Application of Soft Magnetic Composite Material in the Field of Electrical Machines Xiaobei Li 1,2,a, Jing Zhao 1,2,b*, Zhen Chen 1,2, c

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1 Applied Mechanics and Materials Online: I: , Vols , pp doi: / Trans Tech Publications, witzerland Application of oft Magnetic Composite Material in the Field of Electrical Machines Xiaobei Li 1,2,a, Jing Zhao 1,2,b*, Zhen Chen 1,2, c 1 chool of Automation, Beijing Institute of Technology, Beijing , China 2 Key laboratory for Intelligent Control & Decision of Complex ystems, Beijing Institute of Technology, Beijing 10008, China a xiaobeili@163.com, b zhaojing_bit@bit.edu.cn (corresponding author), c chenzhen76@bit.edu.cn Keywords: oft magnetic composite (MC), Permanent Magnet Machine, linear, high speed Abstract. The property of the soft magnetic composite (MC) material is introduced. Take the traditional material used for electric machine, i.e. the silicon steel lamination, as the reference, this paper summarizes the application advantages of MC in the typical electric machine, such as tubular permanent-magnet liner machine, high-speed permanent-magnet machine, claw-pole machine, axial flux permanent-magnet machine and radial flux permanent-magnet machine. MC material has much applied potential in the field of electric machine. Introduction As a new type material, soft magnetic composite (MC) material has the following remarkable characteristics: (1)Isotropic: The material has a good characteristic of isotropic because it is composed of powder particles. This feature can help us break the traditional motor design plan and make analysis of magnetic circuit in 3D. (2)Allows complex shapes: unlike the traditional silicon steel sheet formed by overlying, MC material forms parts through modeling pressing, which makes the process a lot easier when comes to the parts with complex shape. (3)mall eddy current loss: each powder particle has insulation coating, so that the eddy current loss is smaller than silicon steel sheet. Total iron loss of the material is determined by the hysteresis loss, which makes the material especially suitable for high frequency applications. (4)Low cost: the material simplifies the pressing process without leftover material waste, so the costs will be drastically reduced for mass production. More and more people all over the world pay attention to the MC material due to its unique characteristics. Many researchers have compared this new material with the traditional motor silicon steel sheet on many aspects, the results fully showed that the MC has huge potential and wide prospects in the field of motor. In this paper, the application of MC material in the field of motor will be overviewed. Tubular axial flux permanent magnet linear motor Due to the series of advantages of high power density, high efficiency, no end windings, no unilateral magnetic force between stator and rotor, tubular permanent magnet linear machine are more and more popular. Various structures of tubular permanent magnet linear machine (both slotted and slotless machine) have been researched. The results showed that force characteristics of machine can be effectively improved by adopting slotted structure [1]. Magnetic circuit of tubular permanent magnet linear machine is shown in Fig. 1. Either silicon steel sheet or MC can be used in the manufacture of tubular linear permanent magnet machine. When comes to using silicon steel sheet, there are two methods for forming silicon steel sheet: one method is axially stacked, that makes the magnetic lines in machine yoke perpendicular to the silicon steel sheet, as a consequence, on one hand, the magnetic resistance is increased, on the other hand, the eddy current loss will become larger, thus reducing the machine efficiency. Another way is to construct a silicon steel module, as shown in Fig. 2, the magnetic flux can walk along the silicon, however, the processing technology of this kind of machine is very complex, and the space utilization is not sufficient. o using MC material is another method, as shown in Fig. 3, its unique isotropic permeability and simple processing technology (parts can be pressed directly by modeling) make it very suitable for batch process of this kind of machine. Ref.[2] researched on the selection of material of tubular linear machine, they made a comparative study between the modular silicon steel sheet and MC of tubular linear machine. Their results also All rights reserved. o part of contents of this paper may be reproduced or transmitted in any form or by any means without the written permission of Trans Tech Publications, (ID: , Pennsylvania tate University, University Park, UA-06/03/16,20:01:55)

2 4300 Vehicle, Mechatronics and Information Technologies showed that: although the MC is a little worse than modular silicon steel sheet on the machine performance, but it has a huge potential for low-cost production of the machine because of the simple processing technology used MC material. Z Fig.1 Magnetic circuit of cylinder permanent linear magnet motor Lm Z Fig.2. tator core of tubular linear motor used modular silicon steel Fig.3. tator core of ubular linear motor used MC High speed permanent-magnet motor Recently, high speed motor has become research focus in international electrotechnical field. Due to the advantages of high power density, its volume is far less than the low-speed motor with the same output power, which can save materials effectively. The conventional laminated rotor cannot bear the centrifugal force generated when the linear velocity in above 200m/s, so a special material is needed. However, a great loss will be produced in high-strength laminated or solid rotor due to the high-frequency harmonics generated by stator. For example, flux varying frequency of stator core in a motor with 75000rpm rated speed is 25 times of it in a motor with 3000rpm. As for high-speed motor with the same flux density in iron core, the unit iron loss increase by 66~125 times. In order to save energy and reduce the stator and rotor losses, the MC materials can be adopted, it can not only meet the performance requirements of the high-speed and high-frequency stator and rotor, but also simple the process and make lowest of production costs. Claw-pole motor According to the application, claw-pole machines can be classified into claw-pole generator and claw-pole motor. At present, some kinds of claw-pole machine structures have been used more frenquently, such as claw-pole generator with and without brush for automobile, claw-pole generator for aerospace, claw-pole transverse flux motor, and so on. Ref.[3] developed a three-phase claw-pole motor by using MC 500 in UT of Australia, the stator is composed of three sections and each section is composed by two same pieces of parts with claw pole type, the rotor is outer rotor type with surface mounted. The structures of the stator and rotor are shown in Fig. 4. uch a complex stator is hardly made by silicon steel sheet. Recently, Ref.[4] also studies claw-pole motor and puts forward a composite structure of claw-pole motor for hybrid application, as shown in Fig. 5. As the same, this kind of claw-pole motor is also hardly processed by silicon steel sheet, but MC will be a good choice. In a word, the MC material assists and promotes the research and application of claw- pole machine. 5. Axial flux permanent motor Axial flux motor has great application prospect and space because of the high density and high torque characteristics. According to the characteristics of 3D magnetic field about axial flux disk type motor, the motor can be processed in different modes: (1) First, stator cores with rolled lamination can be made with long sheet of steel rolled up and slots cut during the rolling. (2)The second is stator cores with lamination teeth module, the teeth are stacked by laminations in radial direction and yoke in axial direction. Then the teeth are inserted into the yoke, as shown in Fig.6. (3)Third, the stator is directly molded by soft magnetic composite material.

