1、08FTM09AGMA Technical PaperConcept for a MultiMegawatt Wind TurbineGear and FieldExperienceBy T. Wei and B. Pinnekamp,RENK AGConcept for a Multi Megawatt Wind Turbine Gear and FieldExperienceToni Wei and Burkhard Pinnekamp, RENK AGThe statements and opinions contained herein are those of the author
2、and should not be construed as anofficial action or opinion of the American Gear Manufacturers Association.AbstractThe increasing call for the use of renewable energy in all industrial countries demands for the extension ofwind power generation capacity. In central Europe as in parts of the Americas
3、 and Asia, such furtherexpansion is only possible by re-powering -replacement of existing turbines by higher rated ones- or bydeveloping locations in the open sea - offshore. To this end, the gear industry world wide is challenged todevelop and supply the required No. of reliable 5 MW class wind tur
4、bine gears.Thepapersummarizestheconceptevaluationanddesignofthe5MWMultibridwindturbinetransmissionarrangement, test bed measurements with the prototype as well as field experience over a test period of 3years.Copyright 2008American Gear Manufacturers Association500 Montgomery Street, Suite 350Alexan
5、dria, Virginia, 22314October, 2008ISBN: 978-1-55589-939-43Concept for a Multi Megawatt Wind Turbine Gear and Field ExperienceToni Wei and Burkhard Pinnekamp, RENK AGIntroductionContinuous or even increasing demand for electri-cal power combined with concern about fossil fuelresourcesandCO2emission(K
6、yoto-protocol!)anda world wide tendency to step back from nuclearpower are the basic reasons for increasing use ofregenerative power in industrial countries. In Ger-many, as opposed to only 2.6% in 2000, renewableenergy contributed 5.3% of the complete prime en-ergyconsumptionin2006. Windenergyherei
7、ncov-ered a share of 0.85%, figure 1. Same tendenciesapply to other European and world wide countries.The total share of renewable energy to overallelec-trical power production in Germany was 11.8% in2006. Goalbylawistoincreasethissharetoamini-mum of 20 % in the year2020. Similar regulationinother c
8、ountries contributes to the resolutions of theKyoto Protocol.Development in wind energyThetendenciesmaynotapplyexactlytoallindustri-al countries, but the development of wind energy inGermany is certainly an example for a world widechange in power generation over the next 15years.In the last decade,
9、bio mass and wind energy werethe most increasing sources in renewable energy.The only option to meet the mentioned challenginggoalsistofurthersignificantlyincrease windenergyproduction in Germany, figure 2.Figure 1. Prime energy supply in Germany 2006, total renewable (green labels): 5.3% 1Figure 2.
10、 Contribution of renewable energy to power generation in Germany4Even if the demand for electrical power will notincrease in the next decades, in order to reduce theshare of nuclear power and fossil fuel powergeneration wind energy needs to significantly ex-pand. A moderate extrapolation of the curv
11、es infigure 2 mean twice the power generation out ofwind turbines before the year 2020. The prognosisofnewinstallationinwindpower2matchesthisre-quirement, figure 3. Other sources 3 predict up totwice as much growth especially in the field of offshore wind energy production.In order to keep upwith th
12、isgrowth andat thesametime considercost forfoundation andmaintenance,windturbinesinthe5MWclassare mostimportant.In developing these turbines, German manufac-tures are inthe leadworld wide. Themajor shareofthe German offshore wind farms will be equippedwith turbines out of local production. The manuf
13、ac-tures are alreadytoday facingan additionalinterna-tional request for deliveries. Considering similarplanswithoffshorewindfarmsine.g. UK,DenmarkandFranceandworldwide,anexportshareofmorethan 50 % seems realistic for the near future.Therefore, the numbers in figure 3 may even belarger by a factor of
14、 2 to 3.With the predicted growth German wind power in-dustry has rapidly increased its capacity. Inparallelwithacertain saturationof theGerman onshorede-mand international demand was growing. So theexport rate rose from only 59% in 2004 to close to82% in 2008, is expectedto growup to90% in2009andsh
15、ouldthenbeinfluencedtosomeextentbytheincreasing German demand for offshore plants inthe North Sea from 2010.Wind turbines for offshore-applicationGerman wind turbine manufacturers have beenworking for long in developing plants, specificallydesigned for the use on the open ocean, i.e. theNorth Sea wi
16、th medium water depth around 20 moutsidenaturalparkswith lowwater depth,figure 4.This is an exceptional challenge which may not bethe same in most other countries. This develop-ment is necessary due to the fact that in Germanyonly limited space is available onshore and inareaswhere an average of ann
17、ual wind speeds in therange of 10 m/s is available so that wind powerreally is economical.With the offshore variant of the N 90 with 2.5 MWNordex provided the first wind turbine beinginstalled under offshore-like conditions. With thesuccessful installation of several REpower 5M onthe German and Brit
18、ish coast line and 4 units Multi-brid M5000 on the coast line of Bremerhaven/Ger-many, the German wind turbine manufacturersprovedtheirleadingrollinthedevelopmentof 5MWwind turbines. Enercon has built their first directdrive 4.5 MW units already in2002 buthas beenre-luctantforyearswith respectto off
19、shoreapplicationfornottakingadditionalriskandanongoingdemandfor onshore applications.Figure 3. Total power of wind turbines in Germany before 2020; moderate assumptions 25The multibrid conceptAs an example for an offshore design wind turbinethe M5000 is described hereafter. This concept isbased on t
