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Giant low-field reversible magnetocaloric effect at liquid helium temperature of niobium and iron co.substituted EuTiO_(3) co.pounds

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Journal of Rare Earths 2024年第4期42卷 710-715页

作者： Zhihong Hao Quanyi Liu Huicai Xie Yan Zhang Zhaojun Mo School of Rare Earth and New Materials Engineering Ganzhou Innovation Center of Rare Earth Permanent Magnet Material Advanced Manufacturing and Intelligent Equipment TechnologyGannan University of Science and TechnologyGanzhou341000China Ganjiang Innovation Academy Chinese Academy of SciencesGanzhou34119China School of Materials Science and Engineering Taiyuan University of Science and TechnologyTaiyuan030024China

Giant magnetocaloric effect(MCE)materials in the liquid helium temperature region have attracted a lot of attention in the field of low-temperature magnetic refrigeration(MR).In this study,a series of niobium(Nb)and iron(Fe)co.substituted EuTiO_(3) perovskites with cubic structure(space group pm3m)was successfully fabricated,and their magnetic properties as well as cryogenic magnetocaloric effects were investigated in detail.As expected,the introduction of Nb and Fe can significantly modulate the magnetic phase transition and magnetocaloric effect of the EuTiO_(3) co.pounds.With increasing Fe co.centration,two local minima co.responding to the AFM-FM magnetic phase transition near 5.0 K and FM-PM transition near 10 K with no hysteresis in the thermomagnetic curves are observed,which is attributed to an enhancement of FM co.pling.At the same time,the gradually widened-ΔSM-T curves and the two peaks with a broad shoulder lead to co.siderable refrigeration capacity(RC).With the field change ofΔH=2 T,the calculated values of-ΔS_(M)^(max) for the EuTi_(0.9375-x)Nb_(0.0625)Fe_(x)O_(3)(x=0.075,0.1,0.125,0.15)co.pounds are 24.2,17.6,14.5 and 14.0 J/(kg·K),respectively.The co.responding RC values were calculated to be 144.6,138.3,151.2 and 159 J/kg,respectively.Especially,the values of-ΔS_(M)^(max) for EuTi_(0.8625)Nb_(0.0625)Fe_(0.075)O_(3) are 8.6 and 15.1 J/(kg·K)under low field changes of 0.5 and 1 T,respectively.The giant low-field reversible magnetocaloric effect makes them attractive candidates for magnetic refrigeration in the liquid helium temperature region.

关键词： magnetocaloric effect Refrigeration capacity magnetic entropy change Rareearths

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Effect of aluminum on microstructure and magnetic properties of sintered Nd-Fe-B magnets processed by grain boundary diffusion of Tb-Al

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Journal of Rare Earths 2023年第5期41卷 705-712,I0003页

作者： Tinghui Wang Zhaokun Ma Qihang Zhu Lijing Yang Baosheng Liu Yu Zhao Cheng Xu Bizhang Zheng Fangqin Hu Jianzhong Li Qingfang Huang Zhenlun Song CAS Key Laboratory of magnetic Materials and Devices Zhejiang Province Key Laboratory of Magnetic Materials and Application TechnologyNingbo Institute of Materials Technology and EngineeringChinese Academy of SciencesNingbo 315201China co.lege of Materials Science and Engineering Taiyuan University of Science and TechnologyTaiyuan 030024China Baotou Hidyree Technology co. Ltd.Baotou 014030China hangzhou permanent magnet group co. Ltd.Hangzhou 311231China Ningbo permanent magnetics co. Ltd.Ningbo 315201China Fujian Key Laboratory for Rare Earth Functional Materials Longyan 366300China

The grain boundary diffusion process(GBDP)of Tb can improve the co.rcivity of sintered Nd-Fe-B magnets.In this study,the effect of AI on the diffusion of Tb in the GBDP was investigated.The co.tent of diffused Tb-Al was precisely co.trolled by adjusting the magnetron sputtering process.The Tb equivalent of Al was also studied.Results show that AI promotes the diffusion of Tb deeper into the magnet,reducing the thickness of the shell in the co.e-shell structure.This study is helpful for further developing the process,reducing the co.sumption of heavy rare earth elements(Tb),and improving the co.rcivity of sintered Nd-Fe-B magnets.

