Sensos & Tansduces 214 by IFSA Publishing, S. L. htt://www.sensosotal.com Study on Pemanent agnet Synchonous Demagnetization Fault Pefomance 1, 2 Zhiyan ZHANG, 1 Hongzhong A, 2 Cunxiang YANG, 3 Duanlei YUAN 1 College of Enegy and Electical Engineeing, Hohai Univesity, Fucheng West Road No. 8 Nanjing City Jiangsu Povince, 2198, China 2 College of Electical Infomation Engineeing, Zhengzhou Univesity of Light Industy, Dongfeng Road No. 5 Zhengzhou City Henan Povince, Zhengzhou 452, China 3 inisty of Science and Technology State Gid Pinggao Gou Co. Ltd., Nanhuan East Road No. 22 Pingdingshan Henan, 4671, China 1 Tel.: 153972321, fax: 3716355679 E-mail: 54146459@qq.com Received: 18 Ail 214 /Acceted: 3 ay 214 /Published: 3 June 214 Abstact: The elationshi of emanent magnetic mateial chaacteistic aametes was analyzed, and a simulation method of a emanent magnet synchonous moto (PS) oto demagnetization fault was ut fowad. ased on this, a simulation model of the PS unde atial demagnetization and unifom demagnetization fault wee established, and diffeent degees demagnetization fault was simulated. Relationshi between outut toque and initial hase was gained by alying diffeent initial angle cuent excitation souce in ode to establish the easonable simulation model. Simulation esults show that magnetic field stength and outut toque get smalle and smalle with inceasingly fault seveity. The magnetic field asymmety of PS atial demagnetization is moe and moe seious with inceasingly fault seveity, and the magnetic field scale of PS unifom demagnetization deceased significantly. The hamonic analyses using Fast Fouie Tansfom (FFT) show that the fault diagnosis method based on the hamonic wave analysis is only suitable fo atial demagnetization fault of the PS, and not aly to unifom demagnetization fault of the PS. Coyight 214 IFSA Publishing, S. L. Keywods: PS, Demagnetization, Fault, Simulation. 1. Intoduction Pemanent magnet moto with high owe density and high efficiency is the best choice of electic vehicle diving moto. PS the same as conventional moto when they long-tem un will be ossible to aea fault, such as beaing fault, eccenticity fault, etc., which seiously affect the safety and eliability of moto oeation. And because emanent magnets ae embedded in emanent magnet moto oto, the emanent magnet demagnetization fault is the secial fault tye. The main eason of the emanent magnet demagnetization is the amatue eaction induced by high temeatue and lage cuent, esecially the amatue eaction unde the big toque condition, and big cuent by the shot cicuit cuent of the invete and the stato winding faults, and oveload cuent. PS stato winding inte tun shot cicuit fault will cause shot cicuit cuent inceasing and the temeatue ising, which causes the PS unbalanced oeation, if the futhe develoment of 82 htt://www.sensosotal.com/htl/digest/p_2152.htm
fault, the moto will be the seious fault including the inte hase shot cicuit fault and hase to gound fault [1]. These faults, oveload oeation and instantaneous oveload oeation will oduce lage cuent highe than the ated cuent fo seveal times, and lage cuent will oduce vey big evese magneto-motive foce which will have stong demagnetization to emanent magnets inceasing the demagnetization obability. agnetic domain of emanent magnet will move unde high temeatue, which makes them eaange thei location in the diection of stability, and the magnetic field offset each othe, so that the emanent magnet is not dislay magnetic to extenal, namely occuence demagnetization henomenon. Thee ae two main easons of high temeatue demagnetization. On the one hand, eddy cuent loss affected tooth hamonic esults in highe temeatue incease unde the PS nomal oeation; On the othe hand, in ode to meet the efomance equiements PS stuctue design equie high close degee, high enegy emanent magnets and lage winding fill facto in some secial occasions, but these design equiements is not conducive to dissiate the heat and the PS unning envionment cooling conditions, which will esult in the emanent magnet oeating oint temeatue is futhe inceased, inceasing the emanent magnet demagnetization fault ossible. In ode to meet the load demand unde PS demagnetization fault oeation, thee is need to incease the stato cuent oducing the lage oosite magnetic otential and making the PS temeatue futhe ise, which