High Iron Loss Research Articles

Design and optimization of yokeless magnetic gear with asymmetric Halbach permanent magnet array for electric vehicle powertrain

In this paper, a novel 3/27/24 (pole pairs of inner rotor permanent magnet [PM]s/modulator/outer rotor PMs) high torque density yokeless magnetic gear with asymmetric Halbach PM array is presented and optimized for electric vehicle powertrain. The key is to improve the torque performance by replacing the magnetic steel with the light nonmagnetic material as the rotor core and employing the embedded magnetic steel bar as well as trapezoidal PM structure to form a low magnetic resistance in the magnetic circuit. The proposed machine has significant performance improvements in two aspects. Firstly, it has high torque density and low iron loss with the yokeless structure. Secondly, it has a high anti-saturation capability and low torque ripple with the asymmetric Halbach PM array and the embedded magnetic steel bar. The proposed structure is optimized by the co-simulation of the finite-element method and C++ optimization software. For a clear evaluation, the proposed structure is compared with generalized solutions in terms of performance and cost. Comparison results indicate that the proposed solution has the highest output torque, torque density, and torque per PM weight among solutions, reaching 214.1 N·m, 58.2 N·m/kg, and 95.6 N·m/kg, which greatly enhances the performance of the magnetic gear.

Higher Extrusion Temperature Induces Greater Formation of Less Digestible Type V and Retrograded Starch in Iron-Fortified Rice Grains But Does Not Affect Iron Bioavailability: Stable Isotope Studies in Young Women

BackgroundHot extrusion is widely used to produce iron-fortified rice, but heating may increase resistant starch and thereby decrease iron bioavailability. Cold-extruded iron-fortified rice may have higher bioavailability but has higher iron losses during cooking. Thus, warm extrusion could have nutritional benefits, but this has not been tested. Whether the addition of citric acid (CA) and trisodium citrate (TSC) counteracts any detrimental effect of high-extrusion temperature on iron bioavailability is unclear. ObjectivesOur aim was to assess the effects of varying processing temperatures on the starch microstructure of extruded iron-fortified rice and resulting iron solubility and iron bioavailability. MethodsWe produced extruded iron-fortified rice grains at cold, warm, and hot temperatures (40°C, 70°C, and 90°C), with and without CA/TSC at a molar ratio of iron to CA/TSC of 1:0.3:5.5. We characterized starch microstructure using small- and wide-angle X-ray scattering and differential scanning calorimetry, assessed color over 6 mo, and measured in vitro iron solubility. In standardized rice and vegetable test meals consumed by young women (n = 22; mean age: 23 y; geometric mean plasma ferritin: 29.3 μg/L), we measured iron absorption from the fortified rice grains intrinsically labeled with 57ferric pyrophosphate (57FePP), compared with ferrous sulfate (58FeSO4) solution added extrinsically to the meals. ResultsWarm and hot extrusion altered starch morphology from native type A to type V and increased retrograded starch. However, extrusion temperature did not significantly affect iron solubility or iron bioavailability. The geometric mean fractional iron absorption of iron from fortified rice extruded with CA/TSC (8.2%; 95% CI: 7.9%, 11.0%) was more than twice that from extruded rice without CA/TSC (3.0%; 95% CI: 2.7%, 3.4%; P < 0.001). ConclusionsHigher extrusion temperatures did not affect iron bioavailability from extruded rice in young women, but co-extrusion of CA/TSC with FePP sharply increased iron absorption independently from extrusion temperature. This trial is registered at www.clinicaltrials.gov as NCT03703726.

High-Speed Synchronous Reluctance Machines: Materials Selection and Performance Boundaries

This paper presents a comprehensive comparative design exercise of Synchronous Reluctance (SyR) machines considering different soft magnetic materials and a wide range of speeds. First, a general design methodology able to consider all the consequences of selecting different materials is presented. In fact, magnetic non-linearities, rotor structural limitations and the rise of both stator and rotor iron losses are all considered. The adopted design approach allows achieving optimal stator and rotor geometries balancing all these competitive multi-physics aspects and keeping constant the cooling system capability. Both silicon-iron (SiFe) and cobalt-iron (CoFe) alloys with optimized magnetic and mechanical performance are examined to assess the maximum capabilities achievable with a SyR machine technology. The adoption of CoFe alloys leads to machines that outperform the SiFe counterparts up to a certain speed, above which, machines with SiFe provide better performance. Indeed, in the lower speed range, the effect of the higher saturation flux density of the CoFe materials is dominant, while for higher design speeds, their higher iron losses and lower yield strength, with respect to the SiFe ones, make the latter more convenient. All the design considerations are finally validated by comparing the predicted performance with the experimental test results on a 6.5kW, 80krpm SyR machine prototype.

