Available online at www.sciencedirect.com ScienceDirect Procedia - Social and Behavioral Sciences 195 ( 2015 ) 2586 2591 World Conference on Technology, Innovation and Entrepreneurship Application of Finite Element Method to Determine the Performances of the Line Start Permanent Magnet Synchronous Motor Seda Kül a *, Osman Bilgin a, Mümtaz Mutluer b a Selcuk Univerity, Faculty of Engineering, Electrical and Electronic Engineering Department, Konya 42250, Turkey b Second affiliation, Address, City and Postcode, Country Abstract In this paper, low power line start permanent magnet synchronous motor (LSPMSM) is analyzed and simulationed by finite element method using ANSYS RMXPRT and Maxwell 2D/3D modeling software. Parameters of three motor are changed, are modeled than put to the simulation. While the motors are analyzed, motor dimensions aren't changed. After motors are modeled by RMXPRT, the models are transposed to maxwell and observed the magnetic field distribution. The torque and efficiency curve are acquired and compared with each other. Consequently, the results are evaluated in terms of feasibility for the industrial area in terms of efficiency and torque 2015 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/). 2015 The Authors. Published by Elsevier Ltd. Peer-review under under responsibility of Istanbul of Istanbul Univeristy. University. Keywords: line start, permanent magnet synchronous motor 1. Introduction Line start permanent magnet synchronous motor (LSPMSM) is getting more important for academic and industrial area especially constant speed application. Previously, while induction motor preferred out of easy structure and low cost, permanent magnet synchronous motor has advantages like high efficiency torque density and * Corresponding author. Tel.: +90 0332 223 21 70 fax: +90 332 241 06 35. E-mail address: sedakul@selcuk.edu.tr 1877-0428 2015 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/). Peer-review under responsibility of Istanbul Univeristy. doi:10.1016/j.sbspro.2015.06.458
Seda Kü l et al. / Procedia - Social and Behavioral Sciences 195 ( 2015 ) 2586 2591 2587 power factor. But permanent magnet motor has some disadvantages. It doesn t run up without any inverter or power electronic devices. LSPMSM is a hybrid structure which combines of permanent magnet synchronous motor and induction motor. It has same stator structure with induction motor and rotor structure with permanent magnets which inserted beneath the squirrel cage in the rotor. As a result of this hybrid structure it possess both of them advantages. These are line start ability and robustness from the induction motor and high efficiency, torque density and power density (Li, Song, & Cho, 2010). When the dynamic behavior is evaluated starting period can be divided into two region which are asynchronous period and synchronous period. LSPMSM researches have started on 1980s. First, the effects of the magnet materials have investigated (Richter & Neumann, 1984). Ferrite and samarium cobalt was used as a magnet material. Starting process and braking torque effect have examined (Miller, 1984). Synchronization capability is evaluated. After these studies developing new magnet materials like NdFeB LSPMSM have become more efficiency. Different rotor configuration for the motor performance have created and have compared in terms of efficiency and starting performance each other (Libert, Soulard, & Engström, n.d. 2002) (Kurihara & Rahman, 2004). Analytical motor modeling and calculated magnet dimension in steady state and dynamic state have offered (Stoia, Cernat & Hameyer, 2009). Motor have designed using FEM analyses and the reluctance torque effects which are kind of asynchronous torque are obtained ( Takegami, Tsuboi, Hasegawa, Hirotsuka, & Nakamura, 2010). Three motors which have different rotor type have designed and have compared with the efficiency and the losses (Nekoubin, 2011). No load and full load performances in higher starting process with lower voltage and offered some methods have