1、文献翻译原文LOAD PERFORMANCE OF PMLSM IN LOWER SPEEDREGION FED BY SINUOIDAL PWM INVERTERSi Jikai1,2 Chen Hao1 Wang Xudong2 Yuan Shiying2 Shangguan Xuanfeng2（1. China University of Mining and Technology Xuzhou 221008 China2. Henan Polytechnic University Jiaozuo 454000 China）ABSTRACTFor the permanent magnet
2、 linear synchronous motor (PMLSM) fed by sinusoidal PWM voltage source inverter in the lower speed condition without feedback control, load performance isdifferent from the PMLSM working in high speed region. The paper adopts time-step finite elementmethod and field circuit coupling method to invest
3、igate load performance of the PMLSM to drive horizontal transportation system with light load and heavy load condition respectively. It is shown that load performance of the PMLSM in the heavy load condition is highly better than those in light load operation conditions, and operation current become
4、s lower with load increasing. The validity is verified by comparisons of simulation and experimental results.Keywords: Permanent magnet linear synchronous motor (PMLSM), load performances, sinusoidal,PWM (SPWM) inverter, time-step finite element method, field circuit coupling method1 IntroductionThe
5、 permanent magnet linear synchronous motor(PMLSM) has been widely used in many applications from transportation system to office automation and military devices because the motors have lots of merits as high efficient, high accuracy position control, etc1-4. However, it is necessary that load perfor
6、mance of lower speed of PMLSM is profoundly researched, which has lots of characteristics to different from rotating synchronous machine and PMLSM in the high speed region. PMLSM in lower speed region has the essential characteristics that there are large ratio of the motor resistance to inductance
7、and large leakage inductance because of large and effective air gap and lower operation frequency. Lots of PMLSMs have the characteristics because the moving track of PMLSM is limited and the mover steady state running speed of PMLSM is finite. In the Ref.5,specifications of PMLSM were as follow. Th
8、e motor operation frequency was 6Hz, the pole pitch was 30mm. In the literature FEA method for electric machines driven by PWM inverter was proposed and the value of time-step was changed according to theswitching logic of PWM inverter. In the Ref.6, the authors presented the dynamic characteristics
9、 of partially excited permanent magnet linear synchronous motor considering end-effect. The starting and control characteristics related to the capability in PMLSM driving were investigated. The specifications of the motor were as follow. The resistance was 7.6 of sample A, the inductance was 17.6mH
10、, the maximum speed was 2m/s. As the Ref.7shown, the simulation condition was 7V, 3Hz and load thrust was 20N. The dynamic characteristics of the hysteresis current controlled inverter-fed PMLSM with the conductive sheet secondary was analyzed through the time-step finite element method and moving m
11、esh technique, which considering eddy-currents in the secondary aluminum sheet and solid back iron. In the Ref.3, the specifications of PMLSM were as follows. The resistance was 5.2, the inductance was 2.8mH,the motor was running at 0.9m/s. Ref.8 had presented the steady-state performance of PMLSM b
12、ased on sinusoidal ac current source such as larger ratio of resistance and inductance, and the mover in and out the primary. Unfortunately, as for the PMLSM fed by SPWM inverter operated in lower operation frequency region with larger ratio of resistance and inductance and larger leakage inductance
13、, the study of dynamic performance is poor in above-mentioned literatures and it is important to investigate the motor dynamic performance in difference loads conditions.Recently, many numerical methods have been proposed to investigate motors dynamic performance through accurate magnetic field anal
14、ysis. One of the numerical methods based on the finite element method, which is more and more used to accurately investigate dynamic characteristics of specify and new machines structures or asymmetry magnetic field, can consider geometric details and the nonlinear of magnetic circuit9-11. As for PM
15、LSM, it has threephase windings unbalance, magnetic circuit opening, bigger ratio of resistance and inductance of the phase windings, and time harmonic for the motor current existence. It is difficult to study the motor performances adopting the analytical method and the conventional FEM with object
16、ive of one or two poles considering period boundary conditions, additionally considering the linkage questions of outer SPWM inverter and magnetic field, thus, the paper uses total model of the motor FEA to attain transient process performances such as thrust, the mover speed and windings current in
