LBC InverterRequirements

Detailed Inverter Specifications, Testing Procedure, and Technical Approach and Testing Application

Requirements for the Little Box Challenge

Introduction ThankyouforyourinterestintheLittleBoxChallenge.Youmayhaveseenabriefdescriptionoftheinverterprizespecificationsneededtowinonthewww.littleboxchallenge.comwebsite.Thisdocumentisamoreindepthdescriptionofthosespecifications,alongwithsomeinformationregardinghowtheinverterswillbetested.Yourinvertermustconformtotheformfactor,connectorandsafetyrequirementslistedinthisguideinordertobeconsideredfortesting,sopleasereadtheseinstructionscarefully.AlsoincludedinthisdocumentaretherequirementsforwhatmustbesubmittedfortheTechnicalApproachandTestingApplicationdocumenttobesubmittedonorbeforeJuly22,2015.Thelegallybindingtermsandconditionsforthecompetitionarefoundontheregistrationpage.Thesemustbecarefullyreadandagreeduponbeforeenteringthecompetition.QuestionsaboutthisdocumentcanbesubmittedbyfillingouttheformontheFAQsectionofthewww.littleboxchallenge.comwebsite.Asdescribedonthesite,anyquestionthatisansweredwillbereproducedonthesite,withoutidentifyingtheasker,andpostedinapdfforeveryonetoseeinordertoensurefairnessforallcompetitors.Thisdocumentmaybemodifiedperiodicallytoreflectquestions/clarificationscitedonthewebsiteortoreflectupdatedinformationandtestingprocedures.Anyoneregisteredforthecompetitionwillreceiveanemailindicatingthatthereisarevisedversion.

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Table Of Contents

IntroductionTableOfContentsHighLevelPrizeSpecificationsDetailedRequirementsandTestingProcedure

VolumeandEnclosureRequirementsVoltageInputVoltageOutputFrequencyOutputLoadProfileTotalHarmonicDistortion+NoiseEfficiencyInputRippleCurrentandVoltageMaximumExposedOuterDeviceTemperatureElectromagneticComplianceGroundCurrentLimit

Grounding,DeviceConnectionsandSafetyRequirementsGroundingDeviceConnectionsSafetyRequirements

TechnicalApproachandTestingApplicationRequirementTechnicalApproachDocumentTestingApplication

AppendixA:TestingApplicationTemplate/Example

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High Level Prize Specifications Thewinninginverterwillbetheunitwhichachievesthehighestpowerdensity,i.e.fitsinthesmallestrectangularenclosure,whilemeetingthefollowingspecificationsundertestingfor100hours.Apanelofjudgeswilldeterminewhichinvertershavemetthespecifications(e.g.ifanydeviationsaresubstantialenoughtowarrantadisqualification)andmayrequestfurthertestingattheirdiscretionbasedonthedatagathered.Intheeventofatieonvolume,efficiencywillbeusedtodeterminethegrandprizewinner.

Parameter Requirement Comment

Maximumload 2kVA Loadwillbeadjustedsothatatmost2kVAissourcedat240VRMSACoutputat60Hz

Powerdensity >50W/in3 Inaccordancewithmaximumloadandvolumerequirements

Volume

Detailed Requirements and Testing Procedure

Volume and Enclosure Requirements Theinvertermustbecontainedwithinarectangularmetalenclosurewithavolumeoflessthan40inches3.Itistoyouradvantagetomakeeachfaceoftheenclosureflat,sinceanybulgingonafacewillresultinanincreasedassessmentoftherelevantdimensionofheightwidthordepthasshowninFigure1.ThevolumewillbecalculatedasifitwerearectangularprismwithHxWxD,thusanydeviationfrombeingflatwillsubstantiallyincreasethevolumeattributedtothedevice.

Figure1:Invertercrosssectiontoillustratecalculationofheightandwidth(depthcalculatedsimilarly)

Themaximumdimensionmaynotexceed20inchesandtheminimumdimensionmaynotbelessthan0.5inches.Thedimensionsoftheenclosurewillbemeasuredwithdigitalcaliperstoaprecisionof0.05inches.Thebottomoftheinvertermustbelargeenough(eachdimension>=1inch.)toaccommodatethefoursupportpostsdescribedintheMaximumExposedOuterDeviceTemperaturesectionbelow.Openingsintheenclosurearepermitted(e.g.fortheexitandstrainreliefoftheAC,DCandgroundwireconnections,aswellasholestopermitairtoenterandexitforcoolingpurposes).Anyopeningintheenclosuremustbefingersafe,i.e.mustnotallowacylinderofdiameterorgreatertopassthroughit.Anymeshusedshouldberecessedtofitwithintherectangularenclosure.Aprotrudingmeshwilladdtotheeffectivedimensionoftherectangularenclosure,thusincreasingtheassessedvolumeofthedevice.Thevolumeofthewiresandstrainreliefexitingtheenclosurewillnotbecountedtowardsthetotalvolumeoftheenclosure.

