General Analytical Model for Inductive Power Transfer System with EMF Canceling Coils

Transcription

1 General Analytial odel for Indutive Power Transfer System with EF Caneling Coils Keita Furukawa, Keisuke Kusaka, and Jun-ihi Itoh Department of Eletrial Engineering, Nagaoka University of Tehnology, NUT Niigata, Japan * Abstrat- This paper provides an analytial model and design riteria of additional windings for reduing eletromagneti field (EF) generated from indutive power transfer (IPT) systems. In partiular, the aneling oils are onneted to the main transmission oils with ommon-mode onnetion or differential-mode onnetion. Otherwise, the aneling oils are short-iruited. Parameter variation, whih may degrade the system effiieny, ours in the IPT system due to the unwanted oupling between the main transmission oils and the aneling oils. Therefore, theoretial analysis of the IPT system with the aneling oils is onduted in order to evaluate the effets of the EF shielding methods on the system parameter variation. The alulation results of the system parameters agree to the measurement results in the prototype of the four-winding transformer with the error of lower than 5%. Keywords ative shielding, eletromagneti field, indutive power transfer, multiple magneti oupling I. INTRODUCTION In reent years, indutive power transfer (IPT) systems have attrated muh attention in terms of safety and onvenient battery hargers for eletrial vehiles (EVs) [ 5]. The IPT systems ahieve power transmission using a magneti oupling without eletrial ontats. Eletromagneti field (EF) should be onsidered beause EF may ause health impairment or malfuntion of eletrial equipment [5 7]. In partiular, high-power IPT systems suh as quik battery hargers for EVs generate higher level of EF. Therefore, it is neessary to redue EI noise to widespread use of the IPT system. In order to redue EF, many studies have been onduted on iruit topologies, modulation methods and onfigurations of transmission oils [5 3]. In partiular, non-resonant reative shield and ative shield, whih are foused on the onfigurations of the transmission oils, have been proposed [ 3]. Non-resonant reative shielding methods require additional short-iruited oils in order to redue EF []. The magneti flux indues a urrent whih anels the leakage magneti field in the short-iruited oils when a leakage magneti flux rosses the short-iruited oils. However, the EF-redution effetiveness is low at the plae far from the aneling oils beause the magnetomotive fore of the aneling oil is limited by the interlinkage magneti flux []. On the other hand, the ative shielding method employs aneling oils whih are onneted to the main transmission oils or additional power soures [ 3]. In this method, the urrent flowing in the aneling oils is ontrollable with the main oils or the power soures. Therefore, the anellation of the magneti field beomes more effetive ompared to the non-resonant reative shielding method beause the magneti field generated by the aneling oils are ontrollable []. The redution effet of EF by adding oils has been reported in several papers [ 3]. Nevertheless, the influenes on parameter variations of the transmission oil due to the additional oils have not been analytially disussed. In partiular, the magneti flux generated by the aneling oils not only redues the EF but also rosses the main oils as an interlinkage flux. Thus, the selfindutane and the mutual indutane of the entire transmission oil are hanged due to the additional oils. This variation of the self-indutane hanges the resonant frequeny. Thus, the transmission power or the effiieny might be dereased ompared that of the non-aneling oils. This problem in the past work is that the influenes of attahing the aneling oils to the entire IPT systems are not disussed enough. In this paper, the effet of the aneling oils is revealed as fousing on the variations of the equivalent selfindutane and the equivalent mutual indutane of the entire transmission oil, whih is theoretially analyzed using a model of a four-winding transformer. The new ontribution of this paper is providing a general analytial model and design riteria in order to redue the parameter verifiation for the EF aneling oils. In partiular, the aneling oils are onneted in parallel to the main transmission oils when the non-resonant reative shielding method or the ative shielding method are introdued in order to redue EF of transmission oils system. The equivalent self-indutanes and the equivalent oupling oeffiient taking into aount the influene of the aneling oils are alulated from a view of the entire transmission system. Then, the alulation results are onfirmed with measurement of the equivalent self-indutanes and the equivalent oupling oeffiient in

