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Neutron depolarization experiments have shown that the intragranular magnetic domain structure of polycrystalline ferrites exhibits a marked grain size dependence. Below a grain size of around $3~\mu \text{m}$ , the magnetic domain structure changes from the two-domain to the mono-domain state. Ferrites composed of mono-domain grains exhibit low dissipation at megahertz frequencies. This is attributed to the absence of intragranular domain wall movement, i.e., a microscopic origin for dissipation in ferrites has been identified. The implications of this clear observation and evidence for a transition from the mono- to two-domain state in ferrites for micromagnetic theory when a single particle becomes monodomain, as well as for the initial permeability mechanisms in polycrystalline ferrites, are discussed. [ABSTRACT FROM AUTHOR]

Non-oriented (NO) electrical steels are widely used as core materials in rotating electrical machines, whereas for measurements under alternating magnetization (AM), standardized methods exist; measurements under rotational magnetization (RM) prove to represent a significant problem. In this paper, we performed measurements of both circular rotational and alternating losses in rolling and transverse directions for four types of NO materials of different Si contents and thicknesses by means of a hexagonal rotational single-sheet tester at different frequencies and flux density values. The losses were measured by the electrodynamical method and for confirmation also by the thermal (rise-of-temperature) method. The estimated rotational losses by means of established well-known methods are correlated with the measured ones. Literature reports attempt to estimate losses $P^{\mathrm {(RM)}}$ for circular RM on the basis of losses $P^{\mathrm {(AM)}}$ for AM. A loss ratio factor $\Gamma = P^{\mathrm {(RM)}}/P^{\mathrm {(AM)}}$ is defined which is reported to be close to $\Gamma = 2$. In this paper, $\Gamma $ factors were determined for three different grades of material. The results indicate a rather weak dependence of $\Gamma $ on the grade, however, a strong one on the intensity $B$ of induction. In approximation, $\Gamma = 2$ is valid for rather weak induction of the order $B = 0.6$ T. Induction increases in steps of $\Delta B = 0.1$ T yield decreases of loss ratio by about $\Delta \Gamma = 3$ %. This enables a rough estimation of rotational losses. However, the possibility of estimation is restricted to the circular case of constant modulus and angular velocity of the $B$ vector. Other cases are characterized by different values of both eddy current losses and hysteresis losses, RM involving completely different domain reconstructions compared to AM. For increased frequency, the decrease in $\Gamma $ becomes weaker due to more dominant eddy current losses. [ABSTRACT FROM AUTHOR]

In this paper, optimization of the control of an electrical machine allowing a minimization of its total losses is described. It is based on the use of an iron loss model [loss surface (LS) model] coupled to the electromagnetic finite-element simulations of the machine. The LS model is a scalar and dynamic hysteresis model developed many years ago at G2Elab and tested for iron loss prediction in several cases of electric machines. It is first characterized and improved in this paper for M330-35A SiFe sheets. Then, it is associated with a finite-element analysis to compute, in a post-processor mode, the local and global magnetic losses in the machine. For electric vehicle application, the whole torque–speed variation should be investigated. To do that, a quick response surface is constructed from a small number of simulations and the iron loss is determined. Then, a suitable optimization algorithm is developed. This approach is then illustrated by a case study and compared with classical optimization in which only the copper losses in conductors are considered. Gains of up to 50% reduction in the total losses of the machine in certain operating areas are observed. [ABSTRACT FROM AUTHOR]

This paper discusses fundamental physical mechanisms that are responsible for specific errors of standardized methods of magnetic loss measurements on laminated soft magnetic materials. It is shown that the Poyntings theorem offers an exact distinction between localized loss portions on the one hand and total losses on the other hand. Further, a clear distinction is suggested between mechanisms of hysteresis and eddy currents. The correct applicability of experimental measurements proves to be restricted to cases where the Poynting vector is restricted to normal off-plane components. This represents the only case where total losses can be determined on the basis of surface field and cross-sectional averaged induction. As a consequence, physically “correct” loss measurements are to be restricted to sample regions that exhibit mere axial magnetization, in exact ways. This is attainable with a single sheet tester, the homogeneously magnetized region of which is equipped with an induction coil and a large-area tangential field coil, in consistent ways. [ABSTRACT FROM AUTHOR]

This paper investigates the iron loss calculation of permanent magnet (PM) machines undertaking unconventional operations, where the high-frequency alternating armature field is only a fraction of the constant PM field. It is found that the iron loss of PM machines undertaking such unconventional operations cannot be calculated reliably as the conventional summation of all the iron loss harmonics predicted by finite-element (FE) methods due to fake iron loss harmonics. Further investigation is conducted on the influence of current frequency and magnitude, FE mesh, and convergence tolerance on the FE predicted iron loss under unconventional operations. It is then proposed in this paper that the iron loss of PM machines undertaking unconventional operations can be calculated as the summation of only the iron loss harmonics, which are insensitive to the convergence tolerance. The analyses are validated by the experimental results. [ABSTRACT FROM AUTHOR]

The stray load losses in electrical machines represent a non-negligible contribution of the total losses and are a key point for an accurate evaluation of the energy efficiency of the considered device. In this paper, a methodology using the 3-D finite-element (FE) modeling approach and a posteriori loss calculation is presented for the estimation of the stray load losses. The case of a cage induction motor is investigated, and results are compared with the experiment. The simulation is performed at different load conditions using a 3-D FE model with external circuit coupling. [ABSTRACT FROM AUTHOR]

An electrical motor’s inverse thermal model formulates the precision with which its power losses can be predicted from noisy local temperature measurements. This paper proposes constrained linear least square optimization followed by noise smoothing as a method to accurately predict a 37 kW induction motor’s power loss components. The anisotropic heat transfer and complex geometry of the motor are represented well by the motor’s lumped thermal network and 3-D finite element models, which characterize its intrinsic heat-transfer processes. With the inverse solution method, satisfactory temperature to power inverse mapping was achieved for different sets of noisy temperature inputs simulated from analytical and numerical forward solutions. This paper demonstrates that even with measurement noise in input data, if reliable information about the expected response of the system is available, an accurate reconstruction of power losses can be achieved. [ABSTRACT FROM AUTHOR]

This paper deals with iron losses caused by fringing fluxes generated by the concentrated stator windings of an axial-flux permanent-magnet synchronous machine. Fringing fluxes enter the laminated stator stack perpendicularly to the plane of the laminated silicon steel sheets. They cause additional eddy currents and losses in the sheets. Three approaches for reducing these losses are compared experimentally with a dedicated setup. The setup has no moving parts and makes accurate iron loss measurement possible. The first method directly restricts the eddy-current losses by segmenting the lamination surface. The second method deflects the fringing flux by using soft magnetic composite. The third method magnetically short circuits the fringing flux using ferromagnetic wires. The first method gives the best results, with a reduction of 6% of the total iron loss at an induction level of 0.6 T and a frequency of 200 Hz. [ABSTRACT FROM PUBLISHER]

This paper shows that there is very little effect of the silicon content on the hysteresis component of the magnetic losses when two steels with 2.45% and 3.3% silicon were compared. Two non-oriented steels with 2.45 wt% and 3.3 wt% Si have been investigated. The Hysteresis component was measured by two techniques, in an Epstein frame: by a quasi-static test at 5 MHz and by extrapolating the total loss from frequencies above 50 Hz. The results showed that the quasi-static hysteresis loss (5 MHz) is not affected by increased Si content. The method of measurement by extrapolating—from frequencies above 50 Hz—($W_{h}^\ast $) proved inaccurate, as it is influenced by the electrical resistivity of the steels. [ABSTRACT FROM AUTHOR]

Temperature prediction for electrical machines is a crucial concern in order to increase power density and ensure satisfactory life span. For high-reliable thermal analysis, this paper addresses a versatile methodology to apportion the stray load loss (SLL) of the induction machine. The 2-D transient finite-element analysis has been performed to investigate electromagnetic losses. The calculated losses under the rated-load condition are superimposed with the experimental SLL. The synthesized losses are imported to thermal-flow analysis using 3-D incompressible steady computational fluid dynamics. Electromagnetic losses, winding temperature, and air flow rate are measured with the test of a 1.8 MW medium voltage motor, validating the overall analysis and the allocation of SLL. [ABSTRACT FROM AUTHOR]

One of the issues of an iron loss estimation is the modeling of an excess loss. This paper investigates the modeling method for the excess loss under dc-biased conditions. The proposed approach is based on the 1-D finite-element analysis for the silicon steel sheet in the thickness direction considering hysteretic property and skin effect. In addition, the magnetic flux density waveform is divided into the outline loop and minor loops and estimate the excess loss of each loop using the eddy current loss correction factor $\kappa $ taking account of dc-biased conditions. To demonstrate the effectiveness of the proposed method, we compare the estimated loss with measured one for the harmonic wave in single sheet tester. [ABSTRACT FROM AUTHOR]

