Three-Phase AC Current Measurement Using …

1 R2R1R3R4 VREFCCCVCCRshTPS71733 REF3212 VINVCCVREFTDK , 1W0 A to 300 A15 ppm,N = 30002515 INA199 Copyright 2016, Texas Instruments Incorporated1 TIDUBK3A April2016 RevisedJuly 2016 SubmitDocumentationFeedbackCopyright 2016,TexasInstrumentsIncorporatedThree-P haseAC CurrentMeasurementUsingCurrentTransforme rReferenceDesignTI DesignsThree-PhaseAC CurrentMeasurementUsingCurrentTransforme rReferenceDesignBluetoothis a registeredtrademarkof BluetoothSIG, othertrademarksare the propertyof referencedesigndemonstrateshigh-accuracy ,wide-rangeAC currentmeasurementfor a three-phasemotorusingthe zero-driftarchitectureof the designalso featuresa low powerconsumptionof25 mW for a gain stageof 200 as comparedto integratedhigh-precisionresistorsinsidet he INA199deviceallowfor a muchsmallerdesignfootprintand BOMthanwith a designfootprintand BOMcost is muchsmallerthana discretesolutiondue to the integratedhigh precisionresistorsinsidethe E2E ExpertsDesignFeatures % Accuracy(Uncalibrated)for 10%to 100%ofFull-ScalePrimaryCurrent PowerConsumptionof 25 mW for GainStage SmallFootprintEliminatesRequirementof ExternalResistorsfor AmplificationFeaturedApplications Compressors,Chillers,and Blowers(HVAC) ID and FD Fans,ScrewFeeders,and FeedPumps(SteamBoiler)

2 TractionMotor(Escalatorand Elevators)An IMPORTANTNOTICEat the end of this TI referencedesignaddressesauthorizeduse, intellectualpropertymattersand otherimportantdisclaimersand April2016 RevisedJuly 2016 SubmitDocumentationFeedbackCopyright 2016,TexasInstrumentsIncorporatedThree-P haseAC CurrentMeasurementUsingCurrentTransforme rReferenceDesign1 Key SystemSpecificationsTable1. Key SystemSpecificationsSYMBOLPARAMETERSPECI FICATIONSDETAILSCONDITIONMINTYPMAXUNITII NI nputprimarycurrent 1 100 AAs per CT specificationFINI nputcurrentfrequency 50 60 HzAs per CT specificationTeCT turnsratio 3000 As per CT specificationRshBurdenresistance Vo_ErrorMeasuredaccuracyatINA199outputUn calibratedatambienttemperature , , 5mA VINI nputpowersupply(DC) U V WControl UnitThermal BulbExpansion ValveCondenserEvaporatorBeltCompressorMo torContactorCopyright 2016, Texas Instruments April2016 RevisedJuly 2016 SubmitDocumentationFeedbackCopyright 2016,TexasInstrumentsIncorporatedThree-P haseAC CurrentMeasurementUsingCurrentTransforme rReferenceDesign2 SystemDescriptionAn electricmotoris an essentialmovingelementof any requiredin pumps,compressors,and blowersin typicalheating,ventilation,air conditioning(HVAC)

3 ,and suction,jamming,floodback,and stallingcan lead to catastrophicdamageto motorand crucialfor processcontrollersto take torqueand currentare directlyproportionalto eachother,the usercan implementa currentsensemethodto indirectlymonitorthe load diagramin Figure1 showsthe motorcurrentsensingin an GenericHVACC ontrolSystemDiagramMotorUVWC urrent TransformerTIDA-00753 ADS131E08 EVMUSB CablePCCopyright 2016, Texas Instruments April2016 RevisedJuly 2016 SubmitDocumentationFeedbackCopyright 2016,TexasInstrumentsIncorporatedThree-P haseAC CurrentMeasurementUsingCurrentTransforme rReferenceDesignThe currentflowingthrougha conductorcan be detectedusinga resistiveshunt,currenttransformer(CT),Ha ll effectsensor,and so the mostsimpleand designcan be connectedto any onlinesystemusinga split-coreCT.