关键词： Sintered Nd-Fe-Bmagnet Heavy rare earth elements Grain boundary diffusion process co.rcivity

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Effects of bias voltage on co.ting structures and antico.rosion performances of PA-PVD Al co.ted NdFeB magnets

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Journal of Rare Earths 2021年第6期39卷 703-711,I0004页

作者： Yujie Cao Pengjie Zhang Wei Sun Weifeng Zhang Hanzhong Wei Jiquan Wang Bingshan Li Xiaofei Yi Guangqing Xu Yucheng Wu School of Materials Science and Engineering Hefei University of TechnologyHefei 230009China State Key Laboratory of Rare Earth permanent magnet Materials Earth-Panda Advance Magnetic Material Co.Ltd.Hefei 231500China BGRIMM magnetic Materials and Technology(Fu Yang)co. Ltd.Fuyang 236000China BGRIMM Technology group co. Ltd.Beijing 102600China

Al co.ted NdFeB magnets were prepared by plasma-assisted-physical-vapor-deposition(PA-PVD)method fo r enhancing the co.ro sion resistance.Mo rphologies and structures were characterized by an Xray diffractometer and a scanning electron microsco.e.co.rosion behaviors of the samples with different bias voltages were studied by electrochemical methods and neutral salt spray test,respectively.The bias voltage during the deposition process was optimized acco.ding to the co.ting structures and co.rosion resistances.The density and flatness of Al co.ting increase with increasing the bias voltage,and at the same time the thickness decreases.The co.ting density and thickness turn to be stable when bias voltage is 1800 V.Also,the co.rosion behaviors of PA-PVD Al co.tings in different media,such as NaOH,HNO_(3) and NaCl solutions,were studied.The self-co.rosion potentials(E_(co.r)) of PA-PVD Al co.tings almost keep co.stant in NaOH and HNO_(3) solutions with diffe rent co.centrations.However,the self-co.rosion current densities(J_(co.r)) decrease with the increasing co.centrations.E_(co.r) shifts to negative potential and J_(co.r)decreases gradually when increasing the co.centration of NaCl solution.The co.rosion mechanisms of Al co.tings are discussed based on the co.rosion behaviors in different media.

关键词： Physical vapor deposition Plasma assistance Al co.ting Sintered NdFeB co.rosion behavior Rare earths

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Integrated Equivalent Model of permanent magnet Synchronous Generator Based Wind Turbine for Large-scale Offshore Wind Farm Simulation

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Journal of Modern Power Systems and Clean Energy 2023年第5期11卷 1415-1426页

作者： Ming Zou Yan Wang Chengyong Zhao Jianzhong Xu Xiaojiang Guo Xu Sun State Key Laboratory of Alternate Electrical Power System with Renewable Energy Sources North China Electric Power University(NCEPU)BeijingChina China Huaneng group Clean Energy Technology Research Institute co. Ltd.BeijingChina

The high-speed simulation of large-scale offshore wind farms(OWFs) preserving the internal machine information has beco.e a huge challenge due to the large wind turbine(WT) co.nt and microseco.d-range time step. Hence, it is undoable to investigate the internal node information of the OWF in the electro-magnetic transient(EMT) programs. To fill this gap,this paper presents an equivalent modeling method for largescale OWF, whose accuracy and efficiency are guaranteed by integrating the individual devices of permanent magnet synchronous generator(PMSG) based WT. The node-elimination algorithm is used while the internal machine information is recursively updated. Unlike the existing aggregation methods, the developed EMT model can reflect the characteristics of each WT under different wind speeds and WT parameters without modifying the co.es. The access to each WT co.troller is preserved so that the time-varying dynamics of all the WTs co.ld be simulated. co.parisons of the proposed model with the detailed model in PSCAD/EMTDC have shown very high precision and high efficiency. The proposed modeling procedures can be used as reference for other types of WTs once the structures and parameters are given.

关键词： Offshore wind farm(OWF) electro-magnetic transient(EMT) integrated equivalent modelling permanent magnet synchronous generator(PMSG)based wind turbine(WT)

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An Enhanced Sensorless co.trol Scheme for PMSM Drives co.sidering Self-inductance Asymmetry

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CES Transactions on Electrical Machines and Systems 2022年第4期6卷 384-392页

作者： Lijian Wu Zekai Lyu Zekai Chen Jiaming Liu Ying Lu IEEE the co.lege of Electrical Engineering Zhejiang UniversityHangzhou310027China Shanghai Electric Wind Power group co.pany Ltd.Hangzhou310063China the 21st Research Institute of China Electronics Technology group co.poration Ltd.Shanghai200030China

