Analysis and Performance Improvement of WPT Systems in the Environment of Single Non-Ferromagnetic Metal Plates

Transcription

1 energies Article Anlys Performnce Improvement WPT Systems in Environment Single Non-Ferromgnetic Metl Pltes Linlin Tn 1,2, *, Jicheng Li 1,2, Chen Chen 1,3, Chngxin Yn 1,2, Jinpeng Guo 1,2 Xueling Hung 1,2 1 Deprtment Electricl Engineering, Soust University, No. 2 Sipilou, Nnjing , Chin; wldfy@foxmil.com (J.L.); ee_seu_chenchen@126.com (C.C.); siregle@foxmil.com (C.Y.); gjp1992@hotmil.com (J.G.); xlhung@seu.edu.cn (X.H.) 2 Jingsu Key Lborry Smrt Grid Technology Equipment, Zhenjing , Chin 3 Stte Grid Jingsu Economic Reserch Institute, Nnjing , Chin * Correspondence: tnlinlin@seu.edu.cn; Tel.: (ext. 815); Fx: Acdemic Edir: Sheldon S. Willimson Received: 29 Mrch 2016; Accepted: 28 June 2016; Publhed: 25 July 2016 Abstrct: Wireless power trnsfer (WPT) gretly ffected when trnsmsion chnnel surrounded by non-ferromgnetic lic objects lternting mgnetic field intercts conducr, which more n sue in wirelessly chrged electric vehicle (EV) pplictions. Th pper nlyses performnces WPT system in n environment non-ferromgnetic plte. The impednce model WPT system in environment estblhed. Moreover vrition lw coil s equivlent inductnce restnce deduced when coil surrounded by non-ferromgnetic plte. Menwhile, simultions, ory experiments ll confirm tht model correct. Finlly, since system performnce wireless chrging system influenced by non-ferromgnetic s, th pper puts forwrd method improve performnce, tht, plce cores receiving coil plte. Experiments re crried out verify method, desired results re chieved. Keywords: wireless power trnsfer; resonr; ; impednce model; cores 1. Introduction By using resonnce coupling mgnetic fields electric fields trnsmit power, WPT technology hs mny dvntges over cble trnsmsion. Currently it widely used in consumer electronics such s mobile phones, tblets, lpps, electric othbrushes, hutch cbles, TVs, electric crs, electric buses so on for chrging devices supplying power [1 8]. In terms different ppliction environments fields, reserchers t home brod hve conducted in-depth reserch nlys [9 11]. Reserch shows tht, in certin trnsmsion spce, mgnetic coupling resonnt WPT system cn chieve high power trnsfer efficiency (PTE) in ir when trnsmsion chnnel not surrounded by objects. The trnsmsion chnnel ctully not n idel ir trnsmsion medium; re more or less interference from different types objects. Some se objects re interferences from externl obstcles, while some re required for improving system robustness. For exmple, in wireless chrging system for EVs (s shown in 1), trnsmitting coil generlly plced in prking spce on ground receiving coil instlled in electric vehicle chss tht composed plte high strength. The extence mteril chnges dtribution mgnetic field in power trnsfer spce, ffects wireless chrging system. Th effect includes two spects: (1) performnce Energies 2016, 9, 576; doi: /en

2 Energies 2016, 9, Energies 2016, 9, (1) WPT system performnce reduced or wekened, WPT system leding reduced lowered or wekened, trnsferred leding power or lowered PTE; (2) trnsferred model power using ir or PTE; s medium (2) model no longer using ir ccurte. s medium no longer ccurte. ir-gp connected rectifier voltge stbilizing chrging circuit Metl chss receiving coil connect power ground trnsmitting coil The interction EVs wireless chrging system plte. At present, few reserches hve been conducted on chrctertics mgnetic coupling At present, few reserches hve been conducted on chrctertics mgnetic coupling resonnce WPT systems under influence objects. To ddress problem cused by resonnce WPT systems under influence objects. To ddress problem cused by extence objects, n experimentl nlys method one most frequently used study extence objects, n experimentl nlys method one most frequently used study influences externl objects [12,13]. However, th method hs gret limittions, tht, it influences externl objects [12,13]. However, th method hs gret limittions, tht, doesn t effectively ply guiding role in system design only used s n uxiliry mens it doesn t effectively ply guiding role in system design only used s n uxiliry mens nlyze performnce. nlyze performnce. Toshib hs proposed tht mesuring reflection coefficient cn decide wher Toshib hs proposed tht mesuring reflection coefficient cn decide wher brrier brrier exts trnsmitter receiver or not [14]. Reference [15] studies influence exts trnsmitter receiver or not [14]. Reference [15] studies influence ppliction n luminum sheet in WPT system, nlyses influence on system ppliction n luminum sheet in WPT system, nlyses influence on system performnce performnce when externl objects ext in system. In tht pper, reduction in PTE when externl objects ext in system. In tht pper, reduction in PTE observed when observed when smll-size luminum sheet ner trnsmitting coil. smll-size luminum sheet ner trnsmitting coil. In ddition, KAIST scientts hve reported tht mount electromgnetic rdition EVs In ddition, KAIST scientts hve reported tht mount electromgnetic rdition EVs wireless chrging systems cn be reduced by reverse mgnetic field produced through using LC wireless chrging systems cn be reduced by reverse mgnetic field produced through using resonnt coil, reduction cn rech 64%, while dditionl power input not needed [16]. It LC resonnt coil, reduction cn rech 64%, while dditionl power input not needed [16]. furr studied pointed out [17] tht use double LC resonnt coil shielding cn improve It furr studied pointed out [17] tht use double LC resonnt coil shielding cn improve shielding effectiveness (SE), resonnce frequency chnged due environmentl shielding effectiveness (SE), resonnce frequency chnged due environmentl chnges chnges subsequently PTE lowered. By compring PTE two-coil structures subsequently PTE lowered. By compring PTE two-coil structures luminum luminum pltes tht two-coil structures out luminum pltes, it concluded tht pltes tht two-coil structures out luminum pltes, it concluded tht luminum s luminum s effect on reflection coefficient min reson for lowered PTE; by compring effect on reflection coefficient min reson for lowered PTE; by compring PTE PTE four-coil structure luminum plte tht four-coil structure out luminum four-coil structure luminum plte tht four-coil structure out luminum plte, plte, it evident tht luminum s effect on conducr loss min fcr cusing decrese in it evident tht luminum s effect on conducr loss min fcr cusing decrese in PTE, PTE, while, luminum exerts reltively little effects on PTE four-coil system [18]. A study while, luminum exerts reltively little effects on PTE four-coil system [18]. A study done done by Osk Industril University [19] used cores plte conducr by Osk Industril University [19] used cores plte conducr simultneously simultneously improve electromgnetic field WPT system which clculted by improve electromgnetic field WPT system which clculted by Ampere s Lw, but th Ampere s Lw, but th pper does not nlyze modeling WPT systems pltes. By pper does not nlyze modeling WPT systems pltes. By defining SE formul, defining SE formul, University L Aquil in Itly work nlyses bsorption loss, reflection loss University L Aquil in Itly work nlyses bsorption loss, reflection loss dditionl effects dditionl effects multiple reflections trnsmsions, finlly drws conclusion multiple reflections trnsmsions, finlly drws conclusion tht mgnetic mteril tht mgnetic mteril helps improve coupling. The conclusion verified by experiments helps improve coupling. The conclusion verified by experiments simultion in 20 khz simultion in 20 khz system [12,20]. Bsed on TEM wve ory, Lwson ors [21] system [12,20]. Bsed on TEM wve ory, Lwson ors [21] nlyzed how PTE nlyzed how PTE WPT system vries frequency when mteril exts in WPT system vries frequency when mteril exts in system. system. When objects ext, re lwys devition oreticl nlys bsed on When objects ext, re lwys devition oreticl nlys bsed on current models experimentl results. The lternting mgnetic field from trnsmitting coil current models experimentl results. The lternting mgnetic field from trnsmitting coil receiving coil, conducr produce electromgnetic induction coupling receiving coil, conducr produce electromgnetic induction coupling eddy current occurs in objects. The eddy current in objects cretes n induced mgnetic eddy current occurs in objects. The eddy current in objects cretes n induced mgnetic field which ffects originl mgnetic field, thus chnging coil impednce resonnt circuit. Therefore, extence objects breks down system s originl electric resonnce