4 Whenmeasuringisolatedhigh Current ,a CT is preferredbecauseof its betterstabilityand dynamicrangeoverHall comparesthe varioussensortechniquesusedto diagramin Figure2providesan overviewfor testingthe TIDA-00753designwith the existinganalog-to-digital(ADC)evaluation module(EVM).(1)A genericopen-loopHall sensorhas beenusedfor CurrentSensorSENSORPARAMETERRESISTORHALL EFFECT(1)CURRENTTRANSFORMERS huntresistiveload range to m Nonem to sLinearityoverentirerangeVerygoodPoorFai rOffsetproblemYesYesNoSaturationNoYesYes IsolationNoYesYesStabilityovertemperatur eFairPoorGoodFigure2. TIDA-00753 SystemInterfaceR2R1R3R4 VREFCCCVCCRshTPS71733 REF3212 VINVCCVREFTDK , 1W0 A to 300 A15 ppm,N = 30002515 INA199 Copyright 2016, Texas Instruments April2016 RevisedJuly 2016 SubmitDocumentationFeedbackCopyright 2016,TexasInstrumentsIncorporatedThree-P haseAC CurrentMeasurementUsingCurrentTransforme rReferenceDesign3 BlockDiagramThe TIDA-00753designfocuseson the frontend of the CT signalchain,as the blockdiagramin referencehas beengeneratedusingREF3212for high-precisionmeasurements.

5 However,REF2912and REF2030can be usedas TIDA-00753referencedesignfeaturesthe followingdevices: INA199:26-V,bidirectional,zero-drift,low - or high-side,voltageoutputcurrentshuntmonit or TPS717:Low-noise,high-bandwidthPSRR,low- dropout,150-mAlinearregulator REF3212:4-ppm/ C, 100- A, SOT23-6seriesvoltagereferenceFor moreinformationon eachof thesedevices,see theirrespectiveproductfoldersat : Widecommon-moderange: V to 26 V Offsetvoltage: 150 V (maximum)(Enablesshuntdropsof 10-mVfull-scale) Accuracy error(maximumovertemperature) V/ C offsetdrift (maximum) 10-ppm/ C gain drift (maximum) Choiceof Gains: INA199x1:50 V/V INA199x2:100 V/V INA199x3:200 V/V Quiescentcurrent:100 A (maximum) Packages:6-pinSC70,10-pinUQFNTPS717xxGND ENNRINOUTVINVOUT1 Fm(Optional)1 FmCeramicVENV+OUTGNDIN-IN+ V to 26 April2016 RevisedJuly 2016 SubmitDocumentationFeedbackCopyright 2016,TexasInstrumentsIncorporatedThree-P haseAC CurrentMeasurementUsingCurrentTransforme rReferenceDesignApplications Notebookcomputers Cell phones Qi-compliantwirelesschargingtransmitters .

6 Telecomequipment Powermanagement Batterychargers WeldingequipmentFigure4. V to V Availablein multipleoutputversions: Fixedoutputwith V to5 V V V Ultra-highPSRR: 70 dB at 1 kHz and 67 dB at 100 kHz Excellentload and line transientresponse Verylow dropout:170 mV typicalat 150 mA Low noise:30 VRMS typical(100Hz to100 kHz) Small5-pinSC-70,2-mm 2-mmWSON-6,and Mobilephonehandsets PDAsand smartphones WirelessLAN,Bluetooth Figure5. TPS717 TypicalApplicationCircuitfor April2016 RevisedJuly 2016 SubmitDocumentationFeedbackCopyright 2016,TexasInstrumentsIncorporatedThree-P haseAC : Excellentspecifieddrift performance: 7 ppm/ C (max)at 0 C to 125 C 20 ppm/ C (max)at 40 C to 125 C Microsizepackage:SOT23-6 Highoutputcurrent: 10 mA Low quiescentcurrent:100 A Low dropout:5 : Dataacquisitionsystems Medicalequipment TestequipmentFigure6.

7 REF32xxPinoutbsmIII=-2mmEIZ = ()()()()()()msL2ssLmZZREIZZR + = ++ April2016 RevisedJuly 2016 SubmitDocumentationFeedbackCopyright 2016,TexasInstrumentsIncorporatedThree-P haseAC CurrentMeasurementUsingCurrentTransforme rReferenceDesign4 SystemDesignTheoryThe TIDA-00753TI Designhas beendesignedto meethigh accuracydemandswhenmeasuringwideACcurren trangesfor designusescurrenttransformers(CT),whichh avea very high turnsratioand are usedwhenmeasuringthe primarycurrentrangeto a resultof this higherturnsratio,the secondaryburdenresistorof the designcan be specifiedfromm to k dependingon the requiredrangeof signal-to-noiseratio(SNR)is limitedbecauseof the a widecurrentrangemeasurementand lowersupplyrails,the burdenresistormustbe specifiedin m , whichlimitsthe usingan amplifier,the SNRcan beimprovedto BurdenCalculationsBurdenresistanceaffect sthe accuracyof a CT; as burdenresistanceincreases, showsa circuitwith CT burdencalculationswherethe magneticimpedanceof the coreis inparallelwith the the burdenresistanceincreases,the magneticimpedancedrawsmorecurrent,whichr esultsin measurementerrorand nonlinearityfor the CT BurdenCalculationsUse Equation1, Equation2, Equation3, and the CT specificationsavailablefromthe CT manufacturertocalculatethe theoreticalerrorfor differentburdenresistances.

