Analysis on Electromagnetic Interference for Power Plane-Battery Management System (PP-BMS) Enclosure

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1 Sesors & Trasducers 2014 by IFSA Publishig, S. L. Aalysis o Electromagetic Iterferece for Power Plae-Battery Maagemet System (PP-BMS) Eclosure * Yapeg SUN, Liguo ZHANG, Lele QU, Ailig HU Liaoig Key Laboratory of Geeral Aviatio, Sheyag Aerospace Uiversity (SAU), No. 37 Daoyi South Aveue, Shebei Developmet District, Sheyag, , Chia * Tel.: * syp_yh@sia.com Received: 25 July 2014 /Accepted: 30 October 2014 /Published: 30 November 2014 Abstract: Fiite Differece Time Domai (FDTD) is applied to study the characteristics of electromagetic iterferece for power plae-battery maagemet system (PP-BMS) eclosure, for modelig the couplig of a icidet electromagetic pulse (EMP) with a coductig wire through a BMS eclosure ad aperture o it. Simulatio ad aalysis are doe by radius of the wires, icidece agles of EMP i the coditios of differet polarized directio, ad differet aular apertures i cosideratio. The simulatio result shows that iterferece of the electromagetic couplig ito the PP-BMS eclosure ca be affected i differet degrees by above factors. At low frequecy, the larger the radius of the wire peetrated ito the PP-BMS eclosure, the more iterferece is coupled ito the BMS eclosure from electromagetic field. Also, the electromagetic eergy coupled by peetrated wire whe icidet wave radiates aslat is more tha the couplig eergy whe icidet wave radiates the target vertically i the coditio of vertical polarized directio of electric field, ad less i the coditio of horizotally polarized directio of electric field. Furthermore, i the case of the same aperture area, the couplig electromagetic eergy ito the circular aular aperture is smaller tha that ito the rectagular ad the square oes. Copyright 2014 IFSA Publishig, S. L. Keywords: PP-BMS eclosure, FDTD, EMP, electromagetic iterferece. 1. Itroductio Battery maagemet system (BMS) is oe of the key compoets of electric power plaes, the highpower IGBT ad drive motor that geerate a large umber of electromagetic oise is istalled i electric power plae [1-2]. If metal eclosure is ot used i power battery maagemet system, the etire system is difficult to meet the requiremets of electromagetic compatibility, ad more seriously the etire battery maagemet system will ot work properly [3-4]. Because of vetilatio, cable coectios, ad the other issues like maufacturig process, it is ievitable i the metal eclosure that has peetrated wires ad slit aular apertures that followed. Peetrated wires ad slit aular apertures are the mai factors to affect the electromagetic shieldig characteristics for the metal eclosure. So far, the research o electromagetic couplig of aperture ad peetrated wires through PP-BMS eclosure has had great progress. Ad with the extesive applicatio of electromagetic waves ad fast developmet of computer techology, various methods have bee thoroughly studied, such as the Method of Momets (MoM), Fiite Elemet Method 125

2 (FEM), the Boudary Elemet Method (BEM) ad Fiite-Differece Time-Domai (FDTD) method, ad so o [5-11]. FDTD is a direct time-domai algorithm o solvig Maxwell differetial equatios [12]. Z. Youwe did modelig ad calculatio to study the effects of couplig curret i the circuit i the BMS eclosure from the iterferece electromagetic [13]. S. Pegfei researched the rule of electromagetic pulse with differet agles of icidece coupled ito the eclosure with holes o it, i the coditios of horizotal ad vertical polarized directio of E field respectively [14]. However, the researches o differet peetrated wires, differet excitatio situatios, ad o-regular apertures that itroduce electromagetic couplig ito the PP-BMS eclosure are ot eough. Therefore, it is sigificat to study the couplig effect of electromagetic pulse ito the PP-BMS eclosure explorig the protectio research, by radius of peetrated wires, icidece agles of EMP i the coditios of differet polarized directio, ad differet aular apertures i cosideratio. Ad Fiite Differece Time Domai (FDTD) method is used i this paper. 