2 Winding # Winding # Path of leakage magneti flux ain oil Winding #3 ain magneti path Caneling oil Outside of oil Winding #4 Path of leakage magneti flux Inside of oil (a) Outline of transmission oil. (b) Front view with magneti paths. () Configuration of oil at one side. Fig.. Investigated model of transmission oil as example. The solenoid-type transmission oil with the aneling oils (winding # and winding #4). EF upper and under ores is redued by the aneling oils. prototypes of the four-winding transformer. oreover, the effet of EF redution is simulated when the prototypes are installed to the -kw IPT systems. II. CONFIGURATION OF TRANSISSION COIS In this setion, the equivalent self-indutane and the equivalent oupling oeffiient are formulated by a model of the multi-winding transformer when the aneling oils are onneted to the main oils in parallel or shortiruited. The equivalent self-indutane is defined as selfindutanes from a view of a primary side or seondary side of the entire transmission oil. The equivalent oupling oeffiient is defined as a oupling oeffiient between the primary side and the seondary side. Both of the equivalent values are essential to design a resonant frequeny and a transmission power for IPT systems. A. Analytial odel with Four-winding Transformer Figure shows the shemati of the analyzed transmission oils. Although following analysis is possible to be applied to general transmission oils, whih fulfill some onditions as mentioned later, the solenoid-type transmission oil is analyzed as an example. The transmission oil behaves as the four-winding transformer. In order to avoid the additional ore, the aneling oil is wired on the same ore of the main oil. The main oils, e.g., winding # and winding #3, are wired on the ores to the form of the solenoid oils, whereas the aneling oils, e.g., winding # and winding #4, form a pair of the serial retangular oil. As shown in Fig. (a), the aneling oils are plaed on the outside of the primary and seondary ores in order to redue EF whih emits in the diretion of the upper and below the transmission oils. Due to the plaement of the aneling oils, the mutual indutanes between following windings, e.g., winding # and winding #3, winding # and winding #4, and winding #4 and winding #, are negligibly weak. Thus, the relationship between urrent and voltage of eah oil in Fig. is expressed by the four-order indutane matrix as v 0 i v v v d dt i i i 3 4 k 0 i k k 0 0 i d (), k 0 dt i k k i 4 where v m and i m (m =,, 3, and 4) are the input voltage and the urrent of the winding m, mm is the selfindutane of the winding m, and mn (m n, n =,, 3, or 4) is the mutual indutane between the winding m and the winding n, respetively. Here, is equal to. Note that k and k are the oupling oeffiients between the main-oil to the main-oil or the aneling-oil, respetively. oreover, is the indutane ratio 3 /. Figure shows the onnetion diagrams of the nonresonant reative shielding method and the ative shielding method. In the ative shielding method, both of the ases, where the aneling oils are onneted as the ommon-mode oils and the differential-mode oils, are onsidered. In partiular, the ommon mode oils result in the positive mutual indutane between the parallelonneted oils, whereas the negative mutual indutane between the parallel-onneted oils ours in the differential mode oils. III. CACUATION OF EQUIVAENT PARAETERS A. Inverse atrix of Indutane atrix In order to larify the equivalent self-indutane and the equivalent oupling oeffiients, the indutane matrix is alulated. It is onvenient to alulate the urrent of the oils from the input voltage with the inverse matrix of the indutane matrix when onditions of the input voltage is deided as shown in Fig.. The relationship between urrent and voltage of eah oil in Fig. is also expressed by a four-order inverse matrix in () (bottom of next page) and (3) det k k k... (3). where det is the determinant of the four-order indutane matrix in ().