3 Energies 2016, 9, Energies 2016, 9, stte, field which so tht ffects WPT system originl my mgnetic not work field, properly thus chnging or its system coil impednce performnce my resonnt be deteriorted circuit. substntilly. Therefore, In extence ddition, since objects extence breks down eddy system s current originl increses electric eddy current resonnce losses stte, when so power tht WPT trnsmitted, system my it not furr work properly ggrvtes or its system deteriortion performnce system my performnce. be deteriorted The substntilly. impcts In ddition, objects since on systems extence re more eddy complex, current since increses se eddy re current influenced losses collectively when power by permebility, trnsmitted, conductivity, it furr ggrvtes geometry deteriortion objects, system performnce. geometric prmeters The impcts resonr objects coils, on working systems frequency re more complex, or since prmeters. se re influenced collectively by permebility, conductivity, geometry In sum, objects, previous geometric reserch prmeters hs filed resonr build coils, resonnce working power frequency trnsfer or model prmeters. under influences In sum, previous objects. reserch It hs hs filed lso filed build dcuss resonnce power influences trnsfer model objects under on trnsmsion influences prmeters objects. such It hs s lso system filed power, dcuss efficiency influences resonnt objects frequency. on trnsmsion Both oreticl prmeters such experimentl s system power, spects efficiency th problem resonnt need furr frequency. study. Both Th pper oreticl minly dels experimentl two problems: spects how th cope problem need influences furr study. Th pltes pper on minly system dels how two problems: build n ccurte how cope model it. influences pltes on system how build n ccurte model it. 2. The TheInfluence Single-Side Metl Plte on Coil Prmeters 2.1. Influence Single-Side Metl Plte on Single-Turn Coil In order nlyze effect plte plte on coils, on coils, we firstly we firstly nlyze nlyze influence influence plte on plte single on single turn coil, turn coil, on th on bs, th bs, we work we work out out influence influence plte plte on on multi-turn multi-turn coil coil help help superposition superposition method. method. The coil The rdius coil rdius. The ngulr. The frequency ngulr frequency current ω. current The line ω. crossing The line crossing centrl point centrl point coil verticl coil verticl coil surfce coil surfce defined sdefined z x. s The z x. The plte plced plte t plced z = 0 t z = 0 reltive reltive position position coil coil z = d, z which = d, which dplyed dplyed in in 2. The2. thickness The thickness plte plte h. If τ h. If τ volume volume restivity restivity sheet, sheet, n n re restivity re restivity ζ cn be ζ cn described described by τ/h. by τ/h. Z single-turn coil single-turn coil d O plte h/2 -h/2 2. Position dtributions single turn coil plte. According According vecr vecr symmetry, symmetry, in in cylindricl cylindricl coordinte coordinte system, system, mgnetic mgnetic vecr potentil vecr potentil A generted A generted by coil by current coil current A 1 generted A by generted eddy current by eddy re only current in re direction only in direction φ, so th in z, x so th symmetricl. in z x Since symmetricl. electromgnetic Since field electromgnetic independentfield φ, in independent cylindricl coordintes,, cylindricl if B ρ usedcoordintes, indicte if B direction ρ used mgnetic indicte induction direction intensity mgnetic ρ generted induction by coil intensity crrying ρ generted current, so: by coil crrying current, so: 8ÿ A φ ` A 1 φ p 2jζ n B n n n 2µω jζ A 2ζ A + A q A φ Bz ( ) n «j 2ζ µω B ρ (1) n 1 j B (1) n ρ n1 μω z μω Becuse mgnetic vecr potentil eddy current symmetricl round plte, n: Becuse mgnetic vecr potentil eddy current symmetricl round plte, n: A 1 φpρ, zq A φ pρ, zq ` j 2ζ 2ζ µω B ρpρ, zq (2) A (ρ, z) A (ρ, z) j B (ρ, z) ρ (2) μω Eqution (2) shows tht eddy currents induced by plte re pproximtely equivlent mirror electromgnetic field generted by coil t fr side. Th field hs two

4 Energies 2016, 9, Eqution (2) shows tht eddy currents induced by plte re pproximtely equivlent mirror electromgnetic field generted by coil t fr side. Th field hs two components. One component mgnetic flux density imge coil equl opposite current. The or component B field produced by imge coil qudrture current mplitude proportionl 2ζ{ωµ. The coil voltge V induced by electromgnetic field generted by eddy current plte cn be expressed s:. V jωp2πqa 1 φp, dq (3) According Eqution (2), A φ B ρ represent mgnetic vecr potentil mgnetic induction intensity generted by current per unit running through coil respectively. Through furr simplifiction, it cn be obtined tht: Z. Ṿ I jω L ` R jωr2πa φ p, dqs ` 4πζ µ B ρp, dq (4) L represents self-inductnce vrition R represents effective series restnce vrition chnged by presence plte. Also, mgnetic vecr potentil A φ (ρ, z) : A φ pρ, zq µ 2π c Gpkq (5) ρ in which: $ & % Gpkq p 2 2k k kqkpkq Epkq c 4ρ k p`ρq 2`pz dq 2 K ş π{2 0 E ş π{2 0 from Equtions (4) (6), we cn conclude tht: $ & % L µgp R k? dψ 1 k 2 sin 2 ψ 1 k 2 sin 2 ψdψ? q 2`d 2? 2ζd 2`2d2 r Kpkq `? Epkqs 2`d2 2`d 2? 2`d 2 (6) (7) 2.2. Influence Single-Side Metl Plte on Multi-Turn Coil In prcticl pplictions, coil severl turns wound Litz wire commonly used increse inductnce. On bs nlys in Section 2.1, superposition method cn be pplied clculte vritions both L R coil N turns: $ & % ř L N ř L i ` 2 N i 1 M ij i j (8) ř R «N R i i 1

