Tutorial on EV Design-I

7/30/2019 Tutorial on EV Design-I

1/24

u

ElectricVehicleDesign

TaiRanHsu,Ph.D.

DepartmentofMechanicalandAerospaceEngineering

SanJose,California

October12,

2011

TaiRanHsu

nd , , , ,

NewYork,ISBN:9780071543736,1994

SpartanZeroEmissionsHybridHumanPoweredVehicleZEMHHPV,byAmandeep Manik,

ScottMacPherson,HeathFieldsandMarkRafael,SanStateUniversitystudentseniordesign

projectreport,ElectricalEngineeringDepartment,May2008


2/24

Content

Part1TheBasics

HistoryofElectricVehicles

Anatomyof

EVs

DesignforPower

DriveTrain

DesignforVelocityandNochargeCruisingRange

Part2Hybrid

EVs

and

Regenerative

Braking

System

RegenerativeBrakingSystems(RBS)forHybridGaselectricVehicles

TheFlywheelDrivenRBS


3/24

ElectricVehicles PastandPresent

LightWeight,Low Speed

NeighborhoodandLightUtilityVehicles(Limitedtostreetswithlowpostedspeedlimits)

HighSpeed,LongCruisingRange

(Freewaylegal)

NissanLeaf(2010) TeslaRoadster

ChevyVolt(2011) TeslaModelS(2012)


4/24


5/24

DesignforPower

TheveryfirstiteminEVdesignistodeterminehowmuchelectricpower

requiredto

drivethevehicle atatopvelocitywithexpectedpayloadsfora nochargecruising

range.Asimpleformulafromrigidbodydynamicswilldothejob.

thefollowingforces:1)Thefrictionforcesbetweenthewheeltiresandtheroadsurface(Ff)

2 T eaero ynamicresistance Fr

3)Thedynamicforcesassociatedaccompaniedwithanyaccelerations(Fd)

g

V,aFr

Ff

Fd

W=mg

Fg


6/24

ElectricPowerRequirement

Thepower(P)requiredtodrivethevehicleatvelocityVis:

) VFFFFP gdrf +++=wherePhastheunitofhorsepower(hp);Fin(lb);Vin(ft/s)

1hp=550ftlb/s

InSIsystem: PhasaunitofWatt(W):1W=1J/s;(1J=1Nm),

so1W=1Nm s,an 1 W=0.7457 p


7/24

ForcesonRunningEVs

Fr ,

Fd

f

W=mg

Fg

Thetotalweight ofthevehicle(curbwt.+payload)isveryimportantinthedesign

Normally weight distribution is about 45% on front axel

required power for EVs with 4 wheels:

Ff =N = (W/4)

where = coefficient of friction, or rolling resistance factor between wheel tires

and road surface:

= 0.015 on a hard surface (concrete)

= 0.08 on a medium-hard surface (asphalt)

= 0.3 on a soft surface (sand)

The-values may vary with speed V (mph) with: = 0.012 (1 + V/100)


8/24

ForcesonRunningEVs contd

Fr ,

Fd

f

W=mg

Fg

Theaerodynamicdragforce(Fr)tothevehicleisunavoidablewhenitisrunning.Itcanbeexpressedas:

Fr =(Cd AV2)/391 withnegligiblewind

whereFr isin(lb),Aisthefrontalareain(ft2)andVisthevelocityofthevehiclein(mph)

ThedragcoefficientCd fortypicalEVsare:

Cd =0.3to0.35forcars;0.33to0.35forvans;and0.42to0.46forpickuptrucks

CoefficientCd needstobemodifiedwhenthereisarelativewindvelocityofVw present:Cw =[0.98(Vw/V)

2 +0.63(Vw/V)]Crw 0.4(Vw/V)

where Vw =averagewindvelocity(mph);V=vehiclevelocity(mph);Crw =relativewindcoefficient=1.4

formostsedans

Totalaerodynamicdragforceonvehicleis:

Fr =(Cd A

V

2

)/391+[0.98

(Vw/V)

2

+0.63

(Vw/V)]Crw 0.4

(Vw/V)


9/24

ForcesonRunningEVs endsV,a

Fr

Ff

Fd

Dynamicforces(F )tothevehicleneedstobeaccountedforonlyifthevehiclechangesitsvelocity

W=mg

Fg

e.g.,inaccelerationsordecelerations. Themagnitudeoftheseforcesis:

Fd =

Ma

where M = mass in slug or kg in SI system; and a = acceleration with (+) sign and deceleration with

(-) sign in unit of ft/s2 of m/s2 in SI system

Gravitational,orbodyforce(Fg)indeterminingtherequiredpoweronlywhenthevehicletravelson

slopedroads.Itsmagnitudeis:Fg = W Sin

in which W = the total weight of the vehicle; = is the inclination of the road surface. A +ve sign for

traveling up the slope and a ve sign for down-slope traveling.