Fabrication of high-performance low silicon non-oriented electrical steels by a new method: Low-finishing-temperature hot rolling combined with batch annealing

The grain size prior to cold rolling plays an important role in the microstructural, textural evolution and magnetic properties of non-oriented silicon steel sheets. In this work, we proposed a new way to obtain large grain size before cold rolling and applied it to a 1.0 wt% Si-0.2 wt% Al non-oriented silicon steel, i.e., appropriate low-finishing-temperature hot rolling combined with batch annealing. The grain growth process during batch annealing was investigated using a quasi in-situ electron backscattered diffraction (EBSD) technique. It was demonstrated that significant grain growth took place through a strain-induced boundary migration mechanism. Then a large number of in-grain shear bands were formed in the cold rolled microstructure and could provide nucleation sites for Goss ({110} 〈001〉 ) and λ-fiber (〈001〉//ND) recrystallized grains, thus resulting in a coarse-grained and homogeneous recrystallization microstructure with weakened γ-fiber (〈111〉//ND) texture, strengthened Goss and λ-fiber texture. Consequently, superior magnetic properties (B50 = 1.763 T, P1.5/50 = 4.30 W/kg) were obtained. For comparison, the conventional processing route without batch annealing was also investigated. A small-grained and inhomogeneous recrystallization microstructure with pronounced γ-fiber texture was produced in the finally annealed sheet, which could significantly deteriorate both the magnetic induction and iron loss. This work provided a new way to enlarge the grains in hot rolled sheets by low temperature batch annealing instead of the conventional high temperature normalization. Thus a new processing route to fabricate low silicon non-oriented electrical steels with high permeability and low iron loss was established.

Effect of Manufacturing Influences on Magnetic Performance Parameters of Sub-Fractional Horsepower Motors

Depending on the stator lamination manufacturing processes (e.g., punching, laser cutting, clamping, welding, interlocking, and bonding), the motor’s magnetic performance parameters, such as cogging torque, hysteresis torque, and iron losses, can vary significantly. In sub-fractional horsepower (SFHP) permanent magnet motors, the manufacturing influence is typically even more severe because, due to their small dimensions, practically, the whole stator material is likely to be affected. This article analyzes the magnetic performance parameters cogging torque, hysteresis torque, and iron losses of three different stator lamination stacks (i.e., M250-35A punched with interlocking, M250-35A laser cut with bonding, and NO10 laser cut with bonding) of an SFHP single-phase brushless permanent magnet motor often found in automotive fan applications. A rheometer is used for extremely accurate torque measurements in the sub-millinewton meter range, and electron backscatter diffraction measurements are performed to visualize changes in the grain morphology and crystal orientation. The findings reveal that the punched stator with interlocking is affected the most by the manufacturing process, showing the lowest cogging torque yet the highest average hysteresis torque and thus up to 40% higher iron losses. The results presented in this article allow for both making basic stator lamination design choices and translating the iron losses, as well as the hysteresis torque and cogging torque waveforms, of a laser cut and bonded prototype into those of its punched and interlocked mass-produced counterpart.

Analysis of a Hybrid Permanent Magnet Variable-Flux Machine for Electric Vehicle Tractions Considering Magnetizing and Demagnetizing Current

The overall driving cycle efficiency of conventional permanent magnet synchronous machines (PMSMs) for electric vehicle tractions in a wide speed range is constrained due to the large field weakening current and high iron loss in high speed. The series hybrid permanent magnet variable flux machines (HPM-VFMs) which employ both low coercive force (LCF) magnets and high coercive force magnets are proposed to obtain high torque density and flexible air-gap flux density simultaneously. The key of HPM-VFMs design is the accuracy of hysteresis model of LCF magnets and operating principle analysis. This article contributes to clarify operating principle based on hysteresis model of AlNiCo magnets and propose a novel design consideration to reduce magnetizing and demagnetizing current. Based on the theoretical analysis, this article proposes a novel series HPM-VFM, in which the NdFeB and AlNiCo magnets are arranged separately. Furthermore, flux paths are designed to achieve appropriate interaction between two kinds of magnets. The proposed machine has features of wide magnetization state (MS) variation range, low magnetizing and demagnetizing current, and low risk of unintentional demagnetization. By manipulating the MS of the proposed machine, the losses of a wide speed range operation could be reduced. The comparison of efficiency maps and the worldwide-harmonized light vehicles test cycle driving cycle losses between the proposed machine and a conventional interior PMSM proves that the proposed machine achieves higher efficiency for electric vehicle.

Direct assessment of body iron balance in women with and without iron supplementation using a long-term isotope dilution method in Benin and Switzerland

Long-term isotopic dilution measurements of body iron may allow quantification of basal body iron balance and iron gains during an iron intervention with higher precision and accuracy than conventional iron indices. We compared body iron balance before, during, and after oral iron supplementation in women in Benin and in Switzerland. In prospective studies, Beninese (n=11) and Swiss (n=10) women previously labeled with stable iron isotopes were followed preintervention for 90-120 d, then received 50-mg iron daily for 90-120 d and were followed postintervention for 90-120 d. We used changes in blood isotopic composition to calculate iron absorption (Feabs), iron loss (Feloss), and net iron balance (Fegain). Compliance with supplementation was>90%. In Benin, during the preintervention, intervention, and postintervention periods, Fe means±SDs were as follows: 1) Feabs: 0.92±1.05, 3.75±2.07, and 0.90±0.93 mg/d; 2) Feloss: 1.46±1.95, 1.58±1.57, and 1.84±1.61 mg/d; and 3) Fegain: -0.55±1.56 mg/d, 2.17±1.81 mg/d, and -0.94±1.13 mg/d. In Switzerland, the corresponding values were: 1) 1.51±0.37, 4.09±1.52, and 0.97±0.41 mg/d; 2) 0.76±1.37, 2.54±1.43, and 2.08±1.05 mg/d; and 3) 0.75±1.37, 1.55±1.75, and -1.11±1.06 mg/d. Inflammation was low in both settings, and isotopically calculated iron balance was comparable to that calculated from changes in conventional iron indices. Without iron supplementation, Beninese women had lower long-term dietary iron absorption and higher iron losses in the preintervention period than Swiss women. During iron supplementation, both groups had high iron absorption and similar iron gains. However, there was a 3-fold increase in iron losses in the Swiss women during the supplementation and postintervention period compared with the preintervention period. Body iron isotope dilution is a promising new method for quantifying long-term body iron balance and for assessing the impact of iron interventions. The studies were registered at clinicaltrials.gov as NCT02979080 and NCT02979132, respectively.

EFFECT OF A NEW NON-ORIENTED ELECTRICAL STEEL SHEET WITH HIGH MAGNETIC FLUX DENSITY AND LOW IRON LOSS ON INDUCTION MOTOR PERFORMANCE

In this study, we developed and investigated a new non-oriented electrical steel (50H-CP) to be used in mainly induction motors. This material exhibits high flux density and low iron loss. We confirmed the effect of the new material by manufacturing a test motor and comparing its performance against another motor with a standard material (50H350). The efficiency of the motor with 50H-CP showed an improvement of 1% compared to the one with 50H350 because of the low copper losses in the former. Furthermore, the breakdown of the motor losses was evaluated using electromagnetic field analysis. The iron loss was comparable between 50H-CP and 50H350. However, 50H-CP was superior with regard to primary and secondary copper losses. From the above results, the effect of the high magnetic flux density-low iron loss characteristics of 50H-CP was theoretically confirmed.

