Analysis of Shielding Effectiveness of HV Cable and Connector Systems used for Electric Vehicles

Transcription

1 Analysis o hielding Eectiveness o HV Cale and Connector ystems used or Electric Vehicles Aid Mushtaq, tephan Frei Department o Electrical Engineering and I U Dortmund University Dortmund, Germany aid.mushtaq@tu-dortmund.de Kerstin ieert, Jörg Bärenänger EMC est NW GmH Dortmund, Germany sieert@emc-test.de Astract In order to understand and design etter shielding eectiveness (E) o HV cales and connectors or electric vehicles (EV), appropriate measurement methods are required. he ranser Impedance is usually measured using riaxial or Line Injection method. Based on a simpliication o riaxial method, a Ground Plate measurement method has een proposed to evaluate E o cales and the cale-connector system. esults o proposed method have een compared to riaxial method or cale only and Line Injection methods or the cale-connector system. Dierent approaches to analytically model the transer impedance have een discussed. Dependency o weave angle and raid wire thickness on the shield perormance has een simulated in order to etter understand cale shield design. he document gives an overview o mathematical modeling techniques and existing measurement methods or. It proposes a simpliied approach or evaluating or the complete HV cale connector system used in EV. Keywords shielded cales, shielding eectiveness; elecrical vehicle; HV system; transer impedance; EM modeling I. INODUCION Cale and connector system or Electric Vehicles HVapplications should have an eective shielding. Various measurement setups have already een proposed to determine the shielding eectiveness o a HV cales. Most o them like the Line Injection method and the riaxial method [] originate rom the testing o communication cales. HV-connectors are diicult to measure due to the large size. In order to ind appropriate methods or HV automotive cale-connector systems, the known methods are systematically compared in this paper. riaxial and Line Injection methods have een used to measure transer impedance. Based on typical automotive measurement setups a Ground Plate method was developed and investigated. Its measurement results are compared with riaxial method and Line Injection method or cale only and Line Injection method or the cale-connector system. It could e shown that the Ground Plate method can e a simple and roust possiility to speciy the shielding properties o a cale connector system. o support the measurement results, investigations in analytical models ased on Vance, yni and Demoulin have een perormed. he eect on the transer impedance y varying the shield parameters was investigated. he simulation results have een compared with existing and proposed EMC test methods. II. BAIC OF HIELDED CABLE As per [] simple shielded cale can e electromagnetically modeled and represented using inner and outer circuits as shown in ig.. Inner conductor i Inner circuit Interior o the cale shield Exterior o the cale shield Outer circuit Ground plane V i = I I i Ii = Y V V I Y i I V i V Y Fig.. Electromagnetic model o a shielded cale It can e seen that inductive coupling can e represented as transer impedance, whereas the capacitive coupling can e represented as transer admittance Y. Electrical (capacitive) coupling and magnetic (inductive) coupling can e deined as (, ): ' V i ( /m) ranser impedance I x I i =0 ' Y V Ii x V i =0 ( /m) ranser admittance Oten transer admittance is assumed to e small. But or cales with raid shields, transer admittance might e important. When requency increases oth the electric and magnetic ields can penetrate through the apertures thus oth and Y are important to e conred. he apertures in the raid shield can e seen as small dipoles excited through the comination o electric and magnetic ields occurring in the shield. Further details o such aperture polarizailities due () ()