been researched for the industrial application (Lu, Huang, Ye, & Fang, 2012). The influence of the different dimension and magnetic property rotor bar have been observed and calculated starting current and torque (W. Lu, Luo, & Zhao, 2012). This paper shows the optimal design efficiency and torque with regard to winding, magnet material, rotor and stator slot by using the Rmxprt program package in ANSYS Maxwell. The motor performance and torques convenience is examined for the fans systems. The synchronous and asynchronous behaviors are examined and torque characteristics is evaluated. Effect of the breaking torque is investigated. 2. Analysıs Model In this paper low power LSPMSM is designed and analyzed. The performance of a 4 poles 1.1 kw LSPMSM has obtained. This motor is investigated suitability for the fans system. Because, they don t need high starting torque capability so the motor properties is convenience for this system. Some parameters and properties values are given in Table 1. Table 1. Design parameters. Parameters Output power Rated speed Number of poles Outer diameter of stator Inner diameter of stator Air gap length Shaft diameter Thickness of magnet Width of magnet PM material Number of stator slots Number of rotor slots Value 1.1 kw 1500 rpm 4 120 mm 76 mm 0.5 mm 26 mm 36 mm 3 mm NdFeB 24 32
2588 Seda Kü l et al. / Procedia - Social and Behavioral Sciences 195 ( 2015 ) 2586 2591 Rmxprt (Rotating Machine Expert) is a package program which is produced by Ansoft. It provides electromagnetic field analysis, analytical solution of the LSPMSM and it can calculate performance of the machines which have been included. While motor is designed, the program create power circuit automatically. After motor design have been finished, it is possible to create directly Maxwell 2D/3D finite element modeling. Figure 1 shows the cross section of the motor. The motor composes of a stator with armature winding and rotor which contains PM and damper winding for starting directly like induction motor squirrel cage ( Takegami, Tsuboi, Hasegawa, Hirotsuka, & Nakamura, 2010). Fig. 1.Cross section of the LSPMSM The equation of starting performance and torque is given below (Li, Song, & Cho, 2010), k=d/dt: Stator voltage equation is given, R s is the stator winding resistance V k R i sin d qr s d cos q dr s q V k Ri (1) (2) equation is shown rotor voltage 0 p2d Ri d 2d 0 p2q Rdi2q (2) The flux linkage equation can be stated below L i L i L I d d d md 2d md fm L i L i q q q q 2q L i L i L I 2d 2d 2d md d md fm (3) L i L i 2q 2q 2q md q
Seda Kü l et al. / Procedia - Social and Behavioral Sciences 195 ( 2015 ) 2586 2591 2589 I fm indicate dc excitation current When the LSPMSM starting process is examined, the total electromagnetic torque consists of two component which are cage torque and braking torque. Cage torque is produced by the squirrel cage winding in the rotor and the breaking torque is generated by inserted permanent magnet below the squirrel cage (Li, Song, & Cho, 2010). The torque equations are respectively given below: The rotor cage torque is given like that: Pm T X X I I X I I X I I EVI (4) c 2d 2q 2d 2q md d 2q mq q 2d 0 2q 2s The magnet braking torque limiting the starting torque is given: Pm Tm XmdI fmimd Xd XqImd Imq (5) 2 s The total electromagnetic torque: Pm T X X I I X I I X I I E I (6) e d q d q md 2d q mq 2q d 0 q 2s Figure 2 shows the breaking torque produced by permanent magnet. It is acquired by Rmxprt program. Breaking torque depends on permanent magnet material, size and position in the asynchronous operation region. Average torque is cage torque minus breaking torque. While cage torque is an acceleration torque and plays positive effect for the rotor acceleration, breaking torque performs negative acts as a brake in acceleration process ( STOIA, Cernat, Hameyer, & Ban, 2010). Fig. 2.Breaking torque of the LSPMSM After design of the motor is completed by Rmxprt, torque, efficiency and power factor curves are obtained. Asynchronous period torques are given in Figure 3.