NoticeAll

forces

are

related

to

the

WEIGHT

of

the

vehicle.

Minimizing

weight

is

amajorconsiderationindesign


10/24

TypicalDriveTrainofEVs

Wheel

ManualMotor&Differential

GearDriveShaft

TransmissionController

DriveAxles

Wheel

BatteryBanks

&BMS


11/24

DesignofDriveTrain

Threeusefulformula:

h = Tor ue xm hxRevolution/mile / 315120x for selectin motor

Torquewheel =Torquemotor x(OverallgearratioxOveralldrivetrainefficiency()

Speedwheel (mph)=(rpmmotor x60)/(Overallgearratioxrevolution/mile)

where 0.9, Overallgearratio=rpmmotor/rpmwheel

Determine thetorqueofwheels:

Torquewheel =Ff R+Fh

whereR=radiusofdrivingwheeltire,ft;h=distancebetweencenterofgravity(CG)

ofthevehicleandthewheelaxel,ft


12/24

DesignofElectricSystemandBMS

Electricsystemanditsassociatedbatterymanagementsystem(BMS)arethecardiologysystem

ofhumanbodies.MostEVscontainasystemasillustratedbelow:

BatteryCharger

e.g.,48DCV,15A

BatteryBanks

e.g.48DCV,4000Wh ea.

DC DC

Converter

48DCV

SPDTSwitch

120VAC

Power

Source

MainContactor

400AMax

ReverseContactor

400AMax

Electronic Throttle

Motor

Controller

48DCV,250A(1hr)

&ControlSwitching

DCMotore.g.,10hp(40hppeak)

48 72DCVserieswound

ConnectedtoMechanicalDriveSystem


13/24

MajorComponentsinElectricalSystem

ComponentName Picture PrincipalFunction

Batterycharger 15Awallchargerfrom110ACVto

. .,

Main contactor Itisaheavydutysafetyswitch

Reversecontactor Toallowelectronically controlled

Motorcontroller Tocontrolmotorspeedandallowssafe

reversin

DCmotor ThemotorthatdrivestheEV.Should

deliverthemaximumdesigned power

fortheEV


14/24

BatteriesforElectricVehicles

.Nocarcanrunwithoutgastank.Thelargerthegastankthefartherthecarruns.

Batteriesarewherethevehicledrivingenergyisstored. NoEVorHEVcanrunwithoutbatteries.

, .

Characteristics LeadAcid LithiumIon NickeMetalHydride

CommonBatteries

for

Vehicles

Pbacid Liion NiMH

Voltage(v) 12 3.2to3.6percell 1.4to1.6percell

Electrolytec Surfuric

acid Lithium

salts

Alkaline

TheorecticalEnergyDensity 3542 150250 6070

(kW/kg)

TheoreticalAmphr 45 3to12 5to10

.

Regularchargingtime(hr) 4to8 1.5to2 1

Memoryeffect Atlowvoltage No No

Selfdischarge 2to10%/mo 1%/mo >30%/mo

Cost Low Hig Mo erate


15/24


16/24

DesignforVelocity

ThevelocityoftheEVrelatestothespeedofthedrivingmotorandthedrivetrain

o eve c e,ass own y e ormu a:Speedvehicle (mph)=(RPMmotor x60)/(overallgearratioxrevolutions/mile)

where Overallgearratio=RPMmotor/RPMwheel

Revolutions/mile=5280/(d)inwhichd=diameterofwheeltireinft

Thevelocity(orspeed)ofthevehicle(V)inthefollowingformulaisalsorelatedtothe

Obviously,theelectricpower(P)intheaboveequationmustbegreaterthanthepower

requiredto

drive

the

motor

(hpmotor)


17/24

DesignforNochargeRange

ecru s ngrangeo an epen son ow astt eve c etrave sonspec c

roadconditionsandthetrafficenroute.

Thecruisin ran eofanEV R canbeobtainedb usin thefollowin formula:

R =nE Vav/P miles

where n=totalno.ofbatteriesorcells

E =(TheoreticalAmph)x(voltageoutputbyeachbatteryorcell,v)from

characteristicsoftheselectedbatteries(Wh)av = verageve c eve oc ty m es r

P =Requiredpowertodrivethevehicle,W


18/24

DesignCase

A neighborhoodelectricvehiclewithacurbweightat1200lbs andisdesignedtocarrya

payloadof400lbs.thevehicleisdesignedtooperateunderthefollowingconditions:

1) Thevehicleispoweredby2banksofleadacidbatterieswith12voutputbyeachbattery.

