ThefollowinginformationistakefromQ&AbetweenIandmyChiefengineer
Q(1).Howtodefinetheenclosuretoclassifytheminthetwocategories,couldyougiveussomeadvice,weareveryappreciateifyoucangiveussomephotoassample.Andifweclassifytheenclosuretocategory1then,
Answer:Ifyoureadthestandardclosely,ThereareCategory1and2enclosuresforIP5X.Cat1isforequipmentwithelectricalcomponentsthatproduceheat.Theseneedtobetestedwithavacuum.Iftherearenoheatproducingcomponents,thenitcanbetestedorclassifiedasCat2andyoucantestwithoutavacuum.ForIP6X(readsection6),itsaysthattheenclosuremustbeconsideredaCat1(withorwithoutheatproducingcomponents).ThereforeyoumustperformthedusttestwithavacuumonallIP6Xenclosures.
Q(2).Howlongwillweconductthetest?(testcondition:extractionrate—lessthan40volumesperhour,maximumdepression-4kPaMaybewecan’tdothetestunderadepressionmorethan4kPa?)
Firstyoumustdeterminetheexchangeratefortheenclosure.Thisistheleakageratepertheenclosureunderacertainpressure.Standardsays2kPamaximumunderpressure(max.vacuum).Toputthedeviceundervacuum,youuseavacuumpumpattachedtotheenclosureandcreatea2kPavacuumontheenclosure.Onceyoureach2kPa,closeavalvesothatthevacuumismaintainedintheenclosurewiththepressuregaugeinthecircuit.Watchthepressuregaugetoseeifthepressurefallsfrom2kPa.Recordthetimeittakesforthepressuretogofrom2kPato0kPa.Thestandardrequirementis2hourstesttimefora40to60volumeperhourextractionrate(orleakagerate).1hr/40vol/hr=1.5minutes,1hr/60vol/hr=1.0min.Ifthepressurefallsfrom2kPato0kPain1.0to1.5minutes,thenyourleakagerateismorethan40volumesperhour.Ifitismorethan40volumes/hr,thenyoudothedusttestfor2hoursataconstantvacuumof2kPa.Youmustturnonthevacuumpumpandmaintainaconstant2kPavacuumduringthetestfor2hours.
Whencheckingyourinitialextractionrate(leakagerate)Ifyourpressuredropsfrom2kPato0kPainmorethan1.5minutes,thenyourextractionrateislessthan40volumes/hr(ie:enclosureapproachingnoleakageorair-tight).So,youmustconductthetestfor8hours,oruntil80volsofexchangehasoccurred.(ex.3minutestogofrom2kPato0kPa,thenyourunthetestfor60min/3=20exchangesperhour.Then80exchangestestrate/20exchangesperhour=4hours.Themaxtesttimeisnevermorethan8hours.
Ifyourpressuredropsfrom2kPato0kPainlessthan1.0minute,thenyourextractionrateismorethan60volumes/hr(ie:highleakage).So,youmusttryreducingthepressureuntilyougetaextractionrate(leakagetime)ofexactly1.0minuteandnotethepressure(vacuum)thatitoccursat.(ex.Youreducethepressureuntiltheexchangeratetakesexactly1minutetogofrom2kPato0kPa.(ex:Let’ssaythatpressureis1.5kPa.Youwouldthenconductyourtestat1.5kPafor2hours.)
这40倍，60倍体积是指样品内体积的40倍，60倍？
1、关于外壳类型的区别，有那么简单吗？
2、关于试验时间，是不是不需要那么复杂？
我觉得如果用40倍试验外壳体积的抽气率去抽，如果很容易就超过2KPa，那我慢慢降低抽气率，总会有一个抽气率达到一个低于2KPa的压差，如果此时的抽气率为20倍，那我就试验80/20=4h，如果抽气率为5倍，那我就试验8h（因为80/5=16，16超过8，标准要求最长不超过8h）。
如果用40倍抽气率去抽达不到2kPa的压差，但是用60倍抽气率很容易达到，那我只要在40~60之间之间再尝试几个抽气率，如果某个值刚好没超过2kPa，那就用这个抽气率试验2h就ok了。
如果用60倍抽气率还达不到2kPa的压差，那就在40~60之间随意找个抽气率进行2h也可以；当然，我觉得越大的抽气率进灰的量会越多。
不知这样的理解是否正确，请拍砖！
IEC60529