Kriging Surrogate Model-Based Design of an Ultra-High-Speed Surface-Mounted Permanent-Magnet Synchronous Motor Considering Stator Iron Loss and Rotor Eddy Current Loss

Ultra-high-speed (UHS) surface-mounted permanent-magnet synchronous motors (SPMSMs) are widely used for driving air compressors. UHS SPMSMs can suffer from high stator iron loss and rotor eddy current loss due to their high rotational speed and changes in the magnetic flux density when loading. Since these losses do not have a linear trend but change according to the motor design parameters, mathematical models cannot always predict them. This study aims to design UHS SPMSMs based on a kriging surrogate model that takes into account the stator iron loss and rotor eddy current loss. Since the kriging surrogate model is highly predictive for nonlinear inputs, it is the perfect candidate to take into account the stator iron loss and rotor eddy current loss. The design proposed in this study allowed to minimize the size and losses of a motor that satisfied the power specification.

Electromagnetic torque capabilities of permanent magnet flux-switching machine using modular rotor

The use of a segmented rotor electric motor for lightweight electric vehicle applications has gained a lot of attention since the motor must have a high output torque and output power. Segmented rotor motors have performance indices that should be taken into consideration because not every machine is effective. Recently, permanent magnet flux switching machine (PMFSM) in salient rotor has become attractive for provide high torque and power. Undesirably, salient rotor inherited high iron loss and winding loss, Furthermore, PMFSM uses high PM volume and more flux leakage resulting in poor performance. This paper deals with a novel structure of modular rotor PMFSM with non-overlapping winding with minimal iron loss, high torque and high power. 2D finite element analysis (FEA) is used to investigate the performance of proposed motor in JMAG Designer 14.1. Three-phase operation of 12S/10P modular rotor PMFSM was designed and analysed based on the cogging torque, induced back emf, output torque and output power performances. The proposed motor securing the initial torque of 33.30 Nm and power of 12Kw at maximum current density of 30Arms/mm2. From the result it is concluded that modular rotor based PMFSM motor is suitable for light weight electric vehicles.

The Influence of Normalization Temperatures on Different Texture Components and Magnetic Properties of Nonoriented Electrical Steels

The effects of normalization on different texture components and magnetic properties in G50W600 nonoriented electrical steel are studied by electron backscatter diffraction (EBSD). The results show that normalization can coarsen surface {110}‐oriented grains and recrystallized rotated cube or {114}&lt;481&gt;‐oriented grains in the center. Moreover, the highest texture intensity change from original rotated cube texture to the {114}&lt;481&gt; texture with the increase of normalization temperature. Just after the completion of recrystallization in final sheets corresponding to hot‐rolled samples, {111}&lt;112&gt; is the main texture component, while that in final sheets corresponding to normalized samples is {114}&lt;481&gt;. The final sheets normalized at 920 and 980 °C have a higher iron loss and higher magnetic induction than the final sheets corresponding to hot‐rolled samples, which is caused by the fact that normalized samples show finer final grain size, higher volume faction of {100} and {110}, and lower volume fraction of γ‐fiber than hot‐rolled samples. With the increasing of annealing temperature and time, the magnetic induction and iron loss of normalized samples decrease. Furthermore, the final sheets normalized at 940 °C have the best magnetic properties. During final high temperature annealing, the non γ‐fiber oriented grains show a higher growth ability than γ‐fiber oriented grains.

A study on the shape between the stator poles of a homopolar magnetic bearing integrated with four C-shaped cores

There are two types magnetic bearings in general, heteropolar-type magnetic bearing (Heteropolar-type MB) and homopolar-type magnetic bearing (Homopolar-type MB). For each type of magnetic bearing, it has its own disadvantage. Heteropolar-Type MB cost low because of the low usage of the magnet, but high iron loss decides it is difficult to be cooling down. Homopolar-type MB has a low iron loss and can be cooling down easily, but cost is high because of high usage of magnet and has a complex structure. In this paper, our research group focused on the problem and proposed a new Homopolar-Type MB structure unifying four C-shaped cores, which can suppress the iron loss with a low usage of magnet and can be cooling down easily. What’s more, we also considerate the influences by the change of the structure and proposed the optimal one. The excellent characters of the new type Homopolar-Type MB will be shown by 3D-FEA.