17、 different load conditions. Due to the PMLSM fed by SPWM voltage source inverter, the currents of the motor are unknown and voltage includes lots of harmonic components, the effect of using one tool of finite element method is not ideal. Thus time-step finite element method and coupling field circui
18、t method is adopted to investigate load performances of the motor driving horizontal transportation system. The paper presents simulation tools, which using time-step finite element method and field circuit coupling method and experiment to investigate the motor performances in two loads conditions,
19、 light load and heavy load. The paper is organized as follows. In section , the prototype PMLSM is described. FEM model is established in section . Insection simulation results of PMLSM load performances are attained and discussed. In section experimental results are presented. Lastly, in section so
20、me conclusions are drawn.2 Analysis modelThe primary is composed of three-phase windings and core opened slot, and the secondary consists in permanent magnets and the separated magnetism piece which placed on the surface of the iron yoke. Single side type short primary and surface mounted PMLSM are
21、shown in Fig.1, in which permanent magnet magnetization is unanimous to air gap flux axis, leakage flux in poles interval lower and craftwork simple. The specifications of PMLSM are shown in Table.Table PMLSM specificationsFig.1 Physical model of surface permanent magnet linear synchronous motor1 Th
22、e primary 2Tooth 3Slot 4Material of insulating magnet 5Permanent magnet 6The secondary yokeTo take circuit fed by SPWM voltage source inverter and the motor end effects into account, the paper adopts field-circuit coupling method to calculate electromagnetic transient process, solve equation variabl
23、es of magnetic vector potential and the motor phase current, which are combination of electromagnetic field time-step finite element Equ. and threephase windings circuit equations. by electromotive force in the armature windings. Transient field governing equations. in which Az denotes magnetic vect
24、or potential is variable are shown in Eq.(1) according to Maxwell equationswhere Azz-axis component of magnetic vector potentialJsCurrent density of the primary windingsJmEquivalent magnetizing surface current density of permanent magnetThe permeabilityIn the paper, the 2-D model is subdivided into
25、small triangle elements to form a mesh that covers the entire region adopting n-order unit basic function and linear interpolation. After applying the Galerkin method, thegoverning equations. for the analysis model is expressed aswhere AUnknown magnetic vector potential (A is used in Eq.(1) with dif
26、ferent meaning)ICurrent in the windingsS,C,T Coefficient respectivelyG Corresponding matrix of equivalent magnetization current densityEquivalent magnetizing surface current method is adopted to deal with NdFeB type permanent magnet, which is uniformity magnetization, regulation shape, and linear de
27、magnetization. Intensity of magnetization sign is M0.PMLSM resistance and leakage reactance is not neglected due to the motor with large air gap characteristic. According to Ohm law and Faraday electromagnetic induction law, relation of electromotive force and voltage produced the primary three-phas
28、e windings is shown in Eq.(4).where The windings flux linkageLlThe motor leakage inductanceRWindings resistanceUWindings phase voltagewhere NWinding effective turnsBFlux densityS1Winding effective area in the slotS2Coupled effective area of the primary and the secondaryTo PMLSM magnetic circuit and
29、electric circuit are unbalance, thus electric potential of the connector of star point is not equal to zero and the motor phase equations. should be changed as follows.Where U0Output voltage of the inverterg0The inverter switch on-off functionUdDirect voltage of bus linkMaxwells stress tensor is ado
30、pted to calculate PMLSM electromagnetic force, which includes all kinds of harmonics component electromagnetic force. The motor electromagnetic force tangential component is shown in Eq.(9).The motor electromagnetic force normal component is shown in Eq.(10).where L1Winding effective lengthL2Integra
31、l spaceBxx-axis flux density component in the air gap fieldByy-axis flux density component in the air gap fieldFT Electromagnetic thrust forceFN Normal electromagnetic forceMovement equation of PMLSM is shown in Eq.(11).where mMassvThe motor mover velocityFLLoad force4 Simulation resultsThe simulati
32、on conditions are as follows. Line voltage is 30V, module frequency is 2Hz, light load is 50N and high load is 130N, the motor rated synchronous speed is 0.156m/s, which are identical to experimental PMLSM parameters. The simulation results are attained from cosimulation of finite element function o
33、f magnetic field and space state function of outer circuit. The motor voltage results are neglected because the voltage inverter is not almost affected by the outer conditions. Fig.2 shows simulation results of three phase current in load 50N condition. Fig.3 displays simulation result of thrust for
