Reduce Eddy Current Loss Research Articles

Magnet eddy-current losses reduction of an axial-flux in-wheel motor with amorphous magnet metal

The yokeless and segmented armature axial-flux in-wheel motor with amorphous magnet metal (AMM) stator segment has the advantage of low iron losses, but its open-slot structure causes high eddy-current losses of the permanent magnet (PM), which reduces the efficiency and reliability of the in-wheel motor. To avoid the demagnetization caused by the heat generated by PM losses, the mechanism of PM eddy-current losses reduction for the axial-flux in-wheel motor is revealed by the calculation model. In this paper, the time-step three-dimensional finite-element method (3-D FEM) is used to analyze the PM eddy-current loss caused by slotting effects, spatial harmonics, and time harmonics at different speeds. The effect of PM skewing, PM segmentation, and soft magnetic composite (SMC) layer inserted on the top of PM on eddy-current losses are compared. These methods cannot simultaneously meet the requirements of PM losses reduction and the electromagnetic performance of the motor. A novel combined stator segment with the SMC brim arranged on the top of the AMM stator teeth is proposed to improve the amplitude and distribution of the PM eddy-current density. The analysis results show that the combined stator segment can significantly reduce the PM eddy-current loss and improve the electromagnetic performance of the in-wheel motor.

Performance analysis of magnetic gear with Halbach array for high power and high speed

In this study, we propose a non-contact 80 kW, 60,000 rpm coaxial magnetic gear (CMG) model for high speed and high power applications. Two models with the same power but different radial and axial sizes were optimized using response surface methodology. Both models employed a Halbach array to increase torque. Also, an edge fillet was applied to the radial magnetized permanent magnet to reduce torque ripple, and an axial gap was applied to the permanent magnet with a radial gap to reduce eddy current loss. The models were analyzed using 2-D and 3-D finite element analysis. The torque, torque ripple and eddy current loss were compared in both models according to the materials used, including Sm2Co17, NdFeBs (N42SH, N48SH). Also, the structural stability of the pole piece structure was investigated by forced vibration analysis. Critical speed results from rotordynamics analysis are also presented.

Design and Testing of Low Pole Dual-Stator Flux-Switching Permanent Magnet Machine for Electric Vehicle Applications

This paper investigates the design and testing of a high-speed dual-stator 6/4 flux-switching permanent magnet (FSPM) machine. A dual-stator design is used to solve the issue of second harmonic presented in the flux linkage of conventional 6/4 FSPM machine. Different dual-stator designs are investigated and compared against each other in terms of the performance and manufacturability. Comparison between the proposed dual-stator 6/4 FPSM machine and a commonly seen 12/10 FSPM machine is done at 10 kW, 15000 rpm condition. Due to the 60% reduction of the fundamental frequency, a significant reduction in iron loss and magnet eddy current loss is observed, which leads to higher efficiency. A prototype dual-stator 6/4 FSPM motor is built and tested on a dynamometer set up to verify the analytical calculation and finite element analysis results. A comparison is made between measured data and simulation results, and good agreements are achieved.

Study on Multi-DOF Actuator for Improving Power Density

This study focuses on improving the power density of a spherical multi-degree-of-freedom (multi-DOF) actuator. A spherical multi-DOF actuator that can operate in three DOFs is designed. The actuator features a double air gap to reduce eddy current loss. However, a multi-DOF actuator driven by a single actuator exhibits low power density. Therefore, a Halbach magnet array is applied to improve the power density of a spherical multi-DOF actuator, and its output characteristics are compared with those of an existing spherical multi-DOF actuator via finite element analysis. Additionally, the output characteristics are analyzed based on changes in the coil pitch angle and magneto-motive force of the rotating winding. Furthermore, it is necessary for a spherical multi-DOF actuator to move to the command position. Hence, a stability analysis is performed to ensure that the spherical multi-DOF actuator is stably driven based on the command position.

