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1 Univeity of Huddefield Repoitoy Lne, Mk, Sheboub, bdulkim, Gu, Fenghou nd Bll, ndew Invetigtion of Reduction in Moto Efficiency cued by Stto Fult when opeted fom n Invete Dive Oiginl Cittion Lne, Mk, Sheboub, bdulkim, Gu, Fenghou nd Bll, ndew (26) Invetigtion of Reduction in Moto Efficiency cued by Stto Fult when opeted fom n Invete Dive. In: Poceeding 22nd Intentionl Confeence on utomtion nd Computing (ICC). IEEE. ISBN Thi veion i vilble t The Univeity Repoitoy i digitl collection of the eech output of the Univeity, vilble on Open cce. Copyight nd Mol Right fo the item on thi ite e etined by the individul utho nd/o othe copyight owne. Ue my cce full item fee of chge; copie of full text item genelly cn be epoduced, diplyed o pefomed nd given to thid ptie in ny fomt o medium fo peonl eech o tudy, eductionl o not fo pofit pupoe without pio pemiion o chge, povided: The utho, title nd full bibliogphic detil i cedited in ny copy; hypelink nd/o URL i included fo the oiginl metdt pge; nd The content i not chnged in ny wy. Fo moe infomtion, including ou policy nd ubmiion pocedue, plee contct the Repoitoy Tem t: E.milbox@hud.c.uk.

2 Invetigtion of Reduction in Moto Efficiency cued by Stto Fult when opeted fom n Invete Dive M. Lne. Sheboub F. Gu.D. Bll Cente fo Efficiency nd Pefomnce Engineeing Univeity of Huddefield Huddefield, UK mk.lne@hud.c.uk btct Invete diven moto ytem hve een wide ue in induty enegy eduction method. Studie hve been undetken peviouly to undetnd the effect of voltge imblnce on moto efficiency nd deting. Howeve, thi h not been coveed in much detil on invete-diven moto ytem. Thi ppe im to tudy the effect tht moto tto eitnce imblnce hve on moto efficiency when ued on invete-diven ytem. Moto imblnce my emin undetected by the invete dive nd cn eult in oveheting nd pemtue filue of the moto. Moto efficiency monitoing i now of gete inteet due to new IEC tndd defining new C moto efficiency cle nd thi i lo eviewed long with the tndd fo moto efficiency nd invete-opeted moto. Keywod ymmety, Efficiency, Unblnced, Stto eitnce incee, Moto Cuent Signtue nlyi (MCS), Invete Field Opeted Contolle (IFOC), Rndom witching ptten. moto tet ig, the opeting mode i contnt toque becue it i poible to pply full lod to the moto co the opeting peed nge. Figue how the eltionhip between invete fequency nd powe loe in the moto, P fo diffeent pule L fequencie f.lowe pule fequencie led to highe loe P in the moto due to the effect of pek hmonic cuent cued by the educed witching cycle. Conveely, loe in the invete incee with highe witching fequency. It i theefoe popoed to ue the defult witching fequency of 3Khz with the tet invete ued fo thi tudy compomie between moto nd invete efficiency. I. INTRODUCTION The tend fo intlling invete dive to incee efficiency of induction diven ppliction i wideped. Howeve once the moto nd dive i intlled, thee my be little o no ttention pid to continued efficient opetion of the ytem. Stndd IEC , publihed in Mch 24 tipulte thee efficiency level fo thee-phe induction moto, IE to IE3. Phe 2 of the EU efficiency level legiltion (IE3) cme into effect fom Jnuy 25 tting tht thee-phe induction moto with ted output fom 7.5 to 375kW mut now meet the IE3 efficiency level o IE2 when opeted fom n invete dive. Futhemoe, n updted tndd IEC now include fo IE4 moto [] opeted diectly on-line to the upply. Pt 2 of thi tndd DD CLC/TS :28 [2] cove moto diven by invete dive. The tndd lit viou fcto tht cn ffect moto efficiency when opeted fom invete dive nd thee e lited in the tndd. Thee e: - Optimition of moto flux depending on lod - Optimition of pule ptten - Switching fequency Fo fn/pump ppliction, the moto flux i educed t low peed becue of the low toque equiement thi i uully temed qudtic toque opetion. The efficiency of n intlltion- cn intntly be compomied if the enginee elect the wong opeting mode fo the ppliction. On the Fig. Loe of moto due to witching fequency [2] Fcto tht will ffect moto life due to unequl tto eitnce in opetion e inceed te in the moto winding cued by the cuent nd voltge imblnce which cn then led to inceed moto loe nd high unning tempetue eult of imblnced cuent flow. Thi in tun cn cue to toionl ocilltion of the oto, hotening the lifepn of equipment nd conequentilly in evee ce, mechnicl filue [3]. The cue of tto eitnce ymmety e vied but cn be linked to wiing connection cooion due to tmopheic o mechnicl effect in the dive o moto temintion, cble fult o poo intlltion technique t the outet. Figue 2 give the deting cuve to pply when pecentge voltge unblnce i peent. Fig. 2 NEM Deting Cuve to pply fo voltge imblnce If the eduction in moto efficiency cn be meued nd belined t n ely tge, it will be poible to mintin the equipment t the efficiency level it w when fit intlled.

