Abstract
Electric machines with high torque density are needed in many applications, such as electric vehicles, electric robotics, electric ships, electric aircraft, etc. and they can avoid planetary gears thus reducing manufacturing costs. This paper presents a novel axial-radial flux permanent magnet (ARFPM) machine with high torque density. The proposed ARFPM machine integrates both axial-flux and radial-flux machine topologies in a compact space, which effectively improves the copper utilization of the machine. First, the radial rotor can balance the large axial forces on axial rotors and prevent them from deforming due to the forces. On the other hand, the machine adopts Halbach-array permanent magnets (PMs) on the rotors to suppress air-gap flux density harmonics. Also, the Halbach-array PMs can reduce the total attracted force on axial rotors. The operational principle of the ARFPM machine was investigated and analyzed. Then, 3D finite-element analysis (FEA) was conducted to show the merits of the ARFPM machine. Demonstration results with different parameters are compared to obtain an optimal structure. These indicated that the proposed ARFPM machine with Halbach-array PMs can achieve a more sinusoidal back electromotive force (EMF). In addition, a comparative analysis was conducted for the proposed ARFPM machine. The machine was compared with a conventional axial-flux permanent magnet (AFPM) machine and a radial-flux permanent magnet (RFPM) machine based on the same dimensions. This showed that the proposed ARFPM machine had the highest torque density and relatively small torque ripple.
Highlights
As an important component of an electric powertrain system, electric machines are welcomed widely in electric vehicles, electrified aircraft, robots, and so on [1,2,3]
This paper proposes a novel axial-radial flux permanent magnet (ARFPM) machine with Halbach-array permanent magnets (PMs) to solve the above problems
The average torque is nearly proportional to the phase current, the increase of torque becomes a little slow when the current is more than 16 A. It shows that the increase of current will not lead to serious saturation in the machine, which means that the ARFPM Fmigaucrhei1n4e
Summary
As an important component of an electric powertrain system, electric machines are welcomed widely in electric vehicles, electrified aircraft, robots, and so on [1,2,3]. Besides the double-side AFPM machines, the multi-disc AFPM machine is proposed to increase the electromagnetic torque for a propulsion system [21] These structures cannot avoid problems such as ending effect and copper loss brought about by winding ends. There will be large harmonics in the air-gap magnetic flux density when the rotor PMs are too close to the stator. The typical case is that slots on the stator are rectangular, while PMs on the rotor are fan-shaped It will deteriorate the air-gap flux density. The sinusoidal rotor segments can provide variable gaps to reduce the harmonics in the air-gap flux density, but this has high requirements for materials It has to be made of a special material with easy machinability and high magnetic permeability. This paper proposes a novel axial-radial flux permanent magnet (ARFPM) machine with Halbach-array PMs to solve the above problems. In order to suppress the harmonics of air-gap magnetic flux, the PMs are arranged as a Halbach array [I2Inn7,oI2orn8rdd]oe.erIrdtttoecoarsnstuuopaplspspurorpeeispsnssrtteethshnesesihthfhayaerrtmhmhaeoornmnmiicacosgsnonoifcefastaiicoirr-ff-glgauaaipxrp-mgdmaeapnaggsnminteyeattigiiccnnffeltluhtuixecx,,afltthiuhrexegP,aPtMpMh.essTaPahrMreeeasararrraaenngagreerddanaasgsed magnetizatioaanHHdaaasilrlbeabacaHctcihohanalabrraorracfayhyP[aM[22r7rs7,a2,i2y8s8][]r.2.eI7Iltta,2ctca8ean]dn. atIaoltlsscotoahinienntanteleunsnosmsiifbfnyyettrethnhoeesfimfmsyeaaggtghmnneeeetmntiictcasfgflplunuexexrtdidpceeonflnlsuesiitxptyydaiiinernn.tsthAhietseyaaiiinrrgtghaapep.a.TiTrhhegeap. shown in FigmmuaraeTggnh3neeaet,mtiiiznzaaagtctianioosennetidztdhaiiretreieoPcctnMtiiodosnniraoerocfeftPitPooMnMosonsfaiisPrsrMroreewlslaaittsteoedrdeblteatootmettdhahenteounnftuahumcemtubnberueermrdoo,bfefesarseceoghgfmmpseeoegnlnemttsspepanpeitersrrippspeoorllepeopplaeaiirpr..aAiAr.ssAs dtmPsuqMiavrungisad.n,reeeFtdthiwigezinuaavtntroieeoosdtmPsfssdtmPsrunhqo3uMiihqmMiavrxuorbavrduonwgsdimPmiswnaagnsidhswai.n,Midrlses.an,av,renoehettgFenvtegeadriFrsuwtthodmiwieetih,innigwinrbiezwifgsnetezdeninueaoauhinduaFatdsn.vtrniFtretitvtnotrniimeziutheoioigioFeoetsnongoafsaehrFuni,f,nso3rounttimglo3eisiaxriomtrbrgxrdouraobeonmdmmaesmusnnsairfsd3lsteisice,r3lseasgahxhetag,dhehtaagrltrgeea3,aormrhiesein,omr3nncesiibbnwemsmeeibnwdahtseteunidgseriui,sdsnttaaaiicdtsmntsaihidcbttiutghtlazneiunothtasiouuotnesaaesrhgc,ngsaehwcee,nattnleemsetleiiaessltdttaooootsnmiaosoisthemnsdinfznhe,ntstfatncetgaahiucehesagghhaotettghedeaoPahge.lreieaefPnncoeliaMenBmnmrctseMshmmtenmmehhetyticaPtasisraatehsasidcaaaMiiigstlczeabzhdgtelziimogeaonarigcrraumnaursgcrfnentseeemteatetieamseiaecdttioaistgtodtioilrgottrtehoiditinzieaninoedinmazmnnozeoaauncsoegauttandtgtdaatet.onrdidnota.niiroglwinaoiBosazolfisaoioBannmmsttafraytnmmirrnn.rytrrHegtetmidrraihoBaidctbaraiobdociiogabrwoayauciogzrwoutinrlfrnunemhlshatbfnonetciectttttdieatoewctoarstorioittthorcotiooteiihnainncnbioairzehbgnnfsotzeodbteusanooe-trmancntetanotdfathnowttoimbtivrwfoseoiomiiHoaeforfosoeetnirfnnanatHirtenannmanwHttmrehnmygalhdntiioaavbduobeasiciaautiacolrtaaPnthlifushflbahnhmlshfnbarctMteetaaltuarsihiecaaistarseaaccaieonthfoc-clibesnshtcluclgabanodhueguahod-scbrmrauni-rmarrmrittnecsynaetssretivuaroedtivoaraseddrayoa6earnnnri,nneagnnel,nd0nnalotvenlPtygsmgdte°yetgiautavoetMiesieav,rniesiocaenaPnd.nocaeasaPnhglnnrsatMhtmnarliMiteialtsiieopciaasesnpoalasvshnollossltolanasballiiprsblreeaormisrlyreemrsoiyrletrapeas.a6plasnraiars6nenalid0neaorld0igsob°lsepauigrt°equretiyrniaeadriuid.naaisgd.nla6surale0raide◦sl back iron bbaacckkiriroonn back iron bbaacckkiriroonn (a)
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