Page - 48 - in Emerging Technologies for Electric and Hybrid Vehicles

Energies 2017,10, 1217 7.2. Systems forWirelessCharging Wirelesschargingorwirelesspower transfer (WPT)usesaprinciplesimilar to transformer. There isaprimarycircuitat thechargerend, fromwhere theenergy is transferredto thesecondarycircuit locatedat thevehicle. Incaseof inductivecoupling, thevoltageobtainedat thesecondaryside is: v2=L2(di2/dt)+M(di1/dt) (2) Mis themutual inductanceandcanbecalculatedby: M=k √ (L1L2) (3) The term k here is the coupling co-efficient; L1 and L2 are the inductances of primary and secondarycircuit. Figure59showsthe ‘doubleD’arrangement forWPTwhichdemonstrates thebasic principleofwirelesspower transfer bymeansofflux linkages. Avarietyof configurations canbe employedforwirelesspower transfer; someof themmeeta fewdesiredproperties tochargevehicles. InductiveWPT, shown inFigure 60a, is themost rudimentary type, transfer power fromone coil to another just like thedoubleDsystem. CapacitiveWPT (Figure 60b)uses a similar structure as the inductive system, but it has two coupling transformers at its core. Low frequencypermanent magnet couplingpower transfer (PMPT) is showninFigure60c; itusesapermanentmagnet rotor to transmitpower,anotherrotorplacedin thevehicleactsas thereceiver. Resonantantennaepower transfer (RAPT)(Figure60d)usesresonantantennasforwireless transferofpower.Resonant inductive power transfer (RIPT), showninFigure60e,usesresonancecircuits forpower transfer.Onlinepower transfer (OLPT)hasasimilarworkingprincipleasRIPT, it canbeused inrealizingroadways thatcan chargevehicleswirelesslyby integrating the transmitterwith theroadway(pilotprojectsusingsimilar technologyplacedthemjustbeneaththeroadsurface), andequippingvehicleswithreceivers tocollect power fromthere. Schematic for this systemisshowninFigure60f.Characteristicsof thesesystems areshowninTable25. Figure59.DoubleDarrangement forWPT.Fluxesgenerated inonecoil cut theotheroneandinduces avoltage there,enablingpower transferbetweenthecoilswithoutanywiredconnection[27]. 48