20、he following requirements:S Low number of elements to reduce theprobability of failure;S Reduction of weight;S No compromise on safety and reliability withoutjeopardizing cost.It is a development in Germany of MultibridGmbH.(=Ltd), Bremerhaven, in cooperation withRenk AG, Augsburg and is based on an
21、 idea ofAerodyn, Rendsburg.The Multibrid concept has the following mainfeatures:S integration of rotor bearing, reduction gear andmedium speed generator;S hereby short, light weight engine compartment;S sleeve bearings for main gear shafts.Figure 4. Wind turbines of German manufacturers for offshore
22、 application6Figure 5 shows the principle arrangement of thegear components. As opposed to most other windturbines, the complete rotor bearing is integrated inthemachinehousing,alsoaccommodatingthegearparts. Theinputisconnectedtothecasecarburizedannulus which drives 4 planet pinions of the offsetpla
23、net shafts which are accommodated in sleevebearingsinthemaincasing. Bymeansoftheplanetgears and the common sun pinion the power isdirectly transmitted to the rotor of the integratedpermanent magnet synchronous generator. Thereactive torque is elastically supported betweenplanet carrier and casing in
24、side the gear. Thetorque between the drive and the generator is limit-ed by a specially designed torque limiting device,based on the principle of a friction clutch,especiallytolimitshortcircuitoverloadtoanacceptablevalue.The rotor bearing and all bearings carrying more orless continuous forces like
25、weight are antifrictionbearings. All torque loaded bearings are sleevebearings, so that shocks will not influence the life-time of the bearings and there is nearly no load onthebearingsatlowspeed. Thisisconsideredama-jor contribution to bearing lifetime and reliability orprevention of unforeseen bea
26、ring failures.Figure 6 shows the installation in the enginecompartment.Figure 5. RENK WP5000 for Multibrid M5000 schematicFigure 6. 5 MW wind turbine Multibrid M5000 67A comparison of the size of this concept with usualrotorgeargenerator arrangements and directdriven units shows the advantage in siz
27、e, Figure 7,which can also be reflected in a comparison of theweight of the nacelle on top of the more than 100 mhightower. The differenceroughly is100 tonshigh-er weight for the direct drive in comparison to theconventional geared concept and this in turn isanother 100 tons heavier than the fully i
28、ntegratedMultibrid concept with overall 280 tons.Before being installed inthe windturbine, theproto-type reduction gear was extensively tested with apartial load test arrangement. The maximum test-ingpowerwas2MW. Using4planets,loaddistribu-tionontheindividualplanetsandoverthefacewidthis of specific
29、interest to avoid overload on the indi-vidual parts. To verify the design assumption onsuchloaddistribution,straingaugeswereappliedto4 teeth of the input annulus gear in the root fillet ofboth ends of the face width. Figure 8 shows theevaluation of the measurement with respect to dis-tributionoftoot
30、hloadoverthefactwidthofthemeshannulus gear - planet pinion. The contact patterndocumented after some part load fairly well in con-gruence with the calculated load distribution at thatverypartload,asdemonstratedinFigure9. It ises-sential that such comparison can only be made forgear with involute - a
31、nd/or lead correction at a partload where full contact pattern is not yet achieved.Figure 7. Comparison of different conceptsFigure 8. Load distribution over face width; evaluation of strain gauge measurement 48Figure 9. Comparison of calculated and actual contact pattern at part loadFrom the strain
32、 gauge measurement, at the rotorand generator end of the gear teeth of the annulus,the lead deviation from optimum design can be de-rived by calculation: fH=17mm. Assuming thisleaddeviationfortheloaddistributionfactoratnom-inal load, a figure of KH= 1.08 is determined. In asimilar way, theload distr
33、ibutionon the4 planetpin-ions is determined to KH= 1.05. For the gear de-sign, higher factors have been assumed. There-fore,themeasurementdoesnotgivereasonforanylimitation for function and endurance life of the re-duction gears.The first prototype of the Multibrid M5000 has beeninstalled and is in o
34、peration since early 2005 inBremerhaven/Germany. Several inspections alsowith bore scope assistance confirm the excellentconditionofallpartsintheplant. Therefore,thesec-ond to forth turbine have been built and erected be-tween early 2007 and today without changes to themechanical system.ExperienceAs
35、 a shop test, may it be with full, part or overloadnever is realistic enough to represent the actual be-havior it is essential that at least the prototype shallbeequippedwithsufficientmeasuring equipmenttomakesurethatalldesigndataareverifiedandespe-cially the calculated load spectra are within accep
36、t-able limits. Therefore monitoring of representativevalues has been installed.Themonitoreddatahavetobecollectedwithasuffi-ciently high frequency on one hand and have to beevaluated and downsized so that especially trendbehavior can easily be recognized. Therefore asystem as developed for years ina
37、combinedeffortofDalogandRenkisused. Thesystemcontinuous-ly stores minimum and maximum values as well asaveragefordifferentperiods. Sointheendthedatalogging can be minimized to a degree that eventrends over years can be evaluated. On the otherhand it is essential to be able to analyze specialevents.