Inductance asymmetry,which is brought by inherent asymmetric parameters,manufacture tolerance,winding fault,cables with unequal lengths,etc.,of permanent-magnet synchronous machines(PMSMs)can cause current harmonics and inaccurate position estimation.This paper proposes an enhanced fundamental model based sensorless co.trol strategy for PMSMs with asymmetric inductances.The proportional-integral-resonant current regulator is introduced to reduce the seco.d-order harmonics of currents,but there are still negative sequence co.ponents in the estimated back-electromotive forces(EMFs),which can cause the position estimated error.Differing from co.ventional methods in which negative sequences are filtered out before the phase-locked loop(PLL)module,the proposed method directly applies the estimated back-EMF with negative sequences as the reference input of PLL.An improved PLL with a bi-quad filter is proposed to attenuate the arising seco.d harmonic position error and heighten the steady-state accuracy.Then,this position error is used for asymmetric inductance identification and its result is utilized to update the observer model.Furthermore,the dynamic performance is improved by the output limitation on the bi-quad filter as well as the implementation of a fast-locking technique in the PLL.The effectiveness of the proposed scheme is verified by experimental results.

关键词： Inductance asymmetry permanent magnet synchronous machine(PMSM) Position estimation error Sensorless co.trol

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Enhancement mechanism of maximum energy product in hot-deformed Nd-Fe-B magnets by addition of ferromagnetic substances

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Journal of Rare Earths 2023年第12期41卷 1984-1989,I0006页

作者： Lian Wu Xianshuang Xia Wenzong Yin Xu Tang Jinyun Ju Yeyuan Du Renjie Chen Zhiyi Xu Shenglei Che Aru Yan co.lege of Materials Science and Engineering Zhejiang University of TechnologyHangzhou310034China Research Center of magnetic and Electronic Materials Zhejiang University of TechnologyHangzhou310034China CISRI&NIMTE Joint Innovation Center for Rare Earth permanent magnets Ningbo Institute of Material Technology and EngineeringChinese Academy of SciencesNingbo315201China University of Chinese Academy of Sciences Beijing100049China Ganjiang Innovation Academy Chinese Academy of SciencesGanzhou341119China Institute of Physics Chinese Academy of SciencesBeijing100190China

It has been proved that the maximum magnetic energy product(BH)maxof hot-deformed Nd-Fe-B magnets can be effectively improved by adding substances with either high melting point or high saturation magnetization.In this work,we selected a ferromagnetic nano Fe_(55)Ni_(28)co.(17) alloy powders with both high melting point and high saturation magnetization as the dopant to improve the(BH)max.By the addition of 1 wt% FeNico.the remanence increases by over 5%(from 1.36 to 1.44 T),resulting in a significant enhancement of(BH)maxfrom 355 to 396 kJ/m^(3)(from 44.6 to 49.7 MGOe).Microstructure observations reveal that the texture of grain alignment is improved,the co.centrations of ferro magnetic elements(Fe,Ni,and co. in the main phase and intergranular phase are increased so that the magnetization behavior of hot-deformed magnet changes(more easily shows reversible magnetization behaviors),which are the reasons why the high maximum energy product of hot-deformed magnet,is obtained.

关键词： Nd-Fe-B Ferromagnetic substance FeNico.alloys magnetic properties Rareearths

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Recent advances in traction drive technology for rail transit

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Journal of Zhejiang University-Science A(Applied Physics & Engineering) 2023年第3期24卷 177-188页

作者： Jien MA Chao LUO Lin QIU Xing LIU Bowen XU Jiabo SHOU Youtong FANG co.lege of Electrical Engineering Zhejiang UniversityHangzhou 310027China

The traction drive system is the“heart”of rail transit vehicles.The development of sustainable,secure,eco.omic,reliable,efficient,and co.fortable co.temporary rail transportation has led to increasingly stringent requirements for traction drive systems.The interest in such systems is co.stantly growing,supported by advancements such as permanent magnet(PM)motors,advanced electronic devices such as those using silico. carbide(SiC),new-generation insulating materials such as organic silico.,and advanced magnetic materials such as rare-earth magnets and amorphous materials.Progress has also been made in co.trol methods,manufacturing technology,artificial intelligence(AI),and other advanced technologies.In this paper,we briefly review the state-of-the-art critical global trends in rail transit traction drive technology in recent years.Potential areas for research and the main obstacles hindering the development of the next-generation rail transit traction drive systems are also discussed.Finally,we describe some advanced traction drive technologies used in actual engineering applications.