2. Research Method 2.1. This is a Subtitle Example Fiite differece time domai method (FDTD) is a effective umerical method for solvig electromagetic field problems [15-16]. It uses the cetral fiite differece formula to replace the differetial formula of Maxwell time domai curl equatio to get the fiite differece formula of field compoets, ad it uses space grids with the same electrical parameters to simulatio the object of study, set the appropriate boudary coditio, solvig the Maxwell equatio, so as to obtaiig the electric field distributio i grid space [17-20]. FDTD method trasforms the Maxwell curl equatio ito fiite differece formula, ad it establishes the icreasig sequece of discrete time, to alterately calculate the electric field ad magetic field i the three dimesioal space gird. It distributes the electric ad the magetic field of the space i grid form, ad it uses the fiite differece equatios of secod order accuracy cetral differece approximatio to replace the Maxwell equatios which deped o the time variables. The equatios ca be solved with iitial coditios ad absorbig boudary coditios accordig to the time step progressive method, so as to obtaiig the electromagetic field distributio i the space [21-26]. Secod order fiite differece ceter formula is used to represet partial derivative of fuctio to time ad space, the followig FDTD differetial equatios ca be obtaied (for example, i the z directio) as Formula (1) z 2 z 2 x H ( i+ 1/2, j+ 1/2, k) = H ( i+ 1/2, j+ 1/2, k) E ( i+ 1/2, j+ 1, k) Ex ( i+ 1/2, j, k) +Δ ( t / μ) [ Δy Ey ( i+ 1, j+ 1/2, k) Ey (, i j+ 1/2, k) ] Δ x + 1 Ez (, i jk, + 1/2) = Ez (, i jk, + 1/2) + Δt/ ε y 2 y x 2 x 2 ( ) H ( i+ 1/2, j, k+ 1/2) H ( i 1/2, j, k+ 1/2) [ Δx H ( i, j+ 1/ 2, k+ 1/ 2) H ( i, j 1/2, k+ 1/ 2) ], Δy (1) where i, j, k ad are the itegers, i, j, k are the grid umbers of the directio x, y, z i grid space respectively, is the umber of the time step, μ ad ε are the permeability ad permittivity of the medium respectively, Δ x, Δ y, Δ z are the mesh size of the directio x, y, z i grid space respectively, Δ t is the time step, Hz (, i j, k) ad Ez (, i j, k) are the magetic field stregth ad the electric field stregth i poit ( iδx, jδy, kδ z) respectively ad time steps. We assume that the grid of FDTD is cube, which meas the space grid steppig Δ x=δ y =Δ z = δ. Cosiderig the ifluece of FDTD umerical dispersio errors, δ is λ N mi δ, (2) where λ mi is the correspodig wavelegth, N=10. If the computatioal domai cotais oly free space ad perfect coductor, the c λ mi =, (3) f where c is the speed of wave i free space (medium), f is the imum value of cocered frequecy. The grid size of FDTD ca be determied by f. I fact, FDTD space grid is equivalet to a low-pass filter that the frequecy compoets of the pulse which is higher tha f is filtered out whe passig the FDTD space grid i the excitatio pulse, which the results will have a great errors. Ad to guaratee the stability of the umerical couts i the iterative calculatio FDTD, the time of steppig Δ t is 126

3 1 Δ t c (1/ Δ x) + (1/ Δ y) + (1/ Δz) 2.2. Modelig (4) A rectagular PP-BMS eclosure costituted by the perfect coductor is modeled as show i Fig. 1. The eclosure is a cube with a side legth of 200 mm. The thickess of the eclosure wall is 2 mm. where Ei () t is the stregth of electric field of icidet Gaussia pulse, 0 = 1000 V/m, τ determies the width of the Gaussia pulse, τ = 100Δ t, the legth of space lattice steppig Δ x =Δ y =Δ z = 1 mm, ad pulse peak appears at t = t 0. Ad time of steppig Δ t = ps, τ = 100 Δ t, 0 τ = 3τ. E 3. Results ad Discussio 3.1. The Iferece of Wire Radius Fig. 1. BMS eclosure module. Whe cosider the wire which peetrated ito the PP-BMS eclosure, set a hole of 12 mm 12 mm i the ceter of plae xy, ad with a wire through the ceter hole. The legth of the wire is 100 mm with the exposig legth of the wire outside of the eclosure 50 mm. The radius of the wire is r. Whe cosider the couplig effect caused by aular apertures i the BMS eclosure, set aular apertures i the ceter of plae xy. As show i Fig. 2, the shapes of aular aperture of this paper are square aular, rectagular aular ad circular aular. Due to the size data iterface that belogs to mm order of magitude it has more practical sigificace to study the tiy apertures o the order of mm. Aular aperture width is 2 mm. The area of aular aperture area is 200 mm 2 [27-29]. The propagatio directio of electromagetic excitatio source