High-Speed PM Generators for Organic Rankine Cycle Systems: Reduction of Eddy Current Rotor Losses

In an organic Rankine Cycle system, the permanent magnet (PM) generator is directly coupled to high-speed turbine shaft, to increase system efficiency avoiding the gearbox introduction. Current time harmonics induce high-frequency currents in rotor parts, which cause temperature increase. PMs are strongly affected by the operating temperature, since both remanence and coercive force decrease. This article shows that rotor losses of a high-speed PM generator strongly depend on both winding arrangement and power electronic conversion system connected to the generator itself. Several analyses are carried out to compare different solutions.

Microstructure evolution, magnetostrictive and mechanical properties of (Fe83Ga17)99.9(NbC)0.1 alloy ultra-thin sheets

The ultra-thin (Fe83Ga17)99.9(NbC)0.1 sheets with the thickness of 0.06–0.15 mm were prepared from the secondary recrystallized sheets via rolling. The recrystallization texture evolution, magnetostriction and mechanical properties in the rolled sheets during the annealing at 1200 °C for 1.5–3 h were investigated. Results indicated that the magnetostriction of the ultra-thin sheet was closely related to the texture evolution depended on heat-treatment process. The major textures in the as-rolled sheet were {113} and {111} deformed texture, and the saturation magnetostriction was only ~ 63 ppm. However, an ideal {100} texture was obtained in the recrystallized sheets annealed at 1200 °C for 2 h, producing a corresponding magnetostriction of 147 ppm. Based on texture analysis, the appearance of cubic texture is mainly the consequence of the existence of cubic nuclei and transitional orientation {113} in deformed grains as well as the lowest surface energy at the (100) plane. Compared with Goss secondary recrystallized (Fe83Ga17)99.9(NbC)0.1 sheet with a thickness of 0.3 mm, the tensile ductility of cubic recrystallized ultra-thin (Fe83Ga17)99.9(NbC)0.1 sheet was obviously improved from 2.4 to 4.4%, which was mainly attributed to the primary recrystallized microstructure with small grain size and transgranular fracture mode. The ultra-thin cubic textured (Fe83Ga17)99.9(NbC)0.1 sheets could significantly reduce eddy current losses at high frequency, and meet the requirements of low eddy current loss and high toughness for specific applications, such as ultrasonic applications and torque sensors.

Visualization and quantitative evaluation of eddy current loss in bar-wound type permanent magnet synchronous motor for mild-hybrid vehicles

This paper describes the conductor eddy current loss that occurs in a permanent magnet type synchronous motor with a distributed winding stator using a rectangular copper wire designed for mild hybrid system applications for small vehicles. Compared with the conventional round wire inserter method, the space factor can be improved and the coil-end length can be shortened by applying a so-called hairpin windings using a pre-formed into hairpin shape of bar conductor, and as a result, DC current resistance of the armature winding can be reduced. However, since the conductor cross-sectional area tends to increases, the conductor eddy current loss generated by the space harmonics linkage becomes too large to ignore. In order to study the reduction of the conductor eddy current loss, it is important to visualize the spatial leakage flux distribution which causes loss and finely analyze how the magnetic path is formed. Therefore, analysis of the conductor eddy current loss distribution generated in the bar-wound conductor is performed using the CAE model that faithfully reproduces the coil-end shape of the actual machine. Furthermore, it was qualitatively clarified what ratio of conductor eddy current loss at various driving points. Finally, the results of preliminary study on reduction of conductor eddy current loss are reported.

Flange with the Groove Shape to Improve the Efficiency of Large Turbine Generator

This paper presents a new design technique to improve the efficiency of the large turbine generator. The leakage magnetic flux at the generator end region causes the eddy current loss. The eddy current loss also occurs in the flange which supports the stator cores and outside space block at both ends of the generator. We propose a flange with the groove shape to reduce eddy current loss by decreasing the incident area of magnetic flux on the flange. The results of the three-dimensional finite-element analysis show that the proposed method can improve the generator efficiency.

