XITRON XT2640 - Repeatability Requirements; EUT Classifications and Limits Selection

XT2640OperatingManual 13July2016 Page89of187
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18.1.3 REPEATABILITYREQUIREMENTS
BothEN61000‐3‐2and‐12requirethatanassessmentmeetarepeatabilityrequirement.ForEN61000‐3‐2thisiscontainedin
clause6.2.3.1andinEN61000‐3‐12itiscontainedinclause4.2.3.Inbothcasesitisrequiredthatbetterthan5%ofthelimitis
achievedintherepeatabilityofmeasurementofaverageindividualharmoniccurrents,butitisstatedinthestandardsthatthisisnot
arequirementforassessment,butisarequirementfortheselectionoftheassessmenttime.
TherepeatabilityoftheXT2640itselfisfarbeyondtheserequirementsingeneralsoisnotadeterminingfactor;theprimary
determiningfactorsbeingtherepeatabilityofthesupplysource,therepeatabilityoftheEUTharmonicsthemselves,andthetest
timeusedforassessment.
Recommendation:
YoumustconfigureatesttimesuitablefortheEUTwhichallowsyoutoachievethislevelofrepeatability.Seetable1of
EN61000‐3‐12andtable4ofEN61000‐3‐2forsomeguidanceregardingthis.
TheXT2640enforcesnominimumassessmenttimeotherthan1second.ForastableEUTandastablesupplysourcethe
standardsprovidenominimumassessmenttimeaslongasitis“
ofsufficientdurationtomeettherequirementsfor
repeatability
”.IftheEUTandsupplysourcecanmeetthisrequirementwitha1secondassessmenttime,thensuchatime
maybeused,howeveryoumustensurethatthe1.5secondfilteringrequiredbythestandardshasfullysettledpriorto
startinganassessmentsotheEUTmusthavebeenpoweredandstableforatleast10secondspriortostartingthe
assessment,theXT2640doesnotenforcethis.
Asstatedinnote3offiguresA.1andA.2ofEN61000‐3‐2youmayneedtouseasupplysourcewhichsignificantlyexceeds
theirstatedrequirementsinordertomeettherepeatabilityrequirementwithsomeEUTs.Althoughthesenotessuggestan
increasedrequirementforsupplyvoltagestability,experiencehasshownthatthisalsoextendstowaveformshape
repeatability.
WithsomeEUTsyoumayneedtodecidewhethertherepeatabilityrequirementisapplicabletosomeorperhapstoall
harmonics.Thereareprimarilytwosituationswherethismaybeappropriate‐
SomeEN61000‐3‐2classCdeviceswithlowpowerlevelsareunlikelytoenableyoutomeetthisrequirementforany
reasonableassessmenttime,primarilybecausethereisnominimumcurrentlevelstatedfortherepeatability
requirementasitispresentlywordedinEN61000‐3‐2.
IfreportinganassessmentofaEUTwhichisfailingtheassessmentthensomeharmonicsmeasuredmaybevery
significantlyhigherthanthelimit,resultinginanunnecessarilysmallpercentageofthemeasurementasthe
repeatabilityrequirementasitispresentlywordedinEN61000‐3‐2(alsoinEN61000‐3‐12butinpracticethissituation
isfarlesslikelyforthatstandard).
18.1.4 EUT CLASSIFICATIONS ANDLIMITSSELECTION
ForbothEN61000‐3‐2and‐12theXT2640doesnotdecidewhichclassificationaEUTfallsintoandwhichlimitstabletoapply.Itis
yourresponsibilitytoselectthecorrectclassificationand/orlimitstabletoapplywhenassessingaEUTfollowingtheguidelinesof
eachstandardandtakingintoaccountthefeaturesofthespecificEUT.
WhenanassessmentismadetheXT2640takesandrecordsinternallyallmeasurementsrequired,andallsupplyvoltageand
measurementtestingisperformed,inordertomakeanassessmentresultavailableforanyclassificationinEN61000‐3‐2orforany
limitstablewithinEN61000‐3‐12.Thismeansthatyoucanfreelymakeanassessment,andthenchecktheresultsofthatassessment
afterwardstoanyoftheclassifications(butnotchangingbetweenstandards).Thisalsoextendstotheentryofreferencelevelsfor
current,watts,andPFwhichmayberequiredforsomeclassifications,andthenominalUnomandFnomentries,andtheRsceentry;
allofthesemaybechangedfreelyafteranassessmentwithoutrequiringthatanewassessmentbeperformed.Thisprocessiscalled
“reassess”intheXT2640;basicallyitisreassessmentofmeasurementresultsalreadyobtainedfromapriorassessment.
Recommendation:
Whenthereisdoubtregardingwhichclassificationorlimitstabletouseitisrecommendedthatanassessmentbe
performedtothedesiredstandard,initiallytoanyclassification,andthatyousubsequentlygenerateseparatereportsfor
eachpossibleclassificationwhichyoudecideupon.WiththeXT2640thereisnoneedtorepeattheentireassessment
processtoaccommodatethis.
Youmightconsidermakingityourgeneralpracticetogenerateafinalassessmentreportwhichcontainstheassessmentof
theEUTtoallclassifications(orjusttothosewhichtheEUTpasses).Thisgivesthebenefitofremovinganydoubt
regardingwhetherthecorrectclassificationwaschosenforaEUTandmayhelpshouldlaterversionsofEN61000‐3‐2
resultinachangeofclassificationoftheEUT(asstatedinclause5ofEN61000‐3‐2thismayoccurinthefuture).Bypre‐
assessingaEUTagainsteachclassificationyouarealreadypreparedforsuchfuturechanges.
18.1.4.1 EN61000‐3‐2CLASSIFICATIONSAN DLIMITSTABLESELECTION
TheXT2640performsassessmentsdenotedusingthesameclassificationsofEUTforclassesA,BandDasdefinedwithinEN61000‐
3‐2.HoweverEN61000‐3‐2sub‐classifiesEUTswithinits’ClassCclassificationintofoursub‐classes,withintheXT2640theseare
denotedasfollows–
ClassC(tbl2):thesub‐classdefinedbythefirstparagraphofclause7.3a)ofthisstandard.
ClassC(tbl1):thesub‐classdefinedbythesecondparagraphofclause7.3a)ofthisstandard.
ClassC(tbl3):thesub‐classdefinedbythefirstsetofrequirementsinclause7.3b)ofthisstandard.
ClassC(spcl):thesub‐classdefinedbythesecondsetofrequirementsinclause7.3b)ofthisstandard.
ByaccommodatingthisexpandeddefinitionofClassCalongwithclassesA,BandD,thetablewithinEN61000‐3‐2definingthelimits
tobeusedforaEUTisthusexplicitlydefinedandselectedbytheXT2640.
Recommendation: