Increase In Eddy Current Loss Research Articles

Research on Novel Flat Wire Transposed Winding of PMSM for Electric Vehicle

Permanent magnet synchronous motor (PMSM) for electric vehicles is developing higher frequency and speed but triggering a significant increase of eddy current loss. To resolve the eddy current loss issue, a novel flat wire transposed winding composed of double-row multiple parallel strands is proposed. Transposed winding techniques have been proved to be efficient in reducing eddy current loss by preventing the uneven leakage magnetic field induced by high frequency. The proposed transposition further improved this technique in reducing circulating current loss. Taking a 60-kW PMSM as an example, the novel flat wire transposed winding arrangement is carried out. The 3-D field-circuit coupled finite-element models of 360° complete transposed and incomplete transposed winding PMSM are established, and circulating current losses are compared. The analysis results show that incomplete transposed winding has a better performance in reducing the circulating current loss. The transposition method suitable for novel flat wire transposed winding is obtained, and the feasibility of PMSM with novel flat wire transposed winding to reduce winding losses is proven.

Influence of Power Factor on the Performance of Bulb Tubular Turbine Generator

Background: In recent years, many patents have been dedicated to increasing the rated power factor of generators. However, hydro-generators often encounter uncontrollable factors, such as dry season, power network adjustment, and so on, resulting in low power factor operation. In other words, the generator is often in a low power factor operating state. In order to provide data reference for power plant in regulating power factor, it is necessary to analyze the performance of generator in low power factor operation. Objective: The performance of the generator is analyzed when the power factor decreases, and the influence of low power factor operation on the generator is obtained. Methods: Taking a 24MW bulb tubular turbine generator as an example, a 2D transient electromagnetic field model is established. The correctness of the model is verified by comparing the test data and the simulation data. The torque, eddy current loss and air gap flux density of the generator under different power factor are calculated. Results: When the power factor deceases from 0.99 to 0.85, the air gap flux density increases from 0.713 T to 0.749 T, the torque ripple increases from 150.5 kN⋅m to 179.9 kN⋅m, and the rotor eddy current loss increases from 17.48 kW to 18.15 kW. Conclusion: The results show that the torque ripple and eddy current loss will increase with the decrease of power factor when the generator lagging phase operation. The torque ripple and eddy current loss increase by 3.8 % and 1 % respectively with the power factor decrease by 0.02 % with power factor between 0.99 and 0.85.

AgCrO2 formation mechanism during silver inner electrode and Fe–Si–Cr alloy powder co-firing in metal multilayer chip power inductors

Multilayer Fe–Si–Cr alloy chip power inductors have the benefits of a smaller, thinner profile, lower DC resistance and higher rated current. During metal multilayer power inductor co-firing, Fe–Si–Cr alloy powders react with the inner electrode, silver, to form a large amount of hexagonal flaky AgCrO2. The p-type semiconductor, AgCrO2, will cause co-fired Fe–Si–Cr alloy multilayer chip power inductor insulation degradation, hence reducing the power conversion efficiency due to the increase in eddy current loss. The AgCrO2 forming mechanism is investigated in this study. It was observed that silver reacts with the Fe–Si–Cr thermal grown oxide layer, Cr2O3, and subsequently leads to the formation of Ag2CrO4 when the temperature is lower than 650 °C. The formed Ag2CrO4 with low melting temperature then volatilizes at higher temperatures through the pore channels to react with the volatilized Cr2O3 to form the AgCrO2. AgCrO2 will cause Fe–Si–Cr alloy multilayer chip inductor resistivity and breakdown voltage degradation.

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.

Interactions between silver inner electrode and Fe-Si-Cr alloy of metal multilayer chip inductors

The silver diffusion and chemical reaction between Fe-Si-Cr alloy and Ag during multilayer metal power inductor preparation are investigated using scanning electron microscopy, field emission transmission electron microscopy and multipurpose X-Ray thin-film diffractometer. The experimental results show that a large amount of inner electrode, Ag, volatilize and diffuse under air atmosphere during co-firing, resulting in the reaction between Ag and thermally grown oxide layer, Cr2O3, forming flaky AgCrO2. The p-type semiconductor, AgCrO2 will cause the insulation degradation of the co-fired Fe-Si-Cr alloy multilayer chip inductors, hence reducing the power conversion efficiency due to the increase in eddy current loss.

The Influence of Pole-Slot Match on Magnetomotive Force with Concentrated Fractional-Slot Winding

Magnetic field, produced by magnetomotive force (MMF) harmonic waves, is harmful to motors, by reducing efficiency of motors, resulting in demagnetization of permanent magnets and so on. It is also responsible for the increase of eddy current loss and the rise of temperature of rotors. Thus, research on the influence of pole-slot match on MMF with concentrated fractional-slot winding is necessary. This paper aims at researching unit motors with different cooperation of slots and poles. First, basic principle of MMF is described. Then, with different kinds of unit motors, MMF of harmonic waves is analyzed. Based on these analyses, distributive regularities are summarized.