3 Thee e dvntge to induty if deteiotion in moto efficiency cn be clculted by the invete dive whilt the equipment i in-evice. G.. McCoy [4] hve publihed guidnce note fo induty on mintining efficiency of plnt epecilly with egd to voltge unblnce. It i tted tht voltge unblnce of even % equie moto to be deted. Reitnce imblnce hve the me effect nd if unchecked cn led to pemtue moto filue. If conidetion i lo given to the heting effect tht voltge imblnce cn cue, it cn be ccepted tht Montinge ule would pply which tte tht n incee in moto tempetue by C will led to eduction in the moto expected opetionl lifepn by 5%. Studie by Jinghn Zhng [5] et. l. concened the detection of open cicuit fult in PWM convete uing the moto cuent ignl meued. Thi cue imblnce on the upply to the moto nd the eult of thi e obeved fte tnfoming the, b, c phe cuent into the d, q efeence fme fo nlyi. The dignotic method w poved to wok fo ingle nd double tnito open-cicuit fult. Howeve, tudy into the moto efficiency eduction w not noted. Sng Bin Lee [6] et. l. popoed new ttegy fo condition monitoing of djutble peed induction mchine dive ytem tht could be ued fo off-line nlyi of component uch DC link cpcito, electicl cbling, tto nd cble inultion, tto coe nd oto b. The offline technique doe not equie pectl nlyi of the moto ignl o hve ecoue to moto mthemticl model nd by being n off-line tet i independent of moto opeting condition uch fequency o lod tht hve to be conideed in n on-line ytem. Reitive imblnce cn be meued when the moto i t tndtill fom the DC link voltge nd thi cn help to benchmk moto connection condition t tge in the moto opeting life. Cmil P. Slomon et. l.[7] peent wok on induction moto efficiency evlution uing n i-gp toque method bed on the enole toque eqution developed nd ued pticle wm optimiztion method on the dt. Thi wok w cied out on n invete dive tht w fed fom diect upply ouce. The output toque etimted uing the clcultion w comped to the mechnicl output toque nd conideed good ppoximtion. Yunhu Li et. l. [8] peent novel method to detemine the moto efficiency unde vible peed nd ptil lod condition. The model w teted on helthy moto connected to n invete dive with clcultion bed on the moto peed nd powe tken fom the invete dive tndd nlogue o digitl communiction output. The clcultion eo fo thi model wee found to be +/- 5% fo 4-pole moto unde contnt peed condition but the model ccucy i moe uncetin t lowe peed tio condition. Moto Cuent Signtue nlyi, MCS i poven to elibly detect moto fult including winding inte-tun fult, i-gp eccenticity nd boken oto b. Shifi, R. et. l [9] combined MCS nd exmintion of Roto Slot Hmonic to dignoe inte-tun hot-cicuit fult in moto tto winding on non-invete diven moto. Rohn Smi et. l. [] tudied the ely detection of voltge imblnce in thee-phe moto uing ptten clifiction technique uch Pk Vecto Modulu with Wvelet nlyi followed by ptten clifiction. Futhe eech by lwodi et. l. uing MCS [] h lo been conideed with egd to detecting boken oto b nd identify the ditinctive fetue of fequency pect ocited with thee fult. Thi ppe etblihe tht the efficiency nd unblnce of n invete-diven moto cn be meued uing the moto cuent nd voltge ignl meued uing eno connected between the dive nd moto. Vying degee of unblnced condition e meued gint beline moto dt uing pot-ignl poceing technique developed in MTLB. Futhe ignl poceing technique uing pectl nlyi e lo pplied to the dt ecoded nd comped to othe method.. II. TEST FCILITIES ND FULT SIMULTION. Tet Rig The tet ig hown in Figue 3 i deigned to hve tet diving C moto nd loding