Traceable Torque Measurement under Rotation in Nacelle Test Benches : A Good Practice Guide

T aceable To que Measu emen unde Ro a ion in Nacelle Tes Benches – A Good P ac ice Guide – Paula Weidinge Gisa Foye Physikalisch-Technische Bundesans al (PTB), 2019 2 DOI: h ps://doi.o g/10.7795/530.20190111 This guide has been p oduced wi hin he EURAMET p ojec en i led To que Measu emen in he MN m 1 ange. Mo e in o ma ion abou his collabo a i e esea ch p ojec can be ound on he p ojec ’s websi e h ps://www.p b.de/em p/ind14-home.h ml. The aim o his guide is o p o ide p ac ical in o ma ion and ad ice abou o que measu emen and especially abou o que calib a ion in nacelle es benches o nacelle es bench ope a o s. Disclaime Any men ion o comme cial p oduc s wi hin his guide is o in o ma ion only; i does no imply ecommenda ion o endo semen by he pa ne s in his p ojec . The iews exp essed in his guide a e hose o he au ho s and o he EMPIR 14IND14 p ojec eam. Acknowledgemen o unding The p oduc ion o his guide was unded by he Eu opean Me ology P og amme o Inno a ion and Resea ch (EMPIR). The EMPIR ini ia i e is co- unded by he Eu opean Union’s Ho izon 2020 esea ch and inno a ion p og amme and he EMPIR Pa icipa ing S a es. Au ho ship P epa a ion o his guide was led by Paula Weidinge and Gisa Foye o he Physikalisch-Technische Bundesans al (PTB), B aunschweig (Ge many) wi h ex ensi e inpu om all membe s o he EMPIR 14IND14 p ojec eam. The discussion and inpu o all he pa ne s in he p ojec and hei colleagues a e g ea ly app ecia ed. Sugges ion o he quo a ion o he e e ences Weidinge , Paula and Foye , Gisa, 2019. T aceable To que Measu emen unde Ro a ion in Nacelle Tes Benches: A Good P ac ice Guide. Physikalisch-Technische Bundesans al (PTB). DOI: h ps://doi.o g/10.7795/530.20190111 This documen and all pa s con ained he ein a e p o ec ed by copy igh and a e subjec o he C ea i e Commons use license CC by 4.0 (h ps://c ea i ecommons.o g/licenses/by/4.0/). P ojec logo All copy igh and ela ed o neighbou ing igh s o his logo a e wai ed using he CC0 Public Domain Dedica ion (h ps://c ea i ecommons.o g/publicdomain/ze o/1.0/). DOI: h ps://doi.o g/10.7795/920.20190111 1 The uni o o que can also be w i en as MN·m. 14IND14 – To que Measu emen in he MN·m ange Good P ac ice Guide DOI: h ps://doi.o g/10.7795/530.20190111 3 Con en s 1 In oduc ion 4 1.1 Glossa y 4 1.2 Symbols and hei meaning 4 2 Calib a ion se -up 6 2.1 Place o measu e he e e ence o que 6 2.2 To que ans e s anda d 6 2.3 Da a acquisi ion 7 2.3.1 Ampli ie and il e se ings 7 2.3.2 Timewise synch onisa ion o di e en da a se s 7 2.4 Example o a se -up 8 3 Pe o ming a o que calib a ion 11 3.1 P epa a o y ope a ions and es s 11 3.2 Ambien and bounda y condi ions 12 3.3 Signal e alua ion 13 3.4 De e mina ion o he ze o signal 13 3.4.1 S a ic ze o-poin de e mina ion 14 3.4.2 Ro a ional ze o-poin de e mina ion 14 3.5 Quasi-s a ic o que calib a ion 15 3.6 Cha ac e isa ion maps 15 3.7 C oss alk e ec s 17 3.8 Calib a ion in e al 18 4 E alua ion o he calib a ion esul including a measu emen unce ain y 19 4.1 E alua ion o he ansduce o be calib a ed 19 4.1.1 Rela i e indica ion de ia ion 19 4.1.2 Rela i e epea abili y 20 4.1.3 Rela i e esolu ion 20 4.1.4 Rela i e e e sibili y 21 4.2 Measu emen unce ain y 21 4.2.1 Measu emen condi ions 21 4.2.2 Unce ain y con ibu ion o he esolu ion 22 4.2.3 Unce ain y con ibu ion o he epea abili y 22 4.2.4 Unce ain y con ibu ion o he ans e s anda d 23 4.2.5 Expec ed alue o he indica ion de ia ion 23 4.2.6 Example o an unce ain y calcula ion 23 5 Calib a ion ou pu and bene i o he es bench ope a o 24 Glossa y 25 6 Re e ences 26 4 DOI: h ps://doi.o g/10.7795/530.20190111 1 In oduc ion P io o he ma ke launch o wind u bines (also called nacelles), la ge gea boxes and gene a o s, ex ensi e es s, which can be pe o med on a nacelle es bench, a e o g ea impo ance. One such es is he e iciency de e mina ion o he de ice unde es . Fo di ec e iciency de e mina ion, he mechanical inpu di ec ly a he lange o he de ice unde es and he elec ical o mechanical ou pu o he de ice unde es a e o be measu ed. While he ou pu can al eady be measu ed wi h a su icien unce ain y, measu ing he inpu consis ing o o que and o a ional speed poses a p oblem. A b oad a ie y o measu ing ins umen s is a ailable o measu ing o a ional speeds. The o que ha appea s in nacelle es benches, howe e , anges up o se e al MN m and canno easily be de e mined due o he lack o aceabili y possibili ies. This good p ac ice guide in oduces a me hod o acing la ge o que measu emen up o 5 MN m in nacelle es benches using a o que ans e s anda d. This good p ac ice guide comp ises he ollowing sec ions. A lis o he gene al equi emen s on he pe o mance o a o que calib a ion in nacelle es benches including he calib a ion se -up is gi en in sec ion 2. A desc ip ion o he p epa a o y wo k, es s and ins uc ions on a quasi-s a ic o que calib a ion and a o que calib a ion using so-called cha ac e isa ion maps o co e he en i e ope a ion ange o a nacelle es bench as pa o he pe o mance o a o que calib a ion a e ou lined in sec ion 3. Guidelines o he e alua ion o he calib a ion esul s including he de e mina ion o a measu emen unce ain y a e in oduced in sec ion 4. Sec ion 5 again s a es he bene i s o aceable o que measu emen in nacelle es benches o he ope a o s o he es benches and he easibili y o he calib a ion esul s. Fu he in o ma ion abou unde s anding measu emen and measu emen unce ain y can be ound in he Guide o he exp ession o unce ain y in measu emen (GUM) [7] and he In e na ional Vocabula y o Me ology (VIM) [5]. Gene al in o ma ion abou ope a ing p ocedu es in calib a ion labo a o ies is gi en in DIN 17025 [2], while in o ma ion abou s a ic o que calib a ion can be aken om EURAMET cg-14 [6], one o he Eu opean calib a ion guidelines. 