from 1.49 to 1.16 μm were obtained by varying the second milling time from 72 to 324min. It is found that the total losses (P cv) deteriorate when the second milling time over 252 min and the limit particle size is 1.21 μm. The value of initial permeability (μ i) reduces by 20% when the particle size is 1.16 μm due to the uneven distribution of grain size, indicating that uniform microstructure demands suitable particle size. Meanwhile, the eddy current loss (P e) and residual loss (P r) dominate the total loss at 3 MHz playing a significant role in total losses. The hysteresis loss (P h) and eddy current loss (P e) deteriorate gradually at 3 MHz when the particle size is 1.21 μm at 100 °C. The residual loss increases greatly with the particle size decreasing at 3 MHz. An excellent MnZn power ferrite possessing high initial permeability (μ i = 887), high saturation magnetic flux density (B s = 531 mT) and low total losses (P cv = 1940 kW/m3) at 3 MHz-50 mT is synthesized in this research. Highlights • Suitable particle size is demanded for high-frequency low-loss MnZn power ferrite. • The smaller particle size tends to cause abnormal grain growth, leading to coercivity increased. • The sintering density is not completely proportional to particle size and almost a constant when the particle size exceeds the limit value. • The total power loss is greatly increased due to the transition from mono-domain to multiple domain state, leading to the losses composition ratio changed. [ABSTRACT FROM AUTHOR]

This paper presents research work on a 12-slot ten-pole tapered axial-flux permanent-magnet machine utilizing amorphous magnetic material in the stator core. Novel loss separation techniques are described, including mechanical loss and locked-rotor tests. Mechanical loss estimation is based on a combination of experimental tests and 3-D finite-element model analysis using an uncut stator. The locked-rotor test is introduced to separate the stator and rotor losses by eliminating the uncertainty associated with mechanical loss. High rotor yoke losses were identified in the baseline design. The rotor design was modified and a significant improvement in efficiency was demonstrated. [ABSTRACT FROM PUBLISHER]

Novel Fe-based soft magnetic composites (SMCs) with hybrid phosphate-alumina layers were prepared by both sol−gel and ball-milling methods. The effects of the fabrication methods and the addition of Al2O3 particles on the microstructure and the soft magnetic performance of SMCs were studied. The formation of the hybrid phosphate-Al2O3 shell not only leads to the decrease of the total core loss, but also results in the reduction of the permeability and saturation magnetization. However, the degree of decrease caused by the different methods were not identical. The sample with 8% Al2O3 prepared by the sol−gel method showed the best magnetic performance, exhibiting a high-amplitude permeability (μa) of 85.14 and a low total core loss (Ps) of 202.3 W/kg at 50 mT and 100 kHz. The hysteresis loss factor and the eddy current loss factor were obtained by loss separation. The results showed that the samples with the same Al2O3 content prepared by different methods exhibited almost the same total core loss. However, the contribution of the hysteresis loss and the eddy current loss showed an obvious difference in behavior because of the change of the particle shapes and the refinement of the particle size during the ball-milling process.

The pulsewidth modulation (PWM) technique is commonly used to supply modern high-speed electrical machines. The fundamental frequency is typically in the kilohertz range, with switching frequencies of several tens of kilohertz, as determined by the new SiC- or GaAs-based power transistors modules. Switching introduces minor loops in the major hysteresis cycle, with durations of the order of 100~\mu \texts or lower, with the resulting magnetization dynamics influenced by strong skin effect. However, since these minor loops have relatively small amplitude, their constitutive equation may be described by an equivalent permeability (real or complex), depending on the mean slope of the minor loop and its static energy loss. By retrieving this permeability, the classical loss is straightforwardly calculated by analytical solution of Maxwell's equations. In this paper, we measure and calculate, according to the quasi-linear approximation for the minor loops, the magnetic energy losses of 0.194 mm thick non-oriented Fe–Si 3.2% sheets subjected to PWM induction waveform. Minor loop peak amplitudes ranging between 50 mT and 0.2 T and frequencies up to 10 kHz are investigated. The results are consistent with the proposed model, to within 5%. [ABSTRACT FROM AUTHOR]

An electrical variable transmission (EVT) is an electromagnetic power-split device with two mechanical and two electrical ports. It can be used in hybrid electric vehicles to split the power to the wheels in a part coming from the combustion engine and a part exchanged with the battery. Although crucial for the EVT design and evaluation, no papers are found to give a detailed overview of the different loss components in such a machine and how they can be calculated and measured. In contrast to conventional electrical machines, this machine has more degrees of freedom, which can be exploited to measure the different loss contributions separately. This paper proposes a methodology to identify and measure the different loss components in this kind of machines. The proposed method is able to identify the iron losses in stator and inner rotor, the copper losses, bearing losses, and slip ring friction losses separately. To this end, measurements of both torque and speed sensors in different operating points are combined. The methods are applied to identify the different loss contributions in a prototype permanent magnet assisted EVT, both in no-load operation as under load where its functionality as power-split device is evaluated. [ABSTRACT FROM PUBLISHER]