is parallel to the z-axis, icidet electric polarizatio directio is parallel to the y-axis. The selectio of wire radius is based o America Wire Gauge (AWG) stadard i this paper [30]. Calculate the cetral locatio of the eclosure whe wire radius r = 0.51 mm, 1.15 mm, 2.31 mm ad 5.2 mm, to obtai the electric field frequecy domai. Fig. 3 shows that the frequecy compoet of electromagetic iterferece i eclosure has icreased sigificatly with the radius of wire peetrated ito the BMS eclosure becomig larger at low frequecy. It idicates that electromagetic iterferece frequecy compoet of the low frequecy bad is easier coupled ito the eclosure through the wire with larger radius. The differece of compoet at high frequecy ad the resoace frequecy is ot so much related to the radius of wire, for the reaso that the ability i radiatio of the wire greatly ehaced whe the frequecy is higher. Furthermore, the degree of sufferig electromagetic iterferece at resoace frequecy is the strogest. From what has bee discussed as above two poits, we ca see that the larger the radius of wire is, the more the frequecy domai compoet of electric field is itroduced ito the eclosure through the wire, ad the more easily the iterferece eergy is coupled ito the eclosure to cause sigificat iterferece i the eclosure. Fig. 2. Aular aperture model. Icidet radiatio source is a uiform power plae. The propagatio directio is parallel to the wire whe icidet wave radiates the target power plae with hole or aperture vertically. The Gaussia pulse is used as excitatio source i this paper for simulatio, ad the time domai expressio of the Gaussia pulse is: ( t t ) 2 4π Ei () t = E0 exp 2 τ 0, (5) Fig. 3. The iferece of wire radius. 127

4 3.2. Differet Excitatio Situatios Vertically Polarized E Field I the case of vertically polarized electric field, maitaiig the costat electric field itesity of icidet electromagetic pulse, chage the directio of icidet electromagetic pulse. The mai compoets of electric field eergy coupled ito the BMS eclosure by the peetrated wire are cocetrated i the directio of x-axis ad z-axis. While i the magetic field, the eergy is cocetrated i the directio of y-axis. Fig. 4 shows the curve of H y at oe locatio o the wire peetrated ito the eclosure whe the icidet directio of EMP is take 0, 30, 45, ad 60 respectively. I the coditios of the structure of BMS eclosure ad peetrated wire, the couplig rule of the Gaussia pulse i the case of vertically polarized E field is that the couplig magetic field o the wire with the icidet agle of EMP 0 (of 0.08 A/m) is less tha those of the agle of icidece of 30, 45, ad 60. It shows that couplig magetic field eergy of icidet wave radiatig the target vertically (agle of icidece EMP is 0 ) is less tha that of icidet wave radiatig aslat i the case of vertically polarized electric field. compoets of magetic field eergy are cocetrated i the directio of x-axis ad z-axis. Fig. 5 shows the curve of sythesis H of H x ad H z at oe locatio o the wire peetrated ito the eclosure whe the icidet directio of EMP is take 0, 30, 45, ad 60 respectively. I the coditios of the structure of BMS eclosure ad peetrated wire whe the E field is horizotally polarized, the couplig rule of the Gaussia pulse is that the couplig magetic field o the wire reaches the imum (0.1 A/m) whe the agle of icidet EMP is 0, ad decreases with agle of icidece becomig larger, after comparig the total amplitude of the magetic field that sythesized from the couplig magetic field compoet H x ad H z. It idicates that the eergy of magetic field coupled ito the eclosure decreases with icreasig agle of icidet EMP. It also shows that couplig magetic field eergy of icidet wave radiatig the target vertically (agle of icidece EMP is 0 ) is greater tha that of icidet wave radiatig aslat i the case of horizotally polarized electric field. Fig. 5. The sythesis H with Differet Icidet Directio of EMP. Fig. 4. The H y with Differet Icidet Directio of EMP Horizotally Polarized E Field I the case of horizotally polarized electric field, chage the icidet directio of electromagetic pulses (i.e. the agle betwee propagatio directio ad the z-axis), the electric field eergy coupled ito the BMS eclosure by the peetrated wire is cocetrated i the directio of y-axis, ad the mai Compariso Compared Fig. 4 with Fig. 5, we ca see that the magetic eergy coupled ito eclosure by the peetrated wire is differet betwee the two situatios of vertically ad horizotally polarized E field, that is, the magetic field stregth of couplig curret i the coditios of vertically polarizatio electric field is greater tha that of horizotally polarizatio electric field. It idicates that more couplig eergy is itroduced by the peetrated wire i the case of vertically polarized E field tha that of horizotally polarized E field. 128