Eachbankconsistsof4batteriesconnectedinseries. TheDCamphoutputis45/battery.2) Travelsonstraightflatconcretepavedroadswithanaverageslope av =3

o.

3) MaximumspeedVmax =35mphwithanaveragespeedVav =25mph(or36.67ft/s).

Thelatterisusedasthedesignedvelocity

4) Thevehicleisdesignedtoaccelerationfromzeroto25mphin30secondsaftereachstop.

5) Thevehiclehasasmallfrontsurfaceareaof8ft2 withanaerodynamicdragcoefficientCd =0.3.

6) Thevehiclewheeltirediameteris20inches.


19/24

Designforpowerrequirement:

canbeobtainedbytheequation:

whereV=Vav =25mph=25x5280/3600ft/s=36.67ft/s

Thefrictionforce: Ff = W/4 =0.015x(1600)/4=6lbs

Theaerodynamicdragforce:Fr =(CdAV2)/391=(0.3x8x252)/391=1.4lbs

ThedynamicforceFd =Ma=(1600/32.2)x[(36.67 0)/30]=60.7lbs

ThegravitationalforceFg =WSin =1600Sin(3o)=83.74lbs

TotalforcesactingonthevehicleisF =6+1.4+60.7+83.74=151.84lbs

HencetherequiredpowerP =FV=151.84x36.67ftlbs/s=5568ftlbs/s

=5568 550 p =10.12 p

=10.12/0.7457kW=13.58kW


20/24

SelectionofDCmotor:

se e ormu a: pmotor =

orquewheel xmp

x

evo u on m e

x

Intheaboveformula:

Torquewheel =FfR +Fh withR=10/12=0.833ftandh=2ft(estimated)

with forces:Ff=6lbs,Fr=1.4lbs,Fd =60.7lbs,andFg =83.74lbs,

andRevolution/mile=5280(ft/mi)/(2R) (ft/rev) = 1009 rev/mi,

an = . , a common assump on, we ave e orsepower o e mo or o e:

Hpmotor =[6x10/12+(1.4+60.7+83.74)x2]x25(mph)x1009rev/mi/(315120x0.9)=26.39hp


21/24

DesignforNochargeRange

R =nE Vav/P

w ere n=no.o a er es=

E =

(TheoreticalAmph)x(voltageoutputbyeachbatteryorcell,v)fromcharacteristicsoftheselectedbatteries(Wh)

=45(Amph)x12(v)=540Wh

= av = mp

P= Requiredpowertodrivethevehicle=13.58kW=13580W

Hencethenochargecruisingrangeis:

R=8x540x25/13580=0.318mi

ThisnochargecruisingrangeRfortheEVisUNACCEPTABLYLOW!!

Oneneedtoeitherusemoreandmorepowerfulbatteries(n),orcutdownthepower

requirement(P)byreducingtheweight (W)ofthevehicle.


22/24

in nochargecruisingrange:

d

Higher

spe


23/24

EVswithHigher VelocityandBetterNochargeCruisingRange

Maximumvelocity(V)andNochargecruisingrange(R)arethetwomostimportantdesign

.presenceinmarketplace.

Uptillveryrecently,mostEVscouldonlybeusedforwhatistermedasneighborhood

.

LowVandRareprimarilyattributedtothe limitedelectricpowerandtheenergystorage

systemsusinglessthanefficientbatteries.

FordFocus

Electric

MitsubishiI NissanLeaf TeslaModelS

E ectr cVe c esonCurrentMar et

, ,

Milesper

charge

Upto100miles 50to85miles 100miles 160 to300miles

dependto

batterypackSeats Five Four Five Seven

ro ec e

availability

a e a rea y

available

ar y

*Qualifyfor$7,500federaltaxcreditwithpossible$5,000staterebate.Source:MakeWayforElectricVehiclesSanJoseMercuryNews,April3,2011


24/24

Low wei ht

Streamline exterior

Simple drive train DC to get started

o run a ove mp

Use more high frequency components (> 400 Hz)

DC motor that gets 96 volts

AC motor that gets 400 volts

Matching controller and motor impedance

Use high energy density batteries

Date post:	14-Apr-2018
Category:	Documents
Upload:	al-janez
View:	221 times
Download:	0 times

Tutorial on EV Design-I

Documents