The effects of Al content (0.53 ≤ Al ≤ 9.65 wt%) on microstructure, texture, magnetic flux density, permeability, core loss and magnetic domain structure of Fe-Al based electrical steel were measured or observed. Average grain size decreased as Al content increased, but Al contents had no severe effects on texture. Magnetic flux density and permeability tends to decrease as Al content increased. Total core loss P tot was separated into hysteresis loss P h , eddy-current loss P e and anomalous loss P a . As Al increased, P h increased, but P e and P a decreased, so the optimal grain size increased. To reduce core loss of electrical steel with high resistivity, annealing should be conducted at high temperature and for a long time to increase grain size. [ABSTRACT FROM AUTHOR]

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[Display omitted] • Ferrite coated FeSiAl SMCs were achieved by mechanical and chemical method. • The magnetic properties at high frequency were significantly improved. • The frequency stability of μ e and the peak frequency of Q are largely promoted. • The power loss is greatly reduced by NiZn ferrite insulating layer. As a hotspot of soft magnetic composites (SMCs), the magnetic properties and loss characteristics of FeSiAl SMCs at high frequency need to be further optimized. In this study, the FeSiAl with flaky morphology was obtained by mechanical ball milling to improve its permeability, the reduction of power loss and the optimization of magnetic properties were achieved by the Ni 0.4 Zn 0.6 Fe 2 O 4 cladding layer. For comparison, phosphoric acid-passivated flaky FeSiAl was prepared. The results indicated that due to the good coating effect and high resistivity of NiZn ferrite, the Ni 0.4 Zn 0.6 Fe 2 O 4 coated flaky FeSiAl has a high permeability (μ e ≈ 100) with extraordinary frequency stability in the range of 100 kHz–10 MHz, a higher quality factor with the peak occurs in higher frequency bands (Q = 72 at around 1 MHz), and a low relative loss factor of the order of 10−3–10−4 in the range of 20 kHz–8 MHz. In addition, the ferrite-coated flaky FeSiAl also has outstanding high-frequency power loss performance, which can be explained by the coercivity in the VSM results and the reduced eddy current loss obtained by loss separation. This work broadens ideas for improving high-frequency applications of FeSiAl SMCs. [ABSTRACT FROM AUTHOR]

Fig. 1. (a-c) Bubble-like spheres on the surface of the NSMCs and (d-i)cross-sectional TEM images of the FeSiBCuNb NSMC powders with corresponding EDS mapping exhibiting the distribution. [Display omitted] • A continuous, multi-layer, uniform and ultra-thin insulating coating were successfully fabricated. • Excessive addition of zinc stearate decomposes to CO 2 with some small bubble-like spheres on the surface of NSMCs. • After annealing, the NSMCs with 2.0 wt% zinc stearate exhibit high μ e and low P cv. Here, the influence of zinc stearate on the microstructure and soft magnetic properties of the Finemet nanocrystalline soft magnetic composites (NSMCs) was systematically investigated. The results demonstrate that the core loss (P cv) decreases and the effective permeability (μ e) increases of the NSMCs with increasing zinc stearate from 0 wt% to 2.0 wt%, which can be attributed to the reduction of residual stress during compaction. Further increasing zinc stearate up to 3.0 wt%, the P cv increases sharply, while the μ e shows a decreasing trend. It can be considered that the addition of excess lubricant decomposes to CO 2 during annealing, which deteriorates the magnetic properties. After annealing at 560 °C, a thin hybrid layer of only about 53.6 nm containing iron phosphate, ZnO, and SiO 2 is formed in the NSMCs with 2.0 wt% zinc stearate, which exhibits excellent soft magnetic properties such as low P cv of 174 kW/m3 and high μ e of 66.7 at B m = 0.1 T for 50 kHz. In addition, loss separation has been carried out and suggests that the addition of lubricant mainly affects hysteresis loss in the total energy loss of NSMCs. [ABSTRACT FROM AUTHOR]

The transformer tank is normally built of construction steel and has relatively large thickness of 1.2 mm for distribution up to 12 mm for large power transformers. In such thick materials, skin effect becomes much more significant than thin materials due to both frequency and non-linearity. The flux density in the tank can vary in a wide range of some mT to 1800 mT (in the case of having high zero sequence flux) leading to a large variation in the permeability and, consequently, in skin depth. Since the losses are high, the temperature rise can also be a main problem influencing the conductivity that must be considered in the loss calculations. The main contribution of this paper is to study the magnetic losses in the transformer tank steel through the measurements and finite difference-based numerical calculations. Using the loss separation principle, different loss mechanisms are investigated, and the behavior of each at the different level of inductions and frequencies is studied. [ABSTRACT FROM AUTHOR]