5 3.3. Differet Aular Apertures The electromagetic couplig ito aular apertures which have the same aperture area but differet shapes (rectagle, square, circle) are calculated ad aalyzed respectively to compare the differece of couplig iterferece betwee differet aular apertures The Effect of Circular Aular Aperture Fig. 6 ad Fig. 7 are respectively electric field waveform of differet poit o the axis of the eclosure. Fig. 6 shows the electric field waveform of the place 3 cm to circular aular aperture i the eclosure. Fig. 7 shows the electric field waveform of the ceter of the shielded eclosure. The time required that electromagetic pulse spreads from the place 3 cm to aperture i the eclosure ad the ceter of the eclosure to the rear wall of the eclosure ad the reflects back are approximately 1.13 s ad 0.67 s respectively by calculatig. It meets the oscillatig period of the couplig waveforms as show i Fig. 6 ad Fig. 7. Therefore, the first pulse i the figure is the mai pulse of couplig pulse, ad the subsequet pulse is the reflected pulse that the mai pulse reflects back from the rear wall of the eclosure. Due to the reflectio effect of the shielded eclosure, the eclosure resoace pheomeo of electromagetic pulse occurs periodically i the eclosure. Electromagetic pulse spreads i the eclosure ad radiates out from the aular aperture. After a while, the amplitude of electric field iside the eclosure decays. The electric field amplitude of mai pulse i Fig. 6 is larger tha that i Fig. 7. It meas the closer to the ceter of the eclosure, the smaller the electric field amplitude of the mai pulse is. This pheomeo occurs because the eergy of electromagetic pulse decays while the electromagetic pulse spreads. The amplitude of electric field i Fig. 7 has bee ehaced after the mai pulse, which is caused by the reflectio effect of the rear wall of the shielded eclosure. The the electric field amplitude decays. It is because that the electromagetic wave radiates outward eergy from the aular aperture. Fig. 6. Electric field of the place 3 cm to circular aular aperture i the eclosure. Fig. 7. Electric field of the ceter of the eclosure with circular aular aperture The Effect of Square Aular Aperture Fig. 8 shows the electric field waveform of the place 3 cm to the square aular aperture i the eclosure. Comparig Fig. 8 with Fig. 6, we ca fid that the couplig characteristics of the square aular aperture are similar with the circular aular aperture. The electric field amplitudes of the mai pulse of the square aular aperture are a little larger tha the circular aular aperture. Therefore, the shieldig effect of the circular aular aperture is a little better tha the square aular aperture. Fig. 8. Electric field of the place 3 cm to square aular aperture i the eclosure The Effect of Aular Apertures with Differet Aspect Ratio We select three kids of rectagular aular apertures that have the same area but differet ratio of legth to width as the models to study the couplig characteristics of the rectagular aular apertures with differet aspect ratio. The legth ad width of the three rectagular aular apertures are respectively: L=40 mm, W=6 mm; L=30 mm, W=16 mm; L=23 mm, W=23 mm. The area of the rectagular aular aperture is s=(l+4)(w+4)-lw=200 mm 2, as show i Fig. 2. Fig. 9 shows the electric field waveforms of the place 3 cm to the aperture i the eclosure with differet aspect ratio rectagular aular apertures. We ca see that the larger the ratio of legth to width of the 129