5 Energies 2016, 9, N N Energies 2016, 9, 576 L L 2 M 5 16 i ij i1 ij (8) N R Ri The proximity effect skin effect re i1 ignored for clcultion R s long s constrints shown in Eqution (9) [22,23] Eqution (10) [24] re stfied: The proximity effect skin effect re ignored for clcultion ΔR s long s constrints shown in Eqution (9) [22,23] $ Eqution & D ď 3 h (10) [24] re stfied: bh (9) % D h 3 2 2π f µ 0 µ r γ (9) $ 2 h k & e sinhpkdq coshp 2πfμ d μ 0 2 ` r γ D xq (10) % k 2 k d e j2π f µ 0 µ r cosh( γ D x) sinh( kd) 2 (10) where D represents dimeter every inner flexible stred wire, h denotes skin depth k 2 j2πfμ μ 0 r γ wire. F sts for current frequency. µ 0 mgnetic permebility free spce equls 4π ˆ where 10 7 D H/m. represents µ r dimeter reltive mgnetic every inner permebility. flexible stred γ used wire, h denotes represent skin conductivity. depth wire. F sts for current frequency. μ0 mgnetic permebility free spce equls E used denote current density fcr. d spce ny two inner flexible stred wires. 4π 10 x shows exct 7 H/m. μr reltive mgnetic permebility. γ used represent conductivity. E position wire. used denote current density fcr. d spce ny two inner flexible stred wires. Inx shows th pper, exct position reltive mgnetic wire. permebility Litz wire µ r = 1 electric conductivity In th γ pper, = 5.8 ˆ 10reltive 7 S/m. mgnetic The dimeter permebility ech inner Litz flexible wire stred μr = 1 wire electric D = 0.05 mm. The conductivity clculted γ frequency = S/m. rnges The from dimeter ech khz inner ccording flexible stred Eqution wire (9). D = Furrmore, 0.05 mm. ccording The clculted Eqution frequency (10) when rnges current from 0 frequency 200 khz rnges ccording from 0 Eqution 200 khz, (9). Furrmore, vrition current ccording density cn Eqution be neglected (10) when when current frequency spcing rnges from ech0 two 200 inner khz, flexible vrition stred current wires density mm. Thus cn be neglected proximity when effect cn spcing be ignored. ech two inner flexible stred wires mm. Thus proximity effect cn be ignored. 3. Modeling Experimentl Reserch WPT Systems Single-Side Metl Plte 3. Modeling Experimentl Reserch WPT Systems Single-Side Metl Plte 3.1. Modeling Prmeter Idetifiction Systems Single-Side Metl Plte 3.1. Modeling Prmeter Idetifiction Systems Single-Side Metl Plte A mgnetic resonnt WPT system includes trnsmitting coil receiving coil, which re A mgnetic resonnt WPT system includes trnsmitting coil receiving coil, which re plced coxilly, s shown in 3. The trnsmitting coil hs N 1 turns wound in circle rdius. plced coxilly, s shown in 3. The trnsmitting coil hs N1 turns wound in circle rdius The receiving. The receiving coil hs coil Nhs 2 turns wound in circle rdius b. The plte prllel coils N2 turns wound in circle rdius b. The plte prllel coils dtnce dtnce from from plte plte trnsmitter tht tht from from plte plte receiver receiver re c re c d, d, respectively. b Z trnsmitting coil d O c receiving coil h/2 -h/2 3. Position reltion two coils plte. 3. Position reltion two coils plte. The impct plte on inductnce L, mutul inductnce M restnce R cn be clculted ccording Eqution (8). If re no plte, mutul inductnce trnsmitting coil receiving coil cn be described by: d? 4b M 0 µn 1 N 2 bgp p ` bq 2 ` pc dq 2 q (11)

6 trnsmitting coil receiving coil cn be described by: 4b M μ N N bg( ) (11) ( b ) ( c d ) Energies 2016, 9, If re plte, mutul inductnce cn be described s: 4b M M M μ bg( ) (12) b c d If re plte, N 1 Nmutul 2 inductnce cn be described s: ij 0 ÿn ÿn 2 M M ij M 0 µ? d 2 2 i1 j1 ( ) ( ) 4b bgp p ` bq 2 ` pc dq 2 q (12) In conclusion, equivlent i 1 j 1 circuit model systems pltes cn be obtined, s dplyed in 4. Aprt from equivlent model systems out pltes, 4 lso shows equivlent circuit model systems using ir s medium. To simplify nlys, mutul inductnce plte trnsmitting coil neglected. The mutul inductnce plte closer coil mutul inductnce two coils re tken in considertion. In conclusion, equivlent circuit model systems pltes cn be obtined, s dplyed in 4. Aprt from equivlent model systems out pltes, 4 lso shows equivlent circuit model systems using ir s medium. To simplify nlys, mutul inductnce plte trnsmitting coil neglected. The mutul inductnce plte closer coil mutul inductnce two coils re tken in considertion. R 3 L 3 R 1 M 13 M 23 R 2 VS L 1 L 2 R L M 12 C 1 C 2 4. System equivlent circuit plte. 4. System equivlent circuit plte. In 4, R 3 represents loss pltes cused by mgnetic field. L 3 denotes In equivlent 4, inductnce R3 represents loss plte. Circuit mtrix pltes eqution cused n by expressed mgnetic by: field. L3 denotes equivlent inductnce plte. Circuit mtrix eqution n expressed by: Z I. T V. T (13) T T» Z I fiv (13) R 1 ` jx 1 jωm 12 jωm 13 ı ffi T,. where RZ = jx jωm jωm jωm R 2 ` R L ` jx 2 jωm 23 fl, İT İ1 İ 2 İ 3 V T. ı T, V s 0 0 jωm T T T where Z = jωm R 13 jωm R jx 23 R jωm 3 ` jx 12 2 L 2 23, I 3 I I I 1 2 3, V V 0 0 T s, X 1 = ωl 1 1/(ωC 1 ), X 2 = ωl 2 1/(ωC 2 ), X 3 = ωl 3. Since jωm jωm R jx 13 mutul inductnce plte trnsmitting coil neglected, M X1 = ωl1 13 «0. The currents in ech circuit loop cn be clculted by solving Eqution (13) thus, cn be 1/(ωC1), X2 = ωl2 1/(ωC2), X3 = ωl3. described by: Since mutul inductnce $. plte trnsmitting coil neglected, I 1 `Z 22 Z 33 Z23 2 ξ 1 V. s M13 0. The currents in ech circuit loop & cn be clculted by solving Eqution (13) thus, cn be. described by: I 2 Z 12 Z ξ 1 33 V. s (14) %. I Z 12 ZZ ξ 1 13 V. Z s ξ Vs where ξ 1 Z 11 Z 22 Z 33 Z 11 Z Z2 I 12 Z 13; Z impednce Z ξ V trnsmitting coil Z 11 R 1 ` jx 1 ; s (14) impednce receiving coil Z 22 R 2 ` R L ` jx 2 ; impednce plte Z 1 33 R 3 ` jx 3 ; mutul impednce trnsmitting I Z Z ξ V 3 12 coil 13 s receiving coil Z 12 Z 21 jωm 12 ; mutul impednce trnsmitting coil plte Z 13 Z 31 jωm 13 ; mutul where ξimpednce 1 Z Z Z Z Z 2 receiving Z 2 Z coil ; impednce plte Ztrnsmitting 23 Z 32 jωmcoil 23. Z R jx ; impednce receiving coil Z R R jx ; impednce plte Z R jx ; mutul 22 2 L impednce trnsmitting coil receiving coil Z Z jωm ; mutul