DC moto. The C moto i thee-phe induction moto with ted output powe P of 4 kw t be peed N ted of 42 RPM (two-pole pi). Moto ted cuent I ted i 9.2 with mgnetiing cuent I m of 5.2. The C moto i diven by Pke 69 PWM invete with 3 khz witching fequency nd cie fequency elected by ndom ptten geneto enbled by defult. The dive i et to opete in enole vecto contol fo ll tet. The DC moto i hunt-wound deign to pply diffeent loding to the C moto dive ytem. The peed, lod nd tet dution e ll pogmmble fom Siemen PLC theeby llowing fo ccute nd epetble moto loding. The DC moto egenete to the min upply though fou-qudnt two phe DC dive. Dt i cptued uing Sinoce 24Bit /D Dt cquiition unit nd impoted into MTLB fo futhe poceing. Fig. 3 Lbotoy Tet Rig

4 B. Opeting condition The tet cycle conit of five loding incement pplied to tet moto unning t contnt peed. Ech of the five loding incement e epeted thee time, mking totl of 5 lod tep illutted in Figue 4. n exmple plot i hown below thi tet tep digm to indicte how the tet eult e peented. Whee veticl line e hown in ny plot, thee epeent the tt of ech new lod tet cycle. % % Time 2 Fig. 4 Tet cycle nd exmple plot The tet un dt detiling tet un peed, dution of tet nd C moto loding i peented in Tble I. Step numbe TBLE I. RPM TEST CYCLE DT Step dution() (% of moto FLC) C. Moto beline dt In ode to contuct dt et tht cn be ued elible compion between helthy moto nd one with imulted fult, two epte tet un fo the helthy moto wee un with the moto up to full opeting tempetue (Mode in Tble II). The eult of thee tet un will be comped to check the obutne of the teting method. D. Fult Simultion Fo comptive helthy nd fulty moto dt, the dive would be un fo ech tet cycle in the following thee mode follow: TBLE II. Dive Mode Tet Cycle 2 4 Dive opeting mode. Helthy moto uto-tuned 2. Moto with imulted tto fult of.2ω 3. Moto with imulted tto fult of.4ω Thee e numbe of phe eitnce incement vilble on the tet ig in.ω tep obtined by chnging the wiing tpping on the cutom-built eito unit Tet Step The eitnce fult imulted i tht which occu in one winding inide the C moto theeby ffecting only one moto phe in t-connected moto. Thi i indicted in Figue 5. Connecting Cble eitnce M Invete Dive M2 M3.3Ω.3Ω.3Ω Moto Teminl Box U U 2 U 3 R.2Ω R.4Ω Unblnced eitnce F SW R S R S2 R S3 i S i S2 i S3 ψ S ψ S2 ψ S3 Fig. 5 Moto mgnetiing cicuit detiling the tto phe eitnce fult ineted in one of the thee phe connection intenlly in the moto on phe (STR cicuit) The connecting cble eitnce fom dive to moto w meued t.3ω fo ech phe. Theefoe, t the mximum fult eitnce intoduced of.4ω the totl eitnce between the dive nd moto i inceed fom.3ω to.7ω in the fulty phe leg. The dditionl fult eitnce ineted will be efeed to the eitnce R. The effect of eitnce f incee in one phe of the tto equivlent cicuit eqution in t connected mchine i given by: dψ dψ V = Ri+ = V = ( R f + R ) i+ = () Thi imblnce ceted in the tto cicuit h the effect of educing the mgnetic flux geneted by one of the tto winding in popotion to the vlue of R. The effect of thi i f to be tudied fo moto inefficiencie comped to noml unning condition. It i popoed to ue lgoithm developed in MTLB to clculte moto efficiency bed on the following meuement tken fom the tet ig: Phe voltge, b, c Phe cuent, b, c Moto peed Moto tempetue i lo monitoed nd ecoded o tht the genel opeting condition of the moto cn be obeved nd enue tht the effect of moto tempetue on the meued eult i kept to n bolute minimum. E. Effect on VSD Opetion To obeve how the moto model in the enole PWM dive cn ffected by modifiction to tto eitnce, the opetion of n invete model h been tudied. The invete dive in thi tet ig clculte the following vlue to ue in the moto model duing the utotune poce: Mgnetizing inductnce, Roto Reitnce R, Stto eitnce R L M, Lekge Inductnce L σ S, R S. Duing dive opetion, the tet ig dive doe not hve n dptive model to compente fo chnge in tto eitnce duing opetion. The model i only clculted once by the utotune function. To undetnd the influence of the moto