34、ce. In Fig.4, the mover speeds in load 50N condition are shown. Short dash line denotes the mover speed in load 50N condition under elimination of PMLSM detent force by changing end shape. Fig.5Fig.7 show respectively simulation results of three-phase current, thrust force, speed of the PMLSMin load
35、 130N condition. From Fig.2 and Fig.5, it is shown that the three-phase currents of the PMLSM in load 50Ncondition are larger than those of in load 130N condition, according to every load condition the motor phase current is unbalance that a phase current value is almost close to b phase current, bu
36、t both is larger than c phase current value because the PMLSM magnetic circuit is open and armature windings are discontinuous. In terms of comparison with Fig.3 and Fig.6, we can know that the tendency of the thrust force of the PMLSM in load 130N condition is favorable. As shown in Fig.4 and Fig.7
37、, in load 130N condition, the staring performance of the motor iswell and there is little undulation. If the detent force produced armature core length of PMLSM is reduced, the mover speed is basically close to the synchronous speed, but it is impossible that it is absolutely same as synchronous spe
38、ed because there are lots of harmonic components in current fed from SPWM voltageFig.2 Three-phase current in load 50N conditionFig.3 Thrust force in load 50N conditionFig.4 Speed with and without reducing detent force in load 50N conditioninverter and air gap field is unsinuso- idal even if driven
39、system is with feedback control.Fig.5 Three-phase current in load 130N conditionFig.6 Thrust force in load 130N conditionFig.7 Speed in load 130N condition5 Experimental resultsExperimental inverter type is FR-A241E-55K inverter of Mitsubishi corp. Voltage and current hall sensors are used to detect
40、 signs. The mover speed is attained by the rotating encoder for E6B2 type, whose rotating speed can be converted into the motor line speed. Software of the data collection system is edited through Turbo C language.Fig.8 and Fig.11 show three-phase current in load 50N and 130N condition, respectively
41、. Thrust force of the motor in two loads condition is shown in Fig.9 and Fig.12. From Fig.10 and Fig.13, it is shown that there are two speed curves in load 50N and 130N condition. By comparisons of simulation and experiment results, we can see that both are highly compatible.Fig.8 Three-phase curre
42、nt in load 50N conditionFig.9 Thrust force in load 50N conditionFig.10 Speed in load 50N conditionFig.11 Three-phase current in load 130N conditionFig.12 Thrust force in load 130N conditionFig.13 Speed in load 130N condition6 ConclusionsIn the paper, field-circuit coupling method of the time-step fi
43、nite element method and outer electric power circuit is utilized to analyze special load performances of lower speed of PMLSM with large ratio of the resistance to the inductance, large air gap and three-phase unbalance. Analysis results show that load performances of the PMLSM in the heavy load con
44、dition are highly better than light load operation conditions, and operation current becomes lower with load increasing because of the large ratio of the resistance to the inductance and large air gap. Due to existence of detent force, the PMLSM mover speed fluctuates in the range of the synchronous
45、 speed. If the detent force of PMLSM with open loop control is reduced, the mover speed is quite close to synchronous speed.Refrerence1 Wang Xudong, Yuan Shiying, Jiao Liucheng, et al. 3-D analysis of electromagnetic field and performance in a permanent magnet linear synchronous motorC. IEEE Interna
46、tional Electric Machines and Drives Conference, Cambridge, MA USA, 2001: 935-938.2 Bianchi N. Analytical computation of magnetic fields and thrusts in a tubular PM linear servomotorC. Conference Record-IAS Annual Meeting (IEEE Industry Applications Society), Rome, Italy, 2000, 1: 21-28.3 Bon Gwan Gu
47、, Kwanghee Nam. A vector control scheme for a PM linear synchronous motor in extended regionJ. IEEE Transactions on Industry Applications, 2003, 39(5): 1280-1286.4 Gore V C, Cruise R J, Landy C F. Considerations for an integrated transport system using linear synchronous motors for ultra-deep level
48、miningC. IEMD 99, Seattle, Washington, USA, 1999: 568-570.5 Jung In Soung, Hyun Dong Seok. Dynamic characteristics of PM linear synchronous motor driven by PWM inverter by finite element analysisJ. IEEE Transactions on Magnetics, 1999, 35(5): 3697-3699.6 Sang Yong Jung, Hyun Kyo Jung, Jang Sung Chun, et al. Dynamic characteristics of partially excited permanent magnet linear synchronous motor considering end-effectC. IEEE International Electric Machines and Drives Conference, Boston, USA, 2001: 508-515.7 Kwon Byung Il, Woo Kyung Il, Kim Duck Jin,et al. F
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