7 Energies 2016, 9, impednce trnsmitting coil plte Z Z jωm ; mutul impednce receiving coil plte Z Z jωm Energies 2016, 9, According Equtions (8) (13), influence plte on receiving coil cn be represented by: According Equtions (8) (13), influence 2 plte on receiving coil cn be ωm L 23 0 represented by: $ L & L «pωm 2 23q 2 2 ωm L 0 R 23 pωm 23 q 2`R2 0 (15) 2 0 ωm R (15) % R «pωm 23 23q 2 0 R R 0 pωm 23 q 2`R R Power loss cused by eddy currents described by: Power loss cused by eddy currents described by: P 0 ˇ I. 2 P 3ˇˇˇ2 I R0 R (16) System trnsferred power PTE cn be be clculted by: $ ˇ. 2 I 2ˇˇˇ2 RL R 2 L & η ˇ I. 1ˇˇˇ2 R1`ˇ I. η 2 2 2ˇˇˇ2 pr2`r L q` ˇ I. 2 I R I R R 3ˇˇˇ2 I R0 R L 2 % P 0.5 I2 ˇ RL P 0.5 I 2ˇˇˇ2 prl q ˇ. (17) (17) Simultion Experimentl Reserch Coil Coil Single-Side Metl Metl Plte Plte On On bs bs oreticl nlys, simultion ided by by COMSOL crried out out nlyze prmeter vritions receiving coil coil working in in n n environment pltes, s s shown in in Circulr plte plte spirl spirl coils coils re re employed employed in th in th reserch. reserch. Coils Coils re re tightly tightly wound wound so tht so tht turn--turn turn--turn dtnce dtnce negligible. negligible. Coil Coil prmeters prmeters re specificlly re specificlly tbulted tbulted in Tble in Tble Vecr network nlyzer Trnsmitting coil coil Aluminum plte Receiving coil Aluminum plte () () () Simultion Simultion model; model; Experiment Experiment model. model. Tble 1. Coil prmeters. Tble 1. Coil prmeters. Prmeter Vlue Prmeter Externl rdius 20 cm Vlue Externl rdius Inner rdius 16 cm 20 cm Inner rdius Coil turns N cm Coil turnswire N dimeter 2 mm 10 Wire dimeter Frequency f 73 khz 2 mm Frequency f 73 khz Inner restnce R 0.05 Ω Inner restnce R 0.05 Ω A 3 mm thick 30 cm long squre plte mde luminum used in simultion. The electric A 3conductivity mm thick set 30t cm3.5 long 10 7 squre S/m plte reltive mde dielectric luminum constnt used s in well s simultion. reltive The electric conductivity set t 3.5 ˆ 10 7 S/m reltive dielectric constnt s well s reltive mgnetic permebility 1. The system driven by source working t 73 khz so tht compensted cpcir 120 nf chosen.

