Electromagnetic Noise Analysis of High-Voltage …

1 28 Electromagnetic Noise Analysis of High-Voltage Wiring HarnessesFEATURED TOPIC1. IntroductionHybrid electric vehicles (HEVs) and electric vehicles(EVs) are becoming popular these days. Sumitomo WiringSystems, Ltd. has developed and commercialized low- andhigh-voltage wiring harnesses*1for use in HEVs and wiring harnesses connect the battery, inverterand motors installed in an HEV or EV, as shown in Fig. carry a high voltage and a large harnesses are required to be highly reliability indicator is Electromagnetic compatibility(EMC)*2. Specifically, wires in the High-Voltage wiring har-ness connecting the inverter and motor carry a high ACvoltage and current. Electromagnetic filed Noise generatedby them has the potential to produce adverse effects in-cluding the malfunctioning of nearby electrical/electroniccomponents.

2 Consequently, it is necessary to draft a relia-bility design to reduce such Electromagnetic field ensure and improve reliability in the developmentstage, Sumitomo Wiring Systems promotes the use of CAE*3in the early design phase. Presently, the Company uses CAEanalyses to determine the flexural durability of wiring har-nesses (service life prediction with respect to wire break-age resulting from repeated bending) and to estimateprotective grommet insertion and removal forces. More-over, studies are underway on the application of CAE tothe estimation of Electromagnetic field Noise generated bythe High-Voltage wiring harness connecting the inverterand the motor. The present paper reports on the develop-ment of a CAE Analysis technique simulating an estimationof the Noise emitted by High-Voltage wiring High-Voltage Wiring Harness Noise EmissionEstimationFigure 2shows the general structure of a high -voltagewiring harness used in HEVs and EVs.

3 Three wires are pro-vided to carry a three-phase alternating current. One endof the three wires has terminals that connect to an other end has terminals for connection with a , the wiring harness consists of the three wiresbound at both ends and an antinoise shielding , in an automobile, wiring harnesses are laid in abent position. The shielding member that covers the wiresis made of a braided metal wire to be bent with ease, ateach end of which are flat metal connectors to be securedto the inverter and the motor, EMC characteristics of wiring harnesses and otherelectrical components in HEVs and EVs are finally esti-mated by individual automakers in an onboard , auto parts suppliers, including wiring harnessHigh-voltage wiring harnesses that connect an inverter to a motor in a hybrid car need to be designed to suppresselectromagnetic emissions that can interfere with other electric devices nearby when alternating currents flow throughthe wires.

4 To address this issue, we have studied the application of computer-aided engineering (CAE) Analysis to theelectromagnetic shielding design of these harnesses. This paper reports an example application of CAE Analysis to theestimation of Noise emissions and discusses the relationships between the Electromagnetic field and the voltage orcurrent in the : wiring harness, hybrid car, Electromagnetic Noise , CAE Analysis , shieldingElectromagnetic Noise Analysis of High-Voltage Wiring HarnessesKei SUNAGA*, Koji MIYAJIMA and Yoshiyuki MIYAZAKIFig. wiring harness layoutFastener(plastic) TerminalConnection withmotor WireMotorConnection withinverter InverterShielding memberConnectorFig. drawing of High-Voltage wiring harnesssuppliers, need to estimate whether unmounted parts meetthe specifications established by individual automakers onthe basis of the applicable international standards.

5 Eachsupplier has its original EMC estimation 3shows the concept of a test system used to es-timate High-Voltage wiring harness Noise emissions. A metalsheet known as the ground plane is placed on the work-bench. A High-Voltage wiring harness is connected to twometal housings secured on the ground plane. An AC powersupply is connected to the terminal at one end. A terminat-ing resistor is connected to the terminal at the other 3 (a)shows the estimation system in which theshielding member is removed from the High-Voltage wiringharness. The voltage and current supplied by the AC powersupply to the estimation system generate an electromag-netic field in the surrounding space. Under this condition,a probe (antenna) is placed in a predetermined Noise is measured at different frequenciesof the AC power 3 (b)shows the estimation system with a shield-ing member fitted.

6 The shielding member reduces theelectric field and the magnetic field generated in the sur-rounding space. Differences in Noise levels measured in dBwith the two estimation systems are known as shielding ef-fects, which are used as an indicator of wiring harness noiseemission characteristics. The frequency band for estima-tion is generally from 10 kHz to 1 Wiring Harnesses: Voltage, Current and Electromagnetic NoiseThe voltage and current carried by the wiring harnessestimation system generate an electric field and a magneticfield in the surrounding space. The following is the basictheory useful for understanding the relationship betweenthe voltage and current carried by a wiring harness and theelectromagnetic Noise in the space surrounding the charge and current distributions that causeelectromagnetic Noise fall into two types, as shown in Fig.

7 Dipole type is comparable to the charge and cur-rent distributions of a linear antenna. The loop type is com-parable to the distribution of a closed loop current. Thetwo sources of Noise generate an electric field and a mag-netic field in the space close to themselves in the directionsshown in Fig. 4. Figure 5shows theoretical expressions forelectric and magnetic fields generated by the loop items inversely proportional to the cube of R, thesquare of R and R, where R is the distance between the ori-gin and the measurement point shown in Fig. 5, are knownas the quasi-static field, the inductive field and the radia-SEI TECHNICAL REVIEW NUMBER 79 OCTOBER 2014 29AC powerMetal housingTerminating resistorAC currentGround plane (metal)GroundAC voltageMagnetic field(dashed lines) External Electromagnetic field reduced by shielding member Ground(a) with shielding member removed (b) with shielding member providedFig.

8 Wiring harness Noise emission estimation systemFig. types of electrical charge and current distributions that cause Electromagnetic field noiseFig. expressions for electric field E and magnetic field H generated by loop type current in its surrounding spacetion field, direction of the magnetic field generated by theloop type shown in Fig. 4indicates that, when = 90 , themagnetic field determined by the theoretical expression inFig. 5is zero in the r direction (cos = 0) and increases inthe direction (sin = 1).Meanwhile, the theoretical expressions for the electricfield and the magnetic field generated by the dipole typeare obtained by manipulating the theoretical expressionsfor the loop type.

9 More specifically, the magnitude of themagnetic dipole Io S (Io: current; S: area enclosed by loop)is replaced by the magnitude of the dipole qo l (qo: charge;l: distance between charges) to interchange the electricfield and the magnetic field (with the coefficients andminus signs altered). The left part of Fig. 4shows the re-sultant electric field and the resultant magnetic sum, the electric and magnetic fields generated bythe dipole type correspond in an interchangeable way tothe magnetic and electric fields produced by the loop the relationship between the distance R and thewavelength is expressed by R > /2 , the radiation fieldbecomes dominant in the theoretical expressions and theratio of the electric field to the magnetic field takes theidentical value ( )

10 In both types of Noise R < /2 , the quasi-static field and the inductivefield become dominant in the theoretical this condition with the dipole type, the ratio of theelectric field to the magnetic field is larger than that in thecase where the radiation field is dominant, while with theloop type, the ratio is smaller than that in the case wherethe radiation field is dominant. Consequently, when twotypes of Noise source are present concurrently, the dipoletype is the major source of electric field Noise at positionsclose to the Noise sources (R < /2 ), while the loop typeis the major source of magnetic field Noise at the same the above-mentioned relationships as basicknowledge, this section discusses Electromagnetic fieldnoise examined in High-Voltage wiring harness Noise emis-sion estimation.