关键词： Rail transit Traction drive systems Artificial intelligence(AI) permanent magnet(PM)motors Electronic devices

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Analysis and evaluation of electromagnetic vibration and noise in permanent magnet synchronous motor with rotor step skewing

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Science China(Technological Sciences) 2019年第5期62卷 839-848页

作者： DONG QiChao LIU XinTian QI HongZhong SUN Chao WANG YanSong School of Mechanical and Automotive Engineering Shanghai University of Engineering Science Guangzhou Automobile group co. LTD Automotive Engineering Institute

In this paper, a multi-physics simulation model capable of electromagnetic noise prediction is established, and the effectiveness of the established simulation model in predicting and evaluating electromagnetic noise is verified. Based on the verified motor model, a rotor step skewing model which can affect electromagnetic noise is proposed, and the influence of the skewing angle on electromagnetic noise is investigated in detail. By studying the spectral characteristics of the low-order radial magnetic force which has a great influence on electromagnetic noise, the distribution of electromagnetic noise characteristics of the permanent magnet synchronous motor(PMSM) with or without the rotor step skewing is co.pared and analyzed. Therefore, it lays a technological foundation for predicting and suppressing the electromagnetic vibration noise of electric vehicle(EV) driving motor in the electromagnetic design.

关键词： PMSM electromagnetic noise step skewing multi-physics simulation model spectrum analysis

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co.rosion resistance and mechanical properties of (Ho,Nd)FeB magnets

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Journal of Rare Earths 2021年第11期39卷 1409-1414,I0004页

作者： Yujie Cao Youhao Liu Pengjie Zhang Guangqing Xu Jiaqin Liu Jingwu Chen Xiaofei Yi Yucheng Wu School of Materials Science and Engineering.Hefei University of Technology Hefei 230009China State Key Laboratory of Rare Earth permanent magnet Materials Hefei 231500China BGRIMM magnetic Materials and Technology(Fu Yang)co. Ltd.Fuyang 236000China Key Laboratory of Advanced Functional Materials and Devices of Anhui Province Hefei 230009China Institute of Industry and Equipment Technology Hefei University of TechnologyHefei 230009China

(Ho,Nd)FeB magnets with different Ho co.tents were prepared by Ho substitution for part of Nd during the casting process.Effects of Ho co.tents on the co.rosion resistance and mechanical properties of(Ho,Nd)FeB magnets were analyzed by a highly accelerated aging tester,an electrochemical workstation,a microhardness tester,a bending tester,a scanning electron microsco.e and an X-ray diffractometer.Results show that the addition of Ho can change the main phase structure,optimize the distribution of rare-earth rich(RE-rich) phases in grain boundary,and improve the co.rosion resistance and mechanical properties of NdFeB magnets.When the co.tent of Ho increases from 0 to 21.0 wt%,the weight loss of magnets decreases from 2.672 to 0.933 mg/cm^(2),and the microhardness and bending strength increase from 528.74 HV and 374.92 MPa to 633.84 HV and 459.80 MPa,respectively.

关键词： (Ho Nd)FeB magnets co.rosion resistance Mechanical property Microstructure Rare earths

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Torque Improvement of Spoke-type permanent magnet Motor with Auxiliary Stator Using Harmonic Current co.trol Strategy

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CES Transactions on Electrical Machines and Systems 2023年第2期7卷 210-217页

作者： Hao Wu Wenliang Zhao Zheng Li Xiuhe Wang the School of Electrical Engineering Shandong UniversityJinan250061China IEEE the Jinan Heating group co.LTD. Jinan250011China

The spoke-type permanent magnet motor with auxiliary stator exhibits high torque performance owing to the flux focus effects.To further improve its torque density,this paper proposes a co.trol method by using harmonic current strategy.Based on the theoretical analysis,a 3-D torque look-up table by dq-axis current and electrical angle is established with the aid of the finite element method(FEM).The maximum torque per ampere curve at each rotor position is identified and summarized to adequately indicate the relationship between torque and current amplitude of the motor.Through theoretical derivation,it is co.cluded that the minimum torque co.t curve is the co.tour line of?Te/?i2,which can be employed to identify the harmonic current for torque density improvement.co.pared to traditional strategies,the proposed co.trol strategy can increase torque density of forward and reverse torque by 1.22%and 1.40%,respectively.The experimental results verify the analysis and simulation results,as well as prove the effectiveness of the proposed strategy.

关键词： Spoke-type permanent magnet motor Harmonic current Finite element method Torque density Torque co.t

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