5 model on dive opetion, block digm of geneic IFOC (Invete Field Oiented Contolle) invete dive i given in Figue 6 [2]. Cuent IGBT ω * Loop Contolle PI IFOC i * bc Pule λ * d ibc θ Voltge + ω Cuent eno Fig. 6 * ω i the demnded peed, etimto iqd vqd ib Invete FOC digm * d bc to dq tnfom vb C Moto C M (DC Gen) λ the demnded oto flux. When clculting the cuent demnd output fom the IFOC cuent contolle, feedbck fom the ctul moto cuent nd voltge ignl e ued fte tnfomtion fom bc fme to dq nd fom thee to etimte the oto ngle θ. The fequency nd voltge output fom the invete e theefoe dependent on the oto peed, pedicted by the peed etimto. Howeve, in ode fo the peed etimto to clculte peed ccutely, the moto pmete toed in the dive fo the moto model mut coepond to the ctul moto vlue. Fo enole opetion, etimted oto peed ωˆ i clculted fom the tto cuent nd voltge bed on the tedy tte equivlent cicuit of n induction moto hown in Figue 7 i follow: E ˆ ω = λ f d R L L i f m q f λd Whee E, the i gp voltge i clculted bed on the oto tto eitnce nd inductnce: E = V qd R i qd d i (2) L i If the i gp voltge vlue i incoect becue the tto eitnce R toed by the moto model in the dive i in eo, then the oto peed θ etimted by the dive will lo be in eo. f V qd R Fig.7 f i qd L l jω e f f i qd +i qd L m jω e R f i qd qd (3) f ω λ d Induction moto tedy tte equivlent cicuit The imulted fult eitnce hould theefoe not be compented fo by the dive contolle nd it i expected tht moto pefomnce will be ffected by the fult intoduced. III. STTOR IMBLNCE SIMULTION TEST RESULTS Thi ection detil nd compe the tet eult obtined fom the beline tet nd compe thee to the imulted fult tet fo tto eitnce imblnce. It hould be noted tht the moto w bought up to noml opeting tempetue pio to the tet eult being commenced in line with ecommendtion fom EN :24. [3].. Moto Teminl Voltge nd Phe Cuent Following peiod of polonged unning t % lod tble moto opeting tempetue w eched. The wot ce tempetue diffeence w ecoded t 5 C co ll tet. plot of moto voltge, cuent nd peed w tken t ech lod incement but miniml diffeence between helthy nd fult condition w obeved until the moto eched % loding. Figue 8 peent plot of moto voltge, cuent nd peed meued t the % lod point with % peed pplied. Fom thi, it cn be obeved tht the voltge nd cuent eding fo ech phe e moe dipeed unde unblnced condition. Volt (V) Cuent() (pm) Voltge ove thee phe with % peed etting on ig nd vible lod Y: Y: Cuent ove thee phe with % peed etting on ig nd vible lod Y: 7.6 Y: Moto with % peed etting on ig nd vible lod Y: 47 BL2.2.4 Fig. 8 Plot of voltge, cuent nd peed ove 3 phe t % lod condition with % peed etting. BL2 = Beline (Helthy Moto);.2 = Stto Reitnce imblnce of.2ω;.4 = Stto Reitnce imblnce of.4ω. B. Moto Cuent nd Voltge ymmety Figue 9 indicte the eult of clculting moto voltge nd cuent imblnce co ll phe in ccodnce with the NEM definition. Thi define the Line Voltge Unblnce Rte (LVUR) : mximum devition fom line voltge LVUR = (4) vege line voltge [( U U ), ( U U ), ( U U )] mx b lvg bc lvg c lvg LVUR = (5) U lvg Whee U b, U bc nd U c e line voltge.

