An Analysis of a Double-layer Electromagnetic Shield for a Universal Contactless Battery Charging Platform

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1 A Aalyss of a Doubl-lay Elcomagc Shld fo a Uvsal Coaclss Bay Chagg Plafom Absac A pad doubl-lay plaa sucu s mployd o shld h lcomagc EM fld a h boom of a uvsal chagg plafom. Th doubl-lay cosss of a lay of sof fomagc maal ad a lay of coducv maal. Th F f pla ad h copp sh a usd hs xampl. Ths shldg chqu s aalyzd h h xdd asmsso l hoy. Wh h fomulas psd, h shldg ffcvss SE of boh sgl-lay shld ad doubl-lay shld could b calculad ou dcly, hou usg f-lm sofa. A classcal asmg-cvg loop masum has b cad ou o valua h SE of sgl f shld, sgl copp shld ad doubl-lay shld spcvly. Calculad ad masud suls h okg fqucy ag of h chagg plafom fom 00 kz o 500 kz cofm ha h doubl-lay shld has obvously b SE ha sgl-lay shld ad ca achv a SE abov 0dB, hch s commoly accpd by h dusy. Fally, h poal of hs doubl-lay shldg chqu fo a d ag of po lcoc applcaos s dscussd. I. INTRODUCTION A gao of plaa ducv bay chag fo poabl cosum lcoc qupm as sho Fg. has b psd [,-]. Dff yps of poabl lcoc qupm ca b placd ad chagd smulaously o h chagg plafom, gadlss of h posos ad oaos. A mpoa dsg ssu of h chagg plafom s h lcomagc EM shld a h boom of h plafom. If EM fld s o shldd h boom of h plafom, udsabl gy asf ll ak plac h h chagg plafom s placd o a mallc abl. To achv a good shldg ffcvss SE, a pad doubl-lay shld [,0] has b mployd. I [,0], h shldg chqu s aalyzd fom h magc fld hoy, ad h shldg ffcvss s calculad Fg. : Cocp of a uvsal plaa chagg plafom [,-] X. Lu ad S.Y.R.u, Fllo IEEE Dpam of Elcoc Egg Cy Uvsy of og Kog Ta Ch Avu, Koloo og Kog, Cha mal: ohu@cyu.du.hk fom h smulao suls by f lm FE sofa. I hs pap, h SE of hs shldg chqu s aalyzd h h xdd asmsso l hoy [][]. Wh h fomulas psd, h SE of sgl-lay ad doubl-lay shld could b calculad dcly, hou h us of h FE mhod. Som masums a cad ou fom h fqucy of 0 kz o a f mga-z o vfy h calculao mhod. Masud suls of h doubl-lay EM shld sho a good shldg popy h okg fqucy ag of h chagg plafom fom 00 kz o 500 kz. Th poposd doubl-lay EM shld sucu ca b cosucd h flxbl sof magc maals ad coducv maals f cssay. Ths flxbly abls h poposd EM shld o b appld o a d ag of applcaos. II. STRUCTURE OF TE CARGING PLATFORM WIT TE DOUBLE-LAYER SIELD Th coss-scoal sucu of h chagg plafom h h doubl-lay shld s sho Fg.. Th chagg plafom cosss of h lays of hxagoal dgs, hch ca ga magc flux of almos ufom magud ov h sufac of h dg aays. Th plafom s dv by a po v as sho Fg., okg a a fqucy chos h h ag fom 00 kz o 500 kz, hch s coolld by a sadad PWM cool IC. Th doubl-lay shld s placd blo h plafom h a sulag lay sd b hm. I hs