Reverse Salient Pole Design of Interior Pole-changing Permanent Magnet Synchronous Motor

Huimin Wang,Zhongyuan Hao,Xiangyi Li,Guokai Jiang,Liyan Guo 한국자기학회 2024 Journal of Magnetics Vol.29 No.1

In order to prevent the demagnetization of low coercivity permanent magnets, the pole-changing permanent magnet synchronous motor usually adopts I<SUB>d</SUB>=0 control strategy, which has the problems that the reluctance torque of the motor cannot be utilized and the torque density is low. In order to solve this problem, a new type of rotor reverse salient pole structure of pole-changing permanent magnet synchronous motor is proposed in this paper. Based on the comparative analysis of the magnetic field distribution characteristics of the motor under different pole numbers, the common d-axis and q-axis magnetic path under 8-pole and 4-pole are planned, and then the winding inductance L<SUB>d</SUB>>L<SUB>q</SUB> under two pole numbers is realized by setting bar and arcmagnetic barriers and non-uniform reduction of air gap length. On this basis, the Taguchi method is used to set the parameters of the proposed structure, and the motor torque ripple is reduced under the premise of increasing the motor torque amplitude as much as possible under the 8-pole and 4-pole, and the optimal parameter combination of the proposed structure is determined. Through the FEA, it is verified that the motor can produce the maximum torque at the negative current angle before and after the pole change, so as to effectively utilize the reluctance torque, avoid the permanent magnet demagnetization and improve the torque density.

Analysis on Seal Capacity of Magnetic Fluid Seal Using Ring Magnet

Jiawei Liu,Decai Li 한국자기학회 2022 Journal of Magnetics Vol.27 No.1

Magnetic fluid seal is one of the most mature applications of magnetic fluid. When the shaft has a large radial runout, the classical pole piece is easily damaged. Due to its small size, the commonly used pole piece structure harbors problems like poor seal performance under a large gap and poor processability. By exploring the distribution law of the magnetic field on the magnet’s surface, we provided theoretical support for the magnetic fluid seal using axially-magnetized ring magnets. New structures for the magnetic fluid seal using axially-magnetized slotted ring magnets and the magnetic fluid seal using radially-magnetized ring magnets were proposed. Then, comparisons were made between the classical magnetic fluid seal and the magnetic fluid seal using ring magnets. The results revealed that the magnetic fluid seal using axially-magnetized slotted ring magnets and the magnetic fluid seal using radially-magnetized ring magnets exhibited a certain seal capacity, which could replace the classical magnetic fluid seal structure.

자기연마를 이용한 난삭재 Tungsten Carbide Bar의 마이크로 초정밀가공 특성

배중탁,김정수,문상돈,kim han joo 한국기계기술학회 2019 한국기계기술학회지 Vol.21 No.4

Magnetic abrasive finishing (MAF) process is a surface improvement method, which the magnetic field of permanent magnet or electromagnet is used to control the abrasive particles during the finishing process. The magnetic abrasive tools are filled between the N-pole and S-pole of Nd-Fe-B type permanent magnets. Tungsten carbide bar (WC) is a high hardness material and its compressive strength is much higher than the other materials. Therefore, due to its superior mechanical properties, it has been widely used in cutting or machining process. Because the smooth surface of tungsten carbide is required in cutting tools, thus the magnetic abrasive finishing process was applied for achieving its surface accuracy and dimensional accuracy. The results showed that the surface roughness of tungsten carbide bar was improved from Ra: 0.23㎛ to Ra: 0.02㎛ in 120 sec by magnetic abrasive finishing process.

SPM 모터의 극과 슬롯수 변화에 따른 전자기 가진력 특성 연구

송정용(Jeongyong Song),김도연(Doyeon Kim),장건희(Gunhee Jang) 한국소음진동공학회 2013 한국소음진동공학회 학술대회논문집 Vol.2013 No.4

This paper investigates the magnetic excitation force of a surface-mounted permanent magnet (SPM) motor according to the change of pole/slot combination. The characteristics of magnetic flux and radial magnetic force (RFM) due to pole/slot combination were analyzed by using magnetic circuit analysis. Also, the RMF of motors with the variable pole/slot combination was numerically simulated by using the finite element analysis to verify the result of the magnetic circuit analysis. This research shows that RMF ripple is reduced when the number of pole is smaller than the number of slot.