2590 Seda Kü l et al. / Procedia - Social and Behavioral Sciences 195 ( 2015 ) 2586 2591 Figure 3. Asynchronous period torques a) cage torque b) total torque c) breaking torque As stated above breaking torque depends on the magnet dimension and position. So magnet dimension is minimized and the torque curve obtained again like Figure 4. It is seen obviously breaking torque is proportion to magnet size. When the PM size is minimized, breaking torque decreased. Figure 4. Asynchronous period torque with minimized magnet The Maxwell software is used for the transient analysis. Motor behaves as a permanent magnet synchronous motor and runs up synchronous speed. There is only breaking torque on synchronous operation region. Synchronous torque is shown in Figure 5. Magnet dimension effects not only breaking torque, but also efficiency and power factor. Table 2 is shown the efficiency and power factor value for the first and second situation. In second situation magnet dimension is smaller than first situation.
Seda Kü l et al. / Procedia - Social and Behavioral Sciences 195 ( 2015 ) 2586 2591 2591 Figure 5. Synchronous period torque Table 2. Efficiency and power factor value. situation Efficiency Power factor First %91 0.99 Second %90 0.94 3. Conclusion This paper investigates the 1.1 kw three phase 4 poles hybrid LSPMSM for fans systems. Because, they don t need to high starting torque. Rmxprt and Maxwell 2D simulation is applied to designed model and attained the performance curves. For the LSPMSM breaking torque is essential especially in asynchronous starting period, thus the effect of the magnet size is examined. It is seen that breaking torque is proportional to the magnet size directly. Total torque is sum of the cage torque and the breaking torque. Due to the brake effect of the breaking torque in the asynchronous starting period, when the breaking torque is lower, total torque is higher. On the synchronous period breaking torque behaves like an accelerate torque. This situation is viewed with torque curves and examined. References Stoia, D., Chirila, O., Cernat, M., Hameyer, K., & Ban, D. (2010). The behaviour of the LSPMSM in asynchronous operation. Proceedings of EPE-PEMC 2010, T4-45 Li, J., Song, J., & Cho, Y. (2010,). High performance line start permanent magnet synchronous motor for pumping system. In Industrial Electronics (ISIE), 2010 IEEE International Symposium on (pp. 1308-1313). IEEE. Kurihara, K., & Rahman, M. A. (2004). High-efficiency line-start interior permanent-magnet synchronous motors. Industry Applications, IEEE Transactions on, 40(3), 789-796. Libert, F., Soulard, J., & Engstrom, J. (2002). Design of a 4-pole line start permanent magnet synchronous motor. ICEM Lu, Q., Huang, X., Ye, Y., & Fang, Y. (2012). Experiment and analysis of high power line-start PM motor. Przegld Elektrotechniczny, 2 Lu, W., Luo, Y., & Zhao, H. (2012). Influences of rotor bar design on the starting performance of line-start permanent magnet synchronous motor. In Electromagnetic Field Problems and Applications (ICEF), 2012 Sixth International Conference on (pp. 1-4). IEEE. Miller, T. J. E. (1984). Synchronization of line-start permanent-magnet ac motors. Power Apparatus and Systems, IEEE Transactions on, (7), 1822-1828. Nekoubin, A. (2011). Design a Line Start Synchronous Motor and analysis effect of the rotor structure on the efficiency. World Academy of Science and Technology, (57), 5-9. Richter, E., & Neumann, T. (1984). Line start permanent magnet motors with different materials. Magnetics, IEEE Transactions on, 20(5), 1762-1764. STOIA, D., Cernat, M., Hameyer, K., & Ban, D. (2009). Line-start permanent magnet synchronous motors. Analysis and design. In 15 th International Conference on Electrical Drives and Power Electronics, EDPE 2009 Takahashi, A., Kikuchi, S., Miyata, K., Wakui, S. I., Mikami, H., Ide, K., & Binder, A. (2010). Dynamic and steady-state performance of linestarting permanent magnet motors. In Electrical Machines (ICEM), 2010 XIX International Conference on (pp. 1-6). IEEE Takegami, T., Tsuboi, K., Hasegawa, M., Hirotsuka, I., & Nakamura, M. (2010). Calculation method for asynchronous starting characteristics of line-start permanent magnet synchronous motor. In Electrical Machines and Systems (ICEMS), 2010 International Conference on (pp. 1137-1142). IEEE