Page - 50 - in Emerging Technologies for Electric and Hybrid Vehicles

Energies 2017,10, 1217 Table25.Characteristicsofwirelesschargingsystems[87]. Technology Characteristics InductiveWPT • It isnotactuallywireless, justdoesnot requireanyconnection. • Primaryandsecondarycoilsaresealed inepoxy. • Canprovidepowerofeither6.6kWor50kW. • Coaxialwindingtransformercanbeusedtoplaceall the transformercore materialsoff-board. • Losses includinggeometriceffects, eddycurrent loss,EMIaremainlycausedby nonlinearfluxdistribution. • Apiecewiseassemblyof ferritecoreanddividingthesecondarywinding symmetricallycanhelpminimizingthe losses. CapacitiveWPT • Capacitivepower transferorCPTinterface isbuiltwith twocouplingtransformersat thecenter; therestof thesystemissimilar to inductiveWPT. • Capacitive interface ishelpful inreducingthesizeandcostof therequiredgalvanic isolatingparts. • Cheaperandsmaller for lowerpowerapplications,butnotpreferredforhigh powerusage. • Useful inconsumerelectronics,maynotbesufficient forEVcharging. Lowfrequency permanentmagnet couplingpower transfer (PMPT) • Thetransmitter isacylinder-shaped,permanentmagnet rotordrivenbystatic windingsplacedontherotor, inside it if therotor ishollow,oroutside themotor, separatedbyanair-gap. • Thereceiver isplacedonthevehicle, similar to the transmitter inconstruction. • Transmitterandreceiverhave tobewithin150mmforcharging. • Becauseofmagneticgeareffect, thereceiver rotor rotatesat thesamespeedas the transmitterandenergy is transferred. • Thedisadvantagesmaybethevibration,noiseandlifetimeassociatedwith the mechanical componentsused. Resonant inductive power transfer (RIPT) • MostpopularWPTsystem. • Uses twotunedresonant tanksormore,operating in thesamefrequency inresonance. • Resonantcircuitsenablemaximumtransferofpower,efficiencyoptimization, impedancematching, compensationofmagneticcouplingandmagnetizing currentvariation. • Cancouplepower foradistanceofupto40cm. • Advantages includeextendedrange, reducedEMI,operationathighfrequencyand highefficiency. Onlinepower transfer (OLPT) • Hasasimilarconcept likeRIPT,butusesa lowerresonant frequency. • Canbeusedforhighpowerapplications. • Thissystemisproposedtobeapplied inpublic transport systemin[87]. • Theprimarycircuit—acombinationof the inputof resonantconverteranddistributed primarywindings is integrated in theroadway. Thisprimaryside iscalledthe ‘track’. • Thesecondary isplaced invehiclesandiscalledthe ‘pickupcoil’. • Supplyof this systemishighvoltageDCor3-phaseAC. • It canprovide frequentchargingof thevehicleswhile theyareonthemove, reducing therequiredbatterycapacity,whichwill reduce thecostandweightof thecars. • Thecostsassociatedwithsucharrangementmayalsomake its implementationunlikely. Resonantantennae power transfer (RAPT) • Thissystemuses tworesonantantennas,ormore,with integratedresonant inductances andcapacitances. Theantennasare tunedto identical frequencies. • LargeWPTcoilsareoftenusedasantennas; resonantcapacitance isobtainedthereby controlledseparation in thehelical structure. • Thefrequenciesusedare inMHzrange. • Cantransferpowerefficiently fordistancesupto10m. • Theradiationsemittedbymostofsuchsystemsexceedthebasic limitsonhuman exposureandaredifficult toshieldwithoutaffectingtherangeandperformance. • Generatingfrequencies in theMHzrange isalsochallengingandcostlywithpresent powerelectronics technologies. 50