Influence of scan pattern and geometry on the microstructure and soft-magnetic performance of additively manufactured Fe-Si

The influence of geometry and scan pattern on the microstructure evolution and magnetic performance of additively manufactured Fe-3Si components was investigated. To reduce eddy current losses, novel geometries were designed and built and the microstructure and properties of these samples were characterized. The laser scan pattern was shown to strongly influence both the as-built grain structure and strength of the crystallographic texture, resulting in measurable changes in the as-built magnetic performance. In thin wall samples, heat treatment resulted in an increase in the maximum relative magnetic permeability and decrease in power losses in most samples, consistent with grain growth. However, decreases in the spacing between thin walls to increase the stacking factor of the cross-section was shown to result in unwanted electrical shorting between walls and an increase in eddy current losses. Compared to simple parallel plate construction and a mesh structure, a novel cross-section design based on the Hilbert space filling curve was found to produce the lowest power losses. The mechanisms behind these results were explored using a combination of heat conduction and electromagnetic simulations, providing a route for future component and process optimization.

Reduction of Magnet Eddy Current Loss in PMSM by Using Partial Magnet Segment Method

Compared with traditional induction machine and direct current machine, permanent magnet synchronous machine (PMSM) holds many merits like higher torque ability and efficiency when high magnetic co-energy sintered NdFeB magnet is used. However, for the operation with high frequency, the resulted eddy current loss by the permanent magnet (PM) is very high and this kind of loss can bring the PM with high-temperature rise, making the PM face the risk of irreversible demagnetization. To reduce the PM eddy current loss, complete magnet segmentation is an effective method. However, taking this kind of method will increase manufacturing cost and reduce the mechanical robustness of the PMSM. Thus, a partial magnet segmentation method was proposed in the past. In this paper, a new annular partial segmentation (APS) method is proposed for the reduction of the PM eddy current loss, including single-side APS and double-side APS configurations. Considering that the additional process on the PM will reduce the mechanical robustness of the PM and the electromagnetic performance of machine, both the electromagnetic performance and the mechanical strength of the PM have been analyzed, based on 3-D finite-element method. It can be found that if the proposed new annular partial segmentation (APS) method is adopted, the eddy current loss in the PM can be reduced greatly, while the mechanical robustness of the PM can be guaranteed comparing with the traditional partial magnet segmentation method.

Reduction of Eddy Current Loss in Rectangular Coils Using Magnetic Shield: Analysis With Homogenization Method

Rectangular coils have been widely used in rotating machines and transformers because of high space factor and low dc resistance. However, eddy current losses due to skin and proximity effects in the rectangular coils cannot be ignored, especially when carrier harmonic increases. The eddy current loss due to the proximity effect would be effectively reduced by shielding the coils with a magnetic thin layer. In this paper, a method for homogenization-based analysis of a magnetically shielded rectangular coil is proposed. It is shown by the proposed method that the ac-resistance of a motor winding can be effectively reduced by introducing the magnetic shield.