1.1 Glossa y We ha e p o ided a glossa y o echnical e ms ha a ise in he ollowing desc ip ion o a o que calib a ion in nacelle es benches a he end o his documen . 1.2 Symbols and hei meaning Impo an symbols and hei meaning ega ding o que calib a ion in nacelle es benches a e lis ed in Table 1. Table 1 Symbols and hei meaning. Symbol Uni Meaning a % Rela i e esolu ion o he o que measu ing ins umen in he es bench aF % Rela i e esolu ion o he o que measu ing ins umen in he es bench unde load aZ % Rela i e esolu ion o he o que measu ing ins umen in he es bench a e load elease b % Rela i e epea abili y o he o que measu ing ins umen in he es bench sample Hz Sampling equency o he DAQ HNTB/TTS % H Rela i e humidi y measu ed close o he o que measu emen ins umen in he es bench (NTB) and close o he o que ans e s anda d (TTS) k - Ampli ica ion ac o o calcula e he expanded unce ain y based on he combined unce ain y l - In ege numbe o e olu ions ha a e a e aged o e M kN m Inc easing o que load indica ed by he o que ans e s anda d M' kN m Dec easing o que load indica ed by he o que ans e s anda d Mi kN m Inc easing o que load indica ed by he o que measu ing ins umen in he es bench 14IND14 – To que Measu emen in he MN·m ange Good P ac ice Guide DOI: h ps://doi.o g/10.7795/530.20190111 5 Mi ' kN m Dec easing o que load indica ed by he o que load in he es bench Mi    ,M  kN m A i hme ic mean o se e al measu emen s o Mi and M a he same load s ep Mi,0 kN m Residue indica ion o he o que measu emen ins umen in he es bench a e load elease ML kN m To que load s ep nmax min-1 Maximum o a ional speed o he es bench conside ing he de ice unde es nNTB min-1 Ro a ional speed measu ed in he es bench n NTB min-1 A i hme ic mean o he measu emen o o a ional speed q  % Rela i e indica ion de ia ion o he o que measu ing ins umen in he es bench a e aged o e se e al epe i ions q j % Rela i e indica ion de ia ion o he o que measu ing ins umen in he es bench pe load cycle qmax % Maximum alue o q a each load s ep qmin % Minimum alue o q a each load s ep kN m Resolu ion o he o que measu ing ins umen in he es bench o ° En isioned signal esolu ion pe o a ion S mV/V Measu emen signal Sze o. o mV/V Ro a ional o que ze o signal Sze o,s a mV/V S a ic o que ze o signal dwell s Dwell ime be o e measu emen hea s Time o hea up all componen s un il s able condi ions a e eached meas s Measu emen ime depending on he minimum o a ional speed and he numbe o e olu ions ha a e a e aged o e amp s Time o amp up o down o que o o a ional speed s ep s To al measu emen ime pe o que s ep uc % Combined absolu e measu emen unce ain y ui % Unce ain y componen u ep % Unce ain y componen due o he epea abili y u es % Unce ain y componen due o he esolu ion us d % Unce ain y componen due o he deployed o que ans e s anda d U % Expanded absolu e measu emen unce ain y % Rela i e e e sibili y o he o que ansduce in he es bench ϑNTB/TTS °C Tempe a u e measu ed close o he o que measu emen ins umen in he es bench (NTB) and close o he o que ans e s anda d (TTS) 6 DOI: h ps://doi.o g/10.7795/530.20190111 2 Calib a ion se -up Due o se e al cons ain s on nacelle es benches, he ope a o s use di e en me hods in di e en places o measu e he inpu o que o he de ice unde es . An example o a nacelle es bench including he possible posi ions o measu ing o que is depic ed in Figu e 1. In nacelles, he main axis is he x-axis. Consequen ly, he main o que measu ed in nacelle es benches is Mx. Al hough he main axis o o que measu emen in me ology is he z-axis, in he ollowing desc ip ion and ins uc ions, he main axis is he x-axis and he main o que o be measu ed is Mx since his good p ac ice guide is di ec ed a es bench ope a o s. Figu e 1 Examples o o que measu emen op ions in es benches and he coo dina e sys em o a nacelle and, he e o e, he es bench [9]. 2.1 Place o measu e he e e ence o que To de e mine he e iciency o a de ice unde es using he di ec measu emen me hod by de e mining he inpu and ou pu o he de ice unde es , he o que should ideally be measu ed di ec ly a he connec ion lange be ween he es bench and he de ice unde es . In mos es benches, specially designed adap e s a e equi ed o ins all his addi ional o que ansduce o measu e he e e ence o que. A calib a ion o he es bench is no possible wi hou a de ice unde es , because only hen is a o que gene a ion possible. Fo a calib a ion o he ypical es ing ange ( o que and o a ional speed) o he es bench, a sui able es objec ep esen ing equen ly es ed objec s is o be ins alled on he es bench. Ideally, his es objec p o ides ull access o i s con ol sys em o allow he ini ia ion o se e al con ol scena ios dependen on he con olled change o elec ical b aking powe asse ed by he gene a o . All o que ansduce s, he e e ence o que ansduce as well as he o que ansduce in he es bench, mus be aligned e y p ecisely o minimise pa asi ic pe manen loads such as longi udinal and la e al o ces (Fx, Fy and Fz) and bending momen s (My and Mz) on he o que ansduce . Possible misalignmen s a e caused by a lack o plana i y on he adap e s, a lack o concen ici y o he en i e d i e ain, and a w ong dis ance be ween he load applica ion sys em and he de ice unde es . 