Preliminary Studies of Various Rotor Pole Number for Permanent Magnet Flux Switching Machines (PMFSM)

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1 Preliminry Studies of Vrious Rotor Pole Number for Permnent Mgnet Flux Switching Mchines (PMFSM) Lili Iwni Jusoh, Erwn Sulimn, Rjesh Kumr, Ftihh Shfiqh Bhrim & M. Firoz Omr Deprtment of Electricl Power Engineering, Universiti Tun Hussein Onn Mlysi Line 3- Locked Bg 11, Btu Pht, Johor, 864 Mlysi. Abstrct In this pper, study on the slot nd pole number combintions of the single-phse permnent mgnet flux-switching mchine (PMFSM) hs been executed. Four slot designs nmely 2S-8P, 4S-8P, 8S-12P, nd 1S-15P were chosen by nlysing the highest power vlue nd torque in the rotor pole study. The proposed designs were briefly compred in regrds to topology development, mteril nd conditions setting s well s properties setting. A few nlyses hve been crried out such s cogging torque, output power nd torque, nd speed. This study ws crried out using JMAG Designer version 14. with 2D finite-element nlysis (2D-FEA). The simulted result showed tht the proposed design 4S-8P ws the best with produce higher torque with 2.47Nm significntly 33% better thn the 8S-12P nd 1S-15P which come in second plce with 1.65Nm nd 1.7Nm respectively. Keywords: permnent mgnet flux switching mchine, single phse. INTRODUCTION This In the middle of 195s, the concept of the FSM ws founded nd first published [1]. Severl novel nd new FSM mchine topologies hve been estblished for vrious pplictions, rnging from low cost domestic pplinces, utomotive, wind power, to erospce nd getting more populr in recent yers. The new flux-switching motor is very simple motor to mnufcture, nd coupled with power electronic controller demnding only two power semiconductor switches, it hs the potentil to be low cost in high volume pplictions. Furthermore, flux switching mchine hs n electroniclly commutted brushless motor, essentilly offers longer life nd very flexible nd precise control of torque, speed, nd position t no dditionl cost [1]. FSM hs been seen s potentil cndidte for future vrible speed pplictions becuse of its unique merits [2]. Ordinrily, the FSMs cn be chrcterised into three cluster tht re field excittion flux switching mchine (FEFSM), permnent mgnet flux switching mchine (PMFSM), nd hybrid excittion flux switching mchine (HEFSM) [6]. Both PMFSM nd FEFSM hve only one primry source of excittion flux, respectively induced by the permnent mgnet nd the field excittion coil wheres both PM nd FECs both re used for generting flow in HEFSM [7]. Bsed on the literture review, nlysis of the number combintions of slots nd poles of mchine designs should be mde in enhncing mchine s performnce [3]. Vrious combintion of sttor slot nd rotor pole for HEFSM hve been refined for high speed pplictions [4]. An erly exmple of FEFSM lso hs been proposed by the uthor. The impct of rotor pole number on the chrcteristics of single-phse hs been presented. Four topologies 12S-3P, 12S-6P, 12S-9P nd 12S-15P of single phse FEFSM with the segmentl rotor nd non-overlp windings hve been investigted nd compred [6]. In other proposed exmple is study of rotor pole number for ORHEFSM. This pper show the rotor pole number effect on the chrcteristics of outer-rotor hybrid excittion flux switching motor (ORHEFSM) for in-wheel drive electric vehicle (EV) pplictions. The pproprite number of slot pole ply key role in order to define the optiml performnces [9]. The permnent mgnet flux switching mchine ( PMFSM ) hs been populr reserch topic becuse of its high power density nd robust rotor structure. With both PMs nd rmture windings locted in the sttor nd single solid piece rotor similr to the switched reluctnce mchine, PMFSM hs the dvntge of suitbility for high speed drives nd esy cooling of ll ctive prts compred to conventionl PM mchines PM [5]. Bsed on the literture review, design new structure of 12S- 1P PMFSM hs been proposed by the resercher for Hybrid Electric Vehicle (HEV) pplictions, the results nd working principle nd working principle hs lso been discussed [5]. Even so, this pper initilly presents the comprtive combintions of single phse PMFSM number slots nd poles of proposed motor designs nmely 2S-8P, 4S-8P, 8S-12P, nd 1S-15P. In this study, the possible number of rotor pole nd sttor slot is defined by (1). N r N s k 1 (1) 2q Where Nr is the number of rotor poles, Ns is the number of sttor slots, k is the nturl entity hving vlue 1,2,3 nd q is the number of phses. Wheres, the electricl frequency, fe of the proposed motors cn be expressed by (2). f e = N r. f m (2) Where fe is the electricl frequency, fm is the mechnicl rottion frequency nd Nr is the number of rotor poles respectively. The rmture coil current nd number of turns re clculted using (3) nd (4), respectively. The motor s filling fctor is set t.5, to ensure flux moves from the sttor to rotor 1377

