Three-Phase AC Current Measurement Using Current ...

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) TractionMotor(Escalatorand Elevators)

2 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. 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).

4 (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;however,REF29 12and 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.

5 6-pinSC70,10-pinUQFNTPS717xxGNDENNRINOUT VINVOUT1 Fm(Optional)1 FmCeramicVENV+OUTGNDIN-IN+ V to 26 April2016 RevisedJuly 2016 SubmitDocumentationFeedbackCopyright 2016,TexasInstrumentsIncorporatedThree-P haseAC CurrentMeasurementUsingCurrentTransforme rReferenceDesignApplications Notebookcomputers Cell phones Qi-compliantwirelesschargingtransmitters . 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.

6 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. 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)

7 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.(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.

8 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).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.

9 TexasInstrumentsIncorporatedThree-PhaseA C 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)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.

10 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 ()osBurden6 FSIR R R10V+- ++ 6osFSV10V April2016 RevisedJuly 2016 SubmitDocumentationFeedbackCopyright 2016,TexasInstrumentsIncorporatedThree-P haseAC ErrorBudgetingAchievinga betterperformancerequiresan INA199is one exampleofthe zero-drift,low-power,integratedresistord ifferenceamplifiersthat can be usedto monitorcurrentshuntsin this amplifiercomeswith gain variantsof 50,100,and loweroffsetvoltageof 150 V and typicalgain errorof amplifiera bettersolutionfor lowerburdenresistanceof and a lowersecondarycurrent,the slewrate of V/ s is suitablefor showsthat the worst-caseerrorusingthe INA199amplifieris 156 V as comparedto the discretesolution(as shownin Table4).