Electromagnetic interference (EMI) in E-vehicles
The cabling system in a car is comparable to the human nervous system. As long as it works perfectly, no one recognizes it. If it fails, it’s a disaster. Often several processes and applications are impacted or stop functioning altogether.
The enormous increase of electrical and electronic components in hybrid and electric vehicles places increasing importance on the electrical distribution system with respect to quality and reliability of data transmission. Distribution systems use different standards of high-speed data transmission. A flood of data has to be processed, reliably transmitted and the system has to avoid interferences and disturbances.
Currently, up to seven CAN bus systems are incorporated into a vehicle. High amounts of data are transmitted by Flexray and MOST Systems, additional USB and Ethernet links. All systems transmit different amounts of data and have different data transmission standards.
This flood of data in vehicles and the high amount of data transmission systems requires complex data management – and equally sophisticated technical hardware. For this reason, dedicated characteristics for electromagnetic interferences (EMI) and electric and electronic components in hybrid and electric vehicles are required.
In these vehicles, electrical shielding is also required to avoid electromagnetic interference between components and functions. USB interfaces, for example, which are incorporated into a growing number of vehicles to attach mobile music players, have to be shielded to avoid interferences between functions and electrical components.
Shielding is state-of-the-art and the subject of ongoing optimization. The challenge for developer is miniaturization, more cost-effective design and weight reduction, and uniform quality levels for all production plants worldwide.
At the beginning of the e-mobility movement, we see additional challenges. Beside the existing 12V electrical system in vehicles, which is required for driver assistance systems, radios, navigation systems and several other features, a high-power electrical/electronic system will be integrated into electric vehicles. This result will be a system requiring 300 – 400 volts or more.
The high-current, high-voltage operation characteristics of electric vehicles will have an increasing impact on electrical/electronic components in vehicles by electromagnetic interference (EMI): With electric drive system we implement a potential source of disturbance in the vehicle. This disturbance will effect radio reception to a marginal effect, which will be noticeable to the consumer. The high voltage also effects several data transmissions of the low-voltage systems related to assistance – or navigation systems. Impacts to vehicle safety systems have to be protected absolutely.
The effect of the influence of the high voltage electrical distribution systems is subject of a Delphi research project at the company’s technical center in Wuppertal. Delphi is an expert in electrical/electronic architecture for traditional applications, as well as hybrid and electric vehicles.
Fig. 1: Test Equipment for electromagnetic shielding test for high voltage and data transmission cable and connectors
More research is needed on the topic of EMI and its effect on hybrid and electric vehicles, particularly on the necessary separation of high and low-voltage systems. The University of Wuppertal has joined forces with other research partners to investigate a simulation method for high-voltage distribution systems. Delphi is partner of this project and expects to gain new knowledge for the design of future electric/electronic distribution systems. The research will look at questions such as: How do cable, connectors and electronic components need to be shielded to avoid electro-magnetic interferences (EMI)? Currently the cables are shielded individual. Is this sufficient or necessary? How can the weight of each component be reduced? Where should high-voltage cables be placedin vehicles, eventually without shielding, to avoid disturbances and ensure reliable operations? Could we use the chassis as a shielding element?
Fig. 2: Simulation of electric and magnetic field of isolated wires
The power supply cables could also be reduced by considering dynamic power consumption. The shielding could be reduced according shielding requirements. The investigation of new conductor and isolation materials will start on a simulation level before expensive hardware samples are produced and long test processes begin. Simulation methods conducted over the next three years will bring many answers to these questions and allow Delphi to further improve its product offering to hybrid and electric vehicle electrical/electronic architecture.
A relevant factor is weight. In current conventional vehicles, the percentage of cables, electronic and battery is about six percent of total vehicle weight. This percentage will rise to a quarter of vehicle weight in the case of fully electric vehicles. The optimization of weight is another of the more interesting research areas for these emerging vehicles
About the author: Reinhard Felgenhauer is working at Advanced Engineering, Delphi Packard Electrical/Electronic Architecture