Condition Monitoring of Rotating Electrical Machines PDF
Preview Condition Monitoring of Rotating Electrical Machines
Condition Monitoring of Rotating Electrical Machines Peter Tavner, Li Ran, Jim Penman and Howard Sedding TheInstitutionofEngineeringandTechnology PublishedbyTheInstitutionofEngineeringandTechnology,London,UnitedKingdom ©2008TheInstitutionofEngineeringandTechnology Firstpublished2008 ThispublicationiscopyrightundertheBerneConventionandtheUniversalCopyright Convention.Allrightsreserved.Apartfromanyfairdealingforthepurposesofresearch orprivatestudy,orcriticismorreview,aspermittedundertheCopyright,Designsand PatentsAct,1988,thispublicationmaybereproduced,storedortransmitted,inany formorbyanymeans,onlywiththepriorpermissioninwritingofthepublishers,orin thecaseofreprographicreproductioninaccordancewiththetermsoflicencesissued bytheCopyrightLicensingAgency.Enquiriesconcerningreproductionoutsidethose termsshouldbesenttothepublishersattheundermentionedaddress: TheInstitutionofEngineeringandTechnology MichaelFaradayHouse SixHillsWay,Stevenage Herts,SG12AY,UnitedKingdom www.theiet.org Whiletheauthorandthepublishersbelievethattheinformationandguidancegivenin thisworkarecorrect,allpartiesmustrelyupontheirownskillandjudgementwhen makinguseofthem.Neithertheauthornorthepublishersassumeanyliabilityto anyoneforanylossordamagecausedbyanyerrororomissioninthework,whether sucherrororomissionistheresultofnegligenceoranyothercause.Anyandallsuch liabilityisdisclaimed. Themoralrightsoftheauthortobeidentifiedasauthorofthisworkhavebeen assertedbyherinaccordancewiththeCopyright,DesignsandPatentsAct1988. BritishLibraryCataloguinginPublicationData AcataloguerecordforthisproductisavailablefromtheBritishLibrary ISBN978-0-86341-739-9 TypesetinIndiabyNewgenImagingSystems(P)Ltd,Chennai PrintedintheUKbyAthenaeumPressLtd,Gateshead,Tyne&Wear Nomenclature Symbol Explanation A effectivecross-sectionalareaofacoil,m2 A availability,A=MTBF/(MTBF+MTTR) A(t) availabilityfunctionofapopulationofcomponentsasafunction oftime a scalingfactoroftimeinamotherwavelettransform α scaleparameterinapowerlawexpression α andb straincoefficientsforthestrainenergyofthestatorcore n n α cross-sectionalareaofatooth,m2 t α scaleparameterinaWeibullfunction α resistancetemperaturecoefficient,degree/ohm r α skewangleofastator,degree s B(f ,f ) bispectrum 1 2 B radialfluxdensityinanairgap,Tesla b orb statororrotorsideinstantaneousradialfluxdensity,Tesla 1 2 b time-shiftingparameterinamotherwavelettransform β shapeparameterinaWeibullfunction β half-anglesubtendedbyashortedturn,degrees C volumetricconcentrationofadegradationproductinamachine C Carterfactortoaccountforairgapslotting C(y,v) inversewavelettransform C(t) cepstrumfunction c dampingconstantofasupportsystem,N/m/s D dampingfactorforrotorvibrations d rollingelementdiameter,m E Young’smodulusofamaterial E storedenergyinanelectricalsystem,Joules e e specificunbalancee=mr/M,m e(t) instantaneousinducedEMF,V (cid:3) straininamaterial θ MTBFofacomponent,θ =1/λhours θ spacepositioninthestatorfield,degrees 1 θ spacepositionintherotorfield,degrees 2 F parameterfromshockpulsemeasurementofarollingelementbearing xx ConditionMonitoringofRotatingElectricalMachines F (θ,t) forcingfunctiononarotororstatorexpressedincircumferential m angleθ andtimet,N F(t) failuremodeprobabilitydensity,aWeibullfunction ForF−1 forwardorbackwardFouriertransform f firstcriticalornaturalfrequencyofarotorsystem,Hz 0 f orf (t) statororrotorsideinstantaneousmagnetomotiveforce(MMF),N I 1 2 1 1 orN I ,ampere-turns 2 2 f electricalsupplysidefrequency=1/T,Hz se f PWMswitchingfrequency,Hz sw f highermthnaturalfrequenciesofthestatorcore,Hz m f mechanicalvibrationfrequencyonthestatorside,Hz sm f thenthcomponentofanunbalancedforcingfunction n f mechanicalrotationalfrequency=N/60,Hz rm G straingaugefactor G degreeofresidualunbalanceasdenotedbythequantityG =eω G(f ) generalisedpowerspectralfunctionoffrequency,f ,thek thharmonic k k G∗(f ) complexconjugateofG(f ) k k G(m) stiffnessfunctionofanmthnaturalfrequenciesofthestatorcore G(t ) generalisedperiodicfunctionoftime,t n n g accelerationduetogravity,m/s2 g airgaplength,mm g (z) naturalfrequencyfunctionannthsolutionofthebalanceequation n h heattransfercoefficientfromaninsulationsurface,W/m2K h toothdepth,m t I orI statororrotorsidermscurrent,A 1 2 i ori (t) statororrotorsideinstantaneouscurrent,A 1 2 J polarmomentofinertiaofthecorecylinder,joules2 k integerconstant,indicatesthestatorMMFspace harmonics,1,3,5,7… k heattransfercoefficientthroughaninsulatingmaterial,W/mK k stiffnessconstantofasupportsystem,N/m k reflectioncoefficientintherecurrentsurgeoscillography(RSO)test r k integernumberofcommutatorsegmentsinaDCmachine c k/nq Halleffectconstantofanelectronicmaterial k integerconstant,indicateseccentricityordernumber,whichiszero e forstaticeccentricityandalowintegervaluefordynamiceccentricity k integerconstant,indicatesthecircumferentialmodesinavibrating c statorcore k integerconstant,indicatesthelengthwisemodesinavibrating l statorcore k statorwindingfactorforthenthharmonic wn L activelengthofacore,m Nomenclature xxi L inductanceofacoil,H (cid:7) integernumberofstatortimeharmonicsorrotorwinding faultharmonics (cid:8) magneticpermeance λ instantaneousfailurerateorhazardfunctionofacomponentormachine, failures/component/year λ(t) failurerateofacomponentormachinevaryingwithtime, failures/component/year M massofarotatingsystem,kg M massofasupportsystem,kg s m integerconstant m equivalentunbalancemassonashaft,kg µ permeabilityinamagneticfield N orN integernumberofstatororrotorsideturnsofacoil 1 2 N speedofamachinerotor,rev/min N integernumberofrotorslots r N integernumberofstatorslots s n numberofchargecarriersperunitvolumeinasemiconductor n integerconstant,1,2,3,4… n integernumberofrollingelementsinarollingelementbearing b P statorsidepower,watt 1 p (t) instantaneousstatorsidepower,watt 1 p integernumberofpolepairs Q heatflow,watt/m2 Q maximumpartialdischargerecordedinpartialdischargetests m usingacalibratedcoupler,mv q electroniccharge,coulomb q integerphasenumber (cid:9)R changeinresistance R resistance,ohms R shockpulsemeterreading R(t) reliabilityorsurvivorfunctionofapopulationofcomponents asafunctionoftime,failures/machine/year R (t) auto-correlationfunctiononatimefunctionf(t)witha ff delayof gt R (t) cross-correlationfunctionbetweentimefunctionsf(t)andh(t) fh withadelayof gt R resistanceofadevicemadeofthemetalat 0 °C,ohm 0 R resistance,ohm T r effectiveradiusofanequivalentunbalancedmass,m r meanradiusofacore,m mean r radiusofairgap,m airgap S constantrelatedtothestiffnessofawinding,insulationand toothcomponents xxii ConditionMonitoringofRotatingElectricalMachines s slipofaninductionmachine,between0and1 T torque,Nm T temperatur e , °C T periodofawave,sec T(cid:7) volumetricvibrationkineticenergy,joules/m3 T(f ,f ,f ) trispectrum 1 2 3 τ radialthicknessofastatorcoreannulus,m 0 ρ densityofamaterial,kg/m3 σ electricalconductivityofaregion,ohm.m σ andσ radialandtangentialMaxwellstressintheairgap,N/m2 r q τ timedurationofanoverheatingincident,s w τ residencetimeofanoverheatingproductinamachine,or r leakagefactor,s τ timedelayinacorrelationfunction,s u lateraldisplacementofamachinerotor,µm ur anduθ radialandperipheraldisplacementsinastrainedstatorcore,µm V rmsvoltage,volts V machinevolume,m3 V(cid:7) volumetricstrainpotentialenergy,joules/m3 v velocityoftherotor,relativetothetravellingfluxwaveproduced bythestator,m/s ν˙ volumetricrateofproductionofadetectablesubstance,m3/s ν˙ backgroundrateofproductionofthesubstance,m3/s b ν Poisson’sratioofamaterial φ flux,Webers φ contactanglewithracesofarollingelementbearing,degree φ electricalphaseangleofastatorMMFwaveF ,degree s ψ angularfrequencyofanelectricalsupply,rad/s ψ firstcriticalornaturalangularfrequencyofarotorsystem,rad/s 0 ψ electricalsupplysideangularfrequency,rad/s se ψ mechanicalangularvibrationfrequencyonthestatorside,rad/s sm ψ mechanicalrotationalangularfrequency =2pN/60,rad/s rm ψ angularvelocityofaneccentricity,rad/s ecc ψ(t) motherwaveletfunctionoftime W workfunctionforstrainenergyinstatorcore W(a,b) wavelettransform w