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Voltage Input Theinverterwillbetestedusinganearidealvoltagesupplysetat450V.Thispowersupplywillbefloating.Itspositiveterminalwillbeconnectedtoa10wirewoundresistorwhichwillinturnbeconnectedtothepositiveDCinputterminaloftheinverter.Thevoltagesourcewillbeveryclosetoripplefree.

Voltage Output Thevoltageoutputmustbe240VRMSsinglephaseAC,withina+/12Vband.Afteratransientchangeintheloadthevoltageshouldreturntowithinacceptablebandsin0.1secondsorlessandnotleavethebandagainuntilthenextloadchange.Thevoltagewillbemeasuredattheoutputoftheinvertertoensureitremainswithinacceptablebands.

Frequency Output Thefrequencyoutputmustbe60HzsinglephaseAC,withinabandbetween59.7to60.3Hz.Afteratransientchangeintheloadthefrequency,ifitchanges,shouldreturntowithintheacceptablebandin0.1secondsorlessandnotleavethebandagainuntilthenextloadchange.Thefrequencywillbemeasuredattheoutputoftheinvertertoensureitremainswithinacceptablebands.

Load Profile Theinverterwillbetestedunderdynamicloadconditions.Theloadwillbeprovidedbyanelectronicloadbankwhichcanswitchinandoutaseriesoflinearreactive,inductiveandcapacitiveloadsinsmall(

V THD+N = V 1

i=

i=2V +Vi2 Noise2 (1)

WhereV1istheamplitudeofvoltageatthefundamentalfrequency(at60Hz)andVi=V2,V3,V4aretheamplitudesoftheharmonics.V2istheamplitudeat120Hz,V3at180Hz,V4at240HzandVnbeingtheamplitudeatnx60Hz.VNoiseistheRMSvalueofthenoise(e.g.allcomponentsnotatamultipleofthefundamental)withinthemeasurementbandwidth.Similarly,thecurrentTHD+Nisdefinedas:

ITHD+N = I1 +Ij=j=2 I j2 Noise2 (2)

WhereI1istheamplitudeofcurrentatthefundamentalfrequency(at60Hz)andIi=I2,I3,I4aretheamplitudesoftheharmonics.I2istheamplitudeat120Hz,I3at180Hz,I4at240HzandInbeingtheamplitudeatnx60Hz.INoiseistheRMSvalueofthenoise(e.g.allcomponentsnotatamultipleofthefundamental)withinthemeasurementbandwidth.BothVTHD+NandITHD+Nmustremainbelow5%atallloadlevels.TheTHD+Nwillonlybemeasuredduringsteadystateoperationatdifferentloads.Duringanychangeinload,transientbehaviorandTHDmeasurementswillbeignoredfor1secondpriortotheloadchangeand1secondaftertheloadchange.

Efficiency Theinvertermustdemonstrateanefficiencyof>95%.Theefficiencyisdefinedas:

fficiencyE = DCPowerInputACPowerOutput (3)

andwillbedeterminedbymeasuringtheinputvoltageandcurrentandoutputvoltageandcurrent,usingtherealcomponentofthepoweratthefundamentalfrequency.EfficiencymeasurementswillbetakenusingavariationontheCaliforniaEnergyCommission(CEC)efficiencydeterminationmethod.Theinverterefficiencywillbedeterminedbytakingmeasurementsat6differentloadlevelsasshowninTable1.

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OutputACPowerLevel

10%(200VA)

20%(400VA)

30%(600VA)

50%(1kVA)

75%(1.5kVA)

100%(2kVA)

WeightingFactor

0.04 0.05 0.12 0.21 0.53 0.05

Table1:WeightingFactorsforCECefficiencycalculationIntheCECefficiencymethodthesemeasurementsaretakenatthreedifferentvoltagelevels.UnliketheCECmethod,thevoltageoftheDCinputinthiscompetitionwillbetiedtothepoweroutputsinceweareusingavoltagesource+resistorsetup,asdescribedintheVoltageSourcesection.Therefore,eachpartloadmeasurementwilltakeplaceatasingleinputvoltage.Eachofthemeasurementswillbetakenusingapurelyresistiveload.Themeasurementswillbetakenatdifferenttimesduringthedynamicloadtestswiththeloadsspecifiedabove.Eachinverterwillhavethesameloadprofileappliedforthetestsandefficiencycalculation.Inadditiontotherequirementslistedabovetheinvertermustalsohaveanefficiencyof>95%atfull2kVAload.Thereasonforthisissothatateamcannotuseaforcedconvectionorotherwiseparasiticmeansofcoolingonlywhenoperatingatornearfullload,thusobscuringtheparasiticcoolingmethodseffectonefficiency.