Improved Method for Calculating Magnetic Field of Surface-Mounted Permanent Magnet Machines Accounting for Slots and Eccentric Magnet Pole

Yu Zhou,Huaishu Li,Wei Wang,Qing Cao,Shi Zhou 대한전기학회 2015 Journal of Electrical Engineering & Technology Vol.10 No.3

This paper presented an improved analytical method for calculating the open-circuit magnetic field in the surface-mounted permanent magnet machines accounting for slots and eccentric magnet pole. Magnetic field produced by radial and parallel permanent magnet is equivalent to that produced by surface current according to equivalent surface-current method of permanent magnet. The model is divided into two types of subdomains. The field solution of each subdomain is obtained by applying the interface and boundary conditions. The magnet field produced by equivalent surface current is superposed according to superposition principle of vector potential. The investigation shows harmonic contents of radial flux density can be reduced a lot by changing eccentric distance of eccentric magnet poles compared with conventional surface-mounted permanent-magnet machines with concentric magnet poles. The FE(finite element) results confirm the validity of the analytical results with the proposed model.

Improved Method for Calculating Magnetic Field of Surface-Mounted Permanent Magnet Machines Accounting for Slots and Eccentric Magnet Pole

Zhou, Yu,Li, Huaishu,Wang, Wei,Cao, Qing,Zhou, Shi The Korean Institute of Electrical Engineers 2015 Journal of Electrical Engineering & Technology Vol.10 No.3

This paper presented an improved analytical method for calculating the open-circuit magnetic field in the surface-mounted permanent magnet machines accounting for slots and eccentric magnet pole. Magnetic field produced by radial and parallel permanent magnet is equivalent to that produced by surface current according to equivalent surface-current method of permanent magnet. The model is divided into two types of subdomains. The field solution of each subdomain is obtained by applying the interface and boundary conditions. The magnet field produced by equivalent surface current is superposed according to superposition principle of vector potential. The investigation shows harmonic contents of radial flux density can be reduced a lot by changing eccentric distance of eccentric magnet poles compared with conventional surface-mounted permanent-magnet machines with concentric magnet poles. The FE(finite element) results confirm the validity of the analytical results with the proposed model.

초등학교 교과서의 자화실험에서 자화의 세기와 극성에 영향을 미치는 요인 연구

이희진,이영숙,이해인,강호군,김중복 한국현장과학교육학회 2017 현장과학교육 Vol.11 No.1

Different methods of rubbing and attaching for magnetization are introduced in teacher guide books for 3rd and 6th grades of the 2009 Korea national curriculum. Because experimental results are not coherent, teachers are very confused. We have studied factors influencing on magnetization according to methods and investigated changes of magnetic poles in various arrangements of magnets. Firstly, in order to investigate magnetization according to magnetizing methods, we have used two kinds of magnets (neodimum magnet and alnico magnet) for rubbing or attaching, and measured degree of magnetization by MBL magnetic field sensor. Strength of magnets used for magnetization is more sensitive than magnetization methods. Secondly magnetic poles are decided normally by the direction of the magnet in the last action of rubbing or attaching for magnetization. In conclusion, the attaching method for magnetization is more appropriate because there is possibility reducing degree of magnetization during moving the magnet for the next rubbing. Our results can be used for inquiry activities in actual class for 3rd or 6th grades. However, because different initial magnetization could give large fluctuations in magnitude of magnetization, magnetization methods and changes of poles depending on arrangement of magnets should be focused. 2009 개정교육과정 3, 6학년 교사용 지도서에 자화의 방법에 따른 자화의 정도에 대하여 서로 다른 설명이 제시되어 있으며 실제 실험에서도 일관적인 데이터를 얻을 수 없어 초등학교 교사에게 자화에 대한 혼란을 주고 있다. 본 연구에서는 자화의 방법에 따른 자화의 정도에 영향을 미치는 요인과 자화에 따른 극의 변화에 대해 연구하였다. 첫째, 자화의 방법에 따른 자화의 정도에 영향을 미치는 요인을 알아보기 위해 두 종류의 자석(네오디뮴 자석, 알니코 자석)에 쇠못을 문질렀을 때와 붙였을 때의 자화의 정도 차이를 MBL을 활용하여 측정하였다. 문지르기와 붙이기 방법의 차이보다 오히려 자기장이 센 자석일수록 자화의 정도가 강했으며 같은 자석에서도 자기장의 세기가 센 부분에서 자화가 더 잘 되었다. 둘째, 자화에 따른 극의 방향은 마지막 자석의 방향에 따라 자극이 결정되었다. 또한, 자화를 시키는 위치에 따라 자극이 결정되는 것을 알 수 있다. 결론적으로 문지르기를 이용한 자화 방법은 자석을 옮기는 동안 자화에 영향을 줄 수 있기 때문에 붙이기가 더 적절하다. 자화에 대한 이해를 돕기 위해 실시한 이 실험은 초등학교 3, 6학년 자석 관련 실제 수업의 탐구활동에서 유용하게 활용될 수 있을 것이나, 쇠못의 초기 자성 때문에 정량적인 값에 오차가 있을 수 있는 점을 고려하여 자화의 방법과 극의 변화에 초점을 맞추어 지도하는 것이 필요하다.