38、Such events, which normally exceed stan-dard values, are fully stored and can be recollectedany time. An example for such events is given inFigure 10.Thesignalscollectedofcourse dependon theactu-al application. They should reflect the essential be-havior of the plant and its most representative and/
39、orcriticalelements. Thistypicallyistheloadandtheresult in deformation and stress as well as the be-havior of load transmitting elements as e.g. vibra-tionandtemperatureof bearings. Wherevibrationsshall be used for antifriction bearings and tempera-tures are the best indicator for sleeve bearings.Ano
40、ther important parameter is the correlation ofsuch values, because e.g. temperature in a sleevebearing is a function of speed and load.9Figure 10. Example of a braking event of a wind power gearbox where the torque is exceeding aspecified value and therefore it is fully stored.The design allows meas
41、uring most of the parame-ters directly,i.e. withouta transmittingdevice forro-tating elements. Therefore the measurements arerelatively stable and deviations can be corrected orrepaired.For the prototype the transmitted torque is mea-sured via the reactive forces of the suspension asbendingofthe pin
42、s. Inparallel themovement oftheunitelasticsuspensionhasbeenmeasured. Figure11 shows different stress signals representing thetorque, i.e. bending of the suspension and toothbending signal of the annulus gear and the speed.Of course there is relation of the transmitted powertospeedaccordingtothespeed
43、versuspowercurveinstalled.It can easily be noted thatthe correlationcoefficientof all measured values (Ccoeff) is close to unity, i.e.very good and there was no extreme torque alloverthe period. This proves a very smooth operationand/or a perfect function of the torque limiting de-vice installed.Sim
44、ilarly the temperatures of the sleeve bearingsare monitored, as well as the oil inlet temperatureand the oil return temperature. The continuousreadingsfor thewhole lifeperiod sofar showtypicalcorrelation to the power transmitted i.e. speed andload. The trend does not vary over time and thusproves no
45、 change in the bearing, see Figure 12.ConclusionsThe Multibridconcept has been developed on thebasis of medium size; i.e. 1.5 and 2 MW Aerogeardesign.It is a consequent combination of an existing andproven gear design with a compact single rotorbearingandanintegratedmedium speedgeneratorin one combi
46、ned structure. Its main application isoffshore and therefore maximum reliability andavailability is essential. This application result fromgivenneedstodrasticallyincreasetheamountofre-newableenergyinGermanyandEuropewithitslim-ited space at high average wind speed areas.Thedesignisextremelycompactwit
47、hregardtosizeand weight for such power and it has considerableadvantageswithregardtobearingandgearlubrica-tionandmonitoring. Theprototypedesignhasbeenverified at part load tests and shows best perfor-mance at full load after more than 3 years continu-ous operation. Three more units have been10instal
48、ledonshoreandconfirmthisformorethanoneyear. The next units are ready for shipment to beinstalled offshore at a first large German test fieldBorkum West in the North Sea.Serialproductionhasstartedandwillbeintherangeof 100 units per year thus contributing to increasethe percentage of renewable energy
49、according tothe requirements in Germany and Europe.Figure 11. Stress signals at different location representing the torqueand their relation to the speedFigure 12. Bearing temperatures as an example for the planetary bearings and a period of 4500hours in correlation to the speed11References1. German Ministry for Environmental Protection.Information Bulletin January 20072. German Ministry for Environmental Protection.InformationBulletinonDevelopmentofRenew-able Energy, February 20073. Study of German Energy agency (DeutscheEnergie-Agentur Ltd., dena) on ec