Input Ripple Current and Voltage Theinputripplecurrentandvoltagelimitsaredependentonthevoltagesourceconfigurationbeingusedtotestthedevice.Participantsmustplanandtesttheirdesignsaccordingly.Theinputripplecurrent(IRipple)isdefinedas:

IRipple = IAverageI (@120Hz)PeakPeak = IAverage

I I (@120Hz)Max Min (4)Similarly.thevoltageripple(VRipple)isdefinedby:

V Ripple = V AverageV (@120Hz)PeakPeak = V Average

V V (@120Hz)Max Min (5)ThedefinitionofIPeakPeak(@120Hz)andVPeakPeak(@120Hz)isshowninFigure2.Asillustrated,thepeaktopeakvalueistakenoftheenvelopeofthe120Hzoscillations(whicharenotnecessarilyperfectsinusoids)andnarrowspikesordeviationsathigherfrequenciesdonotcountinthemeasurement.

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Figure2:DemonstrationofdefinitionofIPeakPeak(@120Hz)andVPeakPeak(@120Hz)fortheripplecurrentandvoltagemeasurements

BoththecurrentandvoltageripplewillbemeasuredbetweenthepositiveandnegativeDCinputterminalsoftheinverter,ontheinvertersideofthe10wirewoundresistor. ThelimitfortheinputripplecurrentisIRipple

Theambienttemperatureofthetestingenvironmentwillremainbetween15Cand30C.Therearenorequirementsforthetemperaturereachedbycomponentswithintheenclosure.Thebottomsideoftheinverter(thesidetobeparalleltothefloorofthetestinglab)willbesupportedonfourposts,1oneachcorner,1inchhigh,andwithatopareawhichmakescontactwiththebottomoftheinverterofdimensions0.5x0.5inches.Therewillbenosignificantheatconductedthroughtheseposts.

Electromagnetic Compliance ThedevicemustconformtoFCCPart15Brulesintheunintentionalradiatorscategory.MoreinformationaboutFCCPart15BrequirementscanbefoundintheElectronicCodeofFederalRegulationsandelsewhere.TheFCCPart15Bcompliancewillbetestedatcertifiedelectromagneticcompliance(EMC)testinglaboratoryintheUnitedStatesnearthetestingfacility.MoredetailsregardingtheEMCtestingfacilitywillfollowduringthecompetitioninanupdatedversionofthisdocument.DuetothedifficultyofreachingcompliancewithFCCPart15B,especiallywithprototypes,weencourageyoutosubmityourinverterfortestingevenifitmaynotreachfullFCCPart15Bcompliance.IntheeventthatnoinvertersreachfullFCCPart15Bcompliance,thejudgesmaydoarelativecomparisonofEMCperformancebetweeninvertersandstillawardtheprize.

Ground Current Limit Asdescribedinthegrounding,safetyandconnectionssectionbelow,therewillbeawireconnectingthechassisoftheinvertertoearthgroundinthetestinglaboratory.Thecurrentflowingacrossthewiretogroundcannotexceed5milliAmpsatanytimeduringthetesting.Thecurrentflowingacrossthewiretogroundwillbeestablishedeitherbymeasuringthecurrentonthegroundchassisconnectiondirectly,orbymeasuringthedifferenceincurrentbetweenthehotandneutralorhot1andhot2ACoutputconnections.

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Grounding, Device Connections and Safety Requirements

Grounding Theinverterdoesnotneedtoprovidegalvanicisolation.TheDCsupplywillbefloating.Inordertoaccommodatethemostprevalentgroundingconventionsaroundtheworld,twodifferentgroundingconfigurationsarepermissible.ThegroundingconfigurationthattheteamwishestousemustbespecifiedbothduringtheTechnicalApproachandTestingApplicationSubmissionandduringthesubmissionoftheinverteritself.Nopreferencewillbegiventoentriesbasedontherequestedgroundingconfiguration.GroundingConfiguration1:240VsplitphaseconfigurationThegroundingconfigurationforthe240VsplitphaseconfigurationisshowninFigure3.

