Design guidelines to reduce the magnetic field in electric vehicles
Based on the measurements and on extensive simulation work the project arrived on the following design guidelines to, if necessary, minimize the magnetic field in electric vehicles.

Cables

  • For any DC cable carrying significant amount of current, it should be made in the form of a twisted pair so that the currents in the pair always flow in the opposite directions. This will minimise its EMF emission.
  • For three-phase AC cables, three wires should be twisted and made as close as possible so as to minimise its EMF emission.
  • All power cables should be positioned as far away as possible from the passenger seat area, and their layout should not form a loop. If cable distance is less than 200mm away from the passenger seats, some forms of shielding should be adopted.
  • A thin layer of ferromagnetic shield is recommended as this is cost-effective solution for the reduction of EMF emission as well EMI emission.
  • Where possible, power cables should be laid such a way that they are separated from the passenger seat area by a steel sheet, e.g., under a steel metallic chassis, or inside a steel trunk.

Motors

  • Where possible, the motor should be installed farther away from the passenger seat area, and its rotation axis should not point to the seat region.
  • If weight permits, the motor housing should be made of steel, rather than aluminium, as the former has a much better shielding effect.
  • If the distance of the motor and passenger seat area is less than 500mm, some forms of shielding should be employed. For example, a steel plate could be placed between the motor and the passenger seat region
  • Motor housing should be electrically well connected to the vehicle metallic chassis to minimise any electrical potential.
  • Inverter and motor should be mounted as close as possible to each other to minimise the cable length between the two.

Batteries

  • Since batteries are distributed, the currents in the batteries and in the interconnectors may become a significant source for EMF emission, they should be place as far away as possible from the passenger seat areas. If the distance between the battery and passenger seat area is less than 200mm, steel shields should be used to separate the batteries and the seating area.
  • The cables connecting battery cells should not form a loop, and where possible, the interconnectors for the positive polarity should be as close as possible to those of the negative polarity.

Published January 6, 2014

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Coordinator: Andreas Vogl , SINTEF FP7
Duration: 1st May 2011 - 1st February 2014
EU contract FP7-SST-265772 in the Sustainable Surface Transport call in Framework Program 7.