2 eqully without ny flux lekge, the design of the proposed mchines is defined s in (5). I J S N (3) N S A (4) copper Sttor Tooth Width = Rotor Tooth Width Where N, J, α, S, A nd I re number of turns, current density, filling fctor, slot re, copper width nd input current, respectively. The subscript is represent for rmture coil. Initilly, the rotor, sttor nd rmture coil of the proposed design re drwn by using Geometry Editor by JMAG-Designer ver. 14., relesed by the Jpn Reserch Institute (JRI). The effects of slot pole number combintions on the electromgnetic performnce such s cogging torque, flux linkge, bck electromgnetic force (bck-emf), output torque, nd power were nlyzed bsed on 2-D finite element nlysis (FEA). Tble 1 shows the rotor pole study for ech slot number. 5 TABLE I. Ns Nr PERFORMANCE OF DESIGN ROTOR POLE STUDY Flux Linkge Bck Emf Cogging Torque Torque Power (W) VARIOUS DESIGN TOPOLOGIES AND SPECIFICATION PMFSM with wound slient rotor structure is illustrted in Fig. 1. The proposed topology is clerly seen to hve four design which is 2slot-8pole, 4slot-8pole, 8slot-12pole nd 1slot- 15pole. These designs were considered s the best pole combintion in rotor pole study s it resulting in high verge torque nd high power. Figure 1. Slot pole study ) 1S-15P, b) 8S-12P, c)4s-8p, d) 2S-8P Similrly, ll the rmture phses employ the similr winding configurtions nd embedded in the sttor core to form the winding slot. In ddition, PMs with the rrngement of lternte circumferentil directions t every rotor tooth re employed. Since PM volume is limited to only 7g, the finl mchine is more likely to hve less weight but in contrst much high performnces to be obtined in terms of output torque nd power. The type of PM mteril used in developing the design is Neomx35AH, while for rotor nd sttor prts re mde up of electricl steel coded 35A25. The design restrictions nd prmeters of the proposed design re presented in Tble 2. TABLE II. DESIGN RESTRICTION AND SPECIFICATION OF FSM MACHINE Items 2S-8P 4S-8P 8S-12P 1S-15P No. of phse 1 Sttor inner rdius(mm) Sttor outer rdius(mm) Rotor outer rdius(mm) Rotor inner rdius(mm) Rotor tooth width(mm)

Sttor tooth width(mm) Motor stck length(mm) Air gp length (mm) PM Volume (g) 9 9 9 5 2.3.25 7 RESULT AND PERFORMANCE BASED ON 2D-FINITE ELEMENT ANALYSIS A.

2, the proposed design of 2S-8P, 4S-8P, 8S-12P nd 1S-15P show tht flux lines move from the sttor nd return through to the nerest rotor pole to mke complete flux cycle.

Flux lines of FSM ) 2S-8P, b) 4S-8P, c) 8S-12P, d) 1S-15P The flux pth for PMFSM is generted t the PM nd rmture coil.

Evidently, ll the design mchines hve surfced lmost identiclly excited PM flux lines nd distributions similrity s the flux surges from sttor to rotor nd return through the rotor teeth to

Figure 4 shows the cogging torque investigtion of the exmined PMFSM design mchines, with 4S-8P hving the highest pek-to-pek cogging torque t pproximtely 3.

3 Sttor tooth width(mm) Motor stck length(mm) Air gp length (mm) PM Volume (g) RESULT AND PERFORMANCE BASED ON 2D-FINITE ELEMENT ANALYSIS A. Flux lines nd Flux Distribution The flux lines nd flux distribution for the initil design of the single phse re prove in Fig.2 nd Fig.3 respectively. From Fig. 2, the proposed design of 2S-8P, 4S-8P, 8S-12P nd 1S-15P show tht flux lines move from the sttor nd return through to the nerest rotor pole to mke complete flux cycle. () (b) (c) (d) Figure 3. Flux distribution of FSM ) 2S-8P, b) 4S-8P, c) 8S-12P, d) 1S-15P (c) () Figure 2. Flux lines of FSM ) 2S-8P, b) 4S-8P, c) 8S-12P, d) 1S-15P The flux pth for PMFSM is generted t the PM nd rmture coil. Furthermore, the flux distribution is investigted to monitor field sturtion effect on the mchine s shown in Fig.3 (), Fig. 3(b), Fig. 3(c) nd Fig. 3(d). Evidently, ll the design mchines hve surfced lmost identiclly excited PM flux lines nd distributions similrity s the flux surges from sttor to rotor nd return through the rotor teeth to generte in complete flux cycles of PM. (b) (d) B. Cogging Torque The cogging torque nlyses for ll mchine types were dignosed by setting rmture current density, J= Arms/mm2. Figure 4 shows the cogging torque investigtion of the exmined PMFSM design mchines, with 4S-8P hving the highest pek-to-pek cogging torque t pproximtely 3.85Nm, followed by 1S-15P, 8S-12P, nd 2S-8P t 3.99Nm, 1.12Nm, nd.58nm, respectively. The high cogging torque cn be reltively reduced s the study continued t the stge of design refinement nd optimiztion. Bsed on the previous study, cogging torque could be further decrese by rotor polenotching, rotor pole-piring nd rotor skewing. T[Nm] S-12P 4S-8P 1S-15P 2S-8P Electric Cycle[º] Figure 4. Cogging torque performnce for 1S-15P, 8S- 12P, 4S-8P nd 2S-8P 1379

