Interference from Unshielded HV Harnesses with Realistic Groundplane Models

In a vehicle, unintended electromagnetic coupling among sensitive components such as antennas etc. needs to be suppressed to prevent the interference to cables. The cables for power and signal transmission are, therefore, only allowed to be packed in each other’s vicinity after proper shielding. As the shielding decreases the payload for a given vehicle design and increases its cost, it is very relevant to shed light on alternative packaging omitting shielding completely. Accordingly in this report, computations based on 3-dimensional transmission line matrix method will be launched to execute parameter sweeps comprising intercable distance, cable distance to groundplane, cable length, and signal cable termination impedance. A Vector Network Analyzer based experimental study to verify the computational approach is presented. Subsequently, crosstalk effect of realistic groundplane from a vehicle concept is also compared to a simple planar groundplane using 3D Transmission Line Matrix approach. It will be shown that the crosstalk will be kept below the limits as specified by the standards and internal OEM requirements with minimal intercable spacing, eliminating the cable shielding while reducing the environmental footprint.

I. Introduction

Transport electrification is contributing to reduced emissions and improved urban life quality. Battery Electric Vehicle (BEV) are designed in the intersection of multiple disciplines by trading-off the optima. As a system-of-systems, contemporary vehicles involve many sensitive equipment active at several voltage levels. Beyond the natural phenomena, electromagnetic sources of man-made origin generate electromagnetic waves with rich content and may induce interference with sensitive BEV equipment. Attention is needed to prevent the radiation from antenna-mode current on the vehicle cable harness from radiating into surroundings as electromagnetic pollution. Above the legislative obligations, fail-safe operation requires precise dimensioning for electromagnetic design. Hence unintended electromagnetic coupling needs to be suppressed and the critical equipment should be designed conform with the actual law. Standards issued by international committees help in establishing the framework for the design and testing of the equipment. Equipment involved in the BEV are packed efficiently in compact architectures, which may lead to crosstalk among cables. Additionally, future systems comprising faster switching speeds by means of SiC MOSFETs, the crosstalk is forecasted to be a more serious engineering challenge [1]. Commonly in the automotive industry, strategies derived from the CISPR25 standard [2] safeguard radio communication from noise from switching devices, as well as all the equipment sensitive to interference. BEV may comprise many antennas and as a precaution effort is focused into relevant radio frequencies coinciding with FM, DAB, etc. As shown in Fig. 1, the cables are, therefore, usually shielded and they are allowed to be packed in each other’s vicinity independent from the cable content. As the shielding decreases the payload for a given BEV design and increase its cost, it is very relevant to shed light on alternative packaging. A recent Nature article [3] reports that, when presented with a problem, humans are hardwired to add things instead of subtracting. Thus a BEV design which allows for subtracting shielding will have numerous advantages including reduced environmental footprint. In suppressing the crosstalk in BEV, the packaging solutions of cables and their equipotential boundary may lead to optimum Electromagnetic Compatibility (EMC), instead of using shielding. Therefore combining the actual groundplane and cable harness topologies as whole to prescribe crosstalk-minimized installation solutions is an approach worth of quantification.