Isolated Current and Voltage Measurement Using …

1 FILTER FERRITE BEADGNDR = 3m Ohm+5V_ISO1 GND_ISO1 GND_ISO4CH 1 MSP430FR5869CH 2CH 3CH 4CH 5CH 612 BIT SARIRIYIBVRVYVBUARTINTERFACE+EXPANSION I/OJTAGINTERFACELED(x2)COMMS/ IO(Connector)JTAG(Connector)LEDVDD_2 FILTER FERRITE BEADAMC1100 GAIN 8(Iso. Amp)ISO POWER 1+5V_ISO1-5V_ISO1 GND_ISO1 ISO POWER 2+5V_ISO2-5V_ISO2 GND_ISO2 ISO POWER 3+5V_ISO3-5V_ISO3 GND_ISO3 VDD_2 = +5V_ISO4 JUMPER (MSP430 [ ] or ADS131 [ ] EVM INTERFACE)ISO POWER 4+5V_ISO4-5V_ISO4 GND_ISO4 GNDVDD_2+5V_ISO1-5V_ISO1+/- 250 mVAMC1100 GAIN 8(Iso. Amp)AMC1100 GAIN 8(Iso.)

2 Amp)AMC1100 GAIN 8(Iso. Amp)110/ 230 VTERMINALBLOCKTERMINALBLOCKTERMINALBLOCK R = MOhmR = KOhmCH 1 ADS131E08-EVM-PDKCH 2CH 3CH 4CH 5CH 624 BIT Delta-SigmaVDD_2 = 1 OPTION 2 NOTE: FILTER, FERRITE BEAD are optionalSN6501(Transformer Driver)5V_CNTLGNDGND_ISOTLV70450( LDO)TPS7A3001( LDO)+5V_ISO-5V_ISOISO POWERW urth750342354( : )VDD_25V_CNTLTPS7A6533( LDO)GNDPOWER VTI DesignsIsolatedCurrentand VoltageMeasurementUsingFullyDifferential IsolationAmplifierDesignOverviewDesignFe aturesThis TI designdemonstratesusingthe AMC1100-Voltageand CurrentMeasurementUsing.

3 BasedAFEto measurevoltageand Channel-IsolatedCurrentInputsand Groupdesigndetailsmeasuringvoltageinputs in an input-to-IsolatedVoltageInputsBasedon AMC1100 Fixed-outputisolationconfigurationand measuringcurrentGain,FullyDifferentialAm plifiersinputsin a channel-to-channelisolationconfiguration . Provisionto Interfaceto ADS131E08 ADC,Multi-This designalso demonstratespowerisolation,whichChannelS imultaneousSampling,24-Bit,Delta-makesth e designa completesubsystemto measureSigma( ), and EVMfor PerformanceTestingisolatedvoltagesand AFEcan be used OnboardShuntfor ThreeCurrentInputsandin applicationsthat requirereplacingCTs with ThreeVoltageInputsShuntsand potentialdividersare availableonboardtodirectlyconnectcurrent and Low-SideSupplyConfigurableto V or 5 VAMC1100isolationamplifiershavea low nonlinearity AccuracyPerformanceOverFull-ScaleInputer rorand an accuracyof < (175-mVRMS)

4 For Currentand Voltage < to 100%DesignResources IsolatedPowerSupplyGeneratedUsingSN6501 ToolFolderContainingDesignFilesTransform erDriverTIDA-00555 AMC1100 ProductFolder Can Be Interfacedto MCUWithAMC1100 Low-SN6501 ProductFolderSideSupplyConfiguredto VTLV704 ProductFolderFeaturedApplicationsTPS7A30 ProductFolderTPS7A6533-Q1 ProductFolder Portableand AdvancedPowerQualityAnalyzerCSD17571Q2 ProductFolder ProtectionRelays,IEDs,and FaultRecordersADS131E08 EVM-PDKToolFolderMSP430FR5869 ProductFolderASKOur E2E ExpertsWEBENCH CalculatorToolsAn IMPORTANTNOTICEat the end of this TI referencedesignaddressesauthorizeduse, intellectualpropertymattersand otherimportantdisclaimersand August2015 IsolatedCurrentand VoltageMeasurementUsingFullyDifferential IsolationAmplifierSubmitDocumentationFee dbackCopyright 2015, infrastructureapplicationsincludeprotect ion,control,and the gridinfrastructureend applicationsare multifunctionprotectionrelays.