2 to electric and magnetic coupling are discussed in []. Out o two standard measurement methods descried urther in section III, Line Injection method has the aility to measure comined eect due o inductive and capacitive coupling. III. MEAUEMEN EUP FO HV YEM he most commonly used measurement setups are the riaxial method and the Line Injection method [, 3] which are descried shortly in the ollowing susections. A. riaxial Method According to [] riaxial method can e used or measuring the transer impedance o shielded cales at least up to 30 MHz. Figure shows the equivalent circuit o the triaxial test setup. Outer circuit laeled with suscript, consists o outer shield surace and triaxial tue (cylinder) and measures the coupled signal at port. 0 = Port : ource Where: V Center conductor Inner Circuit Inner shield Outer shield L COUPLING Cylinder V F Outer Circuit U F = F = F U N Port : eceiver Fig.. Equivalent circuit o riaxial test setup 0 = N, F: Load resistance o inner circuit at the near and ar end F, N: Load resistance o outer circuit at the ar and near end U : Voltage ed into the inner circuit at the near end U N, U F: Voltage coupled into the outer circuit at near and ar end U U U U N N F N F F N N N U I ku m F, Meas he inner circuit (including cale under test), laeled with suscript, is ed rom source port laeled o network analyzer (). From ig. and using (3-5) it can e seen how parameters are used to ind. U U I L k L U F N F N C N m C F, meas ( db) F N F 0 k L N m C 0 (3) (4) For simplicity and non-reerence measurements, F can e neglected and F can e taken as 50 Ω or matched load. hen (4) gets simpliied to: 50 ( db ) 0 0 (5) k L m C B. Line Injection Method As shown in ig. 3, the outer circuit, laeled y suscript, comprises o Line Injection circuit (Line Injection wire and outer shield o the cale under test). It is ed rom source port o. he inner circuit laeled y suscript, consists o the cale under test is terminated with a matched load, where the induced voltage is measured at port. port : eceiver 0 = F U,e Parallel wires Outer circuit Outer shield Inner shield Inner circuit Inner conductor U N U,ne 0 = N ~ port : ource F Fig. 3. Equivalent circuit o Line Injection measurement setup he main dierence etween Line Injection and riaxial setup is that, in riaxial method the transer admittance (through capacitance) is short circuited at the near end o the outer circuit. Whereas in the Line Injection oth and Y are acting on the cale, we can measure equivalent transer impedance E. Using the measurement process descried in [, 3], ater matching oth inner and outer circuits, we have: U L I n E n c F kmi U, n c, or L U n E n c F ku m, n (6) L (7) A n 0 E n 0 (8) Lk c m Usually the cale shields are not uniorm, so it is recommended to perorm the measurements at dierent angles. Here three angles 0, 0 and 40 were used. C. Ground Plate method Based on the simpliication o riaxial method, a ground Plate method has een proposed which is explained in this section. In riaxial method, a hollow cylinder is used which completes the outer circuit. Based on every DU s size and shape, cylinder has to e customized i.e., re-designed and

3 t [mohm] manuactured along with complex connections in order to accommodate the DU properly, which can make riaxial method costly and time consuming. o to overcome this prolem, to conr voluminous connectors, and to comply more with standard automotive EMC set ups it is proposed to replace cylinder with ground plate. his does not change the network circuit as shown in ig.. Mathematical analysis o the network circuit has een derived conring input and relected waves at ports and using ig.. V IL F Coupling 0 V I L 0 F where (-parameter)= /a a F N N F Coupling 0 V (9) F F N F ILCoupling Lcoupling N (0) Generic ormulation or is given in (0). Additional simpliication o Ground plate method has een suggested y varying termination loads. F Lcoupling F Lcoupling N F N () I F = 0, is calculated using () and i oth F and F =0, then () can e used. F N L coupling N N L coupling ABLE I. F PAAMEE OF HE INVEIGAED HV CABLE Geometrical parameter ymol Value Cross section o the inner conductor A 35 mm² Diameter o the raid D 0.4 mm Diameter o single raid wire d 0. mm Numer o wires in carrier n 8 Numer o carriers N 4 Weave angle Ψ 30 degrees Conductivity σ 5.8x0 7 /m Coupling lengths used Lc 0.4 m &.0 m () Figure 4 shows DU used or cale-connector system measurement. peciications o the measurement setup can e ound in tale. Cale-connector system: Cale =~000mm Connector ox=40mm ABLE II. 40 mm Fig. 4. Cale-connector system 40 mm 45 mm PECIFICAION FO HE MEAUEMEN EUP Measurement setup ymol Value For all measurements & 50 Ω (Port input impedance) N riaxial method Line Injection method Ground Plate method Matched setting hortcircuit setting IV. km 0.6 F F 3 Ω 80 Ω Length 0.4 m & m cale only F 3 Ω m cale only &.4 m caleconnector km 0.6 system F F 0 F 0 F 0 50 Ω EUL & DICUION 0.4 m cale only &.4 m caleconnector system A. Measurement results With riaxial method or m cale without a connector, two measurements were made, one without F (simple / open) and other measurement result with F. Using Line Injection method or m cale only, measurements at three dierent angles (0, 0 and 40 ) were perormed. 0 - riaxial method & Line injection method riaxial imple riaxial with 0 degree LIM 0 degree LIM 40 degree LIM Fig. 5. riaxial method and Line Injection comparison

4 t [mohm] t [mohm] In ig. 5 it is shown that the transer impedance measured rom the riaxial method can e used up to 60 MHz maximum with impedance matching at and up to 0 MHz with riaxial (simple), whereas transer impedance measured rom Line Injection results gives correct result up to 00 MHz ater which irst resonance take place. From the dierence in results or riaxial measurements (simple and with ) it can e seen that mismatches cause decrease in requency range o accurate results. For Line Injection method it can e seen, measurements with dierent angles have very slight variation, especially in this case, when the DU has symmetrical structure. It can e deduced that, at lower requencies, oth riaxial method and Line Injection method results are equally appropriate, whereas at higher requencies, Line Injection method is etter as at higher requencies electric ields (capacitive coupling) can also penetrate through the apertures o the raid. o veriy Ground plate method, its measured results or 400 mm cale were compared with reerence riaxial method and an 40 mm cale-connector system was compared to Line Injection method. Comparison o Ground Plate method with riaxial method: Cale only riaxial method GPM hortcircuit GPM Matched Fig. 6. Comparison o Ground plate method with riaxial method Figure 6 shows comparison o Ground plate method with riaxial method or a cale with 0.4 m length only. It can e oserved that Ground plate method with short circuit setting can produce similar results as riaxial method. Fig. 7. Line Injection measurement setup on cale-connector system o investigate Ground Plate method on cale-connector assemlies, irst Line Injection method is implemented on cale-connector system as shown in ig. 7, this is assumed as a reerence measurement result. Comparison 0 4 o Ground Plate method with Line Injection method: Cale-connector system LIM NE LIM FE GPM Matched GPM hortcircuit Fig. 8. Comparison o Ground Plate method with Line Injection method on cale-connector system (40 mm) In ig. 8, it can e oserved that, oth settings o Ground plate method have higher measured value or than the Line Injection method. Also the DC resistance seems to e higher, indicating a mechanical connection prolem. It is assumed there is a solution, ut more analysis is required in order to improve Ground Plate method. V. ANFE IMPEDANCE CALCULAION As the HV cales used are raided shield cales, only models or the raided shield are conred. In this section, models or simulating the raided shield cales, ased on Vance, yni and Demoulin are presented and discussed [4-6]. he eects o particular geometrical parameters which aect the measurements o shield perormance are shown. Beore analyzing the models, it is necessary to understand the asics o raided shields used or electromagnetic shielding purpose. As analyzed in [3], a metallic raid can e descried completely y 6 parameters o a cale shield, these are Braid shield diameter (D 0 ), raid wire diameter (d), numer o carriers in shield (C), numer o wires in single carrier (n), conductivity o the raid material ( ), and weave angle ( ). A. Vance Model As shown y Vance [7], transer impedance o a raided shield can e calculated as: jl (3) t d h Where d covers the diusion o magnetic ields through the sheath and hole inductance L h covers the penetration o magnetic ields through the apertures in the metal raids. d ( jd ) / 0 sinh[( jd ) / ] (4) Where d is raid-wire diameter and 0 is the per-unit-length raid resistance, skin depth ( ) as descried y (5): 0 (5)

