Page - 332 - in Emerging Technologies for Electric and Hybrid Vehicles

Energies 2017,10, 315 whereB1andB2aretherightandleftmagneticfields, respectively,asshowninFigure9.Whenviewed fromthey-axisdirection, fromthedirectionthe loopof thesensorcoil is facing,BS canbeexpressed in vector formasfollows: Bsy=B 1 y+B 2 y=− μ0I1 2πr1 sinθ1+ μ0I2 2πr2 sinθ2 (8) In(8), I1, I2, θ1andθ2arethecurrentflowandtheangleneededtogenerateB1andB2, respectively. It shouldbenoted that I1 and I2 have the samemagnitudesbutflow inoppositedirections. μ0 is the free-spacepermeability and r1, r2 are the referencepoint distances ofB1 andB2, respectively. InFigure9a, themagneticfieldsensedbythesensorcoil isnearzerobecauseB1andB2 canceleach otherout.As thesensorcoilmoves towards the left, as showninFigure9b, thesensorcoil is relatively moreexposedto theB2magneticfield, thus themagnitudeofB2willbemoredominant thanB1. The oppositephenomenonwilloccurwhenthesensorcoilmoves towards theright,where themagnitude ofB1willbemoredominant thanB2, as showninFigure9c. The inducedvoltage in thesensorcoil,Vse, canbeexpressedas follows: Vse=−dΦdt =− dBSA dt (9) where theequation isbasedonFaraday’s law.Φ, tandA represent themagneticflux, time,andcross sectionalareaof thesensorcoil, respectively.Whenthe loadcoil ismisalignedto the leftor right, the phaseangledifferencebetweenthesensorcoilwill alwayshavea±90degreedifference, respectively. Thephasedifferencewillonlychangewhenthe loadcoil is shifted fromtheright region to the left region,orviceversa.Under theseconditions, thedifference inphasewhenthecoil ismisalignedto the left (showninFigure9b)andright (showninFigure9c)willbearound180degrees. Verificationof theACASSensorCoilUnit throughSimulation 3-DEMsimulationswereconductedtoverify that theplacementof thesensorcoildoesnothave much influenceon thepower transferbetween the source coil and loadcoil, andalso toverify the concept shown inFigure9. The sensor coilwasadded to the simulationmodel shown inFigure4 tomatch theconfigurationshowninFigure8. Thesensor coilparameterswereas listed inTable1. Figures10and11showcomparisonsof the inducedvoltageandmagneticfluxdensityof the loadcoil withthesensorcoil, andtheloadcoilwithout thesensorcoil, respectively,whenalateralmisalignment occurs from−50cmto50cm. Figure10. Simulationresults showing inducedvoltagevs. lateralmisalignment.Acomparisonof load coilswithandwithout thesensorcoil. BasedonFigure10, the twooutputwaveformsarenearly identical, andthemagneticfluxdensity comparison inFigure11showsthat theexistenceof thesensorcoilunit createsalmostno interference with themagneticflowbetweenthe loadcoilandsensorcoil. Thisverifies that theplacementof the sensorcoilhas littleeffectontheperformanceof theoverallWPTsystem. 332