5 Transformerand motormonitoringsystems,powerqualityanaly zers,and be rack-mounted(AC mainsoperated)or portable(batteryoperated).The portablesystemshaverequirementsfor separate(individual)and fully galvanically-isolatedchannelsto measurethe AC-DCvoltageand intelligentelectronicdevices(IEDs)that receiveanalogsignalsfromthe secondaryside of currenttransformers(CTs)and voltagetransformers(VTs).The relaysdetectwhetheror not theprotectedunit is in a trip signalis sent by protectiverelaysto the circuitbreakerstodisconnectthe faultycomponentsfromthe powersystem,if categorizedbasedon the equipmenttype protected,suchas generators,transmissionlines,transformer s,and protectionrelayhas the followingfunctionalblocks: CPU Digitalsignalprocessor(DSP)for processinganaloginputfromCT or VT DigitalI/O DC analogI/O Powersupply CommunicationsThe analoginputrequirementsincludethe following.

6 Currentand voltageinputs Secondaryof CT, secondaryof potentialdivider Numberof currentand voltagechannelsfor protectionrelays 4 to 16 channels Measurementaccuracy 1%Accuratelymeasuringcurrentand voltageis a criticalrequirementfor the functionof a voltageis measuredusinga potentialtransformeror potentialdivider(multipleseriesresistors in adivider).Usinga potentialdividerreducesthe boardsize and improveslinearityperformanceincomparison to a potentialdivider-basedvoltagemeasurement is limitedin that itdoesnot providethe isolationthat requiredfor systemsthat are expectedto conformto commonlyusedto currentinputhas a widedynamicrangein comparisonto the systemperformancedependson the type of the key currentsensorrequirementsare.

7 Measurementaccuracy fromDC to 400 Hz Drift with time,frequency,and temperature Linearityand phaseshift Saturation Reliability Cost Size Safety(isolation)and electromagneticcompatibility(EMC)perform anceTo achievethe requiredperformancestandardslistedabove, selectCTs with a higherlevelof VoltageMeasurementUsingFullyDifferential IsolationTIDUA58 August2015 AmplifierSubmitDocumentationFeedbackCopy right 2015, usingCTs are that they providegalvanicisolation,havelow powerloss,and are notaffectedby the associateddisadvantagesof usingCTs is that theytendto be bulkyand expensiveif the userrequiresa aredisadvantageousto multifunctionprotectionrelayplatforms.

8 Whichare requiredto affectthe performanceof CTs becausethey saturatethe CTsduringfault conditions,whenhigh a magneticfield or frequentexposureto overloadsreducesthe usablelife of the alternativeto usingCTs to measurecurrentis low-valuemetalstripsmadewith Manganin shuntperformancefollowsmostof the havelimitationsin that they do not haveisolation,whichis requiredfor use in followingoptionsdetailthe differentisolationmethodsavailable:Input -to-outputisolation: In this case,all channelsare referencedto the isolationamplifiersrequirepowersupplieso n bothsidesof the : In this case,eachinputchannelis referencedto the isolationamplifiersrequireseparatepowers upplieson the inputside of the isolationbarrierand cansharea commonpowersupplyon the inputscan be appliedin the followingconfigurations:Single-ended.

9 The lowestcost configurationis a single-ended,unbalanced, inputworkswell with afloatingsourcethat has relativelylow IN+ terminalimpedanceto groundmustbe high in comparisonto the sourcedifferentialimpedanceto ground-referencedsources,this type of inputimpliesthat the signaland instrumentgroundsmustbe twovoltagesare typicallynot the same,but if the levelsare closeto eachotherand the signalis relativelylarge,the usercan makethe :Differentialinputamplifiersare mostcommonlyusedin measurementsystemsbecausethey provideahigh gain for the algebraicdifferencebetweentheirtwo inputsignalsor voltages,but a low gain for thevoltagescommonto anothermeansof reducingnoisein differentialinputis balancedbecausethe gainsand impedancesof thetwo inputsare the directlyconnectedto ground,so a differentialinputcan deal withsingle-ended-groundedor.

10 Thereis a limit to the maximumsignalthat eachinputcan handlebecausethe amplifiersare referencedto August2015 IsolatedCurrentand VoltageMeasurementUsingFullyDifferential IsolationAmplifierSubmitDocumentationFee dbackCopyright 2015, voltageinputsare attenuatedby the onboardpotentialdividersand theseinputsdemonstratethefollowingin Table1:Table1. VoltageMeasurementPARAMETERSDESCRIPTIONV oltageinputsprovidinginput-to-outputThre efully-differentialisolationamplifiersar e usedto measurethe providinginput-to-One DC-DCconverteris usedto generatethe samepoweroutputisolationsupplyis connectedto all threeisolationamplifierson the is a groupisolatedreference,whichmeansthat all of the amplifierssharea currentinputsare appliedacrossthe onboardshuntand demonstratesthe followingin Table2:Table2.