The Effect of Abandoned Basic Oxygen Furnace Gas Blowing on the Softening–Melting–Dripping Performance of Full High Cr‐Bearing Vanadia–Titania Magnetite Pellets

It is inevitable to encounter increase in slag thickness, foaming slag, and high iron loss due to excessive formation of titanium carbonitride in blast furnace smelting of full high Cr‐bearing vanadia–titania magnetite (HCVTM). The effects of softening–smelting–dripping properties, the content variation of titanium carbonitride, and mineral element migration process of full HCVTM pellets with abandoned BOF gas (ABOFG) blowing are studied using X‐ray diffraction (XRD), X‐ray fluorescent (XRF), inductively coupled plasma‐atomic emission spectroscopy (ICP‐AES), X‐ray photoelectron spectroscopy (XPS), electron probe microanalysis‐wavelength‐dispersive spectrometer (EPMA‐WDS), and scanning electron microscope‐energy dispersive spectroscopy (SEM‐EDS). ABOFG is a type of neglected byproduct gas resource produced in the steelmaking process with high physical and chemical thermal energies and contains 20–40% CO, 20–30% CO2, 2–5% O2, and 30–50% N2. As the concentration of CO2 in ABOFG increases, the position and height of the cohesive zone decline, and the concentration of titanium carbonitride decreases from 1.424% to 1.035%, which are beneficial to the BF smelting process. In addition, the migration processes of Ti, V, and Cr are also affected, especially Ti tends to enrich in the dripped slag, whereas V and Cr tend to concentrate at the dripped iron.

Iron loss and start‐up ability of a 6/2 switched reluctance machine with different magnetic polarity of windings

This study presents an investigation on iron loss and start-up ability of a 1.5 kW output power with rated speed 5850 r/min 6/2 switched reluctance machine (SRM), which is used as a prime motor to directly drive centrifugal blower. Two winding connection types of the SRM are investigated, including the symmetrical magnetic topology (SyMT) and asymmetrical magnetic topology (ASyMT). The two types are proposed to settle poor self-start ability of the 6/2 SRM and high iron loss density of high-speed SRM. According to the simulation results, the SyMT has merit of self-start ability, i.e. no risk of start-up failure, whereas the ASyMT has advantage of low iron loss, i.e. low iron loss density on stator and rotor. Prototypes are manufactured to confirm and verify the predicted results and the test results prove the correctness of the analyses.

Electrical Steels and Their Evaluation for Automobile Motors

Achieving high efficiency and high torque is an important target in EV motors. This paper describes the effect of the magnetic properties of electrical steels used as core materials for synchronous motors with permanent magnets, which are commonly used as the EV traction motors. It was confirmed that electrical steels, which have high flux density and low iron loss properties can realize high motor efficiency and torque. When PWM excitation is considered, thinner electrical steels are advantageous to suppress increased loss due to higher harmonics. Based on these results, electrical steels having high flux densities and low iron losses at high frequencies were developed.

Modular Rotor Single Phase Field Excited Flux Switching Machine with Non-Overlapped Windings

This paper aims to propose and compare three new structures of single-phase field excited flux switching machine for pedestal fan application. Conventional six-slot/three-pole salient rotor design has better performance in terms of torque, whilst also having a higher back-EMF and unbalanced electromagnetic forces. Due to the alignment position of the rotor pole with stator teeth, the salient rotor design could not generate torque (called dead zone torque). A new structure having sub-part rotor design has the capability to eliminate dead zone torque. Both the conventional eight-slot/four-pole sub-part rotor design and six-slot/three-pole salient rotor design have an overlapped winding arrangement between armature coil and field excitation coil that depicts high copper losses as well as results in increased size of motor. Additionally, a field excited flux switching machine with a salient structure of the rotor has high flux strength in the stator-core that has considerable impact on high iron losses. Therefore, a novel topology in terms of modular rotor of single-phase field excited flux switching machine with eight-slot/six-pole configuration is proposed, which enable non-overlap arrangement between armature coil and FEC winding that facilitates reduction in the copper losses. The proposed modular rotor design acquires reduced iron losses as well as reduced active rotor mass comparatively to conventional rotor design. It is very persuasive to analyze the range of speed for these rotors to avoid cracks and deformation, the maximum tensile strength (can be measured with principal stress in research) of the rotor analysis is conducted using JMAG. A deterministic optimization technique is implemented to enhance the electromagnetic performance of eight-slot/six-pole modular rotor design. The electromagnetic performance of the conventional sub-part rotor design, doubly salient rotor design, and proposed novel-modular rotor design is analyzed by 3D-finite element analysis (3D-FEA), including flux linkage, flux distribution, flux strength, back-EMF, cogging torque, torque characteristics, iron losses, and efficiency.