6 The me method i pplied to meue the diffeence in moto cuent uing the NEM definition. The cuent nd voltge eding how tht thee i noticeble diffeence in cuent nd voltge imblnce when the fult eitnce i intoduced. The mximum i.68v t % loding fo the.4ω fult eitnce. Voltge(V) Cuent() Voltge Unblnce of thee phe (NEM) BL Setpoint (%) Cuent Unblnce of thee phe (NEM) Setpoint (%) Fig. 9 Voltge nd cuent imblnce unde NEM definition C. Moto Efficiency Figue plot the eult of the moto efficiency clcultion bed on hft powe etimtion, electicl input powe etimtion nd powe bed on the no lod cuent method. Intntneou input powe of n c moto i clculted : P = V I + V I + V I (6) n vege vlue of the intntneou powe i tken fo thee efficiency clcultion. The hft powe i clculted : b σ ( I + σ ( I b ) + σ ( I c ) P = (7) 3 ω m I ted Pted ωted Whee i _ vg epeent the veged cuent mple fo i. ω epeent peed in evolution pe econd. The electicl input powe clcultion i bed on the men vlue of ll the meued cuent ignl mple clculted by P = V I + V I + V I ) (8) i c ( b b c c Efficiency by cuent method ue the tndd devition of ll dt point fo i, ib, ic with filte window pplied to clculte ingle cuent vlue I bc t ech dt mple point. I bc = σ ( I ) + σ ( I b ) + σ ( I c ) (9) 3 Bed on the nmeplte moto powe ting, P theoeticl powe output P o i clculted bed on the ctul meued moto peed. Fom thee eult, the efficiency η I i clculted 2 ( I ) follow: bc I m P η I = () 2 I I m Pi Whee I m i the mgnetiing cuent, I i the tto ted cuent. The eult e inconcluive t moto lod below 6% but fom thi point to % lod, thee i conitency to the eult whee the beline dt how inceed output powe, input powe nd efficiency comped to the unblnced eult. Efficiency i educed by ppoximtely.2% fom the fulty moto comped to beline Shft Powe Etimtion Y: 2.48 Y: 2.37 Input Electicl Powe Etimtion Y: 5.55 Y: 5.44 Efficiency by Cuent Method Y:.629 Y:.6 Fig. Moto efficiency clcultion t % loding BL2.2.4 D. Moto Efficiency by i Gp Toque Method Figue peent the efficiency, η clcultion bed on the i gp toque method. The i gp toque T g i clculted fte ubtcting the tto eitnce, coe nd tto ty loe. The following voltge eqution pply fo ll tto winding whee R i the tto (phe) eitnce The i gp toque d = ψ (), b, c v, b, c + RS i, b, c Tg clcultion ued i given below [4]: ( i ib ) [ vc R( ic i )] ( ic i ) [ v B R( i ib )] P Tg ( Nm) = (2) 2 3 The efficiency clcultion i expeed Th ω T g ω W fw WLL η = = (3). Pin Pinput Whee W fw i the fiction nd windge lo nd W LL the oto ty loe. t full lod, the i gp toque efficiency clcultion indicte n inceed efficiency in the moto with unblnced

7 tto winding until the moto i loded up to %. Howeve, the efficiency clcultion do not tke into ccount the dditionl fult eitnce intoduced. - Efficiency Diffeence fom Beline Fig. Moto efficiency clcultion uing i gp toque method When the beline dt i tken the efeence point fo efficiency meuement, the diffeence cn be obeved in moe detil. E. Moto Cuent Spectl nlyi Figue 2 peent compion of cuent pectum between the diffeent opeting mode t the mximum moto peed of 47 RPM. It how tht the 3 d hmonic i inceed fo the two fulty mode t full peed nd t % lod. mplitude mplitude().2.5 (cuent ) unde =(%) Beline(SL) R=.2(SL) R=.4(SL) X: 48.. Y: Fequency(Hz).7.2 (cuent ) unde =(%).4.5 X: 52.3 Y: Fequency(Hz) Fequency(Hz) Fig. 2 Fequency pectl plot of moto cuent ignl unde % nd % lod. IV. CONCLUSIONS Thi ppe h demontted tht it i poible to ue moto cuent nd voltge ignl output fom PWM convete to diffeentite between helthy moto nd moto developing gduted imblnced fult on one tto winding. The eult how tht the NEM