8 Energies 2016, 9, mgnetic permebility 1. The system driven by source working t 73 khz so tht 120 nf chosen To vlidte oreticl simulting results, experimentl protype using receiving coil plte introduced bove designed dplyed in 5b. The vlues To vlidte oreticl simulting results, experimentl protype using receiving coil receiving coil inductnce mesured by oreticl clcultions ccording Eqution (8), by Energies 2016,plte 576 introduced bove designed dplyed in 5b. The vlues 8receiving 16 COMSOL, by 9,experimentl clcultions re 40.67, , μh, respectively. The devition coil inductnce mesured by oreticl clcultions ccording Eqution (8), by COMSOL, simultion vlue system oreticl vlue 0.03% while devition mgnetic permebility 1. The driven by µh, source workingthe t devition 73 khz so tht by experimentl clcultions re 40.67, , respectively. compensted mesured cpcir vlue oreticl vlue 1.8%, both devitions demonstrte 120 nf chosen. simultion vlue oreticl vlue 0.03% while devition mesured vlue cceptble To precion. vlidte oreticl simulting results, experimentl protype using receiving oreticl vlue 1.8%, both devitions demonstrte cceptble precion. Theoreticl clcultion, simultion experimentl mesurement re 5b. employed quntify coil plte introduced bove designed dplyed in The vlues Theoreticl clcultion, simultion experimentl mesurement re employed quntify receiving coil inductnce mesured by oreticl clcultions ccording Eqution (8), by influence plte on receiving coil inductnce specificlly dplyed in 6. influence by plteclcultions on receiving coil inductnce μh, specificlly dplyed in 6. experimentl re 40.67, , respectively. The devition TheCOMSOL, plte plced t different dtnces from receiving coil. Both simultion The plte simultion plced t vlue different dtnces from vlue receiving coil. Both simultion oreticl 0.03% while devition experimentl results vlidte correctness oreticl nlys. It lso indictes tht frr experimentl resultsvlue vlidte correctness oreticl nlys.both It lso indictesdemonstrte tht frr mesured oreticl vlue 1.8%, plte moved wy from receiving coil, less influencedevitions it brings bout. cceptble plte precion. moved wy from receiving coil, less influence it brings bout. compensted Energies 2016, 9, 576cpcir Inductnce(μH) Inductnce(μH) Theoreticl clcultion, simultion experimentl mesurement re employed quntify influence plte on receiving coil inductnce specificlly dplyed in 6. The plte plced t different dtnces from receiving coil. Both simultion experimentl results vlidte correctness oreticl nlys. It lso indictes tht frr plte moved wy from receiving coil, less influence it brings bout. Cl.result Dtnce from coil plte(cm) Effect different dtnces receiving coil coil plte on plte coil inductnce Effect different dtnces receiving on coil inductnce. Cl.result In th pper, plte plced ner receiving coil. Considering dtnce coil plte(cm) plte trnsmittingdtnce coil from lrge enough (d 6 cm), influence plte on In th pper, plte plced ner receiving coil. Considering dtnce 6. Effect different dtnces on receiving nlys. plte on tht coil inductnce. trnsmitting coil cn be ignored bs coil bove It shows neglecting M13 plte trnsmitting coil lrge enough (d ě 6 cm), influence resonble. If we replce luminum plte copper one, we cn get sme results. plte on In th trnsmitting coilplte cn beplced ignored bscoil. Considering bove nlys. shows tht pper, ner on receiving dtnceit Consequently, non-ferromgnetic mterils different electric conductivities hve sme neglecting M resonble. If we replce luminum plte copper one, we 13 plte trnsmitting coil lrge enough (d 6 cm), influence plte cn on get influences on coil prmeters. sme results. Consequently, non-ferromgnetic different electric conductivities trnsmitting coil cn be ignored on bs mterils bove nlys. It shows tht neglecting M13 hve Bsed on If weprotype shown in 5b, effect frequency on inductnce resonble. luminum plte copper one, we cn get sme results. sme influences onreplce coil prmeters. receiving coil nlyzed illustrted in 7, whichelectric shows chnging cure receiving Consequently, mterils 5b, different hve sme Bsed on non-ferromgnetic protype shown in effect conductivities frequency on inductnce coil s inductnce vs. frequency mesured by Vecr Network Anlyzer (Rohde & Schwrz influences on coil receiving coilprmeters. nlyzed illustrted in 7, which shows chnging cure Technology Germny). It cn be 5b, seen when dtnce BsedCo, on Munich, protype shown in tht effect frequency on inductnce plte receiving coil s inductnce vs. frequency mesured by Vecr Network Anlyzer coil nlyzed illustrted 7, which shows chnging cure receiving receiving receiving coil fixed, receivingincoil s inductnce remins lmost unchnged regrdless (Rohde & Schwrz Technology Co, Munich, Germny). It cn be seen tht when dtnce coil s inductnce by proportionl Vecr Network Schwrz frequency vrition. vs. Thefrequency influencemesured inversely Anlyzer dtnce (Rohde & plte plte receiving coil Itfixed, receiving coil s inductnce remins lmost unchnged Technology Co, Munich, Germny). cn be seen tht when dtnce plte receiving coil, which cn be clrified by fct tht smller d leds lrger ΔL. regrdless frequency The influence inversely proportionl dtnce receiving coilvrition. fixed, receiving coil s inductnce remins lmost unchnged regrdless pltevrition. The receiving coil, which cn be clrified by dtnce fct tht smller d leds frequency influence inversely proportionl plte lrger L. receiving coil, which cn be clrified by fct tht smller d leds lrger ΔL. 7. Effect frequency on inductnce prmeters receiving coil. 7. Effect frequency on inductnce prmeters receiving coil. 7. Effect frequency on inductnce prmeters receiving coil.

9 Energies 2016, 9, Energies 2016, 9, Energies 2016, 9, Simultion Experimentl Reserch WPT System Single-Side Metl Plte 3.3. Simultion Experimentl Reserch WPT System Single-Side Metl Plte On bs nlys bove, our ourexperimentl protype single-side plte plte On bs s shown nlys in bove, 8. In our th experimentl protype, protype prmeters single-side trnsmitting coil plte constructed s shown in 8. In th protype, prmeters trnsmitting coil those those constructed receiving s shown coil in re s 8. shown In th in protype, receiving coil re s shown in Tble Tble 1. The 1. The prmeters plte plte introduced trnsmitting in insection coil those used. receiving According coil re s shown simultion result in Tble 1. The experimentl plte introduced mesurement results in shown Section in 3.2 used. s According well s Eqution simultion (12), result reltionship experimentl mesurement mutul inductnce results shown in plte 8 s dtnce well s Eqution clculted (12), dplyed reltionship in mutul inductnce plte dtnce 9. clculted dplyed in 9. DC power DC power Control Circuit Control Circuit Aluminum plte Aluminum plte Inverter Inverter Trnsmitting coil Trnsmitting coil () () () () Simultion Simultion model; model; Experiment Experiment model. model. No plte No plte Clculted vlue Clculted vlue Lod Lod Receiving coil Receiving coil mutul inductnce(μh) Experiment vlue Experiment vlue simultion vlue simultion vlue The dtnce receiving 5 coil 6 7 plte(cm) The dtnce receiving coil plte(cm) 9. Effect plte s dtnce on mutul inductnce coils Effect Effect plte s plte s dtnce dtnce on on mutul mutul inductnce inductnce coils. coils. The dtnce cm in indictes tht plte does not ext. The experimentl The dtnce cm in 9 indictes tht plte does not ext. The experimentl mesurements The dtnce re lso 0 cm included here, 9 indictes presenting tht constent plte result. does lrger not ext. dtnce Thecontributes experimentl mesurements re lso included here, presenting constent result. A lrger dtnce contributes mesurements lrger mutul re inductnce lso included here, presenting trnsmitting constent coil result. receiving A lrger coil, dtnce which contributes indictes lrger mutul inductnce trnsmitting coil receiving coil, which indictes smller lrger influence mutul inductnce plte on trnsmitting system. Th coil why n ir receiving gp usully coil, which set indictes smller influence plte on system. Th why n ir gp usully set smller receiving influence coil EVs chss plte on enhnce system. PTE for Th chrging whyevs. n ir gp usully set receiving coil EVs chss enhnce PTE for chrging EVs. receiving The coil chnges EVs trnsferred chss power enhnce PTE PTE for chrging ccordnce EVs. dtnce vritions cn be The chnges trnsferred power PTE in ccordnce dtnce vritions cn be mesured on bs 8b. In experiment, dtnce trnsmitting coil mesured on bs 8b. In experiment, dtnce trnsmitting coil receiving coil remins t cm. system no cores or mterils used power receiving coil remins t 6 cm. A system no cores or mterils used power