2.2 To que ans e s anda d Fo measu ing he e e ence o que, o which he o que measu emen in a es bench is hen compa ed, a so-called o que ans e s anda d is needed. A ans e s anda d is a measu emen gauge ha bea s a de ined ela ion be ween a physical quan i y, which in his case is o que, and a uni o measu emen , he e kN m. This o que ans e s anda d is o be calib a ed acco ding o EURAMET cg-14 [6], a Eu opean calib a ion guide o DIN 51309 [3], he Ge man o que s anda d. A o que ans e s anda d has o mee se e al equi emen s. Fi s , he ans e s anda d mus ha e a su icien measu emen ange o co e he ope a ional o que ange o he es bench, and i is o be calib a ed o e his measu emen ange. The bes physical p inciple wo king in he MN m o que ange is he de ec ion o s ains by means o al e na ing elec ical esis ance using s ain gauges. The s ain gauges a e glued o a de o ma ion body made o s eel. To gain he equi ed s i ness o he ans e P ime mo e Load applica ion sys em Main gea box Gene a o (load machine) De ice unde es To que based on elec ical powe and o a ional speed To que based on elec ical powe and o a ional speed To que on low speed sha To que on low speed sha wi h addi ional loads To que on high speed sha z y x 14IND14 – To que Measu emen in he MN·m ange Good P ac ice Guide DOI: h ps://doi.o g/10.7795/530.20190111 7 s anda d’s de o ma ion body and a su icien sensi i i y a he same ime, a hollow sha - ype de o ma ion body is bes (p ojec esul aken om [10]). Mo eo e , he ans e s anda d mus wi hs and he occasionally occu ing addi ional mechanical loads c ea ed by he load applica ion sys em as i is ins alled di ec ly a he hub lange o he de ice unde es and is, he e o e, exposed o all simula ed wind loads caused by he load applica ion sys em. E en when no explici addi ional loads a e applied o he d i e ain, he load applica ion sys em deploys loads o s abilise he d i e ain, leading o powe losses and addi ional ic ion o que along he d i e ain du ing o a ion. Fo in o ma ion abou hese addi ional loads and o su eillance easons, he ans e s anda d should be equipped wi h addi ional measu ing b idges o sense bending momen s, and longi udinal and la e al o ces. Addi ional knowledge abou he beha iou o he ans e s anda d unde al e na ing empe a u e (and humidi y) is ad an ageous, since he ambien condi ions in a es bench do no comply wi h he labo a o y condi ions du ing he calib a ion o he ans e s anda d. In gene al, he ans e s anda d has o mee special equi emen s ega ding i s dimensions and weigh . These equi emen s a e no only limi ed by he es benches, bu also by he a ailable o que calib a ion machine ha is used o cha ac e ise he o que ansduce and lead o i being a ans e s anda d. In o de o induce he o que load up o se e al MN m co ec ly and o ensu e he easy moun ing o he ans e s anda d, a lange wi h bo e holes o bol s is an app op ia e ype o connec ion. As men ioned abo e, his migh call o specially designed adap e s o ins all he ans e s anda d in he es bench. 2.3 Da a acquisi ion A imewise synch onised da a eco ding o he o que measu ed by he ansduce o he es bench and by he ans e s anda d can be ealised ei he by one sha ed o by wo synch onised da a acquisi ion sys ems. Rega dless o he da a acquisi ion sys em used, all eco ded da a should be imes amped, and bo h he s a and end ime o he measu emen a e o be documen ed. O he han o s a ic calib a ions, he signals a e o be eco ded con inuously o enable an in es iga ion o he angula accele a ion and i s impac on he o que signals. The quan i ies o be measu ed du ing a calib a ion a e lis ed in Table 2. Table 2 Quan i ies o be measu ed o a o que calib a ion in es benches. Quan i y o be measu ed Symbol Reading Uni To que measu ed by he ansduce in he es bench Mi mV/V kN m Ro a ional speed measu ed by ins umen s in he es bench o he TTS nNTB V min-1 To que measu ed by he ans e s anda d M mV/V kN m Tempe a u e measu emen close o he es bench ansduce and he ans e s anda d ( emp. meas. inside he ans e s anda d) ϑNTB, ϑTTS V °C Humidi y measu emen close o he es bench ansduce and he ans e s anda d (humid. meas. inside he ans e s anda d) HNTB, HTTS V % H Tempe a u e ϑ and humidi y H a e o be measu ed as close o bo h o que ansduce s as possible. Ideally, empe a u e and humidi y a e measu ed inside he ans e s anda d, whe e he s ain gauges a e loca ed, and no only ce ain empe a u e poin s bu also he empe a u e g adien s o e he ansduce s and he adjacen componen s a e o be eco ded. All ansduce measu emen signals should be co ec ed o changes in he en i onmen al condi ions. 2.3.1 Ampli ie and il e se ings All signals should be eco ded using an adequa e sampling equency aking he o a ional speed nNTB and he en isioned esolu ion o o bo h o que signals and he o a ional speed in o accoun . The esolu ion aimed a is o = 1° o he maximum o a ional speed nmax . The lowes limi o he sample equency sample can be calcula ed acco dingly: sample ≥ nmax / o ⋅ 360° , (1) whe e he sampling equency sample is in Hz and he o a ional speed nmax is in s-1. Fu he mo e, a low pass il e should be implemen ed o a oid aliasing e ec s. 2.3.2 Timewise synch onisa ion o di e en da a se s To synch onise all componen s o one da a acquisi ion sys em o wo di e en da a acquisi ion sys ems including all hei componen s, ei he a collec i e ime se e , whe e all associa ed componen s use he same ne wo k ime p o ocol o a simple synch onisa ion signal, which is eco ded and imes amped by he di e en componen s and da a acquisi ion sys ems, can be deployed. Conce ning he accu acy, bo h me hods a e su icien . 