3 Applied Mechanics and Materials Vols Fig.4 The stator and the rotor of three-phase claw -pole motor Fig.5 Claw part diagram of composite structure of hybrid claw-pole motor Ref.[5] makes preliminary research about these three kinds of processing way based on a 10p/12s axial flux motor. The winding of the motor is concentrated and the span length is 1, the winding end has no overlap. The motors with different structures are comparable with the same volume. The MC material can make full use of winding ends space without increasing the motor size, as shown in Fig. 8. The results shows that 10p/12s MC motor with core end make the best performance, which has the optimal no-load back-electromotive force waveform and the average torque. Fig.6 Gear shaper schematic structure of the core Fig.7 MC disk type motor stator Ref [6] studied axial flux motor for automotive drive, and compared the motor of rolled lamination with motor with MC materials on loss. The flux density and loss of the two axial flux motors are summarized in Table 1. The results show that: MC material can significantly reduce the total core loss and improve the motor efficiency, which will further increase the competitive potential in the field of automotive drive. Table.1 Comparison of rolled lamination with motor with MC materials 6. Concentrated winding radial flux motor More and more study are appeared on the concentrated winding fractional-slot motor, the appearance of the MC materials set off boom to this kind of motor once again. Recently, concentrated winding fractional-slot motor is researched [7], and compared the performances of MC motor with end core structure, MC motor without end core and traditional silicon steel sheet motor. MC material is MC500 and silicon steel sheet is DW Fig 8 shows the finite element model of MC motor with end core. The MC and silicon models are exactly the same, both without end core, as shown in Fig 9. Motor with end core does not increase its volume, while the armature winding end space is fully utilized. Table 2 shows the comparison of the performance of the three motors. From the data calculated, it can be seen that MC motor with end core, which is comparable with traditional silicon steel sheet motor in the condition of the same total volume, is much better in performance than MC motor without end core. In addition, MC motor processing is without scrap waste, while the scrap washed down from silicon steel sheet is generally wasted. Comparison data with the three motors in raw materials and final used materials is shown in Table 3. The comparison result indicates that MC motor can take advantage of materials, whose final mass production processing cost may be even lower than the traditional silicon steel sheet motor.

4 4302 Vehicle, Mechatronics and Information Technologies Fig.8 Model of motor with end core Fig.9 Model of motor without end core Table 2 Performance comparison of the three motors Torque[m] Fundamental amplitude of EMF(V) MC motor with end core-no load MC motor without end core-no load traditional silicon steel sheet motor-no load MC motor with end core-full load MC motor without end core-full load traditional silicon steel sheet motor-full load Table 3 Comparison of stator core material volume(mm 3 ) Raw Final used Utilization materials(mm 3 ) materials(mm 3 ) MC motor with end core % MC motor without end core % traditional silicon steel sheet motor % ummary With the efforts of so many researchers, various types of MC motors with kinds of structures have been developed, which is not limited to several kinds of motor structure described above. There are a lot of complex motor structures that cannot achieve by stacked in laminated silicon steel, MC is the ideal alternative. From the above studies on MC, we can see that there is wide range of applications in MC motor and its prospect is very optimistic. Acknowledgment This work was supported in part by Key laboratory for Intelligent Control & Decision of Complex ystems, Beijing Institute of Technology, in part by Basic Research Foundation of Beijing Institute of Technology under Grant and , and in part by Ph.D. Programs Foundation of Ministry of Education of China under Project References [1] J. Zhao, Z. Chen, et al, 16th EML Technology ymposium. Beijing, China, May 15-19, [2] J.B. Wang and D. Howe, IEEE Trans. on Magn., 2005, vol.41, no.10, pp [3] Y.G. Guo, J. G. Zhu, et al., IEEE Trans. on Magn., 2005, vol.41, no.6, pp [4] P. Zheng, Q. Wu, J. Zhao, et al.. Energies. 2012, 5, [5] J. Zhao, P. Zheng, et al.. IEEE VPPC. Lille, France, eptember 1-3, [6] G. Cvetkovski, L. Petkovska, et al., IEEE Trans. on Magn., 2002, vol.38, no.5, pp [7] P. Zheng, Y.ui, et al ICEM, Beijing, China. August 20-23, 2011

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