10 Energies 2016, 9, The chnges trnsferred power PTE in ccordnce dtnce vritions cn be mesured on bs 8b. In experiment, dtnce trnsmitting coil Energies 2016, 9, receiving coil remins t 6 cm. A system no cores or mterils used power lod lod 2 Ω, 2 Ω, trnsferred trnsferred power power PTE re PTE 10 Wre 10 W 80% respectively, 80% respectively, which which re tken re s tken reference s reference vlues vlues normlize normlize performnce performnce system system plte, s dplyed plte, s dplyed in 10. in Similr 10. Similr 9, 9, plte not used plte when not used dtnce when 0 cm. dtnce It cn be 0 concluded cm. It cn tht be re concluded continuous tht re increse continuous both trnsferred increse in power both trnsferred PTE when power dtnce PTE when increses. dtnce In or words, increses. In effect or words, plte effect declining. When plte declining. plte When plced t dtnce plte plced 1.5 cmt wy dtnce from 1.5 receiving cm wy coil from (quite receiving close coil receiving (quite close coil), trnsferred receiving power coil), trnsferred extremely power low due extremely influences low due influences plte, while, PTEplte, pproximtely while, PTE 3.2%, which pproximtely cn be minly 3.2%, cused which cn by be minly fct tht cused extence by fct tht extence plte leds detuning plte leds receiving detuning coil. Th receiving would definitely coil. Th hve would n dverse definitely influence hve n on dverse systeminfluence opertions on system excerbte opertions system performnce. excerbte system Therefore, performnce. in ordertherefore, ddressin th order problem, ddress WPTth systems problem, WPT single-side systems plte single-side should be improved plte should optimized. be improved optimized. 1 No plte 0.8 P/P η/η The dtnce receiving coil plte(cm) Effect Effect plte s plte s dtnce dtnce on on trnsferred trnsferred power power PTE PTE systems. systems Performnce Performnce Improvement Improvement WPT WPT System System Single-Side Single-Side Metl Metl Plte 4.1. Appliction Ferrite Cores Its Effect on Receiving Coil The plte supposed bsorb mgnetic field so coil inductnce decreses ccordingly. As result, it it necessry reduce effect plte on coils by limiting electromgnetic field intensity. Severl Severl cores cores re re plced plced receiving receiving coil coil plte, through plte, through which which electromgnetic electromgnetic field in field close in close region region cn be cn enhnced. be enhnced. As As result, result, lekge lekge field field reduced reduced both self-inductnce both self-inductnce mutul inductnce mutul re inductnce incresed. re Neverless, incresed. Neverless, use cores use produces cores power produces loss duepower eddyloss current. due The eddy power current. loss The proportionl power loss electric proportionl conductivity electric σ conductivity frequency f 2. Consequently, σ frequency mterils f 2. Consequently, smll conductivity mterils re preferred smll conductivity improve PTE. re The preferred cores improve usedpte. in The pper recores DMR95 used in Mn-Zn pper re specific DMR95 dimensions Mn-Zn 7 cmspecific ˆ 2 cmdimensions ˆ 0.5 cm. The 7 strd cm 2 cm power 0.5 cm. lossthe 300 strd mw/cm power khz, mW/cm mt, much smller khz, 200 mt, much smller thn tht mterils whose conductivity @( khz). As result, power loss cused by eddy current extremely low. According 5, COMSOL simultion model system consting receiving coil, plte cores plced m shown in 11. The mgnetic field

11 Energies 2016, 9, thn tht mterils whose conductivity khz). As result, power loss cused by eddy current extremely low. According Energies 2016, 9, 576 5, COMSOL simultion model system consting receiving 11coil, 16 Energies 2016, 9, plte cores plced m shown in 11. The mgnetic field intensity intensity t coil dplyed. The dtnce plte receiving receiving t center center coil dplyed. The dtnce plte coil intensity t center coil dplyed. The dtnce plte receiving 1.5 cm excittion excittion current 1 A. coil 1.5cm current 1 A. coil 1.5 cm excittion current 1 A. ① ① Aluminum plte Aluminum plte ⑥ ⑥ ⑤ ⑤ ③ ③ φ φ eddy current loss eddy current loss Ferrite cores Ferrite cores φ φ Coils Coils ④ ④ () () ② ② System Systemmodel model cores: cores:() ()2D 2Dmodel; model; 3D 3Dsimultion simultionmodel. model. 11. System model cores: () 2D model; 3D simultion model. When cores re not used, mgnetic field intensity round 25 μt s shown in When cores re not mgnetic field intensity round25round µt s shown 12. in When cores reused, not used, mgnetic field intensity 25 μtins shown 12. With increse in number cores, mgnetic field intensity increses With increse increse numberin cores, mgnetic obviously, 12. Within number cores,field intensity mgneticincreses field intensity increses obviously, bout 39 μt by 56% when six cores re used. Since self-inductnce coil bout 39 µt by when sixby cores re coil proportionl obviously, 56% bout 39 μt 56% when six used. Since cores self-inductnce re used. Since self-inductnce coil proportionl mgnetic field intensity, so ppliction cores fesible wy proportionl mgnetictield intensity, field so ppliction ppliction cores fesible wy enhnce mgnetic intensity, so cores fesible wy enhnce self-inductnce. enhnce self-inductnce. self-inductnce. () () 12. () Mgnetic field dtribution; Mgnetic chnging curve vs. numbers cores. Mgnetic field dtribution; Mgnetic chnging curve numbers cores ()() Mgnetic field dtribution; Mgnetic chnging curve vs.vs. numbers cores. According nlyticl results bove, simultion experimentl results According nlyticl results bove, simultion experimentl results reltionship coil s self-inductnce simultion number cores when According nlyticl results bove, experimentl results plte reltionship coil s self-inductnce number cores when plte not used re illustrted in 13, which shows more lrger reltionship coil s self-inductnce tht number cores corescontribute when pltecoil not used re illustrted in 13, which shows tht more cores contribute lrger coil inductnce. Six cores, whose sequence numbers represent different loctions, re used s not used re illustrted in 13, which shows tht more cores contribute lrger coil inductnce. Six cores, whose sequence numbers represent different loctions, re used s shown in 11, cores, inductnce incresed 46 μh different by 15%. It should be tht re inductnce. Six whose sequence numbers represent loctions, renoted used s shown shown in 11, inductnce incresed 46 μh by 15%. It should be noted tht re only one core in ech loction, for exmple, sequence ⑤ represents tht core in 11, inductnce incresed 46 µh by 15%. It should be noted tht re only only one core in ech loction, for exmple, sequence ⑤ represents tht core plced t one coreposition in ech ⑤. loction, for exmple, sequence 5 represents tht core plced t plced t position ⑤. If 5.power loss ignored, results in s 6 13 demonstrte tht proper dtribution position If power loss ignored, results in s 6 13 demonstrte tht proper dtribution cores cn increse while 6 plte hs tht n dverse impct on it. If power loss ignored, inductnce results in s 13 demonstrte proper dtribution cores cn increse inductnce while plte hs n dverse impct on it. 0.5, According resonnt frequency determined by f = 1/2π(LC) use cores which cores cn increse inductnce while plte hs n dverse impct on it. According According resonnt frequency determined by0.5f = 1/2π(LC)0.5, use cores which leds increse in inductnce in decrese resonnt frequency. resonnt frequency determinedlso by f results = 1/2π(LC), use cores which ledson leds increse in inductnce lso results in decrese resonnt frequency. On contrry, plte which results in decrese in inductnce increses resonnt contrry, plte which results in decrese in inductnce increses resonnt frequency. As consequence, proper dtribution number cores ble eliminte frequency. As consequence, proper dtribution number cores ble eliminte influence brought by plte completely, which vitl system stbility. The influence brought by plte completely, which vitl system stbility. The plte plced t dtnce 1.5 cm prt from receiving coil, cores re dded plte plced t dtnce 1.5 cm prt from receiving coil, cores re dded one by one in sequence s illustrted by 11, simultion results mesured one by one in sequence s illustrted by 11, simultion results mesured