Electrical steel (ES) plays an important role in the design of magnetic circuit cores of electrical machines. Separating specific total loss into components is an excellent tool for loss analysis in ES. As is commonly accepted, the specific total loss is separated into three components: hysteresis and both classical and additional eddy current loss components. In addition, the conventional grain-oriented (GO) ES presents the strong anisotropy of magnetic properties, due to the (110) [001] Goss texture, with [001] the easiest direction [parallel to rolling direction (RD)], with intermediate [011] and magnetically worst [111] directions, at angles x = 0 ^\circ , 90°, and about 54° to RD, respectively. However, magnetization angles 0 ^\circ < x < 54 ^\circ and 54 ^\circ < x < 90 ^\circ also play a very important role in the research of specific total loss components. The angular properties of specific total loss under axial magnetization in GO ES should be most preferably evaluated by the use of single-sheet tester with specimens cut at different angles with respect to RD. This paper demonstrates, in the quantitative way, the dependence of hysteresis Ph and additional eddy current Pa specific total loss components on Goss texture. In addition, the results obtained justify the division of specific total loss and its components in two flux density regions: below Bm \le 1 T (the lower region) and above Bm > 1 T (the upper region). This paper is intended to offer a better understanding of phenomena that cause magnetic anisotropy, i.e., different Goss textures. [ABSTRACT FROM AUTHOR]

This paper proposes a tractable and robust numerical method to predict iron losses in electrical steel laminations that are subjected to high-frequency excitations. To achieve this goal, Preisach modeling and the finite-difference method are first employed to simulate the hysteresis loss and eddy current loss, respectively. With this proposed algorithm, a better approximation of the excess loss and its optimal parameter identification is obtained. The proposed algorithm, when compared with conventional engineering models, reduces the errors between the estimated values and the measured values with tolerable computational burden. [ABSTRACT FROM AUTHOR]

We consider dynamic models, both numerical and analytical, that reproduce the magnetization field H ( B ) and the energy loss in ferromagnetic sheet materials with different domain structures. Conventional non-oriented (NO) and grain-oriented (GO) electrical steels are chosen as typical representatives of fine-domain and coarse-domain materials. The commonly-accepted loss separation procedures in these materials are critically analyzed. The use of a well-known simplified (“classical”) expression for the eddy-current loss is identified as the primary source of mistaken evaluations of excess loss in NO steel, in which the loss components can only be evaluated using the Maxwell (penetration) equation. The situation is quite different in GO steel, in which the loss separation is uncertain, but the total dynamic loss is several times higher than that explained by any version (numerical or analytical) of the classical approach. To illustrate the uncertainty of the loss separation in GO steel, we show that the magnetization field, and thus the total loss, in this material can be represented with equal accuracy using either the existing three-component approach or our proposed two-component technique, which makes no distinction between classical eddy-current and excess fields and losses. [ABSTRACT FROM AUTHOR]

In this work, iron-based soft magnetic composites coated with the amorphous SiO 2 layer have been fabricated by utilizing tetraethoxysilane in the reverse microemulsion method, and then the effects of addition amount of SiO 2 and annealing temperature on the magnetic properties were investigated. The results show that the surface of iron powders contains a thin amorphous SiO 2 insulation layer, which effectively decreases the magnetic loss of synthesized magnets. The magnetic loss of coated samples decreased by 87.8% as compared with that of uncoated samples at 150 kHz. Magnetic measurements show that the sample with 1.25 wt% SiO 2 has an acceptable real part and minimum imaginary part of permeability in comparison with other samples. Also, the annealing treatment increased the initial permeability, the maximum permeability and the magnetic induction and decreased the coercivity with increasing temperature in the range 300–600 °C. The results of the loss separation imply that the annealed SMCs have a higher hysteresis loss coefficient ( k 2 ) and lower eddy current loss coefficient ( k 3 ) as compared with the pure iron compacts after the same heat treatment due to the preservation of the SiO 2 layer. [ABSTRACT FROM AUTHOR]

Core losses were estimated for various magnetic core materials magnetized with a duty-cycle-changed symmetrical and asymmetrical rectangular voltage. Each voltage waveform is applied to a transformer and a dc reactor in a dc/dc converter, respectively. Core losses were measured for the four typical magnetic core materials often used in power electronics: 3% grain-oriented silicon steel sheet, 6.5% silicon steel sheet, amorphous material, and nanocrystalline material. Measurement results were evaluated by the loss separation model. An approximation method was proposed for the core loss magnetized with asymmetrical rectangular voltage that divides the total core loss into the core loss of the magnetization from -Bm to Bm and that of the magnetization from Bm to -Bm. This method was confirmed to approximate the core loss accurately except for silicon steel sheet in an extreme duty cycle condition. However, it was demonstrated experimentally that dc component of the magnetic field strength caused this error. [ABSTRACT FROM AUTHOR]