In this paper, the magnetic properties of non-oriented (NO) and grain-oriented (GO) silicon steels with dc-biased induction are measured and analyzed within the wide range of 20–1000 Hz, 0–1.9 T. While by the physical method, we found that all the ac-, dc-, and dc-biased fields do not influence the electrical resistivity of silicon steel, and hysteresis loss is mainly responsible for the iron loss increase when dc-biased induction exists. With the frequency and ac induction going up, the effect of dc-biased induction on iron loss will become weak. Compared with NO steel, iron loss of GO steel is more sensitive to dc-biased induction. The validation shows that existing iron loss models which claim to consider dc-biased magnetic induction are not satisfactory up to now when applied in the wide range of dc-biased induction, ac induction, and frequency. [ABSTRACT FROM AUTHOR]

Inverse analysis is a known mathematical approach, which has been used to solve physical problems of a particular nature. Nevertheless, it has seldom been applied directly for loss reconstruction of electrical machines. This paper aims to verify the accuracy of an inverse methodology used in mapping power loss distribution in an induction motor. Conjugate gradient method is used to iteratively find the unique inverse solution when simulated temperature measurement data are available. Realistic measurement situations are considered and the measurement errors corresponding to thermographic measurements and temperature sensor measurements are used to generate simulated numerical measurement data. An accurate 2-D finite-element thermal model of a 37 kW cage induction motor serves as the forward solution. The inverse model’s objective is to map the power loss density in the motor accurately from noisy temperature measurements made on the motor housing’s outer surface. Furthermore, the sensitivity of the adopted inverse methodology to variations in the number of available measurements is also considered. Filtering the applied noise to acceptable ranges is shown to improve the inverse mapping results. [ABSTRACT FROM AUTHOR]

Magnetic components in power electronic equipment usually suffer from nonsinusoidal excitations. In this paper, a brief description about the existing core loss calculation methods for nonsinusoidal excitations is given. Then calculation formulas of aforementioned methods for two typical excitation waveforms, that is, square and rectangular with variable duty cycle ${D}$ , are derived. Core loss of nanocrystalline FT-3KS, under above two nonsinusoidal excitations, is measured on an established test setup. The accuracy and applicability of each method are discussed theoretically and verified experimentally, especially in terms of different duty cycles and frequencies. It is found that the waveform coefficient Steinmetz equation (WcSE) is more applicable for the case of relatively small harmonics content of magnetic field intensity ${H}$ (normal duty cycle region), while the improved generalized Steinmetz equation (IGSE) has better precision where the harmonics count (extreme duty cycle region). In addition, the IGSE can better follow the changing trend of core loss with ${D}$ and have better frequency applicability than WcSE, which is proven to be not valid in low frequency (where the static hysteresis loss dominates). The results can provide reference for core loss prediction under nonsinusoidal excitations. [ABSTRACT FROM AUTHOR]

Experimental and calculating analysis of magnetic losses for Terfenol-D is a necessary step for the design of high-power magnetostrictive transducer. In order to further research the magnetic energy losses characteristics, a Terfenol-D rod is sectioned along different directions, and these slices are made into several square annular sheet samples. The influences of material magnetization direction on the losses are compared and analyzed. The values of magnetic energy losses are measured to investigate their variations at different frequencies and magnetic densities of driving magnetic field. Furthermore, the traditional losses formula is improved. The values of the hysteresis losses, eddy-current losses, and anomalous losses are separated out, and the losses coefficients are achieved through polynomial curve fitting. This paper can provide theoretical and experimental guidance for the high-frequency applications of magnetostrictive materials. [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]

This paper studies the effect of common-mode voltage elimination (CMVE) on the iron loss of electrical machine core laminations under multilevel converter supply. Three identical magnetic ring cores are excited by either a three-level converter or a five-level voltage source converter to study the behavior of CMVE on a three-phase system. Both multilevel converters are controlled by using a space vector pulsewidth modulation as it is one of the most often used techniques for CMVE. These experimental results are confirmed numerically with a dynamic iron loss model. In addition, the effect of CMVE, at different switching frequencies, on the core loss of a synchronous machine is numerically studied. The results presented in this paper show that the core loss is considerably increased when the CMVE is implemented. However, this iron loss increase in the five-level drive systems is lower compared with the three-level ones. Therefore, it is important that the designers of drive systems take such effects into consideration. [ABSTRACT FROM AUTHOR]

High-speed permanent magnet machines, supplied by pulsewidth modulation (PWM) voltage source inverters, operate with distorted stator currents. Harmonics present in these stator currents deteriorate the machine performance by generating losses. Mostly, these losses are following the machine design using a transient finite-element model. The precise measurement of these rotor eddy-current losses is extremely difficult, hence, only a few papers provide convincing comparisons between predictions and measurements. This paper presents a fast and precise analytical approach, verified with measurements, to consider rotor losses of machines, supplied by PWM voltages, already during the design procedure. [ABSTRACT FROM AUTHOR]