8 DOI: h ps://doi.o g/10.7795/530.20190111 When assigning he squa e-wa e me hod o synch onise he da a se s, he squa e-wa e signal is used o shi he da a in pos -p ocessing and o e ase he empo al shi be ween he wo da a se s. The squa e-wa e can ha e, e.g., an ampli ude o u sync=±5 V and a equency o squa e = 0.2 Hz. While a ough alignmen o he da a se s is achie ed by he logged s a ime and by dis inc i e signal changes as shown in Figu e 2a), he ine synch onisa ion is based on he squa e-wa e signal, which is depic ed in Figu e 2b). An ad an age o he imewise synch onisa ion using a squa e-wa e signal is i s easy implemen a ion in di e en es benches wi h all kinds o da a acquisi ion sys ems. Figu e 2 Timewise synch onisa ion o he da a se s o he o que ans e s anda d and he nacelle es bench using an ideal squa e-wa e signal, which is eco ded by bo h da a acquisi ion sys ems, o a p ecise alignmen o he di e en da a se s. 2.4 Example o a se -up In he example o a calib a ion se -up in Figu e 3, he o que ans e s anda d ha measu es he e e ence o que is placed di ec ly a he hub lange o he de ice unde es as equi ed. Mo eo e , an o e iew o he equi emen s on he ans e s anda d based on a su ey o es bench ope a o s wi hin he EMPIR 14IND14 p ojec is lis ed in Table 3, while he gene al equi emen s ega ding he dimensions and he weigh o he ans e s anda d a e lis ed in Table 4. Figu e 3 The e e ence o que ansduce o calib a e he o que measu emen in a nacelle es bench is ins alled di ec ly a he hub lange o he de ice unde es , whe e he mechanical inpu o he de ice unde es is o be de e mined (4 MW nacelle es bench o he Cen e o Wind Powe D i es a RWTH Aachen). To que ansduce Re e ence o que ansduce Mo o Load applica ion sys em Nacelle 14IND14 – To que Measu emen in he MN·m ange Good P ac ice Guide DOI: h ps://doi.o g/10.7795/530.20190111 9 Table 3 Requi emen s o he RWTH Aachen es bench on o que ans e s anda ds o calib a ing nacelle es benches ega ding he ca ying capaci y aken om [8]. To que Nominal o que kN m ± 6000 Maximal o que kN m ± 7000 To que measu emen accu acy % 0.1 Fo ces and momen s Pa asi ic loads Ope a ing loads Fo ces (Fx, Fy, Fz) kN ± 100, ± 100, ± 100 ± 1450, ± 2000, ± 2000 Maximum o ces (Fx, Fy, Fz) kN ± 100, ± 100, ± 100 ± 2000, ± 3000, ± 3000 Momen s (My, Mz) kN m ± 100, ± 100 ± 7500, ± 7500 Maximum momen s (My, Mz) kN m ± 100, ± 100 ± 15000, ± 15000 Fo ces/momen s mus be ansmi ed Requi emen Measu emen o o ces/momen s Op ional Li ecycles S a ic s ess assessmen (cycles @ max. o que) 5000 Fa igue s ess assessmen (cycles @ max. o que) Failsa e 1012 Kinema ic Nominal o a ional speed min-1 12 Maximum o a ional speed min-1 25 Measu emen du ing o a ion Requi emen Measu emen in bo h o a ional di ec ions Requi emen Table 4 Dimensional equi emen s o PTB’s 1.1 MN m o que s anda d machine on a o que ansduce o be calib a ed and, a e wa ds, o be deployed o calib a e he o que measu emen ins umen in he nacelle es benches o RWTH Aachen. Dimensions Maximum lange diame e o calib a ion machine m 1.25 Maximum lange diame e o es bench m 4.5 Minimum leng h o calib a ion machine m 0.6 Maximum leng h o calib a ion machine m 2.2 Maximum weigh o calib a ion machine 2 Flanges: h ough-hole Requi emen • 30 x M36 on bol ci cle Ø 900 mm Requi emen • Fo es benches, an adap e is equi ed Op ional Addi ionally, he e is a lis o me ological equi emen s on he beha iou o he ans e s anda d in Table 5. Table 5 Me ological equi emen s on a o que ans e s anda d o become an adequa e o que ans e s anda d. Me ological pa ame e s Non-linea i ies ≤ ± 0.05 % Hys e esis ≤ 2.9·10-5 mV/V In e pola ion de ia ion ≤ |0.019| % D i o e ime ≤ 8·10-3 % C eep (sho e m c eep) ≤ |3·10-3| % An example o a o que ans e s anda d o nacelle es bench calib a ion is shown in Figu e 4. This ans e s anda d is owned by PTB, he na ional me ology ins i u e o Ge many, and was p oduced by Ho inge Baldwin Mess echnik GmbH. I has a measu emen ange o 5 MN m and is s a ically calib a ed up o 1.1 MN m wi h an expanded ela i e unce ain y o 8.8·10-4 (k = 2) acco ding o DIN 51309 (which is compa able o EURAMET cg-14) using he wo ld’s la ges o que s anda d machine loca ed a PTB. Due o he e y small non-linea i ies o he o que ans e s anda d, a linea eg ession cu e was asce ained o clockwise o que load applied in inc easing and dec easing s eps: M = 3851.1 kN m/(mV/V) ⋅ S . (2) Abo e 1.1 MN m, a calib a ion is no possible. To p edic he ela ion be ween he ou pu signal and he applied o que, including a p edic ed measu emen unce ain y aking he p edic ion i sel in o accoun , an ex apola ion me hod was de eloped. 16 DOI: h ps://doi.o g/10.7795/530.20190111 So-called cha ac e isa ion maps p o ide a simple solu ion o ec i ying his p oblem. A simila p ocedu e o his has been sugges ed o o a o y powe measu emen [1]. Mos es benches ha e a de ined main di ec ion o o a ion. Fo hese es benches, only one di ec ion o o que load is o be calib a ed. Howe e , i downwind nacelles a e es ed on he es bench, bo h o que applica ion di ec ions a e o be calib a ed. Mo eo e , since nega i e o que can appea du ing b aking scena ios, he e ec o applying nega i e o que on he hys e esis beha iou and he ze o e u n should be analysed o all nacelle es benches. To de ine he measu emen poin s o he cha ac e isa ion maps, he ypical ope a ing ange o he es bench, depending on he commonly es ed de ices, is o be lis ed. The ypical ope a ing ange is depic ed in Figu e 9 in he o m o a blue ec angle. I should be poin ed ou ha he ange o he cha ac e isa ion map is limi ed by he ins alled de ice unde es du