xampl, h f plas a mad of F f maal [5]. Th lav pmably, µ, ad ssvy,, of h F f maal a abou 80 ad 0 5 Ωm, spcvly. Th copp plas a adhbd dcly ud h f plas. Th hckss of h f ad h copp plas a 0. mm ad 70 µm spcvly. III. SIELDING EFFECTIVENESS ANALYSIS WIT TE EXTENSION OF TRANSMISSION LINE TEORY Shldg ffcvss s dfd as h ao b h fld sgh, a a gv dsac fom h souc, hou h shld posd ad h fld sgh h h shld posd [6]. Th ma hch a lcomagc shld asms lcomagc avs has b sho o b aalogous o h ma hch a covoal o- asmsso l asms lccal cu ad volag [][]. Wh fc o Fg., compaso of h lcomagc shld ad h asmsso l s lsd Tabl /05/$ IEEE. 767

2 TABLE I COMPARISON OF TE TRANSMISSION LINE AND TE ELECTROMAGNETIC SIELD Basc quaos Chaacsc mpdac Popagao cosa Tasmsso l dv I di YV c Y Elcomagc shld de jωµ d σ jωε E jωµ σ jωε Γ Y j ωµ σ jωε Fg. : Th coss-scoal sucu of h plafom h doubl-lay shld Fg. : Schmac of h okg ccus [] a a b b a a b Wh a sgl-lay shld s cosdd, h a o boudas, as sho Fg.5b. A h fs bouday, h souc av s flcd ad h asmd fld ca b calculad ou by 5 hch has a smla fom as. 5 Th asmsso coffc coms fom h sul of. I Tabl, ad Y a h dsbud ss mpdac ad shu admac of h asmsso l, spcvly. µ, σ, ad ε a h lccal cosas of magc pmably, lccal coducvy, ad dlcc cosa of h lcomagc shld, spcvly. A. Sgl-lay shldg As sho Fg.5a, h a lcomagc av coms o h fac of o maals h dff chaacsc mpdac, flco occus. Bcaus h chagg plafom s a lo mpdac lcomagc souc, oly h magc av s cosdd []. Th asmd ad flcd flds could b xpssd as: h ad a h asmsso ad flco coffc spcvly, ad hav h foms as sho ad. a b a b Fg. : Aalogy of a asmsso l ad b lcomagc shld [] c Fg. 5: Popagao of avs: a Sgl fac. b Sgl-lay shld. c doubl-lay shld 768

3 A hs m, b dos h chaacsc mpdac of h shld ha ca b calculad ou fom h quao Tabl, ad a dos h cd av mpdac. Fom h dscusso [7], h cd av mpdac s qual o / d jµω h d s h dsac fom h souc o h masum po as sho Fg. 6 so as o m h basc la of physcs: cpocy. Wh h asmd av gos hough h shldg maal, fom h fs bouday o h scod bouday, h magc fld s auad du o h absopo loss sd h ba, ad h auad av could b xpssd as: 6 h s h popagao cosa ha s lsd Tabl ad s h hckss of h lay. A h scod bouday, aoh flco occus. Th flcd ad asmd fld ad could b calculad as: 7 8 I calculag ad fom ad, should b ocd h ha a s h chaacsc mpdac of h shld, hl b quals o h cd av mpdac. Fuhmo, f -flcos occu sd h shld, as sho Fg.5b. Ad oal fld ou of h shld s h sum of all h ou-asmd avs, hch mas: L 9 Th dvao of 9 could b foud h App. Th shldg ffcvss SE of o sgl-lay shld could b calculad h: SE 0 h ad a h chaacsc mpdac ad h popagao cosa of h sgl-lay shld spcvly, ad s s hckss. B. Doubl-lay shldg Th doubl-lay shld could b aalyzd h a smla mhod psd pvously. Th asmd magc fld fom h fs lay o h scod lay s labld as, as sho Fg.5c. I cosss of,,, hch a smla h,, Fg.5b ad could b xpssd as: K M Wh,, coms o h ou-bouday of h scod lay, mul-flco also occus. Th ou-asmd fld cosss of,,..., ad could b xpssd as: M Th oal fld ou of h scod lay s h sum of h ou-asmd fld: So h shldg ffcvss of doubl-lay shld could b calculad h: SE h ad a h chaacsc mpdac of h o 769