5 t [mohm] t [mohm] t [mohm] 4 0 d nc cos (6) In [8, 4] a simpliied relationship or L h has een used: d 0 C Lh exp cos DM (7) Where is the hole width. B. yni Model In addition to Vance model, [9, 0] yni proposed (8), in which an additional term is added or conring the eects o raid inductance. j( L L ) (8) t d h Where L is the transer inductance which arises due to the woven nature o the raid. It is the magnetic leakage occurring at the junction o the raids composing the carrier wires. 0h L tan (9) 4 D M Where D M is the mean raid diameter i.e., D M = D 0 d and h is the radial spindle separation. D. Comparison o imulation Models All three simulation models have een implemented using the parameters given in tale. Comparison o simulation models is shown in ig. 9. It can e seen that or the investigated particular raided shield cale, oth yni and Vance models are almost similar whereas Demoulin model has dierence due to the additional k and terms added to represent the opposing eddy currents lowing in the raided shield wire which varies the curve with increasing requency. Ater cuto requency, diusion and inductive eects play dominant role causing variation in. Figure 9 shows also comparison o reerence riaxial method with simulation models Comparison Comparison o riaxial o riaxial with simulation with imulation models: models Cale only Vance yni Model Vance Model yni Demoulin Model Demoulin riaxial method@udo Model riaxial method Cut-o requency ill Cut-o requency, yni and Vance models give constant DC, whereas Demoulin, has early rise due to added KK actor [Hz] Fig. 9. Comparison o riaxial method with simulation results It can e oserved that the simulated result or Demoulin model is very similar to the measured results. Figure 0 shows slight dierence etween Demoulin model, riaxial and Ground Plate method with short circuit setting. C. Demoulin Model In [, ], Demoulin has proposed (0), a generic model or the raided shield cale transer impedance, which consist o our terms where the additional term is urther deining porpoising eect with depending o on : j 4 t d h j L k e j L (0) Comparison o riaxial with simulation models: Cale only Demoulin Model riaxial method GPM hortcircuit Where sign o L is positive or > 45º and is negative or < 45º. A real co-eicient k which depends on raid parameters and symmetry was introduced. I = 45º, the inductance due to the woven nature o the raid is zero i.e., k 0. For < 45º the ollowing simpliied model can e used: j 4 t d k e j L () where.6 n k.arctan.sin. ncd 3 () Fig. 0. Comparison o riaxial and Ground plate with Demoulin) E. Variation o Geometrical Parameters In [3] dependency o on spindle distance variation (h) has een discussed along with other parameters. In this paper the two actors weave angle and raid wire diameter d, which indirectly aect the cost o the cale, are analyzed. Braid wire thickness was varied rom 0. mm to 0. mm and weave angle rom 0 to 35 in the simulation model. As shown in ig. and also evident rom (8-4) plays an important role and can e adjusted to give lowest dip in the curve or optimized raid. For optimized raids, inductive eects are adjusted in order to cancel out each other to give a lowest value to. In this DU case, 9 degree is the