12 Energies 2016, 9, increse in inductnce lso results in decrese resonnt frequency. On contrry, plte which results in decrese in inductnce increses resonnt frequency. As consequence, proper dtribution number cores ble eliminte influence brought by plte completely, which vitl system stbility. The plte plced t dtnce 1.5 cm prt from receiving coil, cores re dded one by one in sequence s Energies 2016, 9, illustrted by 11, simultion results mesured results re tbulted in Tble 2. Coil inductnce(μh) Exp. result Sim. result Number mgnetic cores Effect coreson on inductnce prmeters receiving coil. Tble2. 2. Receiving coil s prmeter vrition. Coil Inductnce (μh) Resonnt Frequency (khz) Ferrite Cores Coil Inductnce (µh) Resonnt Frequency (khz) Ferrite Cores Simultion Mesured Simultion Mesured Simultion Vlues Vlues Mesured Vlues Simultion Vlues Vlues Mesured Vlues Vlues None None The results in Tble 2 furr vlidte fesibility fsetting influence plte plte by by using using cores. cores. It should It should be noted be noted tht tht needed needed number number cores chnges cores inchnges ccordnce in ccordnce dtnce vritions dtnce vritions plte plte receiving coil. receiving coil Comprtive Experiments on Performnce Systems out Ferrite Cores System performnce enhncement by using mgnetic mterils (s) furr investigted. If If trnsferred power PTE re set s benchmrks when system hs no or mteril two coils in surrounding res, by normlizing mesured results for second time, we cn get vrition curve curve PTE PTE tht tht trnsferred trnsferred power power in ccordnce in ccordnce dtnce dtnce plte plte receiving receiving coil s shown coil s inshown in According 14, 14, increse increse cores, cores, influence influence plte on plte receiving on receiving coils wekened, coils wekened, optimum optimum chieved chieved in certin condition. certin condition. When When optiml optiml stte stte reched, reched, enhncement enhncement effect effect cores on cores inductnce on inductnce receiving coil receiving coil wekening wekening effect effect plte on receiving plte on coils receiving fsetcoils echfset or, ech or, system insystem resonnce in stte resonnce gin. stte Suchgin. s Such 14, s when 14, dtnce when dtnce 1.5 cm, 1.5 number cm, number cores bout cores 5 6; bout for 5 6; dtnce for dtnce 3.5 cm, 3.5 number cm, number bout 4 5; bout for 4 5; dtnce for dtnce 6cm, 6cm, number number bout 3 4. bout When 3 4. When number number cores optiml, cores optiml, influence influence plte on plte receiving on receiving coils cncoils be bsiclly cn be bsiclly fset. Atfset. th time, At th trnsferred time, trnsferred power power PTE hd returned PTE hd returned 90% in 90% presence in presence plte. Of course, plte. itof course, difficult it recover difficult completely, recover becuse completely, rebecuse re losses re in both re losses in both plte plte cores, such s cores, eddy current such s loss eddy orcurrent hysteres loss loss, or hysteres etc. With loss, increse etc. With in number increse in number cores, effect cores, effect cores on receiving coil plys mjor role, which sets WPT systems in stte dhrmony, so trnsferred power PTE WPT systems re decresed gin. When trnsmsion dtnce 6cm, system input voltge, output voltge current wveforms re shown in 15.

13 Energies 2016, 9, cores on receiving coil plys mjor role, which sets WPT systems in stte dhrmony, so trnsferred power PTE WPT systems re decresed gin. When trnsmsion dtnce 6cm, system input voltge, output voltge current wveforms re shown in 15. Energies 2016, 9, Optimum cores number P/P Optimum cores number η/η0 η/η 0 P/P Number mgnetic cores () Optimum cores number Number mgnetic cores P/P 0 η/η 0 Number mgnetic cores (c) 14. Experimentl results: () The dtnce plte receiving coil 3.5 cm; The 14. dtnce Experimentl results: plte () The dtnce receiving coil 6 cm; (c) The plte dtnce receiving coil plte 3.5 cm; Thereceiving dtncecoil 1.5 cm. plte receiving coil 6 cm; (c) The dtnce plte Energies 2016, 9, x receiving coil 1.5 cm. () () 15. Cont.