4 lays, hl ad a h hckss spcvly. By usg 0 ad, h shldg ffcvss SE of h sgl f pla, h sgl copp sh ad h doubl-lay shld could b calculad spcvly ad h suls a plod as sold ls Fg.8. I h calculao, lav pmably, µ of h F f maal s kp as a cosa of 80. Th dsac fom h souc o h masum po, d s h sam h ha xpm ad s qual o 5 mm. IV. MEASUREMENT I h xpm, h chagg plafom s smplfd as a colss PCB asfom [9]. As sho Fg.6, a asmg ad a cvg colss PCB dgs a placd a a spcfd dsac o h sd of h shld ad masums a ak h ad hou h shld o valua h SE [7][8]. Th dsac b hs o dgs s 5mm. Th gomc paams of hs o dgs ad h shld a lsd Tabl. A RF Po Amplf s usd o dv h asmg dg a dff fqucs hough a Ω masum sso. Th cu h asmg dg s kp a 0.5 A RMS. Th cvg dg s op-ccu ad h volag acoss s masud. Fo xampl, Fg.7 gvs ou h xpmal suls h h fqucy s 00 kz, hch s h h ag of h okg fqucy of h chagg plafom. I Fg.7, Ch s h volag acoss h Ω masum sso ad s kp aoud 0.5 V, ad Ch s h volag acoss h cvg dg. Fg.7a-d sho h suaos a hou shldg, b h F f pla as a sgl-lay shld, c h copp sh as a sgl-lay shld ad d h F f pla plus copp sh as a doubl-lay shld spcvly. I mus b ocd ha h scals of Ch Fg.7a-d a 00 mv/dv, 0 mv/dv, 0 mv/dv ad mv/dv spcvly. Fom h masum suls, h SE of such h suaos a 00 kz could b dmd: a: Whou shldg upp ac: 0.5A/dv.; boom ac: 00mV/dv b: Wh F f pla as shld upp ac: 0.5A/dv.; boom ac: 0mV/dv 0 0 SE F log 75/0.7. db SE copp 0log0 75/.5 8. db SE doubl 0log0 75 / db Fg. 6: Sucu of h masug ss c: Wh copp sh as shld upp ac: 0.5A/dv.; boom ac: 0mV/dv 770

5 d: Wh a doubl-lay shld upp ac: 0.5A/dv.; boom ac: mv/dv Fg.7: Masud volags a h fqucy of 00 kz Th masud volags a oh fqucs a lsd Tabl ad h shldg ffcvss db s summazd by h dos Fg.8. Fom h calculad ad masud suls Fg.8, could b s ha: a. h h F f has almos h sam SE ov h fqucy ag fom 0 kz o Mz, bu s SE valu of aoud 0 db s o ough may applcaos; b. h SE of a h copp shld ss galy h h cas of fqucy, hch mas ha copp ca b a good shldg maal h h fqucy s hgh ough as log as h copp loss s accpabl; c. h okg fqucy ag of h chagg plafom fom 00 kz o 500 kz, hs doubl-lay shld shos a good shldg ffcvss, ly abov 0 db. TABLE II GEOMETRIC PARAMETERS OF TE MEASURING SET Gomc Paam Tasmg dg Rcvg dg Copp Tack Wdh 0. mm 0. mm Copp Tack Thckss 0 µm 0 µm Numb of Tus 0 0 Wdg Radus mm mm Dmsos of F Pla Dmsos of Copp sh Fg. 6: Sucu of h masug ss 6mm 6mm 0.mm 6mm 6mm 0.07mm Fg. 8: Calculad ad masud Shldg Effcvss db TABLE III MEASURED RESULTS Masud Volag mv Fqucykz No shld F Copp -lay V. CONCLUSION AND DISCUSSION Ths pap pss a hocal aalyss ad paccal valuao of a doubl-lay EM shldg sucu. Ths aalyss s basd o h xdd asmsso l hoy ad ca ga fas ad asoably accua soluos hou usg h m-cosumg f-lm mhods. Boh calculad ad masud suls ag ll ad hav cofmd h good shldg ffcvss of hs doubl-lay sucu >0dB h okg fqucy ag fom 00 kz o 500 kz of h plaa bay chagg plafom. Fo applcaos h shldg qum a a lo fqucy.g. <00 kz, h shldg ffcvss of h doubl-lay shld hs xampl may o b hgh ough. Th ma aso fo hs s ha, a lo fqucy, oly h f pla acs as h ma cobuo of h shldg ad copp sh s o ffcv as a shld. Th maal chos F has a lavly lo pmably µ 80 compad h oh f maals lk C9 µ 000. Wh h quaos psd hs pap, could b pdcd ha such f maal C9 could achv a hgh SE up o 60 db du o s hgh pmably a lo fqucy. Bu h pmably ad SE of such maal dcass apdly h 77

6 h cas of fqucy [], hl h SE of copp cass h fqucy. So h h hlp of copp sh, h doubl-lay sucu h oh f maal lk C9 may xhb a d-bad shldg ffcvss. Such paccal ok could b cad ou h fuu h h hlp of h aalyss psd hs pap. APPENDIX Rfd o Fg.5b, h dvao of 9 s: 5 L L ACKNOWLEDGMENT Th auhos ould lk o hak h Rsach Ga Coucl of og Kog fo s suppo fo hs pojc RGC Rfc No.: CyU /0E. M. X. Lu s gaful o h Cy Uvsy of og Kog fo povdg h sach scholashp ad sudshp fo hs Ph.D sudy. REFERENCES [] S.Y.R.u ad W.C.o, A gao of uvsal coaclss bay chagg plafom fo poabl cosum lcoc qupm, PESC. 5h Po Elcocs Spcalss Cofc, pp. 68-6, Ju. 00. [] S.C. Tag. S.Y.R.u,.S.-. Chug, Evaluao of h shldg ffcs o pd-ccu-boad asfoms usg f plas ad copp shs, IEEE Tas. Po Elco, vol. 7, pp , Nov. 00. [] R. B. Schulz, V.C.Plaz, D.R.Bush, Shldg Thoy ad Pacc, IEEE Tas. o Elcomagc Compably, vol. 0, pp. 87-0, Aug [] S.A.Schlkuoff, Elcomagc Wavs. Pco, NJ: D.Va Nosad, 9. [5] Maal spcfcao: F, Sof Fs ad Accssos CDROM, Foxcub, 005. [6] D.A.Wso, Elcomagc Compably: pcpls ad applcaos, NY: Mack Dkk, 99. [7] J. R. Mos, Lo-Fqucy Lo Impdac Elcomagc Shldg, IEEE Tas. o Elcomagc Compably, vol. 0, pp. 0-0, Aug [8] Y. Tkl, L. E. McBd, Shldg Impovm by mul-lay Dsg, 990 IEEE Iaoal Symposum o Elcomagc Compably, pp. -, - Aug [9] u S.Y.R. ad Tag S.C., Colss Pd-ccu boad PCB asfoms ad opag chqus US pa applcao sal umb 09/675 [0] u S.Y.R. ad Tag S.C., Plaa pd ccu-boad asfoms h ffcv lcomagc fc EMI shldg, US pa 09/88,5 00 [] Maal spcfcao: C9, Sof Fs ad Accssos CDROM, Foxcub, 005 [] u S.Y.R., Plaa ducv bay chag, UK pa applcao GB8970 ad PCT pa applcao. [] u S.Y.R., Bay chagg sysm, Pa applcao umb GB 996 [] u S.Y.R,, Appaaus fo gy asf by duco, Pa applcao umb GB