Flux and Loss Distribution in Iron Cores With Hybrid T-Joint

Local high iron loss may occur due to the deviation of magnetic flux from the rolling direction of electrical steel in the T-joint area of the transformer core. In this paper, to reduce the iron core loss in the T-joint region, a hybrid iron core model using nonoriented and grain-oriented magnetic materials is proposed. Three-dimensional magnetic field analysis considering the nonlinearity and laminated structure of the original and proposed iron core models is carried out by using the finite element analysis. The flux and iron loss distributions of the original and the hybrid cores are compared. The results show that approximately 2% iron loss reduction can be achieved by using the proposed hybrid structure.

Dull punch line is not a joke – Worn cutting edge causes higher iron losses in electrical steel piercing

Electrical steel is used for the active parts in electrical machinery that form the magnetic circuits because the material experiences low iron loss, and thus, has superior magnetizing properties. A typical electrical sheet has a thickness of 0.5 mm and is punched into its final shape via a piercing process. Piercing causes large deformations and residual stresses in the narrow zone of the cut surface. The deformations and stresses weaken the magnetic properties of the electrical sheet and result in additional losses, as the iron loss increases after piercing [1]. This paper presents a simulation model of the piercing process to evaluate the deformations and stresses on the cut surface. The model is constructed using the commercial FEM solver Deform. There has been an attempt to simulate the magneto-mechanical state of the punched surfaces, but the piercing process itself was not simulated [2]. The electrical steel sheet investigated in this paper is isotropic electrical silicon steel M400-50A (EN 10106-96).

Comparative Analysis of Partitioned Stator Flux Reversal PM Machine and Magnetically Geared Machine Operating in Stator-PM and Rotor-PM Modes

In this paper, the partitioned stator flux reversal permanent magnet (PM) (PS-FRPM) machine and the conventional magnetically geared (MG) machine operating in both stator-PM (SPM) and rotor-PM (RPM) modes are comparatively analyzed in terms of electromagnetic performance to provide design guides for an MG machine regarding an SPM- or RPM-type machine and a higher or lower gear ratio machine. It is found that an SPM-type machine is recommended since both PS-FRPM and MG machines operating in SPM modes have a higher phase back-EMF and hence torque than their RPM counterparts, respectively, as a result of a similar phase flux linkage but a higher electric frequency since the iron piece number is larger than the PM pole-pair number. Moreover, a smaller gear ratio machine is preferred from the perspective of a higher power factor and hence a lower inverter power rating, as the conventional MG machines with higher gear ratios suffer from larger flux-leakage, higher synchronous reactance and hence lower power factors, as well as higher iron losses, than the PS-FRPM machines. However, higher gear ratio machines feature lower cogging torques and torque ripples due to the smaller difference between the PM pole-pair number and iron piece number. Both prototypes of PS-FRPM machine operating in SPM mode and MG machine operating in RPM mode are built and tested to verify the finite element predicted results.

Flux Switching Permanent Magnet Motor using Segmented Outer Rotor Structure for Electric Scooter

Flux switching motor is a type of electric machine that locates both flux source and armature windings on the stator leaving its rotor a simple piece of iron. This machine was developed by combining the toothed stator structure of induction machine and the toothed rotor structure of switched reluctance machine together. Furthermore, it has three types of flux sources which include permanent magnet. Conventionally, the toothed kind of rotor has dominated machines rotor design and has been known for high manufacturing cost and iron loss, resulting to low performance. This calls for worry and the need to overcome it and also reduce the manufacturing cost while securing high torque. This paper presents flux switching permanent magnet motor employing segmented outer rotor for high torque capability. 2D-FEA using JMAG to investigate the motor characteristics in terms of flux linkage, Induce back-emf, cogging torque, maximum average torque and efficiency. Finally, preliminary results and comparison revealed that motors employing segmented rotor are capable of higher torque than conventional toothed rotor.