3 B. Short-iruited Coil When the aneling oils are shorted as shown in Fig. (a), the input voltage is v = v p, v 3 = v s and v = v 4 = 0. Hene, the input urrent is expressed by k vpdt k vsdt i i k k v dt k k v dt p s i 3 det k vpdt k vsdt i 4 kk vpdt k k vsdt...(4). In addition, the onditions of the input urrent i = i p, i 3 = i s are onsidered. The relationship between the voltage and the urrent of the entire transmission oils is shown as ip i k vpdt k i i3 det s k k...(5), vsdt vp peq _ short eq _ short d ip v s eq _ short seq _ short dt i s k k d ip...(6), k k dt i s where peq_short is the equivalent self-indutane of the primary side, seq_short is the equivalent self-indutane of the seondary side, and eq_short is the equivalent mutual indutanes between the primary side and the seondary side. Through the alulation, the self-indutane and the oupling oeffiient of the entire transmission oil are hanged from the original values and k, respetively. The equivalent self-indutane eq-short (= peq_short = seq_short) and the equivalent oupling oeffiient k eq_short are expressed in (7) and (8). eq _ short k...(7) k k...(8) eq _ short eq _ short eq _ short k C. Commom-mode Coil The onditions of the input voltage is v = v = v p and v p i p eq_short v p Winding # Primary side Seondary side Winding #3 i i 3 i k k Winding # Winding #4 k eq_short v 3 = v 4 = v s. Hene, when the aneling oils are onneted to the main oils as the ommon-mode oils as shown in Fig. (b), the input urrent is expressed by (9). In addition, the onditions of the input urrent i p = i + i, i s = i 3 + i 4 are onsidered. The relationship between the voltage and the urrent of the entire transmission oils is shown in (0) and () (next page), where peq_om is the equivalent self-indutane of the primary side, seq_om is the equivalent self-indutane of the seondary side, and eq_om is the equivalent mutual indutanes between the primary side and the seondary side. The equivalent selfindutane eq_om (= peq_om = seq_om) and the equivalent k (a) Short-iruited aneling oils. i 4 Winding # Primary side Seondary side Winding #3 i i 3 i i 4 i s v s eq_short eq_om Common eq_om Winding # Winding #4 k eq_om v p i p k k (b) Caneling oils onneted as ommon-mode oils. Winding # Primary side Seondary side Winding #3 i i 3 i p i k k eq_dif eq_dif Differential Winding # Winding #4 k eq_dif () Caneling oils onneted as differential-mode oils. Fig.. Connetion diagrams of main oils and aneling oils. k k i 4 i s i s v s v s v dt k k k k kk vdt k k k k kk k k v3dt k kk k k k v4dt kk k k k k k k i 3 0 vdt i 0 0 vdt () i det v 3dt i v 4dt k k v dt k k v dt p s i i k k k v dt k k k v dt p s i 3 det k k vpdt k k vsdt i 4 k kk vpdt k k k vsdt (9)

4 oupling oeffiient k eq_om are expressed in () and (3). k k k k k om k k k eq _ om eq _ om eq k k k... () eq om... (3) D. Differential-mode Coil The onditions of the input voltage is v = -v = v p and v 3 = -v 4 = v s when the aneling oils are onneted to the main oils as the differential-mode oils as shown in Fig. (). Hene, the input urrent is expressed by (4). In addition, the onditions on the input urrent i p = i - i, i s = i 3 - i 4 are onsidered. The relationship between the voltage and the urrent of the entire transmission oils is shown in (5) and (6), where peq_dif is the equivalent selfindutane of the primary side, seq_dif is the equivalent self-indutane of the seondary side, and eq_dif is the equivalent mutual indutanes between the primary side and the seondary side. The equivalent self-indutane eq_dif (= peq_dif = seq_dif) and the equivalent oupling oeffiient k eq_dif are expressed in (7) and (8). k k k k k k k k k k k eq _ dif eq_ dif E. Design Criteria of Caneling Coils... (7)... (8) Figures 3 and 4 show the ontour diagrams of the equivalent oupling oeffiients and the equivalent selfindutanes derived from Eqs. (7 8, 3, 7 8), respetively. It is noted that the oupling oeffiient k is fixed at 0., whereas the oupling oeffiient k and the self-indutane ratio are variables. In partiular, k is adjusted by hanging installation loation and onfiguration of the aneling oils, whereas is also adjusted by hanging the number of the turns of the aneling oils. Figure 3(a) shows that k eq_short is improved by inreasing k, whereas k eq_short