Figure3:240VsplitphasegroundingconfigurationInthisconfiguration,the240VRMSACoutputoftheinverterisbetweenterminalsdesignatedAC(Hot1)andAC(Hot2).TheseterminalsconnecttoeachotherthroughanisolationtransformerwhoseothercoilisconnectedtotheACloadbankthatwillapplytheloadprofileasdiscussedintheloadprofilesection.Theisolationtransformeriscentertappedontheinvertersideandconnectedtoground.ThishastheeffectoffixingbothoftheAC(Hot1)andAC(Hot2)linestobe120VRMStoground,180degreesoutofphase,similartowhatwouldbefoundinaNorthAmericanhousehold.Thepurposeofthe100resistorandswitchontheoutputoftheAC(Hot1)istolimittheinrushcurrentsintothetransformeruponstartup.Theswitchwillbeleftopenforaperiodof10secondsuponstartup,andthenwillbeclosed.

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Aseparatewireisrequiredtoconnectthechassisoftheinvertertoearthground.Theresistancebetweenthiswire,asmeasuredinthechassisgroundreceptacleontheNEMA615connector,andthemetalenclosureontheinvertermustbe

Device Connections Itistheresponsibilityofthecompetitortowirethedeviceexactlyasspecifiedbelow.AnydamageordecreaseinperformancethatresultsfromimproperwiringwillbetheresponsibilityofthecompetitorandnotthatofeitherthetestingfacilityorGoogle.Thedevicesubmittedfortestingmustbearectangularmetalenclosurewith5wiresexitingfromit.Eachofthewiresmusthaveadiameterof10AWG,alengthofbetween1012inchesandhaveadequatestrainrelief.Ononeoftheupright/verticalfacesperpendiculartothetestingsurface,twoDCconnectionswiresmustexittheenclosure,onedesignatedDC+andtheothermarkedDC.TheDC+connectionmustbearedwire,theDCmustbeablackwire.TheredDC+wiremustconnecttoaredAndersonpowerproductsPP75DCconnector,theblackDCwiremustconnecttoablackAndersonpowerproductsPP75DCconnector.TheredDC+connectionwillbeattachedtothepositiveterminalofthepowersupply,ontheothersideofthe10wirewoundresistor.TheblackDCconnectionwillbeconnectedtothenegativeterminalofthepowersupply.ThetwoAndersonpowerproductsPP75connectorsshouldnotbeglued,stuck,orotherwisepermanentlyfastenedtogether.Ontheupright/verticalfaceoppositeandparalleltothefacewiththeDCwiresexiting,twoACwireconnectionsandonechassisgroundconnectionmustexittheenclosure.Thechassisgroundwiremustbeagreenwire.Forthe240Vsplitphaseconfiguration,onewireshouldbedesignatedAC(Hot1)andmustbeabluewire,andanothershouldbedesignatedAC(Hot2)andmustbeabrownwire.Forthe240VtogroundconfigurationonewiremustbedesignatedasAC(Hot)andmustbeabluewire,andanothershouldbedesignatedasAC(Neutral)shouldbeawhitewire.ThesethreewiresmustbeconnectedtoaFemaleNEMA615ACelectricalconnector.TheconnectionsontheFemaleNEMA615ACelectricalconnectorwillbedependentonthegroundingspecificationchosen:240Vsplitphaseconfiguration,or240Vtogroundconfiguration.NEMA615connectionsforgroundingconfiguration1:240VsplitphaseThetwoACconnectionsandthechassisgroundconnectionmustbeattachedtotheFemaleNEMA615connectorinthefollowingway:whenlookingstraightaheadintotheoutletsoftheconnector,withthesinglesemicircularflattenedopeningorientedtowardsthebottomandthetwoflatrectangularopeningsaboveitequidistantoneitherside,theAC(Hot1)wiremustbeconnectedtotheleftrectangularoutlet,theAC(Hot2)wiremustbeconnectedtotheright

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rectangularoutletandthechassisgroundconnectionmustbeconnectedtothesemicircularandflatoutletonthebottom.ThisisshowninFigure5.

Figure5:ACandchassisgroundconnectionrequirementsonfemaleNEMA615connectorinthe240Vsplitphaseconfiguration

TheAC(Hot1)andAC(Hot2)pinswillbeconnectedoneithersideofacentertappedtransformertoground,asshowninFigure3.TheothersideofthetransformerwillbeconnectedtoaprogrammableloadbankandthechassisgroundwillbeconnectedtoearthgroundasshowninFigure3.NEMA615connectionsforgroundingconfiguration2:240VtogroundThetwoACconnectionsandthechassisgroundconnectionmustbeattachedtotheFemaleNEMA615connectorinthefollowingway:whenlookingstraightaheadintotheoutletsoftheconnector,withthesinglesemicircularflattenedopeningorientedtowardsthebottomandthetwoflatrectangularopeningsaboveitequidistantoneitherside,theAC(Neutral)wiremustbeconnectedtotheleftrectangularoutlet,theAC(Hot)wiremustbeconnectedtotherightrectangularoutletandthechassisgroundconnectionmustbeconnectedtothesemicircularandflatoutletonthebottom.ThisisshowninFigure6.TheAC(Hot)andAC(Neutral)pinswillbeconnectedtoeithersideoftheisolationtransformerasshowninFigure4andtheAC(Neutral)willbeconnectedtoearthground.