With the change of temperature, magnetic characteristics of electrical steel sheet (ESS) exhibit remarkable variations, in particular, at high-temperature region. If the magnetic field of electromagnetic devices operating under high temperature is analyzed by the magnetization data recorded under room temperature, the analysis findings appear to be quite different from the real ones. In order to understand and apply the real magnetic behavior in ESS, a temperature-dependent hysteresis model is quite necessary. In this paper, a physical background-based Jiles–Atherton (J–A) model is enhanced for revealing temperature effects through the introduction of temperature-dependent parameter on the base of observation of measurement data. In addition, the inaccuracy of J–A model in the range of weak applied field is enhanced with the use of variable parameter set. Ultimately, a comprehensive improvement algorithm of temperature-dependent J–A model is proposed followed by verification through experimental hysteresis data. [ABSTRACT FROM AUTHOR]

In this paper, we investigate the effects of multi-axial mechanical stress on eddy current and hysteresis losses in electrical steel sheets used for rotating machines. First, the variation of these losses with the multi-axial stress is confirmed by material experiments. From the results, appropriate and useful mechanical-electromagnetic modeling for loss analysis of rotating machines is discussed. Finally, the proposed modeling is applied to the combined electromagnetic field and stress analyses of an interior permanent magnet machine to reveal the effects of multi-axial stress on the rotor core loss, which is directly related to the thermal demagnetization of permanent magnets. It is clarified that both the hysteresis loss and the eddy current loss including excess loss depend on the multi-axial stress. As a consequence, the rotor core loss of interior permanent magnet machine increases by the stress caused by centrifugal force. [ABSTRACT FROM AUTHOR]

Based on the base module of Universal Robotics, this paper deals with a 16-pole, 18-slot fractional-slot concentrated-winding permanent magnet synchronous machine (PMSM) for articulated robot applications considering several pole-slot combinations and using an optimum design. The selected PMSM considering the pole-slot combination is optimized and compared both analytically and experimentally. The experimental results confirmed that the proposed PMSM can achieve improved performance at the rated state. Repeatability test results of the proposed smart actuator with a link-attached sphere-mounted retroreflector sensor met the goal of within 100~\mu \textm according to a laser tracker. The analysis results are in good agreement with the experimental results within the maximum 2.5% error in terms of the efficiency. The design, analysis, and experiment with the PMSM for articulated robot applications were conducted successfully. [ABSTRACT FROM AUTHOR]

In this paper, the different temperature dependencies of hysteresis and eddy current losses of non-oriented Si-steel laminations are investigated. The measured iron loss results show that both the hysteresis and eddy current losses vary linearly with temperature between 40 °C to 100 °C, a typical temperature range of electrical machines. Varying rates of hysteresis and eddy current losses with the temperature are different and fluctuate with flux density and frequency. Based on this, an improved iron loss model which can consider temperature dependencies of hysteresis and eddy current losses separately is developed. Based on the improved iron loss model, the temperature influence on the iron loss can be fully considered by measuring iron losses at only two different temperatures. The investigation is experimentally validated by both the tests based on a ring specimen and an electrical machine. [ABSTRACT FROM PUBLISHER]

Recently, novel magnetic materials have been developed for high-efficiency and high power density electric motors. In addition, next-generation semiconductor devices, like silicon carbide (SiC) or gallium nitride (GaN), have been introduced for power converters due to their high-frequency operation. Therefore, high-frequency operation of new magnetic materials is possible when they are driven by GaN or SiC inverters. Nevertheless, iron loss characterization of magnetic materials when they are excited by high-frequency signals have not been conducted yet. This paper introduces the iron losses characterization of a magnetic material at high carrier frequency excitation using a GANFET inverter. This characterization was carried out by the experimental evaluation of iron losses at carrier frequencies from 5 to 500 kHz at different deadtimes. As a result of the measurements, iron losses seem to have a trend to increase at high carrier frequencies and large deadtimes. In addition, filtering is introduced and it seems to be an effective technique for reducing iron losses. [ABSTRACT FROM AUTHOR]

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]

The magnet eddy-current losses of six interior permanent magnet (IPM) machines are investigated for electric vehicle applications in this paper. The armature field, eddy-current density of magnet, the influence of PM depth, the distance of PM layers, and the number of PM segmentation are studied by finite-element analysis. It is demonstrated that increasing the PM depth of first layer and the distance of PM layers can provide more soft iron space for the armature-reaction flux, which can reduce the magnet eddy-current loss. PM segmentation can effectively reduce the PM eddy-current loss, because the eddy-current paths are divided into smaller loops, increasing the effective resistance. An IPM machine with segmented PM is prototyped to verify the analysis. [ABSTRACT FROM AUTHOR]

For the reduction of transformer noise and efficient use of energy, we developed a domain-refined highly grain-oriented silicon steel with a linearly grooved surface by an electrolytic etching method. The steel showed very low iron loss even after a high-temperature annealing process, such as stress relief annealing, while magnetic flux density at 800 A/m, which is one of the very fundamental evaluation criteria for grain-oriented silicon steel, was lower than that without grooves. In light of our previous study, steels with a low flux density are disadvantageous for lowering transformer noise, but there have been no reports on the detailed noise property of this grooved grain-oriented silicon steel. In this paper, we investigated transformer noise as well as the transformer loss for the first time by fabricating three model transformers, each of which comprised one of the following grain-oriented electrical steels: grooved grain-oriented silicon steel having flux density of 1.90 T at 800 A/m, non-grooved grain-oriented silicon steel having flux density of 1.93 T at 800 A/m, and non-grooved grain-oriented silicon steel having flux density of 1.90 T at 800 A/m. As a result, transformer loss exhibited a tendency similar to the loss of a single sheet, and the grooved grain-oriented silicon steel showed the lowest loss. As for noise, even with the lower flux density, the grooved grain-oriented silicon steel showed a very low noise level equivalent to that of the non-grooved grain-oriented silicon steel with the high flux density, while the non-grooved grain-oriented silicon steel with the low flux density showed the largest noise level. From the results of magnetostriction measurements and dynamic domain observation by a newly developed method, it was found that the grooves had little influence on the generation of magnetic domains, which increased magnetostriction and transformer noise. Thus, we confirmed that low noise and low loss properties of the transformer were both realized by the application of the grooved silicon steel. [ABSTRACT FROM PUBLISHER]

The goal of this paper is to investigate the accuracy of modeling the excess loss in electrical steels using a time domain model with Bertotti’s loss model parameters n0 and V0 fitted in the frequency domain. Three variants of iron loss models based on Bertotti’s theory are compared for the prediction of iron losses under sinusoidal and non-sinusoidal flux conditions. The non-sinusoidal waveforms are based on the realistic time variation of the magnetic induction in the stator core of an electrical machine, obtained from a finite element-based machine model. [ABSTRACT FROM AUTHOR]

This paper presents an applied research about the influence of electrical steel sheets on single-phase induction machine (SPIM). The model motors researched in this paper are permanent-split capacitor induction motors operating in two-phase asymmetrical condition. Based on theoretical analysis, an improved iron loss test method for SPIMs is proposed. In addition, this method is compared with conventional approach through experimental research. Besides, the effects of core materials on the performance of SPIMs are investigated by manufacturing and testing several motors with different kinds of non-oriented electrical steel sheets. [ABSTRACT FROM AUTHOR]

This paper presents a generalized dynamic hysteresis model for estimating the iron loss of complex flux waveforms. A versatile measurement system is developed to experimentally investigate the magnetic and iron loss properties of the studied soft magnetic material over a wide range of ac and dc excitation. With the measured hysteresis loop data available, an improved dynamic hysteresis model is proposed to properly include the impact of the flux density changing rate, instantaneous magnetization state, and time history of magnetic flux on dynamic field modeling. Experimental results have confirmed the desired accuracy of iron loss predictions over broad operating ranges, including conditions of pure sinusoidal fields, non-sinusoidal flux waveforms with superimposed harmonics, and flux waveforms in the presence of pre-magnetized dc-bias fields. The model parameters identified from symmetrical hysteresis loops can be utilized to predict the iron loss over a variety of conditions, making it a generalized tool for the iron loss estimation of complex flux waveforms. [ABSTRACT FROM AUTHOR]

To evaluate the iron losses of motors and three-phase transformers, the rotational iron loss should be considered. A simple numerical calculation method of the rotational iron losses under rotational flux with high flux density and different axis ratios is proposed in this paper. First, it is shown that the method of decomposing the rotational flux into the directions of the major and minor axes of the rotational flux is effective in calculating the rotational iron losses of the non-oriented and grain-oriented electrical steel sheets in low magnetization region. Then, the simple iron loss calculation method is improved to consider the decrease of rotational hysteresis and anomalous eddy current losses in high magnetization region under circular rotational flux and verified by comparing with measurement results. Furthermore, it is improved to be applicable to rotational iron loss calculation under rotational flux with different axis ratios and verified by comparing with measurement results. [ABSTRACT FROM AUTHOR]