In Part I of this two-part paper, fundamental concepts of interlaminar fault and its consequences on magnetic cores were presented. An equivalent configuration, which was proved by FEM modelling, was proposed for magnetic cores with interlaminar fault. In this Part II paper, based on the equivalent configuration of the core and equivalent circuit of eddy current path, an analytical model is developed to estimate eddy current power loss of magnetic cores with interlaminar faults in a wide range of magnetizing frequency. Important factors, such as skin effect, nonuniform flux density distribution, complex relative permeability and nonlinear relation of B (H), which are often neglected in the literature, are highlighted. Packs of two, three, and four Epstein-size laminations of conventional grain oriented were shorted together artificially to measure the extra power loss caused by the interlaminar fault and support the analytical modeling. It was found that in the magnetic cores affected by interlaminar fault, the skin effect is a determinant factor in the magnetic properties determinations, even at low frequencies. [ABSTRACT FROM AUTHOR]

Using atomic layer deposition and high-temperature annealing to fabricate coatings for Fe-6.5 wt%Si powder reduce the hysteresis losses of the resultant composites drastically without sacrificing the permeability properties, and keep the eddy current losses at a relatively low value. The core loss of annealed FeSi SMCs is 39.67% lower than that of composites prepared using raw Fe-6.5 wt%Si powder, meanwhile the permeability remains at relatively high value (at B = 100 mT, f = 50 kHz). The decreasing of the core loss is mainly attributed to hysteresis loss reduction caused by grain growth. And the low eddy current loss is guaranteed by the uniform, complete, compact coating layer formed the surface of FeSi particles, which transforms to a protective and insulating layer containing silicate and metal oxide after annealing. On the premise of ensuring the integrity of the insulation layer, the annealing temperature of powder is significantly increased by surface modification, so as to reducing the hysteresis loss meanwhile controlling the eddy current loss. [Display omitted] • Low core loss Fe-Si soft magnetic composites were prepared. • Nano-Al 2 O 3 was deposited on the surfaces of Fe-Si powders by ALD. • A protective and insulating layer formed at the interface after annealing. • Hysteresis loss reduced obviously due to the grain growth. • Decline of hysteresis loss dominates the dramatic reduction of total loss. [ABSTRACT FROM AUTHOR]

Abstract: A method for measurement of frequency dependent electromagnetic core loss of a permanent magnet generator is presented. Core loss of a PM generator is measured at electrical frequencies ranging from 4 to 14 Hz. Core loss in the same interval is simulated using the finite element method and frequency domain loss separation. The specific loss is both extrapolated from specific loss at 50 Hz and measured directly at 4, 8, 12 and 16 Hz. Core loss simulations based on extrapolated specific loss are 38–53% smaller than measured loss. Core loss simulations based on specific loss measured at 4, 8, 12 and 16 Hz are 19–23% smaller than measured loss. [Copyright &y& Elsevier]

This paper presents an alternative computationally efficient approach to the thermal design of compact wound components. The method is based on the use of anisotropic lumped regions within 3-D thermal finite-element analyses. The lumped regions replicate the multimaterial composites used in the construction of wound components. Material data for these lumped regions are obtained experimentally, accounting for the thermal anisotropy. Input loss data for the analysis were derived by combining electromagnetic finite-element iron loss calculations with experimental ac copper loss correlations. The technique is applied to a design of a high-energy-density filter inductor. Thermal measurements from prototype inductors are compared with the theoretical predictions showing a good agreement. [ABSTRACT FROM AUTHOR]

Abstract: This work investigated the magnetic losses of heat treated iron-based soft magnetic composites with a thin MgO insulating layer produced by sol–gel method. The samples were characterized by energy dispersive X-ray spectroscopy, X-ray analysis and Fourier transform infrared spectroscopy. The results show that the surface of the powders contains a thin layer of MgO insulation. The loss results indicate that the hysteresis part for both the core loss and total loss factor was approximately the same for the MgO-insulated compacts and conventional SOMALOYTM samples with phosphate insulation after annealing at 600°C. But the MgO-insulated compacts exhibited significantly lower eddy current contribution of both core loss and total loss factor with respect to SOMALOYTM samples after annealing. Also the contribution of eddy current in the iron particles for MgO insulated compacts (k p =0.91) was noticeably higher than this contribution for SOMALOYTM samples (k p =0.18) after annealing due to the higher electrical resistivity of the MgO-insulated compacts. [ABSTRACT FROM AUTHOR]