▁can ▁be ▁manufact ured , ▁but ▁only ▁for ▁up wind ▁machines ; ▁def lection ▁of ▁bl ades ▁in ▁a ▁down wind ▁machine ▁results ▁in ▁increased ▁tower ▁clear ance . ▁Fe wer ▁bl ades ▁with ▁higher ▁rot ational ▁spe eds ▁reduce ▁peak ▁tor ques ▁in ▁the ▁drive ▁train , ▁resulting ▁in ▁lower ▁g ear box ▁and ▁generator ▁costs . ▁ ▁System ▁reli ability ▁is ▁affected ▁by ▁bla de ▁count ▁primarily ▁through ▁the ▁dynamic ▁loading ▁of ▁the ▁rot or ▁into ▁the ▁drive ▁train ▁and ▁tower ▁systems . ▁While ▁align ing ▁the ▁wind ▁tur bine ▁to ▁changes ▁in ▁wind ▁direction ▁( y aw ing ), ▁each ▁bla de ▁experiences ▁a ▁cy clic ▁load ▁at ▁its ▁root ▁end ▁depending ▁on ▁bla de ▁position . ▁This ▁is ▁true ▁of ▁one , ▁two , ▁three ▁bl ades ▁or ▁more . ▁However , ▁these ▁cy clic ▁loads ▁when ▁combined ▁together ▁at ▁the ▁drive ▁train ▁sh aft ▁are ▁symmet r ically ▁bal anced ▁for ▁three ▁bl ades , ▁yield ing ▁sm o other ▁operation ▁during ▁tur bine ▁y aw . ▁Tur b ines ▁with ▁one ▁or ▁two ▁bl ades ▁can ▁use ▁a ▁pivot ing ▁te eter ed ▁hub ▁to ▁also ▁nearly ▁eliminate ▁the ▁cy clic ▁loads ▁into ▁the ▁drive ▁sh aft ▁and ▁system ▁during ▁y aw ing . ▁A ▁Chinese ▁ 3 . 6 ▁M W ▁two - bla de ▁is ▁being ▁tested ▁in ▁Den mark . ▁M ing y ang ▁won ▁a ▁bid ▁for ▁ 8 7 ▁M W ▁( 2 9 ▁* ▁ 3 ▁M W ) ▁two -