is not varied by. eanwhile, Fig. 4(a) shows that the eq_short is dereased by inrease k, and eq_short is not also varied by. Hene, the parameter variation with the short-iruited aneling oils is not influened by the number of the turns of the aneling oils. k k k p k k i i i vpdt i i i det v dt vp peq _ om eq _ om d ip v s eq _ om seq _ om dt i s k k k k k d ip k dt i s k k k k k k s 3 4 k s k k k k k k v dt k k v dt p s i i k k k v dt k k k v dt p s i 3 det k k vpdt k k vsdt i 4 k kk vpdt k k k vsdt k k k k k ip i i vpdt i i3 i4 det s k vsdt k k k k vp peq _ dif eq _ dif d ip v s eq _ dif seq _ dif dt i s k k k k k d ip k dt i s k k k k k k (0) () (4) (5) (6)

5 keq_short = 0.9 keq_short = keq_short = keq_om = keq_om = keq_dif = keq_dif = Coupling oeffiient k 0. 0 keq_short = keq_short = keq_short = keq_short = keq_short = 0. Self-indutane ratio Coupling oeffiient k 0. keq_om = 0 keq_om = keq_om = keq_om = keq_om = keq_om = 0. Self-indutane ratio Coupling oeffiient k 0. 0 keq_dif = keq_dif = keq_dif = keq_dif = keq_dif = 0. Self-indutane ratio (a) Short-iruited. (b) Common mode. () Differential mode. Fig. 3. Relationship among equivalent oupling oeffiients, oupling oeffiient between main oil and aneling oil, and self-indutane ratio. The oupling oeffiient k is 0.. Variation range of the oupling oeffiient between the main oil and the aneling oil k is from 0 to 9, whereas range of the self-indutane ratio is from 0 to 0. keq_dif = Coupling oeffiient k 0. 0 Self-indutane ratio eq _ 0.9 short Coupling oeffiient k Self-indutane ratio eq _ om Coupling oeffiient k Self-indutane ratio eq _ dif (a) Short-iruited. (b) Common mode. () Differential mode. Fig. 4. Relationship among ratio of equivalent self-indutanes to self-indutane of main windings, oupling oeffiient between main oils and aneling oils, and self-indutane ratio. Conditions of k, k, and are same as in Fig. 3. Figure 3(b) shows that k eq_om is improved by inreasing k or. Figure 4(b) shows that eq_om is dereasing due to the inrease in k or the derease in. Thus, in order to avoid the parameter variation whih is aused by the ommon-mode-onneted aneling oils, not only the number of the turns of the aneling oils should be designed larger than the number of the turns of the main oils, but also the aneling oils have to be plaed lose to the main oils. Figure 3() shows that k eq_dif is improved in the range of high k and high. eanwhile, Fig. 4() shows that eq_dif is dereasing due to the high k and the derease in. Therefore, not only the winding turn should be muh larger than the main oils, but also the aneling oils have to be installed apart from the main oil in order to avoid the parameter variation whih is aused by the differentialmode-onneted aneling oils. However, setting the aneling oils apart from the main oils degrades a aneling performane of EF. There is the trade-off between the parameter variation (dereasing of the equivalent self-indutane) and the aneling performane. Thus, an operation frequeny or the onstrution of a transmission oil should be redesigned, when the aneling oils are installed in order to redue EF. As a onlusion, it is shown that the design riteria for the three onnetion methods of the aneling oils at the view point of avoiding the parameter variations as follows: ) the short-iruited onnetion (non-resonant reative shield) the long distane between the main oils and the aneling oils. the low self-indutane of the aneling oils. ) the ommon-mode onnetion installation of the aneling oils by the main oils. twie times or more the number of the turn of the aneling oils ompared with the main oils. 3) the differential-mode onnetion the long distane between the main oils and the aneling oils. twie or more the number of the turn of the aneling oils ompared with the main oils. The advantage of avoiding the parameter variations is reduing the mismath between the operation frequeny and the resonant frequeny, whih is neessary to operate IPT systems under the onditions of the high effiieny and the high power transmission. IV. EXPERIENTA VERIFICATION WITH PROTOTYPE TRANSISSION COI The self-indutanes and the mutual indutanes of the wired oils are measured in order to onfirm Eqs. (7 8, 3, 7 8) with the prototype four-winding transmission oil.