Effect of the Thickness of Cr Interlayer on the High-Frequency Characteristics of FeCoTa/Cr/FeCoTa Multilayers

The effect of non-ferromagnetic Cr interlayer on the high-frequency ferromagnetic properties (HFFMPs) was investigated by use of FeCoTa/Cr/ FeCoTa triple layered films. In conventional thought, the metal interlayer gives rise to a high eddy current loss and therefore a deteriorated HFFMP. However, it is found that HFFMPs depend on the thickness of Cr interlayer. The HFFPMs are improved by Cr-interlayer with a thickness less than 12 nm (sample C1). Comparing with the Cr-interlayer-free FeCoHf single layered film (sample C0), the magnetic anisotropy field of C1 dramatically increases from 185 Oe for C0 to 558 Oe for C1. As a consequence, a high ferromagnetic resonance frequency over than 3 GHz is achieved for sample C1. When the thickness of Cr-interlayer is more than 120 nm (C2), the HFFMPs are reduced due to the increase of eddy current loss and magnetic decoupling between the ferromagnetic layers.

Thickness Effects on Microwave Magnetic Properties of FeCoBSi Films Deposited on Flexible Substrate

The FeCoBSi thin fllms were deposited on the ∞exible mylar substrates by DC magnetron sputtering. The as-deposited fllms showed as an amorphous structure. Permeability characteristics in the range of 0.5{18GHz were investigated. The values of permeability increased with an increasing thickness of the fllms when the thickness was less than 1m. This unusual result may be due to the various microstructures, stress or defects of the fllms. When the thickness was more than 1m, the values of both permeability and resonance frequency decreased signiflcantly. The results may be attributed to the increase of eddy current loss. The electric properties, including sheet resistance and resistivity for the fllms with various thicknesses, have also been investigated.

RETRACTED: Magnetic properties of iron-based soft magnetic composites with MgO coating obtained by sol–gel method

Soft magnetic composites with a thin MgO insulating layer were produced by a sol-gel method. Energy dispersive X-ray spectroscopy, X-ray analysis, Fourier transform infrared spectroscopy, density measurement and compositional maps confirmed that thin layers of MgO covered the iron powders. Coercivity measurement showed that the stress relaxation and reduction of hysteresis loss efficiently occurred at 600 °C. At this temperature, the phosphate insulation of commercial SOMALOY™ samples degrade and their electrical resistivity, magnetic permeability and operating frequency decreases noticeably. The results show that the MgO insulation has a greater heat resistance than conventional phosphate insulation, which enables stress-relief at higher temperatures (600 °C) without a large increase in eddy current loss. The results of annealing at 600 °C show that the electrical resistivity and ferromagnetic resonance frequency increased from 11 μΩ m and 1 kHz for SOMALOY™ samples to 145 μΩ m and 100 kHz for the MgO insulated composites produced in this work.

Core loss evaluation of segment core in turbine generators by torque method

AbstractThis paper presents core loss evaluation of a turbine generator model stator. The stator configuration does not make the magnetic flux distribution uniform, and the induction harmonics make the core loss calculation difficult. In this evaluation, the core losses are measured by rotating stator torque.As a result of the measurements, a half‐lap‐stacked stator obtains lower core losses and larger percentage of eddy current losses than a block‐stacked stator. In addition, a gap between each segment makes in‐plane eddy current loss increase. © 2006 Wiley Periodicals, Inc. Electr Eng Jpn, 158(2): 64–71, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.20407

トルク法によるタービン発電機セグメントコアの鉄損評価

This paper presents core loss evaluation of a turbine generator model stator. The stator configuration does not make the magnetic flux distribution uniform, and the induction harmonics make the core loss calculation difficult. In this evaluation, the core losses are measured by rotating stator torque. As a result of the measurements, a half-lap-stacked stator obtains lower core losses and larger percentage of eddy current losses than a block-stacked stator. In addition, a gap between each segment makes in-plane eddy current loss increase. © 2006 Wiley Periodicals, Inc. Electr Eng Jpn, 158(2): 64–71, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.20407

Study on the building factor of a stacked core made of amorphous sheets (abstract)

There are some factors increasing the building factor of a transformer assembled from amorphous sheets. One of the factors may be the localized irregularity of magnetization property. Such an inhomogeneity is caused by the localized mechanical stress or the inhomogeneous temperature distribution during annealing. Various stacked cores which are composed of amorphous sheets with inhomogeneous magnetic characteristics as shown in Fig. 1 have been investigated. Each half of the sheet is annealed uniformly at different temperature from the other half. The frequency characteristics of power losses are measured to clarify whether the main cause of the total loss increase is due to the hysteresis loss or the eddy current loss. The obtained results show that the incremental loss is mainly due to the increase of eddy current loss. The increase of eddy current loss may be due to the transverse flux across the interlaminar gap. Therefore, the relationship between power losses and gap length has been examined. The obtained results denote that the eddy current loss is increased by the transverse flux. The experimental results are also checked by numerical analysis of the flux distribution in stacked cores using the finite element method.

Magnetic domains and high permeability in Ni-Fe-Cu-Mo alloys

Magnetic domains have been observed in material with composition close to 77% Ni-14% Fe-5% Cu-4% Mo for both vanishingly small and finite values of K1, the first anisotropy constant. An initial permeability of 70 × 103 was obtained. The domain structure was governed by random internal stresses in the material and no clear dependence on grain orientation or K1 was established. The application of tensile stress caused a reduction in permeability and an increase in eddy current loss. Bar-type domains are formed whose spacing diminishes with increasing stress. The results are shown to be in agreement with theory based on the μ* effect.