4 C. Initil Torque Performnces The resulting dt of initil torque performnces for four design mchines re plotted in Fig.5. The investigtion of torque performnces ws crried out t mximum rmture current densities, J=3 Arms/mm2 for ll design mchines. Figure 5 shows performnces of output torque for ll PMFSM designs, nd 4S-8P computed the highest performnce t 2.47Nm, followed by 2S-8P, 8S- 12P, nd 1S-15P t 1.45Nm, 1.65Nm, nd 1.7Nm, respectively. P[W] s-8p 4s-8p 8s-12p 1s-15p 2.5 T 2 2S-8P 4S-8P 8s-12p 1S-15P J[Arms/mm²] Figure 6. Ouput power versus rmture current densities, J Figure 5. Ouput torque versus rmture current densities, J The clcultion of output power cn be executed by mnipulting the dt of torque nd speed. Since ll the required dt hve been obtined in the previous nlysis, eqution (8) is used to substitute them in. Subsequently, for the rottionl on fixed xis, the clculted power is equl to the multipliction between torque nd ngulr velocity of the rotting piece, which re is defined by equtions (6), (7), nd (8). P = (6) ω = 2πS 6 J (Arms/mm²) (7) P = τ ( 2πS 6 ) (8) Where P is power in kilowtt (kw), τ is torque in Newton metre, nd S is speed in revolution per minute (r/min). Therefore, Fig. 6 emphsizes on the 1S- 15P design, which hs contributed to the highest output power, pproximtely 42.7W, followed by 8S-12P, 4S- 8P, nd 2S-8P t W, 212.2W, nd 56.5W, respectively. D. Torque nd Power Versus Speed The torque nd power versus speed curves of the designed PMFSM design of, 1S-15P, 8S-12P, 4S-8P nd 2S-8P is plotted in Fig. 7, nd Fig. 8. The nlysis results shows tht design torque versus speed of 1S- 15P, the initil speed 2327 r/min nd the resulting torque is 1.65Nm, while the corresponding power reches 42.7W. Design slot 8S-12P t the initil speed of 185 r/min, the resulting torque is 1.65Nm, less compred to 1S-15P FEFSM with corresponding power reches W. Design slot 4S-8P with the initil speed of r/min, the resulting torque is 2.47Nm nd power with 212.2W. Finlly, for the design 2S-8P shows the initil speed of Nm, torque t 1.45Nm, with corresponding power reches 56.5W. As finl point, the overll performnces of the proposed mchine designs re visulized in Tble 3.The resulting dt of initil torque performnces for four design mchines re plotted in Fig.5. The investigtion of torque performnces ws crried out t mximum rmture current densities, J=3 Arms/mm2 for ll design mchines. Figure 5 shows performnces of output torque for ll PMFSM designs, nd 4S-8P computed the highest performnce t 2.47Nm, followed by 2S-8P, 8S-12P, nd 1S-15P t 1.45Nm, 1.65Nm, nd 1.7Nm, respectively. T s-8p 4s-8p 8s-12p 1s-15p Speed(r/min) Figure 7. Torque versus speed chrcteristic 1S-15P PMFSM 138