method of clculting imblnced cuent nd voltge i mot effective unde imblnced fult condition nd fo wide nge of lod. n dvntge of the NEM method i tht the efeence dt et could be mpled with the moto in evice nd unde nge of lod condition. Thi method conitently indicted n incee in imblnce fo cuent nd voltge fo ll lod nge t contnt peed. Efficiency eduction of.2% obeved in figue 8 would not be cue fo concen unde genel opetion nd my be difficult to detect in el-wold condition. If it i poven tht the technique e enitive enough to detect thi eduction in efficiency elibly nd epetedly then field tet cn be cied out to ignl fult t efficiency loe gete thn 5%. Fom Figue 2 thi equte to voltge unblnce of 2.5%. In expeimentl tet cied out mplitude().6 (cuent ) unde =(%) fo thi ppe, the mximum voltge unblnce meued w time le t.267%. It h been hown tht the moto cuent pectl ignl nlyi method h been hown to be elible indicto when the moto i unning t cloe to ted lod nd i n ltentive to the time-domin nlyi fo detecting the eveity of the fult. The efficiency clcultion e le concluive fo educed moto lod but it i well known tht moto e le efficient when opeting unde educed lod condition nd in genel, moto hould be ized to opete towd thei full lod ting to mximie efficiency of the intlltion. Theefoe, the efficiency clcultion method could be choen fo ppliction tht un the moto towd the full-lod e fo gete effectivene. REFERENCES [] Efficiency cle fo IEC line moto. [2] DD CLC/TS :28 Rotting electicl mchine. Guidnce fo the deign nd pefomnce of.c. moto pecificlly deigned fo convete upply [3] Mibbi, D., G. Seifodt, nd M. Heidi. Effect of unblnced voltge on opetion of induction moto nd it detection. IEEE Intentionl Confeence on Electicl nd Electonic Engineeing, 29. [4] Gilbet. McCoy nd John G. Dougl, Whington Stte Univeity; Enegy Mngement fo Moto-Diven Sytem Reviion 2 Mch 2 [5] Jinghn Zhng, Jin Zho, Dehong Zhou, nd Chenggung Hung, High-Pefomnce Fult Dignoi in PWM Voltge-Souce Invete fo Vecto-Contolled Induction Moto Dive, IEEE Tnction On Powe Electonic, Vol. 29, No., Novembe 24 [6] Sng Bin Lee, Jinkyu Yng, Jongmn Hong, et l. New Sttegy fo Condition Monitoing of djutble Induction Mchine Dive Sytem, IEEE Tnction On Powe Electonic, Vol. 26, No. 2, Febuy 2 [7] Cmil P. Slomon, Wilon C. Snt n, Luiz E. Boge d Silv, Gemno Lmbet-Toe et. l. Induction Moto Efficiency Evlution Uing New Concept of Stto Reitnce IEEE Tnction On Intumenttion nd Meuement, Vol. 64, No., Novembe 25 [8] Yunhu Li,Mingheng Liu, Joephine Lu, Bei Zhng, novel method to detemine the moto efficiency unde vible peed opetion nd ptil lod condition, Be-Tech Inc., Omh, NE 687, US, [9] Shifi, R. nd M. Ebhimi, Detection of tto winding fult in induction moto uing thee-phe cuent monitoing. IS tnction, 2. 5(): p [] Rohn Smi, Venkteh Rjgopln, Jeffey Mye, ok Ry, et. l. (25) Ely Detection of Voltge Imblnce in Thee-Phe Induction Moto; 25 meicn Contol Confeence June 8-, 25. Potlnd, OR, US [] lwodi,, Gu, Fenghou nd Bll, ndew; Compion of Diffeent Technique fo Induction Moto Roto Fult Dignoi. Mechnicl Sytem nd Signl Poceing 5-5 (25) p [2] Mohmed S. Zky (22) Stbility nlyi of nd Stto Reitnce Etimto fo Senole Induction Moto Dive. IEEE Tnction On Indutil Electonic, Vol. 59, No. 2, Febuy 22 [3] BS EN :24 Rotting electicl mchine Pt 2-: Stndd method fo detemining loe nd efficiency fom tet (excluding mchine fo tction vehicle) [4] Bin Lu, Thom G. Hbetle, Ronld G. Hley (28) Nonintuive nd In-Sevice Moto-Efficiency Etimtion Method Uing i-gp Toque With Conidetion of Condition Monitoing. IEEE Tnction On Induty ppliction, Vol. 44, No. 6, Novembe/Decembe 28