Topical advances in synthesis for energy-efficient magnetoplumbite nanoferrites

Next-generation magnetic devices will be planar, smaller, light weight, and will do well beyond the present state-of-the-art devices. For this to become a reality, advances in ferrite materials must first be realized. Due to superior coercivity and lower material and processing cost, magnetoplumbites are preferred over the other types of hard ferrites. Magnetoplumbites are important hexagonal ferrites with formula RFe12O19 where R may be barium (Ba), strontium (Sr) or lead (Pb). Energy losses are important issues in these magnetic materials. Although SrFe12O19 have many advantages, but to lower the energy losses we need to improve the resistivity by reducing eddy current losses. Sr-Ba nanoferrites have potential for next generation of energy-efficient magnetic devices. Gadolinium (Gd) belongs to the lanthanide series. In this work, Sr hexaferrites and Sr-Ba hexaferrites doped with rare earth metal like Gd were synthesized to increase their resistivity. Strontium barium hexaferrites with composition Sr1−xBaxFe12−yGdyO19 (x = 0.0, 0.25 and y = 0.0, 0.20) were synthesized by without water and surfactants (WOWS) sol–gel method and co-precipitation method, respectively. All the synthesized samples showed hexagonal structure with P63/mmc space group. Crystallite sizes obtained using Scherrer’s formula were in nanoregime. DC electrical properties as a function of temperature and dielectric spectroscopy as a function of frequency were evaluated and are correlated with the structural properties. A comparative study of different proportions of iron oxide and Gd dopant was carried out, and composition with x = 0.25 and y = 0.20 seems to be a suitable combination for high-frequency efficient devices.

A gear efficiency improvement in magnetic gear by eddy-current loss reduction

A gear efficiency improvement in magnetic gear by eddy-current loss reduction

Additive manufacturing of soft magnetic materials and components

Additive manufacturing of soft magnetic materials and components based on laser powder bed fusion (L-PBF) offers new opportunities for soft magnetic core materials in efficient energy converters. For more favorable material compositions like FeSi6.7 (strategy 1) with larger electrical resistivity and close-to-zero magnetostriction a maximum permeability of μmax = 31,000, minimum coercivity of Hc = 16 A/m and hysteresis losses of 0.7 W/kg at 1 T and 50 Hz have been realized. To further reduce eddy current losses significantly, novel topological structures like inner slits (strategy 2) and multilayered structures of alternating layers of electrically insulating material and soft magnetic material (strategy 3) are suggested. Feasibility, functionality and potential of the different strategies (and combinations thereof) are discussed based on first prototypes and supporting simulations. The results are compared to conventional electrical steel and SMC (soft magnetic composites).

Magnet Eddy Current Loss Reduction in Permanent Magnet Machines

Magnet eddy current loss is very important for any types of permanent magnet (PM) machines, especially for high-speed PM machine since it increases significantly with rotating speed and has a great effect on the temperature of a magnet and, hence, the electromagnetic performance, as well as irreversible demagnetization of the magnet. In this paper, a new method is proposed to reduce the rotor PM eddy current loss. The auxiliary slots with an optimized size and position are proposed. By this mean, the asynchronous spatial harmonics caused by the armature reaction and the conventional slots can be partially decreased by the harmonics produced by the introduced auxiliary slots. It is proved that the rated on-load magnet eddy current loss can be reduced as much as 81.5% by this method, whereas the rated on-load torque is only decreased by 4.8% in the 3-slot/2-pole machine. In addition, it also shows that the proposed method could offer a better performance in a machine with relatively larger air gap length and it is also effective for other slot/pole combinations.

Magneto-impedance properties of thin-film type sensors using CoNbZr/SiO2 multilayer films

Abstract Thin-film magneto-impedance (MI) sensors have attracted much attention because of their advantages such as high sensitivity at room temperature and ease of miniaturization. However, further improvement in their sensitivity is required for detecting weak biomagnetic signals such as the magnetic fields of the brain. Since the high-frequency permeability of magnetic multilayer films with insulator layers improves due to the reduction in eddy current loss in the films, sensors using such multilayer films are expected to show a larger impedance change. In this paper, we fabricated sensors using Co85Nb12Zr3/SiO2 multilayer films and investigated their properties to evaluate the effect of their use on the sensor properties. The high-frequency permeability of the multilayer films improved as compared with that of CoNbZr single-layer films due to the reduction in eddy current loss. Because of the improvement in the permeability, the maximum impedance change ratio (ΔZ/Z) of the sensors using the multilayer films increased from 140% to 280% as compared with that of the sensor using the single-layer films. Thus, the use of magnetic multilayer films is effective for increasing the ΔZ/Z value of MI sensors.