ing he calib a ion measu emen s. Fo ha eason, he de ice unde es is o be picked acco dingly. Figu e 9 Schema ic depic ion o a cha ac e isa ion map based on he ypical es ing ange o a nacelle es bench wi h a uni o m dis ibu ion o he measu emen poin s. When he e a e no pa icula poin s wi hin he ope a ing ange which need o be calib a ed explici ly, such as ypical maximum o que loads o ce ain de ices unde es , he load s eps should be sp ead e enly as shown in Figu e 9 in he o m o he Xs. In gene al, he calib a ion should co e he en i e ope a ing ange o he es bench by epea ing he s anda d calib a ion wi h di e en combina ions o o que load and o a ional speed (Figu e 10). To in es iga e he in luence o o a ional speed on he o que measu emen , he e a e wo di e en ca ego ies o cha ac e isa ion maps: o CM1 (CM1a and CM1b in Figu e 10), he o que is pe iodically ixed while he o a ional speed is al e ed s epwise; and o CM2 (CM2a and CM2b in Figu e 10), he o a ional speed is kep cons an pe iodically while he o que load is inc eased and dec eased. All o ms o he cha ac e isa ion map ha e he same ope a ing ange. To de e mine he hys e esis o he es bench o que ansduce , each calib a ion poin should be me wice du ing one load cycle: i s when aising he inc emen and second when a enua ing i again. A en ion is o be paid o omi ing o a ional speed s eps close o eigen equencies o he sys em, which would lead o undesi ed dynamic e ec s. He e again, bo h he o que and o a ional speed can be inc eased o accele a ed espec i ely s epwise as a amp, a s ep o a sine, whe eby he amp is he mos common one. Mo eo e , i his ype o combined calib a ion is no su icien , single calib a ions o each ypical load, so-called pa ial ange calib a ions, can be pe o med. Fo a s a is ical e alua ion o he calib a ion measu emen s, each cha ac e isa ion map is o be epea ed wice o each load s ep is o be passed a leas ou imes. Should a calib a ion like his no be possible a all due o a lack o access o he con ol sys em o he de ice unde es , he calib a ion has o be pe o med in he median o he ypical es ing ange (see Figu e 9c)) wi h a sui able s anda d de ice unde es . Because o he se -up and he pe manen ly ac ing con ol sys ems in a es bench, he de e mina ion o he ansduce c eep is no possible, which should no pose a p oblem. A leas one map pe ca ego y (CM1 and CM2) is o be pe o med in o de o in es iga e he in luence o he o a ional speed on he o que measu emen . I a closed loop con ol is no possible, hen pe o ming only CM2 is su icien , since he ep oducibili y o CM1 would no be good wi hou a closed loop con ol anyway. To que Ro a ional speed ypical es ing ange measu emen poin To que Ro a ional speed To que Ro a ional speed 14IND14 – To que Measu emen in he MN·m ange Good P ac ice Guide DOI: h ps://doi.o g/10.7795/530.20190111 17 Figu e 10 Example o di e en load s ep sequences o a calib a ion wi h o que being inc eased (and dec eased) and o a ional speed being accele a ed and decele a ed a each o que s ep and ice e sa. 3.7 C oss alk e ec s The assembly p ocess and he in eg a ion o he nacelle in o he es bench a e challenging, because o he la ge masses and dimensions o nacelles. Fo example, a 5 MW nacelle has he ollowing dimensions: 6.5 m heigh , 6.5 m wid h and 17 m leng h and a o al mass o 290 . E en a e y accu a e assembly leads o an axis misalignmen be ween he main sha o he es bench and he hub o he nacelle. This axis misalignmen may be in he ange o up o 0.5 mm and, he eby, i may gene a e pa asi ic loads in he o m o o ces (Fx, Fy, and Fz) and bending momen s (My and Mz) unde o a ion. The con ol sys em o he load applica ion sys em ies o keep hese pa asi ic loads o ze o. Howe e , due o he inaccu acy o he con ol sys em, he pe ec limi a ion o he pa asi ic loads o ze o is no possible in mos cases. Consequen ly, an applica ion o pu e o que du ing he calib a ion is no possible. Figu e 11 shows examples o he addi ional loads on he o que ans e s anda d wi hin he a e aging sequence o e an in ege numbe o dis inc o a ions (he e six o a ions). Addi ional in luences on he o que ansduce a e no desi ed as hey no only ha e an in luence on he in ended measu ing b idges bu also on he o he measu ing b idges, which causes an unin en ional signal al e a ion. Figu e 11 Pa asi ic loads du ing he calib a ion a he o que s ep o 1000 kN m and o a ional speed o 6.5 min-1. 18 DOI: h ps://doi.o g/10.7795/530.20190111 The close su eillance o addi ional loads is, he e o e, necessa y o a oid unwan ed in luences on he o que measu emen . Howe e , mos pe iodic in luences o addi ional loads can be neglec ed due o he a e aging o he o que signal. To pu posely s udy c oss alk in luences on he o que signal, cha ac e isa ion maps simila o Figu e 12 a e sugges ed. Figu e 12 Schema ic p inciple o in es iga ing he c oss alk in luence on he o que signal caused by addi ional loads. 