PERFORMANCE OF HEAVY-DUTY PLANETARY GEARS

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1 THE INTERNATIONAL CONFERENCE OF THE CARPATHIAN EURO-REGION SPECIALISTS IN INDUSTRIAL SYSTEMS 6 th edton PERFORMANCE OF HEAVY-DUTY PLANETARY GEARS Attla Csobán, Mhály Kozma 1, 1 Professor PhD., Eng. Budapest Unversty of Technology and Economcs, Budapest, Hungary ABSTRACT Wnd energy s wdely spread n the world owng to the shortages of fossl energy and ts envronmentally frendly character. The economy of wnd turbnes can be ncreased usng large equpment producng electrc power up to 5 MW. Large wnd turbnes need heavy-duty drve systems wth great power/weght rato, hgh effcency and hgh gear rato. There were performed theoretcal nvestgatons on heavy-duty planetary gears beng able to transfer the hgh power from the wnd turbne to the generator. KEYWORDS Planetary gear, dfferental gear, wnd turbne 1. INTRODUCTION Use of wnd energy s not only an envronmentally frendly technology, but the huge wnd farms havng many wnd-turbnes produce electrc energy economcally. The development of wnd energy ndustry n Europe s one of the quckest among ndustry branches. More and more off-shore wnd turbnes are planted along the sea shores explotng the benefcal wnd flow producng twce more electrc energy than the wnd turbnes an the land Accordng to the expectatons the off-shore wnd farms wll produce at least 2 MW electrc power. Such a large scale plans can be comng true only plantng more and more huge wnd turbnes reachng the power as hgh as 5 MW The man structure elements of wnd turbnes are rotors, generators and drve systems transmttng power from the wnd wheels to the generators. The drve system ncreases the slow rotaton speed of the rotor up to the rotaton speed beng necessary to the proper operaton of the generator. The man parts of the drve systems are tooth gear boxes, whch are often planetary gears beng able to meet the followng strct requrements stated aganst the drve systems: Hgh load carryng capacty (hgh power/mass rato) Hgh gear up rato n the range from 6 to 22 (low gear rato) Hgh effcency. Solutons meetng these requrements are two- and three-stage planetary gears consst of smple planetary gears KB. Varyng the nner gear rato (rato of tooth number of rng gear and sun gear) of the smple planetary gear stage KB the performance of planetary gear can be changed and talored to the requrements. Recently some new types of planetary gears (dfferental planetary gears) have been appeared n drve systems of large wnd mlls, whch can dvde the appled power between the 73

2 planetary stages, so ncreasng the load carryng capacty of the planetary drves [1, 2]. The performance of such a planetary gear depends on ts knematcs, ts nner gear ratos and the connectons between the planetary stages. Only detaled calculatons can reveal the behavor of such planetary gears and show the best constructon for a gven applcaton. In a recently publshed paper [1] the performance of three planetary gears: a two-stage planetary gear KB+KB, a three-stage planetary gear KB+KB+KB and a dfferental planetary gear GPV were compared, sketches of structure of whch are presented n Fg 1, 2 and 5. In ths paper two further dfferental planetary gears are dscussed. Ther structure can be seen n Fg. 3 and 4. Fg. 1 Planetary gear KB+KB Fg. 2 Planetary gear KB+KB+KB Fg. 3 Dfferental planetary gear Fg. 4 Dfferental planetary gear PV Fg. 5 Dfferental planetary gear GPV 2. COMPARING THE PROPERTIES OF PLANETARY GEARS In the followng the gear rato and the gear effcency of dfferent planetary gears (Fg.1-5) and also the power dstrbuton between the gear stages are compared, whch were calculated usng the equatons developed by us. In ths calculaton the lmts of geometry were not taken nto consderaton (the values b were ncreased wth rsng the number of teeth of rng gear whle the axs dstances were also ncreased). The results of our analyss are presented n the Fg In the fgures the followng notatons are used: b - s the rato of the number of teeth of sun gear and rng gear at the frst stage, b - s the rato of the number of teeth of sun gear and rng gear at the second stage 74