Safety Requirements On/OffSwitch,LEDindicatorandTurnonDelayThedevicemusthaveaclearlylabelledon/offtoggleswitchontheenclosure.Whenthetoggleswitchisintheoffposition,novoltageorcurrentistobepresentontheACsideevenwhentheDCsideislive.

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Figure6:ACandchassisgroundconnectionrequirementsonfemaleNEMA615connectorinthe240Vtogroundconfiguration

Whentheswitchisintheonposition,thedevicemustdetectthattherehasbeenavoltageof>300Voltsforatleast5secondsbeforeoutputtingtotheACside.ThereshouldbenovoltageorcurrentoutputontheACsideuntilthistime.WhenthereislivevoltageontheACside,agreenindicatorlightlocatednexttotheon/offswitchshouldbeilluminated.WhenthereisnovoltageontheACside,theLEDshouldbeoff.FuseConfigurationforTestingSetupInordertoprotectboththeinvertersbeingtestedandtheequipmentbeingusedforthetest,thefollowingfuseswillbeusedatthedifferentlocationsinthetestingsetup:

BetweentheresistorattheoutputofthevoltagesupplyandthepositiveDC+terminaloftheinverter:10A,500VDCslowblowfuse.

BetweenthenegativeterminalofthepowersupplyandthenegativeDCterminaloftheinverter:10A,500VDCslowblowfuse.

BetweenthetheAC(hot)or(hot1)terminaloftheinverterandtheAC(hot)or(hot1)inputtotheisolationtransformer:12A,240VAC,slowblowfuse.

BetweenthetheAC(neutral)or(hot2)terminaloftheinverterandtheAC(neutral)or(hot2)inputtotheisolationtransformer:12A,240VAC,slowblowfuse.

Thesefusesarenottobeprovidedbythecontestparticipants.Theywillbeincorporatedintothetestsetup.Theirvaluesareincludedsothatparticipantswillunderstandwhatcircumstancesmayleadtoablownfuse.FurtherInverterSelfProtectionMeasures[Tobeincludedbytestingpartnerinupdatedversionofthisdocument]

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Technical Approach and Testing Application Requirement Inorderfortheirinvertertobeconsideredfortesting,theteamsmustsubmitatechnicalapproachandtestingapplicationdocumentonorbeforeJuly22,2015.Thoseregisteringforthecompetitionwillreceivemoreinformationbyemailaboutthesubmissionguidelinesinearly2015.Thisapplicationwillbereviewedbyapanelofjudgesandnomorethan18finalistswillbeselectedfortesting,andachancetowintheGrandPrizeof$1million.Thecriteriabywhichthesubmissionswillbeevaluatedis:

Didtheteamsadequatelyandclearlypresentthehighleveloverviewoftheapproachtheyweretaking,meetingalltherequirementsforcontentlistedbelow?

Didtheirapproachmakesenseintermsofbeingabletoachievewhattheyclaim? Didtheysubmittherequireddataandsafetyinformationrequiredinthetesting

application? Didthatdatavalidatetheperformancetheyareclaiming? Forthetechnicalapproachandtestingapplicationsthatmeetallofthecriteriaabove,is

theteamclaimingtoachieveoneofthe18highestpowerdensitiesofallthequalifyingapplicants?

TeamsmeetingalloftheserequirementswillbeinvitedtobringtheirinvertersinpersontothetestingfacilityintheUnitedStatesinOctober2015.

Technical Approach Document Inordertobeconsideredfortesting,participantsinthecompetitionmustsubmitatechnicalapproachdocumentnottoexceed4pages.Thisdocumentshoulddescribeatahighlevelwhatapproachandinnovationstheteamareusingtoachievethehighpowerdensitiesclaimedfortheirinverters.Inaddition,a1pageappendixwithbiographicalinformationaboutthekeymembersofyourteammustalsobeincluded.Thepurposeofthisdocumentistwofold.First,itwillallowapanelofjudgestoassessthelikelyviabilityofyourinverterdesignanddecidewhetherthesubmissionshouldqualifyasafinalistfortesting.Second,asubsetofthetechnicalapproachdocumentssubmittedwillbemadepublicbyGooglesothattheworldmayseethenewtechniquesandinnovationswhicharenowmakingthesehighdensitiespossible.Thelevelofdetailrequiredinthetechnicalapproachdocumentismeanttobehighlevelandnotdivulgeanytradesecrets.ThecontentanddescriptionsofthedeviceshouldbecomparabletoashortIEEEpapermeanttoexplainconceptuallyhowanewdevicecanworkwithoutrevealingallthedetailsabouttheexactvaluesofcomponentsused,norgoingintodetailsaboutthecontrolalgorithmsandothermoredetailedaspects.Generalcontentguidelinesinclude:

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Powerdensityachieved:thevolumeoftherectangularenclosureusedandthusthe

resultingpowerdensityachievedataloadof2kVAshouldbespecified. Switchlevelschematics:schematicsshouldbedetailedenoughtorevealwhatgeneral

topologyisbeingused,butnotincludeeverypassivecomponentorothercircuitdetail. Orderofmagnitudepassivecomponentvalues:Forpassivecomponentswhichtypically

takeupalargevolume,orareotherwisecriticaltothetheconceptualdesignofthecircuit,anorderofmagnitudevalueforwhatwasused(e.g.10sofmicrofaradsvs.100sofmicrofarads)isacceptable.

Orderofmagnitudefrequencyvalues:Forswitchingfrequenciesusedincreatinganalternatingcurrentoutputfromadirectcurrentthroughapulsewidthmodulationorothertechnique,specifyingtheorderofmagnitudeoffrequencyused(e.g.10sofkilohertzvs.100sofkilohertz)isacceptable.

Semiconductordevicetype(s):Participantsshouldspecifythetypeofsemiconductorswitchingdevicesthattheyareusing(e.g.silicon,galliumnitride,siliconcarbide,etc.).Participantsmayormaynotspecifythevendorsandprovidersofthesesemiconductorswitchingdevicesattheirdiscretion.Thesameistrueofanynovelpassivecomponentsused.

Participantsarefreetoincludemoredetailthanthisattheirdiscretion.Thetechnicalapproachdocumentshoulddescribeanyandallofthekeyinnovationsbeyondthecurrentstateoftheartwhichenabledtheinvertertoachievethesehighpowerdensities.Inadditiontoanygeneralcontentabouttheinnovationsused,theymustprovideclearlyindicatedsectionsonwhatinnovationstheyhaveusedtoconfrontthefollowingchallengestoincreasinginverterpowerdensity:

120Hzinputcurrent/voltageripplerequirement:ThetypicalsolutiontominimizetheinputcurrentrippleontheDCsideoftheinverter,whichisdetrimentaltotheoperationofPV,batteryandothersystems,hasbeentoincludelargeamountsofenergystorageintheformofoftenunreliable,largevolumeelectrolyticcapacitors.Participantsmustdescribewhatmeansthathaveusedtomeettheinputripplecurrent/voltagerequirementswhileminimizingthevolumerequired.

MiniaturizationofcomponentsforDCACconversion:Thetypicalmethodsof

switchingafixedvoltageDCsignalintoAC,suchaspulsewidthmodulation(PWM),requiretheuseofpassivecomponentstosmoothsquarewavepulsesintoasinewavewithminimalharmonicdistortion.Theenergystoragerequirement,andthusthesize,ofthesepassivecomponentscandiminishasthefrequencyofthesesquarewavepulsesisincreased.ThesehigherfrequenciesmaynowbeattainableeitherthroughtheuseofwidebandgapsemiconductorssuchasGalliumNitride(GaN)andSiliconCarbide(SiC),orthroughnewtopologiesusingtraditionalsiliconsemiconductors.Participantsmustelaborateonwhichofthesemethods,orothers,theyhaveusedtominimizethesizeoftheDCACswitchingcomponents,andwhyitisthepreferredsolutionforachievinghigh

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powerdensities.Theymayalsoincludeanyadvancesinthepassivecomponentsthemselves.

Thermalmanagement:Theamountofheatgeneratedbythesystemwilldecreaseastheefficiencyofthesystemincreases,butevenattherequiredefficiencyof>95%atfullloada2kVAinvertercangenerateupto100Wattsofheatwhichmustbedissipatedinordertopreventanunacceptabletemperaturerise.Thehigherthepowerdensityoftheinverter,thelesssurfaceareaisavailableforthisheattobedissipatedacross.Thelocalthermalmanagementrequirementsinthesystemmayberelaxedbyusingdevices(e.g.widebandgapsemiconductors)thatcanoperatereliablyatelevatedtemperatures.Newpassiveoractivethermalmanagementapproachesmaybeusedtomanagetheheatthatdoesgetgeneratedanddistributeitevenlyacrossthesurfaceareaoftheenclosuretoavoidthepresenceofhotspotsabove60C.Thetechnicalapproachdocumentmustdescribewhatinnovationsinthermalmanagementarebeingusedtoachievetherequiredspecificationsatthesehighpowerdensities.