3.8 Calib a ion in e al Fo es benches in ol ed in de elopmen es s o es benches in gene al o in he de elopmen o he de ices unde es , he calib a ion in e al should no exceed 12 mon hs. The calib a ion in e al o he o que measu emen ins umen in he es bench highly depends on he se -up and he usage o he es bench and he quali y p ocedu e in he es bench. Fo es benches, which a e mainly used o de e mine he e iciency o he de ice unde es , he ecommenda ion o he calib a ion in e al is a he long a up o 24 mon hs. A e e e y change o he unde lying eg ession cu e o any main enance o alignmen conce ning he o que measu emen ins umen , a ecalib a ion is equi ed. Ideally, a calib a ion a he beginning and a he end o a de ice unde es being assembled and es ed would be p e e able. In eali y, howe e , he u ilisa ion and ac i i y o he es bench need o be conside ed as well. 14IND14 – To que Measu emen in he MN·m ange Good P ac ice Guide DOI: h ps://doi.o g/10.7795/530.20190111 19 4 E alua ion o he calib a ion esul including a measu emen unce ain y The se -up o calib a ing a o que ansduce in a es bench by using a o que ans e s anda d is compa able o a e e ence o que calib a ion machine. In a e e ence o que calib a ion machine, a calib a ed and e y well-known o que ansduce is deployed o calib a e ano he o que ansduce . Due o he simila i y o he se -up, he e ec s du ing he calib a ion a e analogous. O he han he load cycles, which a e based on EURAMET cg-14, he e alua ion o he calib a ion esul is based on ISO 7500-1 [4]. ISO 7500-1 desc ibes he calib a ion o a o ce measu emen sys em in ma e ial es ing machines. He e, he deployed me hod does no necessa ily demand ha he exac load s eps a e me . Ins ead, an indica ion de ia ion be ween he ansduce o be calib a ed and he ans e s anda d is calcula ed. Fo he o que calib a ion in es benches, he calib a ion esul is adap ed o he calib a ion esul in ISO 75100-1 and consis s o : • he ela i e indica ion de ia ion q, • he measu emen unce ain y uc o he indica ion de ia ion, and • he e e sibili y (in case inc easing and dec easing o que load was applied). The calib a ion esul is no a classi ica ion o he ansduce calib a ed as is common o calib a ions. The calib a ion esul can be used in he o m o : • a look-up able ( o co ec he esul by consul ing he able), • a eg ession cu e ( o co ec he esul in pos -p ocessing), o • a co ec ion o he unde lying eg ession cu e o he es bench ansduce ( equi es a second calib a ion o he es bench ansduce using he co ec ed eg ession cu e o de e mine he measu emen unce ain y). The e alua ion o an example o a o que calib a ion unde cons an o a ion can be ound in he ollowing publica ions: P. Weidinge , G. Foye , S. Kock, J. Gnaue , R. Kumme 2018 P ocedu e o o que calib a ion unde cons an o a ion in es iga ed on a nacelle es bench in P oc. o Senso en & Messsys eme 2018, Nu embe g, Ge many P. Weidinge , G. Foye , S. Kock, J. Gnaue , R. Kumme Calib a ion o o que measu emen unde cons an o a ion in a wind u bine es bench submi ed o JSSS. 4.1 E alua ion o he ansduce o be calib a ed The pe o mance o he o que ansduce o be calib a ed can be e alua ed by he ela i e indica ion de ia ion q, he ela i e epea abili y b, he ela i e esolu ion a, and he de e mina ion o he ela i e e e sibili y when a calib a ion o dec easing o que is desi ed. All he ollowing subsec ions a e adap ed om ISO 7500-1. 4.1.1 Rela i e indica ion de ia ion The ela i e indica ion de ia ion qj(ML) is he de ia ion o he o que measu emen ins umen in he es bench om he o que ans e s anda d ela i e o he eal o que alue measu ed by he o que ans e s anda d pe load s ep ML. I is o be calcula ed o each o he a leas wo epea ed load cycles j (1 and 2) o cha ac e isa ion maps: qj(ML) = Mi,j(ML) - Mj(ML) Mj(ML) ⋅ 100% , (14) wi h j = 1,…, n , whe e Mi is he inc easing o que load indica ed by he o que measu ing ins umen in he es bench, and M is he inc easing o que load indica ed by he o que ans e s anda d. The calib a ion esul is ep esen ed as a ela i e indica ion de ia ion q (ML), which is he a i hme ic mean o he ela i e indica ion de ia ion pe epe i ion qj(ML): q (ML) = 1 n∑qj(ML) n j = 1 . (15) Figu e 13 is an example o a depic ion o he ela i e indica ion de ia ion o a quasi-s a ic load cycle unde cons an o a ion. To assess he calib a ion esul and he in e ela ion be ween he applied o que 20 DOI: h ps://doi.o g/10.7795/530.20190111 and he o a ional speed, no only is he ela i e indica ion de ia ion o be calcula ed, bu also he s anda d de ia ion o his alue. Depending on he s anda d de ia ion o he epea ed measu emen s, a dis inc ion be ween he o que de ia ions con ingen on he di e en applied o a ional speeds can be made. Figu e 13 Example o indica ion de ia ion o ou epe i ions and a e aged indica ion de ia ion. 4.1.2 Rela i e epea abili y The quali y o epea ing he o que measu emen s in he es bench is desc ibed by he ela i e epea abili y b. This ela i e epea abili y is calcula ed o each load s ep sepa a ely and is he di e ence be ween he maximum indica ion de ia ion qmax and he minimum indica ion de ia ion qmin pe load s ep: b(ML) = max j(qj(ML)) - min j(qj(ML)) . (16) The ela i e epea abili y is an impo an con ibu ion o he measu emen unce ain y and an example o his is illus a ed in Figu e 13. 4.1.3 Rela i e esolu ion Mos es benches a e s a e o he a and display he applied load digi ally. The e o e, he ocus ega ding he esolu ion lies on digi al o que displays. In gene al, he esolu ion depends on he esolu ion o he ampli ie ’s A/D con e e and he da a sa ing o ma . Howe e , i he indica ion luc ua ion exceeds his esolu ion, he esolu ion is o be summed up by hal he span o he indica ion luc ua ion. The indica ion luc ua ion is o be de e mined wi h he p ime mo e and he de ice unde es swi ched on, bu wi h no load applied. To de e mine he indica ion luc ua ion, he signal is o be a e aged pe e olu ion o e he a e aging sequence as depic ed in Figu e 14, hen he minimum and maximum o he a e aged signals pe e olu ion a e o be ound and he di e ence is calcula ed. Subsequen ly, he ela i e esolu ion a is o be de e mined o each load s ep depending on he applied load: a(ML) = (ML) M(ML) ⋅ 100% , (17) wi h (ML) = max l l(ML) - min l l(ML) 2 , (18) whe e M is he o que load o he obse ed load s ep (a e aged alues o all epe i ions). The esolu ion is o be ep esen ed in he same uni as he measu ed o que. epea abili y e e sibili y 14IND14 – To que Measu emen in he MN·m ange Good P ac ice Guide DOI: h ps://doi.o g/10.7795/530.20190111 21 Figu e 14 Schema ic igu e on how o de e mine he indica ion de ia ion pe load s ep. 4.1.4 Rela i e e e sibili y Fo he special case ha a eg ession cu e o dec easing o que load is demanded, he ela i e e e sibili y o he dec easing load can be de e mined. Howe e , i is o be emphasised ha he e e sibili y highly depends on he maximum o que load applied be o ehand. To de e mine he ela i e e e sibili y, he deployed o que ans e s anda d mus be calib a ed o dec easing o que load. Mo eo e , o he e e sibili y measu emen s, only one dec easing load cycle is o be pe o med. Based on he de ia ion be ween he o que measu emen alues o inc easing and dec easing load s eps (Figu e 13), he ela i e e e sibili y is calcula ed: = M - M' M  ⋅ 100% . (19) 4.2 Measu emen unce ain y As men ioned abo e, he p e ailing calib a ion se -up is compa able o a e e ence calib a ion machine, whe e he ansduce o be calib a ed is compa ed o a na ional s anda d. Thus, in gene al, o an NTB calib a ion, he in luences on he ansduce o be calib a ed a e he same as hose in a e e ence o que s anda d machine bu e en la ge . The measu emen unce ain y i sel is based on he a o emen ioned ac o s and consis s o he ollowing unce ain y con ibu ions: • he esolu ion, • he epea abili y, and • he o que ans e s anda d. All his esul s in he bes expec ed alue o he indica ion de ia ion and he co esponding expanded measu emen unce ain y. The ollowing e alua ions a e based on ISO 7500-1 and a e adap ed o a o que calib a ion unde o a ion. 4.2.1 Measu emen condi ions In gene al, he in luences on he o que ansduce o be calib a ed a e he same as hose in a e e ence o que s anda d machine bu e en la ge . The Ishikawa diag am in Figu e 15 lis s examples o possibly occu ing in luences a ec ing he calib a ed o que measu emen in a nacelle es bench. Mos in luences can be quan i ied and ca ego ised by he a o emen ioned p epa a o y ope a ions and es s. Addi ionally, all se -up-speci ic e ec s, i.e., misalignmen s and ic ion in di e en componen s a e di ec ly pa o he calib a ion esul and ha e al eady been conside ed in he measu emen unce ain y by de e mining he epea abili y. Eme gency b aking, which may occu and is o be es ed unde no mal es ing condi ions, should be a oided du ing he calib a ion p ocess. A e eme gency b aking, he es bench is o be ope a ed wi h maximum o que load in he d i ing di ec ion o a leas 3 min and a new ze o signal is o be de e mined. In doing so, he hys e esis e ec due o he opposi e o que load is minimised. 1 2 3 4 5 6 22 DOI: h ps://doi.o g/10.7795/530.20190111 In he case ha di e en ampli ie s we e used o he calib a ion o he o que ans e s anda d han o he calib a ion in he nacelle es bench, he di e ence be ween he di e se ampli ie s is o be accoun ed o in he measu emen unce ain y o e en he indica ed o que alue. Because o he signal a e aging o e a ce ain numbe o e olu ions, he dead-weigh in luence on he o que signal can be neglec ed. Figu e 15 Ishikawa diag am lis ing he in luences du ing he calib a ion o he o que measu emen in nacelle es benches. 4.2.2 Unce ain y con ibu ion o he esolu ion The unce ain y con ibu ion o he ela i e esolu ion o he o que measu emen ins umen in he es bench u es o each examined load s ep is he squa e oo o he sum o he ollowing componen s squa ed: • he unce ain y componen due o he ela i e esolu ion o he o que measu emen ins umen in he es bench unde load, which is deno ed as aM di ided by 2√3 because o he assump ion o a ec angula dis ibu ion, • he unce ain y componen due o he ela i e esolu ion o he o que measu emen ins umen in he es bench a e load elease, which is deno ed as aZ di ided by 2√3 (same assump ion o a ec angula dis ibu ion). The ela i e esolu ion o he o que measu emen a e load elease is pa o he indica ion de ia ion o e e y load s ep because o he a o emen ioned a ing o he o que alues o e e y load s ep. The unce ain y con ibu ion o he ela i e esolu ion can be calcula ed o e e y load s ep as ollows: u es(ML) = √(aM(ML) 2√3)2 + (aZ 2√3)2 . (20) As he ela i e esolu ion a is exp essed in he uni %, he absolu e unce ain y con ibu ion o he ela i e esolu ion u es is exp essed in % as well. 4.2.3 Unce ain y con ibu ion o he epea abili y As men ioned be o e, he ela i e epea abili y is conside ed as an unce ain y con ibu ion o he o al unce ain y o he indica ion de ia ion. The unce ain y con ibu ion o he epea abili y u ep is he s anda d de ia ion o he bes expec ed alue qi in % and he ela i e mean indica ion de ia ion q  in %, whe e n is he numbe o epe i ions pe load s ep: u ep(ML) = √1 n (n - 1) ∑ (q j (ML) - q (ML))2 n j = 1 . (21) Sampling equency Dead-weigh Misalignmen Humidi y Tempe a u e/ Temp. g adien s P essu e D i Measu emen unce ain y En i onmen al condi ions C eep To que ans e s anda d Calib a ed o que in he wind u bine es bench S abili y Resolu ion EMC Measu emen condi ions Misalignmen s Pa asi ic loads LAS To que in e sion F ic ion in di . comp. Ampli ie s To que ansduce Ze o-poin de ia ion Repea abili y Re e sibili y C eep Fil e Negligible Gene al e ec s Se -up speci ic e ec s Ro a ional speed 14IND14 – To que Measu emen in he MN·m ange Good P ac ice Guide DOI: h ps://doi.o g/10.7795/530.20190111 23 4.2.4 Unce ain y con ibu ion o he ans e s anda d The unce ain y con ibu ion o he o que ans e s anda d us d is gi en by he ela i e calib a ion unce ain y o he ans e s anda d ucal, which is s a ed in i s calib a ion ce i ica e, and addi ional possible unce ain y con ibu ions (A, B, and C) due o de ia ing empe a u e and humidi y du ing he calib a ion measu emen s, d i o e ime, and de ia ions because o he deployed combined linea eg ession cu e o inc easing and dec easing o que load. The unce ain y con ibu ion o he o que ans e s anda d is calcula ed acco ding o he ollowing: us d(ML) = √(ucal(ML))2 + A2 + B2 + C2 . (22) As he unce ain y con ibu ion o he o que ans e s anda d is shown as a ela i e unce ain y, i is exp essed as a pe cen age (%). 