8 (1)(2)(3) April2016 RevisedJuly 2016 SubmitDocumentationFeedbackCopyright 2016,TexasInstrumentsIncorporatedThree-P haseAC ErrorBudgetingBecausethe inputfull-scalevoltageis very low, a gain stageis requiredto obtaina gainstagecan be a simpleinvertingamplifieror discrete,invertingamplifierwith externalpassivecomponentslimitsthe accuracyof a the sakeof this designthat a basicinvertingamplifierconfigurationhas beenusedas shownin Figure8. This exampleusesan LMV321amplifierwith an R1, R2, and R3 of 1 k , , and 980 with a drift of 25 InvertingAmplifierFor lowerinputvoltagerangeoffsetvoltage,inpu tbias currenterrordominates,whileat highervoltagerangegain amperrorbudgetingcan help to explainthe errorcontributionof anamplifierduringinputmeasurement(seeFig ure9).

9 Figure9. SimplifiedModel()() ()()1IB_Drift12n_Drift3 p_Drift2RV1R R IR IR =+ - POffset _ Driftn _ DriftII+()Bias _ DriftOffset _ Drift2II2 -Offset _ DriftIBias _ DriftI()()()()1IB12n3 p2RV1R R IR IR =+ - POffsetnII+()BiasOffset2II2 -OffsetIBiasIop_driftGainop_driftcl_drif tGainAIdeal1 AB100 Ideal - + cl _ driftBop _ driftAopenGainopenclosedGainAIdeal1 AB100 Ideal - + openGainopenAIdeal1 A50 = + April2016 RevisedJuly 2016 SubmitDocumentationFeedbackCopyright 2016,TexasInstrumentsIncorporatedThree-P haseAC CurrentMeasurementUsingCurrentTransforme rReferenceDesignAn errorbudgetrequirescomputingthe total loop gain errorand bias currenterrorof the showsthe calculationsfor the total loop gain and bias Computationof DC ErrorREFERENCENOPARAMETEREQUATIONVALUEUN ITERROR1 Open-loopgain atambient15000 2 Closed-loopgainat 3 Totalloop gainerrorat ambientTambient % at max temp10000 5 Closed-loopgaindrift at max 6 Totalloop gainerrorat max tempTMAX_TEMP % current250nA 8 Inputoffsetcurrent50nA 9In225nA 10Ip275nA 11 Inputbias currenterror currentdrift500nA 13 Inputoffsetcurrentdrift150nA 14In_Drift425nA 15Ip_Drift575nA 16 Inputbias currentdrift error (RMS)

10 6 FSEB andwidth10V 4 MAX_TEMPT10 IB_DriftIB6 FSVV10V- ()OSOS_DriftMAX6 FSVVTemp2510V - 4ambientT10 6 IBFSV10V 6osFSV10V April2016 RevisedJuly 2016 SubmitDocumentationFeedbackCopyright 2016,TexasInstrumentsIncorporatedThree-P haseAC CurrentMeasurementUsingCurrentTransforme rReferenceDesignThe usercan calibratethe offsetvoltage,bias currenterror,and gain error(at ambienttemperature) usercan also calibrateerrordriftsas a resultof temperaturechangebyusingsoftwarelogicfor errordrift with respectto the temperature;however,the outputnoisedensitycannotbe showsthe contributionof eacherrorfor a full-scalevoltagerangeof , whichcorrespondsto a full-scaleprimarycurrentof 100 ErrorBudgetingfor InvertingAmplifier (PPM) 3 Gainerror %4000 Absolutebest-caseerrorRMS(A) (A) 5 Inputbiascurrentdrift Drift best-caseerrorRMS(A) worst-caseerrorSUM(A) 2000 HzResolutionbest-caseerror(C) (C) (A + B + C) (A + B + C) showsthat the worst-caseerrorusinga discreteamplifieris The gain errorand noisevoltageaffectthe AC performanceand contributean errorof 36 V in the (RMS)6 FSEB andwidth10V Gain nonlinearity in ppm()MAXPPMGain DriftTemp25C - 4 Gain error % 10 ( )CM6 FSVCMRR dB102010V ()