14 Energies 2016, 9, () (c) (d) When When plte plte 6cm 6cm wy wy from from receiving receiving coil, input coil, input current-voltge current-voltge output output current-voltge wveforms vry different numbers cores: () out cores; 8 current-voltge wveforms vry different numbers cores: () out cores; 8 cores; cores; (c) 6 cores; (d) 3 cores. (c) 6 cores; (d) 3 cores. In summry, forementioned results demonstrte tht by using strong mgnetic conductive In summry, mteril forementioned plced results objects demonstrte receiving tht by coil using resonbly, strong mgnetic we cn reduce conductive mteril effect plced objects on WPT objects systems effectively receiving coil mximize resonbly, PTE. we cn reduce effect objects on WPT systems effectively mximize PTE. 5. Dcussion 5. Dcussion Problems cused by mterils hve be tckled gurntee pplictions WPT technology Problems in cused mny fields, by such s mterils chrging hve for EVs, smrt-phones, be tckled intelligent gurnteehousehold pplictions pplinces, WPT technology or relevnt in mny industries fields, such so s on. chrging The mgnetic for EVs, field smrt-phones, cused by intelligent s results household in decrese pplinces, or system relevnt performnce. industries In ddition, so on. Themodeling mgnetic fieldnlys cusedin bysuch s complicted results in decrese environment system re performnce. hrd implement In ddition, since it modeling includes coupling nlys mgnetic in such field, complicted electric field environment het re field. hrd Reserches implementddressing since it includes se sues coupling re still mgnetic t beginning. field, electric The pper fieldintends het field. improve Reserches PTE ddressing WPT systems seworking sues re in still environment t beginning. The pper mterils intends reduce improve PTE influence WPT systems se working mterils in environment system performnce. mterils reduce influence se mterils on systemto performnce. be more specific, non-ferromgnetic plte used in th pper simulte working To be more environment specific, non-ferromgnetic mterils. A bsic plte nlys used in th completed pper simulte corresponding working environment solutions improve PTE mterils. re proposed. A bsic nlys High-frequency completed mgnetic corresponding conductive mterils solutions re improve employed PTE re proposed. system performnce High-frequency obviously mgnetic enhnced conductive by ir mterils proper re dtribution, employed which system provides performnce fesible wy obviously tckle enhnced problems by ir in proper WPT dtribution, system which single provides side fesible plte. wy Menwhile, tckle problems quntittive in WPT nlys system not crried single out side due plte. complexity Menwhile, quntittive system working nlys in environment mterils, so simultion combined experimentl verifiction not crried out due complexity system working in environment mterils, widely used in pper, cusing difficulties in system design. Moreover, use mgnetic so simultion combined experimentl verifiction widely used in pper, cusing difficulties in system design. Moreover, use mgnetic mterils increses overll costs. The comprome reducing expenses developing technology improve system performnce wht we need consider in future reserch. Anywy, performnce improvement WPT systems working in environment mterils gret significnce promote wide pplictions WPT technology. 6. Conclusions Th pper studies effect non-ferromgnetic pltes on resonnt WPT systems, estblhes n impednce model contining pltes. Through compring model clcultion results, simultion results experimentl results, which re in ccord ech or, we verify correctness model. When non-ferromgnetic mteril exts round coils, intrinsic resonnt frequency lowered, effect cused by mteril round coil produces eddy current loss, which not conducive effective trnsmsion energy

15 Energies 2016, 9, system. Therefore th pper uses mgnetic chrctertics mgnetic mteril, rebuilds circultion chnnel for mgnetic field plte coils, thus wekening its effect on coils. By mens oreticl nlys experiment, th pper proves correctness th pproch. The performnce improvement WPT systems not only complicted mth problem, but lso key problem which needs be solved urgently prcticl ppliction. Th pper only investigtes systems non-ferromgnetic pltes, but our reserch results provide certin reference vlues in irregulr system modeling, fesible solution improve system performnce in environment. Acknowledgments: Th work ws supported in prt by Ntionl Nture Science Youth Foundtion Chin (No ), Nture Science Youth Foundtion Jingsu Province (No. BK ), Fundmentl Reserch Funds for Centrl Universities, Science Technique Project Funds Stte Grid Jingsu Electric Power Compny (No. J ). Author Contributions: Linlin Tn designed model performed clcultions experiments. Linlin Tn, Xueling Hung Jicheng Li proposed reserch pic nlyzed dt. Chen Chen, Jinpeng Guo, Chngxin Yn helped write prt simultion progrms. All uthors contributed writing mnuscript, hve red pproved finl mnuscript. Conflicts Interest: The uthors declre no conflict interest. References 1. Shinohr, N. Power out wires. IEEE Microw. Mg. 2011, 12, S64 S73. [CrossRef] 2. Kim, J.; Sun, C.; Suh, I. A proposl on wireless power trnsfer for medicl implntble pplictions bsed on reviews. In Proceedings 2014 IEEE on Wireless Power Trnsfer Conference (WPTC), Jeju, Kore, 8 9 My 2014; pp Shin, J.; Shin, S.; Kim, Y.; Ahn, S.; Lee, S.; Jung, G.; Jeon, S.; Cho, D. Design Implementtion Shped Mgnetic-Resonnce-Bsed Wireless Power Trnsfer System for Rodwy-Powered Moving Electric Vehicles. IEEE Trns. Ind. Electron. 2013, 61, [CrossRef] 4. Tylor, J.A.; Low, X.N.; Csnov, J.; Lin, J. A wireless power sttion for lpp computers. In Proceedings 2010 IEEE on Rdio Wireless Symposium (RWS), New Orlens, LA, USA, Jnury 2010; pp Kim, J.; Bien, F. Electric field coupling technique wireless power trnsfer for electric vehicles. In Proceedings 2013 IEEE on TENCON Spring Conference, Sydney, Austrli, April 2013; pp Cho, I.; Kim, S.; Moon, J.; Yoon, J.; Jeon, S.; Choi, J. Wireless power trnsfer system for docent robot by using mgnetic resonnt coils. In Proceedings 2013 IEEE 5th Interntionl Symposium on Microwve, Antenn, Propgtion EMC Technologies for Wireless Communictions (MAPE), Chengdu, Chin, Ocber 2013; pp Wng, Z.; Wei, X.; Di, H. Design Control 3 kw Wireless Power Trnsfer System for Electric Vehicles. Energies 2015, 9, 10. [CrossRef] 8. Bsr, M.R.; Ahmd, M.Y.; Cho, J.; Ibrhim, F. Appliction wireless power trnsmsion systems in wireless cpsule endoscopy: An overview. Sensors 2014, 14, [CrossRef] [PubMed] 9. Kng, J.; Prk, H.; Jng, J.; Lee, K. A design wide input rnge, high efficiency rectifier for mobile wireless chrging receiver. In Proceedings 2014 IEEE on Wireless Power Trnsfer Conference (WPTC), Jeju, Kore, 8 9 My 2014; pp Son, H.; Kim, J.; Prk, Y.; Kim, K. Efficiency nlys optiml design circulr loop resonnt coil for wireless power trnsfer. In Proceedings 2010 Asi-Pcific Microwve Conference, Yokohm, Jpn, 7 10 December 2010; pp Chen, W.; Ching, R.A.; Yoshid, S.; Lin, J.; Chen, C.; Lo, W. A 25.6 W MHz wireless power trnsfer system 94% efficiency GN Clss-E power mplifier. In Proceedings 2012 IEEE MTT-S Interntionl Microwve Symposium Digest (MTT), Montrel, QC, Cnd, June 2012; pp. 1 3.

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