Some actual questions at the development of up-to date PMSM motors

1. Someactualquestionsatthedevelopment of up-todate PMSM motors IstvanSzenasy

3. Demagnetizationproximityinpermanent magnet synchronousmotors and itspreventionmethods • The permanentmagnet demagnetization fault is thespecial fault type. • The main reason of thepermanent magnet demagnetizationis thearmaturereactioninducedby • largecurrent, especiallybigtorqueconditions, theoverloadcurrent, • and bigcurrentbytheshortcircuitcurrentof theinverter, and thestatorwindingfaults. • Efficientprevention: researchingforadequatecontruction, basedoninvestigations and analysis

4. Demagnetizationcalculations • The analyticalmodelsgenerallybasedoncalculations of magnet-circleresistances. • In a fractionalnumber of slot per polemachineaswellasourPMSM’s, theanalyticalmodel is more complicated. • The actual magneted states of magnet-circlearefunctionsof rotor–angle and theangle of current-vectoralso. • Nowadaysallthistasksaresolutionedby FEA methods, whichworksratherdetailedway and fast.

5. Ourfractionalnumber of slot per poletype PMSM, forlowercoggingtorque and smoothelectromagnetictorque

6. 2nd version withdecreasedsize of toothtangdepth, forinvestigationsonly

7. The winding’s main parameters, which is special version duethefractionalslot per poletype PMSM

8. Regenerativebrakingby 240 % speed and 135 degrees of currentvectorangle, withverysmoothelectromagnetictorque

9. Coggingtorqueduetheourreasearching 0,05 Nm only

10. Fluxdensitywithoutloading

11. Fluxdensityat 100 % current and 0 degreevectorangle

12. Investigationstodeterminethedemagnetization • Infolytica FEA softwercapabletoinvestigate and determinethestatesinmagnetswichareclosetodemagnetizationandcanshowsitsvalues • Withan iterativewaywefoundtheadequatevalue of currentwithoutdemagnetizationrisk. • The flux-weakeningincreasetherisk of thisoccurencemainlyingenerativebrakingoperations.

13. Thisfigureshowsthisstateat 40 degrees of currentvector and 640 A of motor current, atmotoring. The peakvalue of demagnetizationinblobof 1 T

14. Thisfigureshowsthisstateat 40 degrees of currentvector and 508 A of motor current, at motoring. At 508 A there is notanydemagnetization

15. The 30 degree and greatercurrentvector-rotatingareneededtoreachtheadequatefield-weakening, here by 515 % current and 30 degrees

16. 150 degree of vectorangleoccurinbrakeoperating, soinvestigatetheriskofdemagnetization is veryimportant. Atthecurrent of 515 % of nominalvalue : themeasureofdemagnetization ‘s peak is high, 0.851 T, butitsarea is nottoolarge

17. Atregenerativebraking, here is 474 % current and 150 degreesvectorangle, withoutdemagnetization

18. Effects of variedairgap and twosize of toothtangdepth • Wehavedoneexaminationsbyvariedto air gapvalues of oursynchronous motor resarchingtheeffects of air gapfordemagnetizationpredictions. The air gapvalueswassetfrom 3.0 to 0.7 mm and theresultswill be shown. • Weexaminatedthebehaviourallabovementionedquestionsforvariedslotformsof statorlamination. Atdevelopingprocedureinourmotorsweinvestigatedtheeffects of consequenceofpartiallymodifiedslotforms. Ourdealsweretoachievingtheminimalcoggingtorque, theminimalrippleinelectromagnetictorque, theadequtefield-weakeningpossibilities etc. Now, wedealt an important part of slot, thetoothtangdepth. Wedecreaseditsthicknessfrom 3 to 2 mm and analizeditsconsequences.

19. Method of investigations • Weinvestigatedtheoccur and measure of demagnetizationunderchange of torqueloadangleregardingtofield-weakeningapplyingofthis PMSM, from 3000 to 9000 rpm. • Weexaminedthedemagnetization’smeasurefrom 0 to 180 degree of currentvectorangle, increasingthisstepbystepof 5 degrees. • The results of thisexaminationareunderworking out butwe had knownsomevaluesinaeria. • Regardingtooccurrence of maximum demagnetizationthe most importantdomainin motoring is 30 to 50 degreesand ingeneratoroperation is 130 to 150 degrees. • Sincethedemagnetizationpredictioningeneratoroperationwashigherwithsome percent thanin motoring theangleparameterininvestigationswasmainly of 150 degrees.

20. The 1st version of toothtangdepthwithdesignedairgap

21. The 2nd version of toothtangdepth is 2 mm Thisactionmodificatethemagneticresistances of magnet circle, increasethearmatura-reactionsby motor currents and thedemagnetizationoccurlowercurrents, soincreasetherisk of irreversible magnet damage .

22. Motor currentsin limit of demagnetization, in % of nominalcurrent, byvariedthe air gap, and fortwosizes of toothtangdepth

23. Results and experiences • In 2nd version dueitsdecreasedtoothtangdepththereserveagainstdemagnetization is lower, • buteveninthisstatetherearea 5 timesreservefortolerate an extremcurrentpeaks , forexamplefrom a systemfailureorashort-circuit. • Inour 1st version thisreserve is 8 to 10 times , sothe motor is veryprotected . • Ingeneralthereserveagainstdemagnetization is more lowerthenourPMSM, 2 to 3 times, estimatedaboutitstoosmallairgapand thegenerallyusedslotform, fromasynchronousmotor’s. • Increasedthethickness of toothtangdepthand with an adequateslotform, thisresultsdueinvestigations and developpingincreasetheoperationsafety of vehicle’s PMSM byhighdegree. • This PMSM wellruninourelectriccar, and itsother unit is runningonour motor-test apparatusin 5th laboratory.

24. Conclusions Fromcurveswecanseethatatthis motor type - thedesignedpointatairgap of 1.3mm is an optimalvalue, - atlittleairgaptheimportance of size of toothtangdepth is small, - abovethisairgapthe limit of demagnetization is increasinghardly, butatdecreasedairgapdiminishveryfast, - theincreasedairgaphaveseveralotheradvantagesin a PMSM construction. Theseresultsgive a reallysafetyagainstdemagnetization. This PMSM wellruninourelectriccar, and itsother unit is runningonour motor-test apparatusin 5th laboratory.

25. IstvanSzenasyPhd • JKK, Szechenyi University, Gyor • Contact • Email: szenasy @sze.hu • Tel.: 36-96-503400/3258 • Web: http://uni.sze.hu/