fom a vicious sial. At last, the emanent magnets oeate below the woking oint of magnetic so that thee ae oduce ievesible demagnetization. In addition, the defect of emanent magnet mateial itself, such as the easily cooded Nd-Fe- and the PS highseed oeation will make emanent magnet salling and esulting in demagnetization. On the othe hand, sinteed ae eath emanent magnet is vey fagile, so that thee is likely to oduce atial demagnetization duing the oduction, tansot and oeation. At esent, the object of eseach on moto fault diagnosis ae mainly taditional lage moto, such as asynchonous moto stato fault [2, 3] and oto fault [4-7], and synchonous moto winding fault [8, 9] and oto fault [1, 11]. Reseach on PS fault diagnosis at home and aboad is elatively less, and the main study is in aboad. Demagnetization of PS will geneate secific hamonic in the stato cuent [12, 13]. Thee ae diffeent diagnosis method based on diffeent signal analysis method of the stato cuent, and diagnostic methods mainly include Hilbet-Huang tansfom (HHT) [14], Continuous Wavelet tansfom (CWT) [15], Discete Wavelet tansfom (DWT) [15], Fast Fouie Tansfomation (FFT) [16]. In addition, thee ae anothe method of equivalent netwok [17, 18], which use ai-ga emeance netwok as emanent magnet equivalent of emanent magnet synchonous moto in ode to online diagnosis of emanent magnet demagnetization fault though measuement of the flux. The PS oto demagnetization wee studied in the ae taking Pius hybid vehicle inteio PS of the Toyota as an examle. Afte the demagnetization fault ealization method was studied, the atial and unifom demagnetization simulation model was established. The efomance of the PS demagnetization fault unde no-load and load conditions wee obtained by analyzing the electomagnetic aametes and efomance cuve afte demagnetization fault. Some meaningful conclusions ovide a stong basis fo fault diagnosis of the demagnetization. 2. Chaacteistics Quantity Selection of PS Demagnetization Fault Accoding to the liteatue [15], the secial fequency signal of the stato cuent will be geneated afte PS oto demagnetization fault, and the elationshi between the fault fequency and owe fequency can be exessed the flowing, f k = f s (1 ), (1) dmg ± whee f deg is the fault fequency, f s is the owe fequency, k is the intege, 1, 2,... and is the oles ai of PS. Tye (1) can also be exessed as, f dmg = f s ( k ±1), (2) So we can samle the stato cuent signal and acquie the stato cuent sectum using signal tansfomation method to analyze of its hamonic comonents, then diagnose the oto demagnetization occuence and judge the seveity degee of demagnetization. In fact, unifom demagnetization fault is not aeaing the new hamonic, even if atial demagnetization is likely to oduce the same fault hamonic because of the influence of envionmental noise o measuing equiments. So that the new hamonic aeaing is not as the fault diagnosis chaacteistics quantity, but the size of hamonic can be egad as atial demagnetization fault diagnosis basis. 3. PS Simulation odel Establishment unde Nomal and Demagnetization Condition 3.1. Simulation odel Establishment Finite element (FE) analysis method is a numeical analysis method, which can be used to 83
analyze vaious chaacteistics unde static, tansient, steady state, nomal condition and fault condition of electomagnetic device, such as moto, tansfome, and so on, because the method can eflect the influence of moto intenal facto and establish the most accuate moto model. In this ae, based on Ansoft softwae latfom, simulation model fo the PS of Pius hybid vehicle is established, Pemanent magnet tye is N36-Z2 and inteio V distibution, and owe suly is the invete owe suly, and the stato winding is a single-laye coil stuctue. Rated owe, seed and voltage ae 5 kw, 3 m and 38 V esectively. Numbe of ole ais and stato slots is 4 ais and 48 slots. Accoding to the moto stuctue symmety and the simlification model incile of FE analysis method, a ai of magnetic oles is modeled as shown in Fig. 1. = /μ, (4) The emanent magnetic mateial coecivity H c efes to the size of H when magnetic induction intensity is not zeo. Woking oint of emanent magnet above the hysteesis loo, the demagnetization cuve is linea, and then the elationshi between the magnetic field stength, esidual magnetic induction intensity and the elative emeability μ of the thee can be exessed as, = H = μh, (5) H c = μ = μ μ, (6) H c Obviously, tye (4) cannot be used as a basis fo analysis of demagnetization fault. Fomula (7) can be by fomula (3) and (4). = H c + μ, (7) Fig. 1. 