6 t [mohm] DC resistance t [mohm] optimized value o the weave angle, while keeping all other parameters same. Demoulin Eect o variation in weave angle Weave angle rom 0 till 9 degrees decrease Weave angle rom 9 till 30 degrees again increases Lowest value or this DU achieved with Optimum weave angle at 9 degree Fig.. Eects o variation in weave angle 0º to 35º Variation o diameter o single raid wire has greater eect on the resistive part and diusion part (skin eect) o the transer impedance as shown in ig.. For good shielding and achieving lower values o, raid wire diameter can e optimized against the weight and cost requirements. Demoulin Eect o variation in raid wire diameter Increasing raid-wire diameter decreases the DC resistance and skin eect part o o the hield Fig.. Eects o variation in raid-wire diameter 0. mm to 0. mm VI. CONCLUION he dierent measurement methods or shielding perormance o shielded cales have een analyzed and compared. In order to cater or oth cale and large connector systems, a new Ground Plate method has een proposed, which has een compared with riaxial and Line Injection methods or oth cale only and cale-connector systems. For riaxial method, measurements up to 60 MHz are possile. For Line Injection method three dierent angles were investigated or measuring the transer impedance. As the cale was coaxial having symmetrical ield distriution, the measured shield perormance at all angles is similar. Method seems to e valid or HV cales up to approximately 00 MHz. When comparing oth riaxial and Line Injection methods together, or lower requencies elow 50 MHz, they give similar results. Aove Line Injection method provides etter results. Proposed Ground Plane method has een compared with riaxial method with similar results with short circuit setting or the cale. For cale connector system comparison was done etween Groud Plane method and Line Injection method. Here a dierence o m till cut-o requency, and early rise in with requency could e oserved. It is assumed that there is a connection prolem in setup. More analysis is required in order to reduce the dierences. Furthermore simulation models or HV raided shielded cales have een reviewed and veriied with measurements. Dependency o transer impedance on the weave angle and raid-wire diameter has een analyzed. ACKNOWLEDGMEN he work in this paper was partly unded y the European Union (EFE), the Ministry or Economic Aairs, Energy and Industry o North hine-westphalia and the Ministry or Climate Protection, Environment, Agriculture, Conservation and Consumer Aairs o North hine-westphalia as part o the IE-IN project with reerence numer EM-0A. EFEENCE [] Communication cales peciication or test methods Part-6 o EN5089 : Electrical test methods o Part -6 Electromagnetic perormance (English version). [] esche, F., Ianoz M., Karlsson,, EMC analysis methods and computational models, John Wiley & ons, New York (997) [3] chippers, H., Verpoorte, J, Otin,., Electromagetic Analysis o Metal Braids, Proc. O the 0 th Int. ymposium on Electromagnetic Compatiility (EMC Europe 0), York, UK, pp , eptemer 6-30, 0 [4] Hoet, L. O., Hostra, Measured electromagnetic shielding perormance o commonly used cales and connectors, IEEE ransactions on Electromagnetic Compatiility, Vol. 30, No. 3, August 988. [5] Dole, C.W., Kincaid, J.W., creening Attenuation o Long Cales, paper no.04-04, IWC 49th,(Nov. 000) [6] hou, G., Gong, L., An improved Analytical Model or Braided Cale hields, rans. on EMC, 3(), IEEE, 6-63,(May 990) [7] Vance, E., hielding Eectiveness o Braided-Wire hields, rans. on EMC, 7(), IEEE, 7-77, (May 975) [8] Akcam N., Karatas, M., Measurement o transer impedance and screening attenuation eects on cales using tri-axial method, IJPE Journal, issue 0, Vol. 4, No.,03-07, March, (0) [9] yni, M., he transer impedance o coaxial cales with raided conductors, Proc. EMC ymp. Wroclaw, Poland, 40-48, (976) [0] ali,., An Improved Model or the ranser Impedance calculations o raided Coaxial Cales, rans. on EMC,IEEE, 33(),39-43,(99) [] Demoulin, B., Kone, L., hielded cale transer impedance measurements, IEEE-EMC Newsletter, Fall 00, pp [] Demoulin, B. Kone, L., hielded cale transer impedance measurements high requency range 00 MHz - GHz, IEEE-EMC Newsletter, Fall 0, pp [3] Bluhm, M., Peroglio, E., Pierucci, G., quizzato, V., ich,.e., "Measurements o transer impedance with the line injection method on cales and connectors," IEEE International ymposium on EMC 000, vol., pp.599,604. [4] Coates, A., Gavrilakis, A., Al-asadi, M., Duy, A. P., Hodge, K., Willis, A., EMC ehaviour o cale screens. ource