6 Winding # (main oil) Winding # (aneling oil) Gap 0 Winding #3 (main oil) Winding #4 (aneling oil) Table I. Experimental results: equivalent oupling oeffiient and indutanes of prototype four-winding transformer. Connetion of aneling oils Short-iruited Common mode Differential mode Indutane matrix as 4-winding transformer [H] Self-indutane of main winding easured value 396 H Self-indutane ratio easured value 7.94 Coupling oeffiient k easured value 8 Coupling oeffiient k easured value 78 Equivalent primary self-indutane easured value 334 H 396 H 36 H Calulated value 338H 394H 4H Error of alulated equivalent primary self-indutane.3% %.3% Equivalent seondary self-indutane easured value 33 H 39 H 35 H Calulated value 338H 394H 4H Error of alulated equivalent seondary self-indutane.9% %.7% Equivalent mutual indutane easured value 67.5 H 73.0 H 43.3 H Calulated value 7H 7.H 46.6H Equivalent oupling oeffiient easured value Calulated value Error of alulated oupling oeffiient.7%.% 4.9% Prop of primary-side ore Unit: mm (a) Front view. (b) Top view. () Side view. Fig. 5. Outline of prototype four-winding transmission oils. The main oils are wired on enter of the ores (winding # and winding #3). The aneling oils are put on top of the primary ore and bottom of the seondary ore (winding # and winding #4). The aneling oils onstrut the serial two oils. The four props support the primary-side ore. Figure 5 shows the prototype of the transmission oil. In order to shield EF on the top and below, the aneling oils shaped double-d are put on the outside ores. The ore material is ferrite (TDK Corp., N87). The number of turns of the main oils is 30 with 3.5-mm insulated wires, whereas the number of turn of the aneling oils is 30 with enameled wires. Note that the number of turns of the primary side and the seondary side are the same. Table I shows the measurement results of the four-order indutane matrix, the equivalent self-indutanes and the equivalent oupling oeffiients in the eah onnetion. In order to ompare the equivalent self-indutane, the equivalent mutual indutane, and the equivalent oupling oeffiient, both the measured values and the alulated values are shown. In partiular, the alulated values of the equivalent self-indutanes orrespond to the measured values with a maximum error of.7%. The self-indutane is the important fator beause the IPT system should be designed to resonate at the transmission frequeny. Thus, a preise alulation is ruial for the design of the IPT system. Besides, the maximum error of the equivalent oupling oeffiients is 4.9%, whih is larger than the error of the equivalent self-indutane beause of the influene of the ignored magneti oupling between following windings, i.e., winding # to winding #3, winding # to winding #4, and winding #4 to winding #. V. EF REDUCTION WITH CANCEING COIS A. Ciruit and odel Configuration In order to onfirm the effet of the EF redution, the prototype transmission oil is simulated with JAG (JSO Corporation). JAG is a software for the eletromagneti field analysis with a finite element method. Figure 6 shows the iruit onfiguration in the simulation model, whereas Table II shows the speifiation of the iruit. The IPT system is onstruted with S/S topology, whih has the resonant apaitors onneted to both of the primary side and seondary side of the transmission oil in series. The input voltage is the sinusoidal wave for fousing on fundamental frequeny. The apaitanes of the resonant apaitors C s, C s are deided in order to resonate with the onsidered at a resonane frequeny of khz. Noted that operating frequeny is deided by the resonant onditions of the resonane apaitanes and the equivalent self-indutane suh as eq_short, eq_om, or eq_dif. The output power is kw by adjusting the value of the equivalent load resistane