ElectromagneticCompliance(EMC):Thepossibleuseofhigherfrequencies,new

componentsinasmallerformfactoroffersbothchallengesandopportunitiesforlimitingboththeconductedandradiatedelectromagneticinterferencewithinacceptablelimitsforFCCPart15Bcompliance.Participantsmustdescribethestepstakentolimittheelectromagneticinterferenceofthedevicewhileconsumingtheminimumpossiblevolume.

Biographicalinformationappendix(maximum1page):Inadditiontothetechnicalmateriallistedabove,competitorsmustsubmita1pageappendixwithbriefdescriptionsofthekeymembersofyourteam.Thismustcontainonetotwoparagraphsperteammemberwithinformationontheirprofessionalandacademicbackground,beginningwiththeteamspointofcontact.DescriptionsshouldbesimilartowhatwouldbefoundattheendofanIEEEpaperinajournalsuchasIEEETransactionsonPowerElectronics.Photosareoptional.Thetechnicalapproachdocumentshouldconformtothefollowingformattingguidelines:

Mustbewritteninenglish Musthavetheteamnameandregistrationcodeclearlyindicatedatthetopofthefirst

pageofthedocument Use8.5x11inchpagesize Minimum12pointfontforbodytext Minimum9pointfontinfigures,tablesandcaptions Minimum1inchmarginsonallsides Notexceed4pagesinlength+1pagebiographicalappendix Citationsarewelcome,butentrantsshouldnotexpectjudgestodoathorough

examinationofseveralcitationstoevaluatethemeritoftheapproach

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Technicalapproachdocumentswhichsimplyrefertothecontentofexternalcitationswithoutbrieflyexplainingtheircontentandspecificrelevancetothehighpowerdensityinverterapplicationarefrowneduponandmayresultinadisqualificationfrombeingafinalistfortesting.

Testing Application Atestingapplicationdocumentmustbesubmittedalongsidethetechnicalapproachdocument.Thisdocumentpresentsdatatakenbyeachteamontheirinvertersasaproofoftheirviability,alongwithasafetyquestionnaireneededfortesting.AtemplateofthetestingapplicationisincludedinAppendixAofthisdocument.Participantsdonotneedtofollowtheexactcolor/formattingschemelistedbutshouldfollowthegeneralguidelinesandprovidethedatainaveryclear,legibleformat.Failuretodosomayresultindisqualification.Thesafetyquestionnairewillbeprovidedinanupdatedversionofthisdocumenttobepostedduringthecompetition.Thetestingapplicationconsistsof:

Maximum1pageTechnicalspecificationsheet:Inthisdocument,competitorswilllisttheperformanceoftheinvertertheythemselveshavemeasuredonthefollowingmetricswhiletestingtheirinverterona2kWpurelyresistiveloadat240+/12VACoutput.Theinvertershouldberunforlongenoughtoallowittoreachthermalequilibriumpriortothesemeasurementsbeingtaken.Asdescribedabove,theinvertershouldbetestedwhilereceivinganinputfroma450Vnearidealpowersupplyinserieswitha10wirewoundpowerresistor.Thespecificationsmeasuredandreportedshouldbe:

Groundingspecification:Theteammustspecifyiftheirinverteristobetestedin

the240Vsplitphaseconfigurationor240Vtogroundconfiguration.Seethegroundingsectionaboveformoredetails

Maximumloadtested(mustbe2kVAorabove,correspondingto~28.8loadat240VAC)

Volumeoftherectangularenclosure(inch3) Dimensionsofrectangularenclosure(LxWxH,inches) Resultingpowerdensityat2kWload(watt/inch3) DCvoltagemeaninput(volts) DCcurrentmeaninput(amps) ACvoltageRMSoutput(volts) ACcurrentRMSoutput(amps) DCtoACefficiency(%) Voltagetotalharmonicdistortion+noise(%) Currenttotalharmonicdistortion+noise(%)

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Inputripplecurrent(%)Ipeakpeak/Iaverage(@120Hz) Inputripplevoltage(%)Vpeakpeak/Vaverage(@120Hz) Maximumtemperaturereachbytheenclosure(C) Ambienttemperatureoftestingenvironment(C)

TheseshouldbeorganizedinatableasshownintheexampleinAppendixA.