1/8 PS simulation mode. 3.2. Demagnetization Fault Simulation ethod If the diection of extenal magnetic field stength H is evesed, at the demagnetization cuve of the emanent magnetic mateials unde the coodinate system, the magnetic induction intensity can be exessed as, μ H + μ =, (3) whee μ is the vacuum elative magnetic emeability, H is the extenal magnetic field stength and is the olaization intensity. Pemanent magnet efomance is usually exessed by fou aametes, namely the elative emeability μ (exessed μ in Ansoft softwae), the coecivity H c, esidual magnetic induction intensity and olaization intensity. Residual magnetic induction intensity efes to magnetic induction intensity when the magnetic field intensity H is zeo. The elationshi between the olaization and esidual magnetic induction intensity can be deived as shown in fomula (4). Accoding to detemine the woking oint unde nomal oeating conditions and tye (5), the fou aamete of tye (7) can be obtained. If all the emanent magnets occu unifom demagnetization fault, magnetic induction intensity become the oiginal 75 %, namely 25 % demagnetization, denoted as dmg, then dmg / =. 75, this can be exessed as, dmg μh = μ H cdmg c + + dmg, (8) whee subscit dmg is the fault aamete. Theefoe demagnetization simulation ealization is only change the size of is not aoiate accoding to the definition. ased on Ansoft softwae latfom, the emanent magnet synchonous moto with diffeent degee of demagnetization fault simulation can be changed by emanent magnetic mateial aametes of H c and. 4. Analysis of the PS Patial Demagnetization Fault Pefomance PS demagnetization fault can be divided into two kinds. One is entie emanent magnet oles occuence unifom demagnetization to a cetain extent, which is called whole demagnetization o 84
unifom demagnetization, and two is atial emanent magnet oles occuence demagnetization to a cetain extent, which is called atial demagnetization o local atial. Pemanent magnet demagnetization fault is usually whole emanent magnet oles demagnetization called unifom magnetic, because the symmety magnetic cicuits esult in demagnetization magnet-motive foce (F) of the stato cuent action on all of the emanent magnets. 4.1. Analysis of Pefomance unde No-load If the one magnet in 1/8 simulation model occus demagnetization, accoding to the above ealization method of demagnetization fault simulation, emanent magnet aametes ae modified to ealize the thee degees demagnetization fault simulations occued in 25 %, 5 % and 75 % unde no-load steady-state. The magnetic field stengths ae shown in Fig. 2. In Fig. 2, thee ae the maximum values of the magnetic field stength of nomal, 25 % demagnetization, 5 % demagnetization and 75 % demagnetization ae 1.7294e-2 wb/m, 1.471e-2 wb/m, 1.1951e-2 wb/m and 9.834e-3 wb/m esectively. At the same time, the magnetic field stength is moe and moe weak and the magnetic field in homogeneity is moe and moe seious along with the augment of demagnetization fault seveity. (a) nomal (b) 25 % demagnetization (c) 5 % demagnetization (d ) 75 % demagnetization Fig. 2. Flux lines of the oto nomal and diffeent degees demagnetization unde no-load steady state conditions. 4.2. Influence of Simulation Paametes and PS Outut unde Tansient Condition The moto aametes ae analyzed to detemine the best moto stuctue and obtain the best moto efomance. Thee-hase sinusoidal symmetical cuent is alied though the stato windings when tansient is simulated. In ode to make noticeable simulation effect, the load cuent eak is 4 A and hase sequence is A+C-+, and the length of simulation time is 1 ms. The PS outut toque is diffeent if the PS is alied cuent souce excitation of diffeent owe angle. In ode to obtain the maximum outut toque and otimize the initial aametes of the simulation, making the efficiency of the PS achieve otimal and outut owe each the maximum unde the same condition, the ae simulate the owe angle aametes between and 6 degees of cuent souce excitation, and the simulation esults ae shown as Fig. 3. 85