weightperunitlengthperunitcircumferentialangleofastatorcore cylinder,N/m w ,w,w andw weightsofacoreyoke,teeth,insulationandwindings, y t i w respectively,kg X secondharmonicmagnetisingreactance,ohm m2 X secondharmonicleakagereactance,ohm 12 z longitudinaldistancefromthecentreofamachine,m Z surgeimpedanceofawinding,ohm 0 Preface Condition monitoring of engineering plant has increased in importance as more engineeringprocessesbecomeautomatedandthemanpowerneededtooperateand supervise plant is reduced. However, electrical machinery has traditionally been thought of as reliable and requiring little attention, except at infrequent intervals whentheplantisshutdownforinspection.Indeedthetraditionalapplicationoffast- acting protective relays to electrical machines has rather reduced the attention that operatorspaytotheequipment. Rotatingelectricalmachines,however,areattheheartofmostengineeringpro- cesses and as they are designed to tighter margins there is a growing need, for reliability’s sake, to monitor their behaviour and performance on-line. This book isaguidetothetechniquesavailable. Thesubjectofconditionmonitoringofelec- tricalmachinesasawholecoversaverywidefieldincludingrotatingmachinesand transformers. To restrict the field the authors deal with rotating machines only and withtechniquesthatcanbeappliedwhenthosemachinesareinoperation,neglecting themanyoff-lineinspectiontechniques. Thefirsteditionofthisbook,ConditionMonitoringofElectricalMachines,was writtenbyPeterTavnerandJimPenmanandpublishedin1987byResearchStudies Press,withtheintentionofbringingtogetheranumberofstrandsofworkactiveatthat timefrombothindustryandacademia.Inacademiatherewasagrowingconfidencein themathematicalanalysisofelectricalmachines,incomputermodellingofcomplex equivalent circuits and in the application of finite-element methods to predict their magneticfields.Inindustrytherewasgrowinginterestinprovidingbettermonitoring forlargerelectricalmachinesasrisingmaintenancecostscompetedwiththeheavy financialimpactoflargemachinefailures. The original book was primarily aimed at larger machines involved in energy production,suchasturbinegeneratorsandhydrogenerators,boilerfeedpumps,gas compressors and reactor gas circulators. This was because at that time those were theonlyplantitemscostlyenoughtowarrantcondition-monitoringattention.Italso reflectedthefactthatoneoftheauthorsworkedinthenationalisedgeneratingutility, colouringhisapproachtothesubject. The original book showed that, in respect of condition monitoring, electrical machines are unusual when compared with most other energy conversion rotating plant.Theall-embracingnatureoftheelectromagneticfieldintheenergyconversion process,whichistheraisond’êtreoftheelectricalmachine,enablesoperatorstoinfer farmoreabouttheiroperationfromtheirterminalconditionsthanisusuallythecase withnon-electricalrotatingmachinery.Inthisearlierworktheauthorswereinspired xiv Conditionmonitoringofrotatingelectricalmachines by a much earlier book by Professor Miles Walker, The Diagnosing of Trouble in ElectricalMachines,firstpublishedin1921. Ourbookcoveredtheelementalaspectsofelectricalmachineconditionmonitor- ingbutexposedanumberofimportantfacetsofunderstandingthathavesubsequently leadtoagreatdealoffurtherwork,namely • theelectromagneticbehaviourofelectricalmachines, • the dynamic behaviour of electrical machines, particularly associated with the controlnowavailablewithmodernpowerelectronics, • thebehaviourofelectricalmachineinsulationsystems. Each of these facets have now matured and are a rich source of fundamental knowledge that has been related to the behaviour of machines in their operating state, especially under fault conditions. Two examples of this further work are Professor Peter Vas’, Parameter Estimation, Condition Monitoring and Diagnosis ofElectricalMachines,publishedin1996;andGregC.Stone’s,ElectricalInsulation forRotatingMachines, Design, Evaluation, Ageing, TestingandRepair, published in2004. Theeconomicsofindustryhasalsochanged,particularlyasresultoftheprivati- sationandderegulationoftheenergyindustryinmanycountries,placingfargreater