7 k,k eq_short,k eq_om,k eq_dif f f short f om f dif V in C s os in eq_short eq_om eq_dif eq_short eq_om eq_dif C s R eq Equivalent iruit of prototype four-winding transmission oil Fig. 6. Ciruit onfiguration of simulation model. The prototype four-winding transformer is equivalent to the two-winding transformer when the aneling oils are shorted or onneted to the main oils in parallel. For individual onnetion suh as when the aneling oils are shorted, the equivalent self-indutane, the equivalent oupling oeffiient and the operation frequeny are hosen eq_short, k eq_short and f short differently. 0 Winding # (aneling oil) Winding # (main oil) Winding #3 (main oil) Case 30 Core Gap: 0 Winding #4 (aneling oil) Unit: mm (a) Front view. (b) Top view. () Side view. Fig. 7. Outline of CAD model of prototype four-winding transmission oil. The size of the ores and the ases mathes the prototype fourwinding transformer; the oils are onstruted as the solid model, and the material of the ores is PC40. The ases are treated as air, whereas the thikness of the ases and the main oils is 5 mm. Table II. Simulation onditions. Parameter Symbol Value Input AC voltage V in 5 Vrms Rated power P.0 kw Operation frequeny without aneling oils f khz Operation frequeny of short-iruited operation f short khz Operation frequeny of ommon-mode operation f om khz Operation frequeny of differential-mode operation f dif 5.5 khz Resonant apaitors C s,c s 8.56 nf R eq beause the output urrent of the S/S resonant iruit is inversely proportional to the equivalent mutual indutane of the transmission oil at the C resonane. Figure 7 shows the omputer-aided-design (CAD) model of the transmission oil on JAG. The struture and the size of the CAD model are based on the prtototype four-winding transmission oil as shown in Fig. 5. The wires are expressed as the olored solid models. Noted that the eddy urrent and hysteresis loss are not onsidered. B. EF Redution Effet with Caneling Coils Figure 8 shows the simulation results of the magneti flux distribution under the eah ondition. The result is obtained on the ross-setion of the enter of the transmission oil as a representative ase. Note that the input power fator os in is unity when the operation frequenies of Fig. 8(a) (d) are khz, khz, khz, 5.5 khz, respetively. The flux distributions on the top and bottom of the transmission oils dereases with the short-iruited onnetion and differential-mode onnetion in omparison with the flux distribution without the aneling oils. The magneti flux distribution of Fig. 8(a) (d) are 3.8 T, 9.4 T,.6 T, and 8.06 T at the 50-m bottom of the seondary ore as the representative values, respetively. In addition, the magneti density at the outside of the aneling oil dereases by the aneling oils. oreover, the effet of EF redution is more effetive with the differential operation than that with the short-iruited onnetion. VI. CONCUSION In this paper, the effet of the aneling oils on the parameter variation of the IPT system was onsidered regarding to the equivalent self-indutane and the equivalent oupling oeffiient. Three onnetion methods of the aneling oils, i.e. the short-iruited onnetion, the ommon-mode onnetion and the differential-mode onnetion, were evaluated. The alulated equivalent values agreed with the measured values through the indutane measurement using the prototype transmission oil attahed the aneling oils. The relative error between the alulated values and measured values was 4.9%. In addition, EF redution near the aneling oils were onfirmed with the short-iruit onnetion (by 3%) and the differential-mode onnetion (by 4%) in the simulation using JAG. Above of the results, the design riteria fousing on avoiding the parameter verifiations are as follows: the aneling oils far from the main oils at the short-iruited onnetion. the aneling oils losed to the main oils with