6 rectagular aular aperture is, the more easily the icidet pulse coupled ito is. Ackowledgemets This work was supported by the Special Fud for Civil Aircraft of The Miistry of Idustry ad Iformatio Techology of Chia, the Sciece ad Techology Foudatio of Liaoig Provice of Chia (Grat No ), the Aeroautical Sciece Foudatio of Chia (Grat No. 2011ZC54009) ad the Foudatio of Liaoig Provicial Departmet of Educatio of Chia (Grat No. L ). Refereces Fig. 9. Compariso of the electric field i the place 3 cm to the aperture with differet respect ratio whe the electric is parallel to the short side of the aperture. 4. Coclusios Fiite differece time domai (FDTD) method is applied i this paper, to model ad simulate the couplig iterferece i the body of PP-BMS eclosure, with differet peetrated wire, differet excitatio situatios, ad differet excitatio situatios, ad differet o-regular apertures uder the actio of the electromagetic pulse. The experimet data shows that: 1) The larger the radius of the wire peetrated ito the PP-BMS eclosure, the more electric field itesity i the ceter of the eclosure is ehaced. 2) The electromagetic eergy coupled by peetrated wire whe icidet wave radiates aslat is more tha the couplig eergy whe icidet wave radiates the target vertically i the coditio of vertical polarized directio of electric field, ad less i the coditio of horizotal polarized directio of electric field. Ad compared with the situatio of horizotally polarized directio of electric field, more electromagetic eergy is coupled whe the directio of electric field is vertically polarized. 3) For the three kids of shapes (rectagle, square ad circle) of aular apertures with the same area, the couplig eergy of the square aular aperture ad the circular aular aperture is obviously smaller tha the rectagular aular aperture, ad the couplig eergy of circular aular aperture is a little smaller tha the square aular aperture. Furthermore, the rectagular aular aperture with larger ratio of legth-to-width ca couple more electromagetic iterferece whe the directio of E-field is parallel to the short side. Therefore, coductig wire peetrated ito PP-BMS eclosure must be strictly cotrolled, to avoid affectig stable operatio of the iteral electroic circuit i the eclosure that from the outside iterferece. Ad the shape ad the size of the aular aperture o PP-BMS eclosure should be properly set accordig to the coclusios so that the harm of electromagetic iterferece is miimized. [1]. K. W. E. Cheg, B. P. Divakar, H. J. Wu, K. Dig, Battery-Maagemet System (BMS) ad SOC Developmet for Electrical Vehicles, IEEE Trasactios o Vehicular Techology, 60, 1, 2011, pp [2]. Garche J., Josse A., Battery Maagemet Systems (BMS) for Icreasig Battery Life Time, i Proceedigs of the Telecommuicatios Eergy Special Coferece, 2000, pp [3]. Zhag W., The Electromagetic Iterferece Model Aalysis of the Power Switchig Devices, TELKOMNIKA Idoesia Joural of Electrical Egieerig, 11, 1, 2013, pp [4]. Sudo T., Sasaki H., Masuda N., Drewiak J. L., Electromagetic Iterferece (EMI) of System-opackage (SOP), IEEE Trasactios o Advaced Packagig, 27, 2, 2004, pp [5]. Mi L., Joe N., Drewiak J. L., DuBroff R. E., Hubig T. H., Va Dore T. P., EMI from Airflow Aperture Arrays i Shieldig Eclosuresexperimets, FDTD, ad MoM Modelig, IEEE Trasactios o Electromagetic Compatibility, 42, 3, 2000, pp [6]. Moss C. D., Grzegorczyk T., O'Neill K., Jiau K., A Hybrid Time-domai Model of Electromagetic Iductio from Coductig, Permeable Targets, IEEE Trasactios o Geosciece ad Remote Sesig, 44, 10, 2006, pp [7]. Carpes W. P., Picho L., Razek A., Aalysis of the Couplig of a Icidet Wave with a Wire iside a Cavity Usig a FEM i Frequecy ad Time Domais, IEEE Trasactios o Electromagetic Compatibility, 44, 3, 2002, pp [8]. Georgakopoulos S. V, Birtcher C. R, Balais C. A., HIRF Peetratio Through Apertures: FDTD Versus Measuremets, IEEE Trasactios o Electromagetic Compatibility, 43, 3, 2001, pp [9]. Hadjira B., Feham M., Abri M., Compact ad Itegrated Routig Photoic Crystals Structures Desig Usig the Twodimesioal FDTD Method, TELKOMNIKA Idoesia Joural of Electrical Egieerig, 1, 3, 2012, pp [10]. Leviata Y., Hudis E., Eiziger P. D., A Method of Momets Aalysis of Electromagetic Couplig through Slots Usig a Gaussia Beam Expasio, IEEE Trasactios o Ateas ad Propagatio, 37, 12, 1989, pp [11]. Sarha M. Musa, Matthew N. O. Sadiku, Fiite Elemet Approach for Coupled Striplies Embedded i Dielectric Material, TELKOMNIKA, 11, 1, 2013, pp

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