The analyses of flux distributions and losses in transformer cores need highest expenditure if performed in experimental ways. This paper presents a novel combined methodology for the evaluation of local and global loss building factors BF. As a first step, the local patterns of the dynamic induction vector B(t) were calculated, by means of a novel numerical “magnetic anisotropic circuit calculation (MACC) methodology. The latter considers the core materials non-linear permeability functions in rolling direction and transverse direction, as well as non-linear effects of overlaps in corners and T-joints. In a second step, the calculated induction patterns were exactly simulated on the hexagonal Vienna rotational single sheet tester and the corresponding local losses p were measured electrodynamically. Finally, the values p were allocated to the corresponding core positions, taking into account the entire core geometry. BF of the core was estimated from the total of loss values weighted to the corresponding volume portions. The method was applied for a three-phase core of highly grain-oriented material, magnetized with BNOM = 1.7 T. The procedure shows the local distributions of losses, yielding also information on those of eddy currents and rotational magnetization (RM). As an example, the T-joint, as the area of highest RM, yields a local loss increase of about 50%. Apart from RM, the local induction variations—including waveform distortions, caused mainly by circulating magnetization—prove to have a high impact on losses, locally yielding 50% as well. These highly convincing results indicate that the complicated sensor studies of cores can partly be replaced by: 1) numerical modeling of induction distributions and 2) subsequent allocations of loss values as detected by RSST simulations. [ABSTRACT FROM AUTHOR]

A magnetic properties measurement system with the frequency-domain feedback control method is developed in this paper. The system can generate non-sinusoidal waveforms consisting of harmonics with variable orders, contents, and phase angles. Core loss measurement of soft magnetic composite materials under both the sinusoidal and non-sinusoidal excitations is performed. In terms of the harmonic order, content, and phase angle, the effects of harmonic for core loss are analyzed. The frequency-domain Bertotti equations are used to predict the core loss and then compared with the experimental results. The applicability of this method for non-sinusoidal waveforms is also discussed in detail. [ABSTRACT FROM AUTHOR]

A testing platform for the magnetic properties of a ring sample made of soft magnetic composites SOMALOY is established in this paper. The core loss is measured under sinusoidal conditions to verify the original Steinmetz equation (OSE). The accuracy of OSE is improved by modifying the coefficient in the formula. Then it is extended to the modified Steinmetz equation, which is suitable for prediction of core loss under non-sinusoidal excitation. On this basis, the calculated and the measured value under non-sinusoidal excitations with different harmonic orders and contents are compared. The results show that the core loss difference between the calculation and the measurement is very small, which verify the accuracy of the modified model. [ABSTRACT FROM AUTHOR]

This paper investigated the magnetic properties of novel soft magnetic composite (SMC) with ferrite nanofibers. Material consists of FeSi powder covered by resin and different amounts of Ni0.3Zn0.7Fe2O4ferrite nanofibers. We prepared SMC with very high specific electrical resistivity. FeSi/resin (0.49 wt% ferrite) sample exhibits the highest electrical resistivity ($6.05~\Omega \cdot \text{m}$) due to low interparticle contacts. The image analysis of SEM pictures was used for the evaluation of effective area, in which local eddy currents are flowing. The FeSi/resin (0.49 wt% ferrite) sample displays the lowest total losses in the measured frequency range due to the highest specific electrical resistivity and appropriately covered FeSi particles. Loss separation and the analysis of movable magnetic objects were performed for all studied materials. [ABSTRACT FROM AUTHOR]

The losses of permanent magnet synchronous machine (PMSM) are always cared in the machine system, since the losses mainly determine the temperature-rise and efficiency of the machine. An indirect-testing method for the losses of PMSM has been proposed in order to measure the losses without any mechanical load in the test. The aims of this paper are to analyze the influence factors on this method and discuss the application of this method. The influences of the pole–slot combination, saturation, harmonic content, and frequency on the test error are analyzed. To validate the analysis, the indirect-testing losses and the direct-testing losses are compared with the test of a PMSM prototype. [ABSTRACT FROM AUTHOR]

Accurate measurements of magnetic losses in laminations are a prerequisite for their theoretical assessment, as well as for satisfying calculations of energy dissipation in engineering systems. The standardized and universally applied measurement method, used as a reference for the definition of the material quality in the specification standards, is based on the Epstein test frame magnetizer. Its success relies on the reproducibility of the performed measurements. Its limitations come, on the one hand, from cumbersome sample preparation and, on the other hand, from a certain divergence of the measured loss figures from the true loss figures. Similar systematic differences between measured and true loss values are also observed with the standard single-sheet tester (SST) method. In both cases, measurements under bidimensional induction are or cannot be envisaged. The design of new measurement setups and magnetizers overcoming the drawbacks of the Epstein and SST methods and possibly becoming recognized standards in the future is welcome, but challenging. This paper is devoted to a comprehensive discussion of the state of the art in the alternating and 2-D measurements of energy losses in soft magnetic materials for electrical applications. We will summarize, in particular, measuring solutions proposed in the current literature, and we will discuss in detail recent developments achieved in the authors’ laboratories regarding 1-D measurements with compensated permeameters and 2-D measurements at high inductions and high frequencies. [ABSTRACT FROM AUTHOR]

