Page - 29 - in Emerging Technologies for Electric and Hybrid Vehicles

Energies 2017,10, 1217 Table13.Relativeenergyandpowerdensitiesofdifferentenergystoragesystems[63]. Storage EnergyDensity PowerDensity Battery High Low Ultracapacitor Low High Fuelcell High Low Flywheel Low High Table14.Vehiclesusingdifferentstoragesystems. StorageSystem VehiclesUsingtheSystem Battery TeslaModelS,NissanLeaf Fuelcell+battery ToyotaMirai,HondaClarity Flywheel Porsche911GT3RHybrid 5.MotorsUsed Thepropulsionsystemis theheartofanEV[64–69],andtheelectricmotorsits right in thecore of the system. Themotor converts electrical energy that it gets from the battery intomechanical energywhichenables thevehicle tomove. Italsoactsasageneratorduringregenerativeactionwhich sendsenergybackto theenergysource. Basedontheir requirement,EVscanhavedifferentnumbers ofmotors: theToyotaPriushasone, theAcuraNSXhas three—thechoicedependson the typeof the vehicle and the functions it is supposed toprovide. References [4,23] listed the requirements foramotor forEVusewhich includeshighpower, high torque,widespeedrange,highefficiency, reliability, robustness, reasonable cost, lownoiseandsmall size. Direct current (DC)motordrives demonstratesomerequiredpropertiesneededforEVapplication,but their lack inefficiency,bulky structure, lack in reliabilitybecauseof the commutatororbrushespresent in themandassociated maintenancerequirementmadethemlessattractive [4,30].With theadvanceofpowerelectronicsand control systems,differentmotor typesemergedtomeet theneedsof theautomotivesector, induction andpermanentmagnet (PM)typesbeingthemost favoredones [23,30,70]. 5.1. BrushedDCMotor Thesemotorshavepermanentmagnets (PM)tomakethestator; rotorshavebrushes toprovide supply to thestator.Advantagesof thesemotorscanbe theability toprovidemaximumtorque in low speed. Thedisadvantages,ontheotherhand,are itsbulkystructure, lowefficiency,heatgenerated becauseof thebrushesandassociateddrop inefficiency. Theheat isalsodifficult to removeas it is generated in thecenterof therotor. Becauseof thesereasons,brushedDCmotorsarenotused inEVs anymore [70]. 5.2. PermanentMagnetBrushlessDCMotor (BLDC) The rotorof thismotor ismadeofPM(most commonlyNdFeB [4]), the stator isprovidedan alternatingcurrent (AC)supplyfromaDCsource throughaninverter.As therearenowindings in the rotor, there is no rotor copper loss,whichmakes itmore efficient than inductionmotors. This motor isalso lighter, smaller,betteratdissipatingheat (as it isgenerated in thestator),morereliable, hasmore torquedensityandspecificpower [4]. Butbecauseof its restrainedfield-weakeningability, the constant power range is quite short. The torque alsodecreaseswith increased speedbecause of back EMFgenerated in the statorwindings. The use of PM increases the cost aswell [30,70]. However,enhancementofspeedrangeandbetteroverall efficiency ispossiblewithadditionalfield windings [4,71]. SucharrangementsareoftendubbedPMhybridmotorsbecauseof thepresenceof bothPMandfieldwindings. But sucharrangements tooare restrainedbycomplexityof structure; thespeedratio isnotenoughtomeet theneedsofEVuse, specifically inoff-roaders [30]. PMhybrid 29