철도차량용 45kW급 마그네틱 기어드 동기전동기 이중 회전자의 설계 신뢰성 분석 연구

홍성용,박찬배 한국철도학회 2022 한국철도학회논문집 Vol.25 No.5

Magnetic geared permanent magnet synchronous motors (MG-PMSM) for railway vehicle traction have a double-airgap structure in which a stator that creates a three-phase rotating magnetic field is located on the outside of a magnetic gear composed of an inner rotor and an outer rotor. MG-PMSM, which has a coaxial dual rotor structure, has a complex structure compared to those of general traction motors, so manufacturing technology is as important as design technology. Therefore, in this paper, a design reliability analysis study of a dual rotor related to a 45kW-class MG-PMSM for railway vehicles was conducted for the first time in Korea. First, a design model of a 45kW-class MG-PMSM having a dual rotor was derived through an optimized design technique. To analyze the design reliability of the derived MGPMSM dual rotor structure, demagnetization strength characteristics of the permanent magnets were analyzed; next, mechanical/structural stiffness analysis of the inner permanent magnet rotor and the outer pole-piece rotor was performed. Finally, it was suggested that the 45kW-class MG-PMSM design model with the derived dual rotor structure achieved structural reliability when manufactured.

Magnetization Characteristics Analysis in a Pole Changing Memory Motor Using Coupled FEM and Preisach Modeling

Jung Ho Lee,Seung Chul Lee 한국자기학회 2011 Journal of Magnetics Vol.16 No.4

This paper deals with the magnetic equivalent circuit modeling and permanent magnet (PM) performance evaluations of a pole changing memory motor (PCMM). We use a coupled transient finite element method (FEM) and Preisach modeling, which is presented to analyze the magnetic characteristics of the permanent magnets. The focus of this paper is on the evaluation of characteristics such as the magnetizing direction and the pole number of the machine under re- and de-magnetization conditions.

Improvement of Cogging Torque Characteristics of Magnetic-Geared PMSM for Railway Vehicles using Pole-piece Skew

박찬배,정거철,조익현 한국철도학회 2019 한국철도학회논문집 Vol.22 No.9

In general, the slot opening structure of a stator core generates cogging torque when the rotor rotates in apermanent magnet synchronous motor (PMSM). If the cogging torque is excessively large, it may cause vibration andnoise during operation of the PMSM. In the case of a magnetic-geared permanent magnet synchronous motor (MGPMSM),cogging torque is generated during operation of the PMSM because the outer rotor, made of magnetic material,and the inner rotor, in which the permanent magnet is inserted, are arranged in double. Therefore, in this study, the skewtechnique, generally used in electric motors, is applied to reduce the cogging torque of MG-PMSM. The design of theMG-PMSM is first studied for the application to a railway vehicle driving system of an MG-PMSM structurally integratedwith a magnetic gear and a PMSM. In addition, a method is studied to structurally reduce the cogging torque ofthe MG-PMSM simply by skewing the pole pieces of a low speed rotor made of magnetic material.