Measuring the high-frequency magnetic losses of high performance, low-loss magnetic materials is a challenging issue due to the parasitic elements in measurement circuits. Performing loss measurements at a specific temperature applies more constraints on the development of measurement setups. In this paper, we focus on hysteresis loops ( $B$ – $H$ loop) measurement technique and we propose a new compensation method aimed to reduce the effect of parasitic elements and to ameliorate the measurement precision. The magnetic losses measured with the thermal method are used as a reference to evaluate the precision of the proposed compensation technique. In order to measure loss at higher temperatures, we propose a calibration method. Measurements are performed between −10 °C and 110 °C. Our approach can be used to develop simple and precise laboratory setups for magnetic measurements. [ABSTRACT FROM PUBLISHER]

We have already reported a prediction method of flux losses (FLs) in bonded magnets and showed good agreement between the calculated losses and the measured ones. In this paper, we improve our previously reported method, and investigate a FL of a Nd–Fe–B-bonded magnet under external magnetic fields. To verify the validity of the prediction method for the FL, we evaluated and calculated a FL of a cylindrical Nd–Fe–B-bonded magnet under the external magnetic fields of −240, −480, and −720 kA/m. The FL of the magnet exposed at 120 °C depended on the strength of the external field, and the measured values of the loss were 8.79% for −240 kA/m, 61.2% for −480 kA/m, and 149.9% for −720 kA/m. The calculated values were 6.44%, 61.1%, and 141%, and we obtained good agreement between the measured and calculated ones. From the results, we conclude that our improved method is effective to predict the FL of the Nd–Fe–B-bonded magnets under external magnetic fields. [ABSTRACT FROM PUBLISHER]

The stresses and strains generated during punching of electrical steel laminations degenerate the magnetic properties in the region near the cut edge. The existing work has tended to focus on strips, with estimates of the damaged width ranging from less than 1 up to 10 mm. In this paper, ring samples, which are more representative of motor laminations, are considered. Increasing the diameter of the samples and, therefore, increasing the proportion damaged by the punching allowed the creation of mathematical models to describe and analyze the power loss and estimate the extent of the damaged region. Five samples each measuring five laminates high with a constant outer diameter of 200 mm and various inner diameters (150, 160, 170, 180, and 190 mm) were stamped from coils of M250–35A and M330–35A of a non-oriented electrical steel. A simple model was initially proposed, where power loss is proportional to the ratio of the undamaged to the total width and the square of the flux density passing through that region. An average width for the damaged region was calculated at 0.31 mm for the two materials. [ABSTRACT FROM AUTHOR]

The obtaining of excellence in magnetic properties of grain-oriented silicon steel processed through Steckel mill has been a big challenge to APERAM. Due to the characteristics of this process, with larger susceptibility to temperature variation, and consequently, the variation of properties along the length, a precise control of the process and product parameters is required. This paper will focus on the effect of hot rolling temperature and chemical composition, specifically the carbon content and Mn/S ratio, on the behavior of manganese sulfide precipitates. Evaluating the process data, it was identified that an adjustment in the range of hot rolling temperature could contribute to reduce the observed occurrence of variation in magnetic loss, concentrated in regions near the head of the hot rolled coil, that appeared as a bulge at the core loss charts. Precipitation-time-temperature curves were obtained, considering the typical chemical composition to this steel, based on the literature and experimental models, and comparisons with current practices were done. Experiments were carried out at the plant, searching the temperature setting, in which the rolling process would be started within the range of sulfide precipitation, according to the theoretical prediction. The results of the first tests have already indicated a trend of decline in the occurrence of the phenomenon mentioned. Additional chemical composition and process adjustments were done to guarantee stabilization of magnetic properties along the coil length. [ABSTRACT FROM AUTHOR]