5 TABLE III. Numbe r of Slot Pole PERFORMANCES COMPARISON OF SLOT NUMBER AND POLE Coggin g torque Mximu m power (W) Mximu m torque Speed (r/min) 2S-8P S-8P S-12P S- 15P T Figure 9. 1S-15P 8S-12P 4S-8P 2S-8P 1S-15P vg 8S-12P vg 4S-8P vg 2S-8P vg Electric Cycle (ᵒ) Instntneous torque of 1S-15P, 8S-12P, 4S-8P nd 2S-8P PMFSM P(W) Figure 8. 2s-8p 4s-8p 8s-12p 1s-15p Speed(r/min) Power vesus speed chrcteristic 8S-12p PMFSM CONCLUSION In this pper, the nlysis of the slot pole combintion for the single-phse PMFSM hs been crried out nd compred. The initil output performnces for flux distribution, cogging torque, speed, output power, nd torque hve been exmined. As result, the 4S-8P PMFSM structure hs composed the highest initil output torque, which produced 2.47Nm, compred with the other three designs nmely 2S-8P t 1.45Nm, 8S-12P, nd 1S-15P t 1.65Nm nd 1.71Nm respectively. ACKNOWLEDGMENT This reserch ws prtly sponsored by the Centre for Grdute Studies UTHM nd Ministry of Higher Eduction Mlysi (MOHE). REFERENCES E. Instntneous Torque Chrcteristics The instntneous torque profile for initil 2S-8P, 4S-8P, 8S- 12P nd 1S-15P is illustrted in Fig. 9. The 4S-8P design hs the higher torque which is pproximtely 2.3Nm more thn 1S-15P, 8S-12P nd 2S-8P design which is torque is t 1.72Nm, 1.64Nm nd 1.44Nm respectively. Menwhile, the pek-pek torque for 4S-8P design is highest t 3.85Nm. Although pek-pek of the instntneous torque for 4S-8PP is high, further design refinement nd improvement will be conducted in the future to get the trget torque, s well s method of reducing the cogging torque. resulting dt of initil torque performnces for four design mchines re sketched in Fig.5. The investigtion of torque performnces ws crried out t mximum rmture current densities, J=3 Arms/mm2 for ll design mchines. Figure 5 shows performnces of output torque for ll PMFSM designs, nd 4S-8P computed the highest performnce t 2.47Nm, followed by 2S-8P, 8S-12P, nd 1S- 15P t 1.45Nm, 1.65Nm, nd 1.7Nm, respectively. [1] A. Z. Husin, E. Sulimn, nd T. Kosk, Design studies nd effect of vrious rotor pole number of field excittion flux switching motor for hybrid electric vehicle pplictions, IEEE 8th Interntionl Power Engineering nd Optimiztion Conference (PEOCO), IEEE 8th Interntionl, Lngkwi, pp , 214 [2] C. Pollock, H. Pollock, R. Brron, J. R. Coles, D. Moule, A. Court nd R. Sutton, Flux-switching motors for utomotive pplictions, IEEE Trnsctions on Industry Applictions, vol. 42, no. 5, pp , October 26 [3] E. Hong, M. Lecrivin nd M. Gbsi, A new structure of switching flux synchronous polyphsed mchine with hybrid excittion, Power Electronics nd Applictions Conference, Europen Alborg, pp. 1-8, 27 [4] E. Sulimn, M. Z. Ahmd, T. Kosk, nd N. Mtsui, Design optimiztion studies on high torque nd high power density hybrid excittion flux switching motor for HEV, Procedi Engineering, Vol. 53, pp , Mrch

6 [5] E. Sulimn, T. Kosk, Y. Tsujimori nd N. Mtsui, Design of 12-slot 1-pole permnnt mgnet fluxswitching mchine with hybrid excittion for hybrid electric vehicle, Power Electronics, Mchines nd Drives (PEMD), 5th IET Interntionl Conference on, Brighton, UK, pp. 1-5, 21 [6] M. F. Omr, E. Sulimn, F. Khn, G. M. Romln nd M. K. Hssn, Performnces comprison of vrious design slot pole of Field Excittion Flux Switching Mchines with segmentl rotor, IEEE Conference on Energy Conversion (CENCON), Johor Bhru, pp , 215 [7] M. Jenl nd E. Sulimn, Investigtive study of novel permnent mgnet flux switching mchine employing lternte circumferentil nd rdil permnent mgnet, ARPN Journl of Engineering nd Applied Sciences, Vol. 1, pp , 215 [8] M. Z. Ahmd, E. Sulimn, Z. A. Hron, nd F.Khn, FEA-Bsed design study of 12-slot 12-pole outer-rotor dul excittion flux switching mchine for direct drive electric vehicle pplictions, Applied Mechnics nd Mterils, Vol. 66, pp , August 214 [9] M. Z. Ahmd, E. Sulimn, Z. A. Hron nd Kosk, Impct of rotor pole number on the chrcteristics of outer rotor hybrid excittion flux switching motor for in wheel drive EV, Interntionl Conference on Electricl Engineering nd Informtics (ICEEI), pp , 213 [1] S. E. Ruch nd L. J. Johnson, Design principles of fluxswitch lterntors, Trnsctions of the Americn Institute of Electricl Engineers. Prt III: Power Apprtus nd Systems, vol. 74, Jnury

Comparative Performance of FE-FSM, PM-FSM and HE-FSM with Segmental Rotor Hassan Ali Soomro a, Erwan Sulaiman b and Faisal Khan c

Comparative Performance of FE-FSM, PM-FSM and HE-FSM with Segmental Rotor Hassan Ali Soomro a, Erwan Sulaiman b and Faisal Khan c Department of Electrical power Engineering, Universiti Tun Hussein Onn