4.2.5 Expec ed alue o he indica ion de ia ion The esul o he o que calib a ion is he bes expec ed alue o he mean ela i e indica ion de ia ion q (ML) o he o que measu emen ins umen in he es bench. Mo eo e , an expanded measu emen unce ain y U(ML) belongs o his ela i e indica ion de ia ion, which is he p oduc o he co e age ac o k and he combined unce ain y uc(ML): UU(ML) = k ⋅ uc(ML) = k ⋅√∑(uj(ML))2 n j=1 = k ⋅√(u es(ML))2 +(u ep(ML))2+(us d(ML))2 . (23) Addi ional unce ain y con ibu ions may be in luences o he deployed ampli ie s o he o que ans e s anda d o signi ican in luences o he ic ion o que. I is ecommended o use a co e age ac o o k = 2. In ce ain cases, k can also be calcula ed based on he numbe o e ec i e deg ees o eedom as s a ed in he GUM. Anno a ion: he measu emen unce ain y is an absolu e measu emen unce ain y o he ela i e indica ion de ia ion, which is ep esen ed in he uni %. The absolu e measu emen unce ain y has he same uni as i s e e ence alue. Consequen ly, he uni o he absolu e measu emen unce ain y is %. 4.2.6 Example o an unce ain y calcula ion An example o a calcula ion o he measu emen unce ain y o o que calib a ion unde cons an o a ion is gi en in P. Weidinge , G. Foye , S. Kock, J. Gnaue , R. Kumme Calib a ion o o que measu emen unde cons an o a ion in a wind u bine es bench submi ed o JSSS. This pape co e s a comple e conside a ion o a o que calib a ion unde cons an o a ion in a nacelle es bench including he measu emen unce ain y budge and he empe a u e di e ence be ween he calib a ion labo a o y, whe e he o que ans e s anda d was calib a ed, and he condi ions du ing he nacelle es bench calib a ion. Mo eo e , a de ailed calcula ion o he ela i e indica ion de ia ion o ou measu emen epe i ions is gi en. The expanded (k = 2) absolu e measu emen unce ain y U(ML) o he bes expec ed alue o he ela i e indica ion de ia ion is calcula ed including he unce ain y con ibu ion o he o que ans e s anda d, which comp ises he d i o he ansduce , he empe a u e in luence and he unce ain y o he ampli ie calib a ion (special case). 24 DOI: h ps://doi.o g/10.7795/530.20190111 5 Calib a ion ou pu and bene i o he es bench ope a o The esul o a o que calib a ion in nacelle es benches can be exp essed in di e en o ms: • a look-up able (pos -p ocessing), • a eg ession cu e (pos -p ocessing), o • a co ec ion o he o que ansduce s unde lying he ans e cu e (addi ional calib a ion equi ed a e wa ds). In gene al, he possibly occu ing indica ion de ia ions in he o que measu emen o a nacelle es bench can be co ec ed by all he di e en o ms o he calib a ion esul . Mo eo e , he calib a ion gi es a measu emen unce ain y o he calib a ed ange, which is again a con ibu ion o he measu emen unce ain y o he e iciency de e mina ion. Tes bench ope a o s can bene i om knowing he de ia ion be ween hei in e nal o que measu ing ins umen and a aced na ional o que s anda d and co ec ing his de ia ion o ob ain a mo e accu a e o que measu emen esul . Fu he mo e, a e a calib a ion, he p ecision including he epea abili y o he o que measu emen ins umen in he nacelle es bench is de e mined. Based on his, no only can he e iciency o de ices unde es be de e mined mo e eliably, bu also he da a o alida e simula ions and he epea able componen es ing gain c edibili y. Wi h he s anda dised calib a ion o o que measu emen s in nacelle es benches, e iciencies o de ices es ed on di e en es benches can be compa ed o each o he eliably. 14IND14 – To que Measu emen in he MN·m ange Good P ac ice Guide DOI: h ps://doi.o g/10.7795/530.20190111 25 Glossa y • Calib a ion: ope a ion ha , unde speci ied condi ions, in a i s s ep, es ablishes a ela ion be ween he quan i y alues wi h measu emen unce ain ies p o ided by measu emen s anda ds and co esponding indica ions wi h associa ed measu emen unce ain ies and, in a second s ep, uses his in o ma ion o es ablish a ela ion o ob aining a measu emen esul om an indica ion (VIM 2.39). • Cha ac e isa ion map: load cycle co e ing he ypical ope a ion ange o a nacelle es bench. The cha ac e isa ion map is limi ed by he de ice unde es ins alled du ing he calib a ion. • C oss alk e ec : in luence o addi ional mul i-axial loads no only on he espec i ely in ended measu ing b idges bu also on he o he measu ing b idges, which causes an unin en ional signal al e a ion. • Load cycle: ange o applied load on a measu ing ins umen du ing calib a ion. • Measu emen unce ain y: non-nega i e pa ame e cha ac e ising he dispe sion o he quali y alues being a ibu ed o a measu and, based on he in o ma ion used (VIM 2.26). • To que ans e s anda d: calib a ed and e y well-known o que ansduce , which is used o ace o que measu emen o he na ional s anda d. • Ze o signal: o se alue o a ansduce in non-loaded condi ion. The ze o signal is used o a e all measu emen signals o he ollowing load cycle.