A New Coil Structure to Reduce Eddy Current Loss of WPT Systems for Underwater Vehicles

Wireless power transfer systems in seawater inevitably suffer some energy loss as a consequence of eddy current loss. Here, we present a coil structure utilizing two transmitter coils placed symmetrically adjacent to each side of the receiver coil. This coil arrangement, termed a 1 × 1 × 1 structure, yields improved power transfer efficiency. The eddy current loss caused by the transmitter coils in a 1 × 1 × 1 system can be reduced to roughly half of that in a 1 × 1 system, with one transmitter coil and one receiver coil. The experimental results show that the power transfer efficiency from the transmitter to the receiver is improved by nearly 10%. After the introduction of equivalent eddy current loss impedance into the circuit, two arrangements of the 1 × 1 × 1 circuit topology are investigated. They consist of a shared or separately compensated capacitance topology. It is found that the shared-compensated capacitance topology is more robust to the change of mutual inductance than the separately compensated capacitance topology. This kind of structure is very useful in underwater vehicle applications.

Thermographic Measurement and Simulation of Power Losses Due to Interlaminar Contacts in Electrical Sheets

Ferromagnetic cores of electrical machines and transformers are constructed from laminated electrical sheets to reduce eddy current losses. Burrs are formed at the edges of electrical sheets during punching and cutting. These burrs deteriorate the insulation of adjacent sheets, make interlaminar contacts and cause interlaminar currents to flow across the stack. It is essential to know the interlaminar conductivity and the size of the contacts to estimate additional losses in the electrical machine. In this paper, the size of the interlaminar contacts formed by the burrs is estimated using a novel thermographic measurement method and an analytical method. The initial temperature rise of the contacts is used in the analytical model to estimate the contact size. The electromagnetic and thermal finite element formulations validate the results obtained from the analytical method. Moreover, the results obtained from the measurement, the analytical method, and the finite element method are compared. The study shows that the initial temperature rise method can be used to estimate the interlaminar contact size and electromagnetic losses if the temperature is measured immediately after energizing the sheets.

Multi-objective Optimization of Permanent Magnet Adjustable Speed Driver Base on RSM Model and NSGA-II

To optimise the structure of a permanent magnet adjustable speed driver (PMASD), a multi-objective optimization design method for increasing the output torque and reducing the eddy current loss was proposed. Firstly, the three-dimensional finite element method model of a PMASD was established, the influence of the main configuration parameters in the PMASD on the output torque and the eddy current loss was analyzed, and the reasonable range of the parameters was determined. When taking the minimal eddy current loss and maximum output torque as the optimal objectives, the secondary response surface numerical model equation was built using the Central Composite Design experimental method and the Response Surface Methodology. Then, while ensuring that the output torque of the PMASD is not less than the rated torque, the NSGA-II was used to perform multi-objective optimization based on the response surface model and the Pareto optimal solution sets for two objectives was obtained. Finally, the minimal eddy current loss model and maximum output torque model were selected to compare with the initial model that was not optimized. The simulation results proved that the output torque of the minimal eddy current loss model increased by 6.54% based on the reduction of eddy current loss by 0.81% and the output torque of the maximum output torque model increased by 24.41% based on an increase in eddy current loss of 10.51%: the performance of both optimization models had been improved significantly. The optimization results show that this method improves the transmission performance of the PMASD.

Finite element analysis of multi‐turn magnetoplated coils using homogenization method

AbstractMagnetoplated wires (MPW) are effective to reduce eddy current losses in power devices such as converters and contactless power transfer systems. In the conventional finite element analysis (FEA) of MPW, elements must be sufficiently smaller than the skin depth. This results in large number of unknowns. This article proposes a homogenization method using complex permeability for FEA of magnetoplated coils so as to circumvent this problem. The coil impedances obtained by the proposed method with coarse elements are shown to agree well with those computed in the conventional FEA with fine elements.