3 b - s the rato of the number of teeth of sun gear and rng gear at the thrd stage. η - s the gear effcency - s the gear rato. (Speedng gear rato s 1/) Fg. 6 and 7 shows that the planetary gear KB+KB can reach a hgh speedng gear rato (low gear rato), and a good effcency, whch vary wth changng the values of b. The three-stage planetary gear KB+KB+KB results hgher speedng gear rato but at lower gear effcency. Ths fact can be seen when the curves of the Fg. 6 and 7 are compared wth the curves of Fg. 8 and 9. Even at the same gear rato, the effcency of three stage-planetary gear KB+KB+KB s lower than the two-stage planetary gear KB+KB KB+KB b'=-1 b'=-6 b'=-3 b'= b'=-1 b'=-6 b'=-3 b'=-2 KB+KB b" Fg. 6 Planetary gear KB+KB Fg. 7 Planetary gear KB+KB b'=-1 b'=-6 KB+KB+KB b'=-5 b'=-3 b'= Fg. 8 Planetary gear KB+KB+KB b'=-8 b'=-1 b'=-2 KB+KB+KB b'=-2 b'= Fg. 9 Planetary gear KB+KB+KB At the two- and the three-stage planetary gears all powers transmt through each stages of planetary gears. At dfferental planetary gears there are possbltes to dstrbute the power between two planetary stages resultng hgher load carryng capacty at the same szes or decrease the szes and mass of planetary gears at the same appled power. s a dfferental planetary gear nput shaft of whch drves the rng gears of both planetary stages. Calculated characterstcs of planetary gear are presented n F Dagrams n these fgures show that the effcency of planetary gears s hgher than the planetary gears KB+KB and especally KB+KB+KB due to the power dstrbuton. The power ratos of the two stages P4 /P4 are lower at hgher value of b, but ncreasng wth rsng the gear ratos of planetary gears (Fg. 12). The calculated characterstcs of planetary gears PV (Fg 4) are presented n Fg

4 The power rato of dfferental planetary gears PV (Fg. 13) changes n the opposte drecton wth ncreasng the planetary gear rato than at the planetary gears (Fg. 12), but t also decreasng wth ncreasng the gear rato. Its values are a lttle hgher at the same gear rato than the power ratos of planetary gear. The planetary gear PV also s sutable to transmt power at hgh gear up rato wth hgh effcency. There s not too much dfferences between ther effcency, thanks to the power dstrbuton. 97 b'=-1 b'=-6 b'=-3 b'=-2 b'=-2 b'=-3 b'=-6 b'=-1 Fg. 1 Planetary gear b'=-1 b'=-6 b'=-3 b'= b" Fg. 11 Planetary gear P4"/P4' b'=-3 b'=-1 b'=-6 b'=-2 Fg. 12 Planetary gear Pk"/P4' b'=-2 b'=-1 b'=-6 PV b'=-3 Fg. 13 Planetary gear PV 97 b'=-1 b'=-6 b'=-3 b'=-2 PV Fg. 14 Planetary gear PV PV b'=-1 b'=-6 b'= b" Fg. 15 Planetary gear PV b'=-2 76

5 A thrd varant of the dfferental planetary gear s the type of GPV (Fg 5), whch has three planetary stages. Its nput shaft drves both the carrer of the frst planetary stage and the rng gear of the second planetary stage, whle the thrd planetary stage has two drver elements: the rng gear s drven by the sun gear of the second stage and the carrer s drven by the sun gear of the frst stage. The behavor of ths planetary gear was presented n an earler publcaton [1]. As t was proved dfferental planetary gear GPV s sutable to transmt power at hgh gear up rato at hgh effcency (Fg. 16). Its effcency s much hgher than the effcency of three-stage planetary gear KB+KB+KB (Fg. 17). b=-2 b=-3 b=-6 b=-1 97 GPV b'= Fg. 16 Effcency of planetary gears GPV as a functon of gear rato at dfferent nner gear ratos of thrd stage KB+KB+K GPV KB+KB Fg. 17 Effcency of planetary gears as a functon of gear rato, when all nner gear ratos beng equal 3. CONCLUSIONS The results of the theoretcal nvestgatons presented above allow drawng the followng conclusons: The dfferental planetary gears dstrbutng the appled power between two planetary stages have hgher effcency than the three-stage planetary gears. The power rato of the two planetary stages depends on the gear up rato of the dfferental planetary gears: hgher the gear up rato leads to lower power rato. There are not too many dfferences between the effcency of dfferental planetary gears presented above. Further nvestgatons have to be executed to determne, whch varant of the dfferental planetary gears are most benefcal to transmt hgh power at hgh gear up rato and hgh effcency. The nvestgatons wll be contnued to determne the optmum structure of dfferental planetary gears takng nto consderaton also the results of nvestgatons on materals of gears and on lubrcants [7, 8]. 4. REFERENCES 1. Csobán, A., Kozma, M.: Comparng the performance of heavy-duty planetary gears. Gépészet 26, Ötödk Országos Gépészet Konferenca. Budapest, May 26. Excepted for publcaton. 2. Gold, P.W.: Wndenergeanlagen mt Getrebe. Antrebstechnk 6/ Berger, G.: Wndenergeanlagen effzenter gemacht. Antrebstechnk 6/

6 4. Terplán, Z.: Fogaskerék-bolygóművek. Műszak Könyvkadó, Budapest, Müller, H.W.: De Umlaufgetrebe. Sprnger-Verlag. Berln, Kozma, M.: Hajtásrendszerek. Műegyetem Kadó Kalácska G.- Eberst O.- Keresztes R.: Investgaton of frcton of polymer gears. 8th Internatonal Conference on Trbology. Veszprém. June 24. p Kalácska G.- Kocss Z.- Keresztes R.: Developed test method for laboratory evaluaton of engne ols. 8th Internatonal Conference on Trbology. Veszprém. June 24. p

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