Maximum2pagesWaveformscreencaptures:ParticipantsmustprovidesamplewaveformimagesoftheDCinputandACoutputoftheirinvertersatfulloutputonapurelyresistiveload.Thewaveformtracesshouldbetakenwithasamplingrateofatleast10kHz.

Eachimageshouldbebetween45inchesinwidthand34inchesinheight.Thereshouldbe1traceperimage(currentorvoltage)foratotalof4images,2oneachpage.

DCinputwaveforms:Mustshowbetween4660Hertzcyclesofbothinputcurrentandvoltageatfullloadwithclearindicationofthevoltageandcurrentdivisions.Thiscorrespondstoa66100millisecondoscilloscopetrace.

ACoutputwaveforms:Mustshowbetween4660Hertzcyclesofbothinputcurrentandvoltageatfullloadwithclearindicationofthevoltageandcurrentdivisions.Thiscorrespondstoa66100millisecondoscilloscopetrace.

Maximum2pagesExtendeddevicetesting:Participantsmustprovideaplotof1

secondmeasurementsofthefollowingquantitiesoverthecourseof3hoursoftestingandtwodifferentloadconditions:2kVApureresistiveload,and1kVApureresistiveload.

DCvoltagemeaninput(volts) DCcurrentmeaninput(amps) ACvoltageRMSoutput(volts) ACcurrentRMSoutput(amps) Eachimageshouldbebetween46inchesinwidthand12inchesinheight.

Thereshouldbe1traceperimage(currentorvoltage)foratotalof8images,4oneachpage

Maximum2page:Devicepictures:Theparticipantsmustsubmit3picturesofthe

invertertobesubmittedfortesting.

Apicturefromthetopofthedevicewiththeenclosureremoved.Theentiretyofthedevicemustbewithintheboundsofthepicture.Thetoplevelcircuitcomponentsshouldbevisible.Thisisonlyusedtoestablishthatyouhaveanactualviabledevicefortesting.Thispictureshouldbebetween46inchesinbothwidthandheight.

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Apicturewiththeenclosureinplace,takenfromthetop.Thewiresexitingthedeviceandtheproperconnectors(NEMA615andAndersonPowerProductsPP75perinstructionsabove)mustbeclearlyvisible.Ameasuringtapeorrulershouldbepresentinthepicture,withthemarkingslegible,forscaleandtovalidatethedimensionsstated.Thispictureshouldbebetween46inchesinbothwidthandheight.

Apictureofthedevicewiththeenclosureinplacetakenfromtheside.Ameasuringtapeorrulershouldbepresentinthepicture,withthemarkingslegible,forscaleandtovalidatethedimensionsstated.Thispictureshouldbebetween46inchesinbothwidthandheight.

Maximum[X]pages:Safetyquestionnaire(tobeprovidedbytestingpartnerin

updatedversionofthisdocument).Participantsmustanswerthequestionsrelatingtosafetyandhazardousmaterialsinformationneededtoconductthetestingatthetestingfacility.

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Appendix A: Testing Application Template/Example

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TestingApplication:TechnicalSpecificationSheet

TeamName:TemplateTeam RegistrationCode:*******************

Parameter Value(TemplateExampleOnly!)

GroundingConfiguration 240Vtoground

Maximumloadtested 2.06kVA/28

Volumeoftherectangularenclosure 35in3

Dimensionsofrectangularenclosure 7inchx5inchx1inch

Resultingpowerdensityat2kWload 57.1W/in3

DCvoltage(RMS)input 395.8V

DCcurrent(RMS)input 5.4A

ACvoltage(RMS)output 240.2V

ACcurrent(RMS)output 8.6A

DCtoACefficiency(CECMethod) 95.5%

Voltagetotalharmonicdistortion+noise 4.4%

Currenttotalharmonicdistortion+noise 4.4%

Inputripplecurrent 16.1%

Inputripplevoltage 2.2%

MaxTemperatureofEnclosure 56C

AmbientTemperatureofTest 28C

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TestingApplication:WaveformScreenCaptures


DCInputVoltage

DCInputCurrent

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ACOutputVoltage

ACOutputCurrent

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TestingApplication:ExtendedTestingData


2kVALoadDCVoltageInput

2kVALoadDCCurrentInput

2kVALoadACVoltageOutput

2kVALoadACCurrentOutput

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1kVALoadDCVoltageInput

1kVALoadDCCurrentInput

1kVALoadACVoltageOutput

1kVALoadACCurrentOutput

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TestingApplication:DevicePictures


TopViewEnclosureOff:

TopViewEnclosureOn:

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SideViewEnclosureOn:

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TestingApplication:SafetyQuestionnaire


[Tobeincludedinupdatedversionofthisdocument]

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LBC InverterRequirements

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