VFD + BACnet = Increased $avings - cdn.ymaws.com · What to Expect • Mechanical regulation methods • VFD basics • How VFDs save energy • BACnet basics • Using VFDs and BACnet

EdwardTomProductManagerYaskawaAmerica,Inc.

VFD+BACnet=Increased$avings

WhattoExpect•  Mechanicalregulationmethods

•  VFDbasics•  HowVFDssaveenergy•  BACnetbasics•  UsingVFDsandBACnettogethertosaveadditionalenergy

BeforeWeStart…Howmanyare:•  Maintenance?•  Buildingengineers?•  Buildingmanagers?•  Consultingengineers?•  Distributors?•  OEMs?•  Others?

BuildingAutomationSystem(BAS)Objective

Buildingperformanceandcomfort– Whatiscontrolled?

•  Flow– Air– Water

RegulatingFlowMechanicalMethods

– Dampers– Valves– Variablepulley

Possibleissues– Motorisconstantlyrunningatfullspeed– Motorcycledon/offtoregulateflow

•  Largevariancefromsetpoint

MotoratFullSpeedWhyisamotorrunningatfullspeedanissue?

– Alwaysdrawingcurrent•  Systemlosses(I2R)•  Lowpowerfactor

MotorCyclingWhyiscyclingamotoronandoffanissue?

– Startingamotoracrossthelineresultsin6–8timesmotornameplatecurrent.

•  Mechanicalstress•  Electricalstress•  Canresultindemandchargesduringpeaktimes!

Startingcurrent

Motorfullloadcurrent

6xto8xMotorFLA

Time

Curren

t

AlternateOptionIsthereanalternateoption?

– RegulatemotorspeedwithaVFD.

Time

Motorsp

eed

MotorratedspeedSystemfeedback

WhatisaVFD?VFD=VariableFrequencyDrive

– Alsoknownas•  Drive•  Adjustablefrequencydrive(AFD)•  Adjustablespeeddrive(ASD)•  Inverter

HowDoesaVFDWork?•  IncomingpowerisatafixedACvoltageandfixedfrequency,e.g.460Vac,60Hz.

•  InordertocontrolanACmotor,thevoltageandfrequencyneedtobeadjusted.

VFDBasicOperation•  VFDtakestheincomingvoltageandconvertstoDC.

•  ItinvertstheDCbacktoACbypulsingitinaregulatedfashion(pulse-widthmodulationorPWM).

EnergySavingsHowdoesthisprocesshelpmesaveenergy?

–  Improvedpowerfactor•  Closetounity

– Affinitylaws

PowerFactorPowerfactorcanbeviewedashowefficientlytheloaddrawspower.

– Lowerpowerfactor=higherdisplacement=higherreactivepower

PowerFactor

AngulardisplacementbetweenVoltageandCurrent

VoltageCurrent

Θ

ReactivePowerReactivepoweriswastedenergy.

– HigherreactivepowerincreaseskVA.

– HigherkVArequiresalargertransformer.

– HigherkVAcanincreaseutilitycompanydemandcharges.

VFDInputCurrentVFDdrawscurrentonlywhenneeded.

– Reactivepower≈0– Apparentpower≈realpower

PowerFactorwithStandardVFD

Voltageandcurrentnearlyin

sync

VoltageCurrent

VFDFrontEnd•  VFDfrontendconsistsofdiodebridge•  CurrentflowsthroughthediodebridgetochargetheDCcapacitors(DCbus)– ThisonlyhappenswhenDCbusvoltageislowerthanincomingACvoltage

3-phaseinput

DCcapacitor

Diode Bridge

DC Bus

AffinityLaws

05

101520253035404550556065707580859095

100

% of

…...

Speed (RPM)

Flow - Torque - Output Power

Flow Rate Torque (Pressure) Output Power

𝐹𝑙𝑜𝑤↓1 /𝐹𝑙𝑜𝑤↓2  = 𝑅𝑃𝑀↓1 /𝑅𝑃𝑀↓2  

𝑇𝑜𝑟𝑞𝑢𝑒↓1 /𝑇𝑜𝑟𝑞𝑢𝑒↓2  = (𝑅𝑃𝑀↓1 /𝑅𝑃𝑀↓2  )↑2 

𝑃𝑜𝑤𝑒𝑟↓1 /𝑃𝑜𝑤𝑒𝑟↓2  = (𝑅𝑃𝑀↓1 /𝑅𝑃𝑀↓2  )↑3 

Two Motors Run by Drives

SavingsExampleAcross the Line

1 fan @ full speed

100% Speed à 100% Flow 100% Speed à 100% Torque 100% Speed à 100% Power

2 fans x 12.5% Power each fan = 25%

75% Power Reduction!

2 fans each @ half speed

50% speed à 50% Flow 50% speed à 25% Torque

50% speed à 12.5% Power

Pulse-widthModulationVFDsusesInsulated-GateBipolarTransistors(IGBT)foroutput

–  InvertsDCbacktoAC•  Accomplishesthisthroughpulse-widthmodulation

IGBT

AdditionalBenefitsLessmechanicalwear

– Beltslastlongerwithcontrolledrampofmotor

Lowersystemcomplexity– Reducesneedtodeterminetheoptimalgearboxorpulleyratio.

Betterregulation– Acrossthelineoperationresultinasinglespeed.Thisspeedmightnotbeoptimal.

BACnetOverviewBACnetisBuildingAutomationControlnetwork

– CreatedandMaintainedbyASHRAE•  1995–BecameASHRAE/ANSIStandard135•  2003–BecameISO16484-5

– ProvidesinteroperabilitythroughthoroughtestingoutlinedbyBACnetTestingLaboratories(BTL)

PICSProtocolImplementationConformanceStatement(PICS)

– RequiredforALLdevices– Definesthedevice

•  Devicetype•  Objectssupported•  Connectiontype•  …andmore!

BACnetObjectsWhatisanObject?

– Canbethoughtasa“Datapoint”– Definedbyproperties

Property Value

Object_Identifier AV10

Object_Name OutputFrequency

Object_Type AnalogValue

Present_Value 21.21

Units Hz

Client/ServerModel•  Client–Sends

informationrequestorcommandtoserver.

•  Server–Respondstoclient’sinformationrequestorperformsrequestedcommand.

Whatisyouroutputfrequency(AV10)?

I’moutputting21.21Hz.

BACnetAdvantage#1Simplification

– ReducefrommanywirestoTWO.•  Start,stop,frequencyreference,andmiscellaneousmonitorsneedatleastonewireforeachsignals.

BACnetAdvantage#2Data

– Moredatacanbeprovidedthroughtwowires.– YOUpickthedatayouwant.

MaximizeSavings•  Coordinatedcontrol

– LotsofdevicesonaBACnetnetwork.Usethemtogether!

WhatWeAccomplished•  Drawbacksofmechanicalregulation

•  VFDbasics•  HowVFDsprovideenergysavings•  BACnetbasics•  Howthecombinationcanincreasesavings

Questions?