Shape-giving production steps in the manufacturing of electrical machines often introduce plastic deformation and residual stress into the soft magnetic material, thus decreasing the magnetic quality and locally increasing both the static and dynamic hysteresis losses near the cut edges. Different models have been published, aiming to describe the changing local magnetization and loss behavior. Current approaches often consider permeability deteriorations by subdividing the soft magnetic material into the slices of different material properties. Three cut edge models are discussed here, where two describe the changed local polarization and the third estimates the resulting global iron losses. This paper presents a continuous material model for an efficient numerical model of the local magnetization. By replacing effortful sliced models, the continuous model is independent of the discretization and converges in the case of coarse meshes to the sliced model. [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 investigates the effectiveness of a parallel finite-element method based on a domain decomposition method taking account of nonconforming mesh connection between moving and fixed parts in magnetic field analyses of rotating machines. Numerical results of interbar current analyses in a cage induction motor that verify the effectiveness of the proposed method are presented. [ABSTRACT FROM AUTHOR]

Effect of mechanical stress on the magnetic loss of electrical steel sheets is analyzed utilizing the statistical loss theory. The focus of this paper is on the variation of the excess loss component with the applied stress and its correlation with the hysteresis loss. The model and its correlation are validated by performing comprehensive measurements at various combinations of induction levels, frequencies, and stresses. It is found that the excess losses can be modeled with sufficient accuracy by their correlation with the hysteresis losses over a wide range of stresses, frequencies, and flux densities. [ABSTRACT FROM AUTHOR]

The design of energy-efficient electrical machines requires the accurate estimation of iron loss. There are minor hysteresis loops in the case in which a flux density waveform includes higher harmonics, and it is possible that the conventional iron loss calculation methods do not accurately estimate minor-loop loss. Therefore, iron loss of the hysteresis loop with minor loops estimated using a conventional iron loss calculation method could differ from measurements. This paper investigates a method of calculating iron loss based on the dc-biased magnetic properties. [ABSTRACT FROM AUTHOR]

This paper investigates a novel estimation method for iron losses considering hysteretic property and skin effect simultaneously. In the proposed method, iron losses considering both hysteretic property and skin effect are estimated by utilizing a 1-D finite element method as a postprocessing of the usual 2-D analyses based on ordinary magnetization curve. To demonstrate the effectiveness of the proposed iron loss estimation method, we compare numerical results with measured ones. Furthermore, the proposed method is applied to iron loss analysis of an interior permanent magnet motor fed by pulsewidth modulation inverter. [ABSTRACT FROM PUBLISHER]

The stray load losses (SLLs) in electrical machines represent a nonnegligible contribution of the total losses and a key point for an accurate evaluation of the energy efficiency of considered device. In this paper, one aspect of these SLLs, the end-region leakage fluxes and losses, is investigated and considered for the case of a high-power cage induction motor. The study is performed at locked rotor, no-load, and rated load conditions using a 3-D finite-element modeling approach. The influence of the leakage flux on the end-region conductive parts of the motor is analyzed together with the eddy current loss calculation. Finally, the SLLs are calculated and compared with the experimental measurements based on the IEEE standard 112-method B test. [ABSTRACT FROM PUBLISHER]

In this paper, a comparative study of the effect of different converter topologies on the iron loss of nonoriented electrical steel is presented. Three converter topologies are considered in this investigation; namely: two-, three-, and five-level power converters. Moreover, the effect of the carrier frequency on both the iron loss and converter loss is introduced. The experimental results show a dramatic increase of the iron loss for the two-level converter, especially for low levels of the carrier frequency. Furthermore, the increase of the iron loss is negligible for the multilevel converter topologies. Specifically, the use of the five-level converter, even at a low value of the carrier frequency, results in lower iron losses than the three-level converter at a relatively higher carrier frequency. [ABSTRACT FROM AUTHOR]

This paper presents the development of novel permanent magnet synchronous motors made of a soft magnetic composite (SMC) material. They have 3-D magnetic flux but also hollow stator teeth, which can give a reduction of copper losses and motor volume. It is clarified that the efficiency can be improved by using the SMC core instead of the conventional laminated core, and by introducing a hollowed out section for the winding, namely, an overhang at the tip of the teeth. In addition, the part of the core which has high iron loss is clarified by the 3-D finite element analysis. [ABSTRACT FROM AUTHOR]

This paper describes a methodology to characterize soft magnetic materials for a core loss model, which is capable of predicting both instantaneous and average loss. The characterization method dispenses with the need for close loop control, which significantly extends the range of non-linearity and frequency that can be covered with a given experimental apparatus. It derives the various model coefficients from a combination of quasi-static \(B\) – \(H\) loop measurements, known material properties and dimensions and dynamic loss measurements on arbitrary (i.e., non-sinusoidal) flux density. The methodology is applied to a sample of Vacodur S+Cobalt Iron. [ABSTRACT FROM AUTHOR]