emphasisontheimportanceofreliableoperationofplantandmachinery,throughout thewholelifecycle,regardlessofitsfirstcapitalcost. Finallytheavailabilityofadvancedelectronicsandsoftwareinpowerfulinstru- mentation,computersanddigitalsignalprocessorshassimplifiedandextendedour abilitytoinstrumentandanalysemachinery,notleastintheimportantareaofvisu- alisingtheresultsofcomplexcondition-monitoringanalysis. Asaresult, condition monitoring is now being applied to a wider range of systems, from fault-tolerant drivesofafewhundredwattsintheaerospaceindustry,tomachineryofseveralhun- dredmegawattsinmajorcapitalplant.Thevalueofthefundamentalcontributionto theseadvancesbymanyanalystsoverthelast20yearscannotbeunderestimatedand theywillplayamajorpartinthefuture. In this new book, Condition Monitoring of Rotating Electrical Machines, the originalauthorshavebeenjoinedbytheircolleagueDrLiRan, anexpertinpower electronics and control, and Dr Howard Sedding, an expert in the monitoring of electrical insulation systems. Together we have decided to build upon the earlier book,retainingthesamelimitswesetoutatthestartofthispreface,mergingourown experience with that of the important machine analysts through the years to bring the reader a thoroughly up-to-date but practicable set of techniques that reflect the workofthelast20years.Thebookisaimedatprofessionalengineersintheenergy, process engineering and manufacturing industries, research workers and students. Wehaveplacedanadditionallimitonthebookandthatistoconsiderthemachine itselfratherthanitscontrolsystems.Whilerecognisingtheenormousgrowthofthe applicationofelectronicvariablespeeddrivesinindustry,wedonotdealwiththeir specificproblemsexceptinpassing.Weacknowledgethatthisisimportantforfuture growthbutleavethisareaofinvestigationtoafutureauthor. Preface xv The examples of faults have concentrated on conventional machines rather than the emerging brushless, reluctance, permanent magnet and unusual topology machines. This is because the industry is still dominated by these conventional machines. The ‘failure mode’ information for newer designs has not yet emerged butwillbebasedonearliermachineexperience.Inthiseditionwehaveomittedcase studiesbecausetherangeofapplicationofcondition-monitoringtechniquesonelec- tricalmachinesisnowsowideandcomplexthatitisdifficulttoselectappropriate applicationsfromwhichgeneralconclusionscanbedrawn. Wehaveintroduceda‘Nomenclature’sectionandextendedthereferencestocover major recent journal papers and books that have illuminated the subject, including someoftheolderseminalworks,whichstilldeservescrutiny.Theauthorshavealso taken the opportunity to correct errors in the previous book, rearrange the material presentedandaddimportantinformationaboutfailuremechanisms,reliability,instru- mentation,signalprocessingandthemanagementofrotatingmachineassetsasthese factorscriticallyaffectthewayinwhichconditionmonitoringneedstobeapplied. Finally, the diagrams and photographs representing the machines, the monitoring systemsandthesignalprocessingusedhavebeenupdatedwhereappropriate. PeterTavner DurhamUniversity,2006 Contents Preface xiii Acknowledgments xvii Nomenclature xix 1 Introductiontoconditionmonitoring 1 1.1 Introduction 1 1.2 Theneedformonitoring 4 1.3 Whatandwhentomonitor 7 1.4 Scopeofthetext 9 1.5 References 10 2 Construction,operationandfailuremodesofelectricalmachines 13 2.1 Introduction 13 2.2 Materialsandtemperature 14 2.3 Constructionofelectricalmachines 16 2.3.1 General 16 2.3.2 Statorcoreandframe 18 2.3.3 Rotors 18 2.3.4 Windings 18 2.3.5 Enclosures 20 2.3.6 Connections 26 2.3.7 Summary 26 2.4 Structureofelectricalmachinesandtheirtypes 26 2.5 Machinespecificationandfailuremodes 33 2.6 Insulationageingmechanisms 35 2.6.1 General 35 2.6.2 Thermalageing 36 2.6.3 Electricalageing 36 2.6.4 Mechanicalageing 37 2.6.5 Environmentalageing 38 2.6.6 Synergismbetweenageingstresses 39 2.7 Insulationfailuremodes 39 2.7.1 General 39 2.7.2 Statorwindinginsulation 40 2.7.3 Statorwindingfaults 45
The list of books you might like