8 agneti flex density T m 50 m T (a) Without aneling oil. 9.4 T (b) Short-iruited oil agneti flex density T m 50 m T 8.06 T () Common-mode oil. (d) Differential-mode oil. Fig. 8. agneti flux distribution of prototype transmission oil. The transmission oils are plaed at the enter of the ontour plots (orange or yellow area). The upper-side ore is the primary side. The bottom-side ore is the seondary side. Note that the operation frequeny is different for eah the simulation onditions, whih are shown in Table II. Transmission powers of without-aneling oil, short-iruited onnetion, ommon-mode onnetion and differential-mode onnetion are 99 W,.6 kw,.03 kw and.7 kw, respetively. the large number of the turn at the ommon-mode onnetion. the aneling oils far from the main oils with the large number of the turn at the differential-mode onnetion. Future plans are onsiderations of the parameter verifiations introdued ross ouplings between aneling oils. REFERENCES [] T. izuno, T. Ueda, S. Yahi, R. Ohtomo and Y. Goto: "Dependene of Effiieny on Wire Type and Number of Strands of itz Wire for Wireless Power Transfer of agneti Resonant Coupling", IEEJ Journal of Industry Appliations, Vol. 3, No., pp (04) [] H. Ishida, H. Furukawa and T. Kyoden: "Development of Design ethodology for 60 Hz Wireless Power Transmission System", IEEJ Journal of Industry Appliations, Vol. 5, No. 6, pp (06) [3] K. Kusaka, and J. Itoh: "Development Trends of Indutive Power Transfer Systems Utilizing Eletromagneti Indution with Fous on Transmission Frequeny and Transmission Power", IEEJ Journal of Industry Appliations, Vol. 37, No. 5, pp (07) [4] R. Ota, N. Hoshi and J. Haruna: "Design of Compensation Capaitor in S/P Topology of Indutive Power Transfer System with Buk or Boost Converter on Seondary Side", IEEJ Journal of Industry Appliations, Vol. 4, No. 4, pp (05) [5] Su Y. Choi, Beom W. Gu, Seog Y. Jeong and Chun T. Rim: Advanes in Wireless Power Transfer Systems for Roadway- Powered Eletri Vehiles, IEEE Trans. PE, Vol.3, No. pp.8-36 (05) [6] D. Shimode, T. urai and S. Fujiwara: "A Study of Struture of Indutive Power Transfer Coil for Railway Vehiles", IEEJ Journal of Industry Appliations, Vol. 4, No. 5, pp (05) [7] T. Watanabe and. Ishida: "Study on the influene of the magneti field and the indued eletrial field in human bodies by wireless harging systems", EVTe and APE 06, (06) [8] K. Kusaka, K. Inoue and J. Itoh: "Radiation Noise Redution using Spread Spetrum for Indutive Power Transfer Systems onsidering isalignment of Coils", Energy Conversion Congress and Exposition, pp (07) [9] T. Campi and Silvano Cruiani auro Feliziani: "agneti Shielding of Wireless Power Transfer Systems", Institute of Eletronis, Information and Communiation Engineers, 5A-H, pp (04) [0] S. Kim, H. Park, J. Kim, J. Kim, and S. Ahn: "Design and Analysis of a Resonant Reative Shield for a Wireless Power Eletri Vehile", IEEE TRANSACTIONS ON ICROWAVE THEORY AND TECHNIQUES, Vol. 6, No. 4, pp (04) [] J. Park, D. Kim, K. Hwang, H. Ho Park and S. Il Kwak: "A Resonant Reative Shielding for Planar Wireless Power Transfer System in Smartphone Appliation", IEEE TRANSACTIONS ON EECTROAGNETIC COPATIBIITY, Vol. 59, No., pp (07) [] T. Shijo, K. Ogawa,. Suzuki, Y. Kanekiyo and. Ishida: "EI Redution Tehnology in 85 khz Band 44 kw Wireless Power Transfer System for Rapid Contatless Charging of Eletri Bus", IEEE Energy Conversion Congress and Exposition (06) [3] S. ee et al., Ative EF anellation method for I-type pikup of online eletri vehiles, in Pro. IEEE Appl. Power Eletron. Conf. Expo., pp (0)