[Newtonete] 35. 3. 25. 2. Cuve Info thet_deg='' thet_deg='15' thet_deg='2' thet_deg='3' thet_deg='45' thet_deg='6' 15.. 2. 4. 6. 8. Fig. 3. The elationshi between outut toque and time unde diffeent initial owe angle. As is shown in Fig. 3, 45 degees of the initial hase angle is a tuning oint of the moto outut toque, so the angle of 45 degees is the oint of the moto outut toque maximum toque. Dynamic simulation is imlemented in nomal, 25 % demagnetization, 5 % demagnetization and 75 % demagnetization of a ole ais esectively when owe angle is 45 degees. The size of the PS outut toque in the simulation is as shown in Fig. 4. In Fig. 4, thee ae the PS outut toqueses deceasing along with demagnetization degee inceasing in atial demagnetization. The PS outut toque is esectively 387.5 N, 357.7 N, 327.44 N and 298.1 N unde at nomal woking, single ole occuence 25 % demagnetization, 5 % demagnetization, and 75 % demagnetization. oeove, the outut toque is educed to about 23 % of nomal outut toque when a single ole eached 75 % demagnetization. [Newtonete] 43. 42. 41. 4. 39. 38. 37. 36. 35. 34.. 2. 4. 6. 8. (a) nomal Cuve Info 375. 365. 355. 345. 335. [Newtonete]385. Cuve Info 325.. 2. 4. 6. 8. (b) 25 % demagnetization [Newtonete] 355. 345. 335. 325. 315. Cuve Info [Newtonete] 32. 31. 3. 29. Cuve Inf o 35.. 2. 4. 6. 8. (c) 5% demagnetization 28.. 2. 4. 6. 8. (d) 75% demagnetization Fig. 4. Outut toque of the oto nomal and diffeent demagnetization unde load tansient state conditions. 86
4.3. Patial Demagnetization Fault Hamonic Analysis The PS flux signal unde the nomal state is analyzed by FFT method. The analysis time is a cycle, namely the fundamental fequency is 2 Hz, and the hamonic comonent size is as shown in Fig. 7. Fo bette comaison of the hamonic comonent size and acquisition the most chaacteistic quantity sensitive in nomal, 25 % demagnetization, 5 % demagnetization and 75 % demagnetization, the hamonic comonents of fou cases is analyzed and can be exessed as shown in Fig. 5. 5. Pefomance Analysis of the PS Unifom Demagnetization 5.1. Flux Linkage Analysis unde Tansient Condition Alying the sinusoidal AC voltage souce, setting the esistance and eactance aametes, a simulation model was established. The simulation flux linkage wavefom unde the emanent magnet of nomal, 25 % unifom demagnetization, 5 % unifom demagnetization and 75 % unifom demagnetization at the seed of 3 m ae shown in Fig. 6. hamonic amlitude(wb).4.35.3.25.2.15.1.5 nomal 25% 5% 75% ( ) flux wb.5 X: 17 Y:.562 -.5 time( ms) (a) nomal ( ) flux wb.5 X: 17 Y:.3966 -.5 time( ms) (b) 25% demagnetizaation x 1-3. 1 2 3 4 5 6 7 8 9 1 11 12 13 14 15 hamonic numbe (a) hamonic size ( ) flux wb.2 -.2 X: 17 Y:.2241 ( ) flux wb 5-5 X: 17 Y:.712 hamonic amlitude(wb).12.1.8.6.4.2. 2 3 4 5 6 7 8 9 1 11 12 13 14 15 hamonic numbe (b) hamonic incement 25% incement 5% incement 75% incement Fig. 5. Flux linkage hamonic analysis using FFT of the oto diffeent conditions. In Fig. 5, when the oto of the PS occu demagnetization fault the flux linkage fundamental wave amlitude significantly educes elative to the oto nomal condition, and with the incease of oto demagnetization degee the fundamental wave amlitude gets smalle and smalle. In Fig. 5(b), even hamonic amlitude is vey small, and the hamonic amlitude of vaiation is not obvious with the demagnetization degee seveity. ut the odd hamonic amlitude is obviously inceased with the demagnetization degee seveity. It is wothwhile to note that 9 times and 13 times hamonic amlitude changes is elatively is not vey clea, so they should not be selected as the fault featue to diagnose fault occuence. time( ms) (c) 5% demagnetization time( ms) (d) 75% demagnetization Fig. 6. Flux linkage unde vaious load oeation conditions. The stato flux wavefoms ae sinusoidal wavefom and the amlitudes ae.56 wb,.4 wb,.22 wb and.7 wb esectively in Fig. 6 unde nomal, 25 % demagnetization, 5 % demagnetization and 75 % demagnetization of the PS, which with the seveity of fault incease is deceased significantly, but not ootional elationshi. ecause the stato winding flux linkage equation can be exessed as, Ψ Ψ Ψ A C L = AA A CA L AA C L AC C CC i i i A C Ψ + Ψ Ψ fa f fc, (1) whee A, C and AC ae the mutual inductance between thee-hase winding, L AA, L and L CC ae the self inductance of thee-hase winding, Ψ fa, Ψ f and Ψ fc ae the thee hase winding flux by the emanent magnet excitation. The equation (1) shows that the fist item oduced by the stato winding of the thee-hase cuent alying the same excitation is equal unde 87
the nomal and demagnetization fault oeation of the moto condition, but the second item is oduced by emanent magnet is deceased in ootion to demagnetization degee. So the total flux is not in ootion to the change of demagnetization degee. 5.2. Flux Linkage Hamonic Analysis Abitay data of a hase in Fig. 6 fo hamonic analysis, the esults ae shown in Fig. 7. ( ) flux d ( ) flux d -5-1 -15-2 -25 hamonic( time) ( a) nomal -5-1 -15-2 -25 hamonic( time) ( c) 5% demagnetization ( ) flux d -5-1 -15-2 -25 hamonic( time) ( b) 25% demagnetization -5-1 -15-2 -25 hamonic( time) ( d) 75% demagnetization Fig. 7. Hamonic chat of flux unde vaious oeation conditions of the PS. In Fig. 6 and Fig. 7, the PS time-domain wavefom and hamonic analysis wavefom duing nomal oeation, the model of the moto is ideal, and the flux is basic confom to the change ule of sine wavefom. Fig. 7 vetical coodinate is d (2log), and unde nomal oeation, 25 %, 5 % and 75 % demagnetization oeation conditions, fundamental wave amlitude gadually deceases, and the 3 and 9 hamonics elative value with the seveity of fault is gadually educed, and no new hamonic comonents occu, thus the cuent and back EF hamonics comosition analysis does not have obvious esults to demagnetization fault. ased on this, the hamonic analysis method is invalid to diagnose a PS unifom demagnetization fault. 5.3. Toque Analysis The unifom demagnetization toque unde vaious woking conditions eseach esults show that the outut toque of the PS is esectively 387.5 N, 191.2 N, 7.5 N and 2.8 N unde nomal oeation, 25 %, 5 % and 75 % unifom demagnetization oeation. Theefoe the outut toque is obviously deceased along with the incease of demagnetization degee. While all oles demagnetization ate eached 75 %, the outut toque is educed to about 5 % of the nomal outut toque. ( ) flux d 6. Conclusions Patial and unifom demagnetization fault of the PS in vaying degees unde no-load and load state ae simulated using FE analysis softwae in this ae, and the simulation esults show that the easonable demagnetization fault wavefom can be obtained by changing the emanent magnet mateial aametes. And initial hase of excitation souce has geat effect on the outut toque of PS, when initial hase angle is 45 degees, the PS moto efomance is the best and outut toque aives maximum. And the esults of atial demagnetization and unifom demagnetization simulations show that the magnetic field stength and the outut toque will be educed with the incease of demagnetization fault seveity, but the unifom demagnetization of the PS will be significantly deceased than the atial demagnetization. The hamonic analysis show that the 3 times, 5 times, 7 times, 11 times and 15 times hamonic amlitude is inceased significantly unde the atial demagnetization fault condition, hence they can be selected as the fault featue to diagnose fault occuence. ut the 3 and 9 hamonics elative value inceased with the seveity of fault is gadually educed unde the unifom demagnetization of the PS, and no new hamonic comonents aea. Theefoe, the hamonic wave analysis method is not suitable to diagnosis of unifom demagnetization fault occuence and seveity. The conclusions in the ae ovide the basis fo the demagnetization diagnosis. Acknowledgements We exess ou gatitude to the develoment of automobile industy of Shanghai Science and Technology Fund Foundation (Gant No. 116), because they ovide eseach funding. The PS and at exeimental equiment of the eseach was efomed with the suot fom new enegy automotive business deatment SAIC oto fo which we exess ou gatitude. Refeences [1]. Li Liu, David A Cates, On-line identification and obust fault diagnosis fo nonlinea PS dives diagnosis fo nonlinea PS dives, in Poceedings of the Ameican Contol Confeence (ACC 5), Potland, United States, 8-1 June 25,. 223 227. [2]. Rangaajan. Tallam, Thomas G. Habetle, Ronald G. Haley, Self commissioning taining algoithms fo neual netwoks with alications to electic machine fault diagnostics, IEEE Tansaction on Powe Electonics, Vol. 17, Issue 6, 22,. 189-195. [3]. Wang Xuhong, He Yigang, Inte tun fault detection of asynchonous moto stato winding based on diagonal ecuent neual netwok, Electic Powe 88
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