WEMS is a EUREKA project with partners from Sweden, Switzerland, Belgium and Austria. There will be a EU-directive on workers exposure to electromagnetic fields demanding that the employers shall show compliance with the limits in the directive. The directive covers the whole frequency range from 1 Hz up to 300 GHz. Limits for radio frequency field already exist in several countries. The main problems with the implementation of the directive will be in the low frequency range. The limit in this frequency range is expressed as the induced electric field strength in the body, which only can be calculated.
Sweden is responsible for one work package in the project Development of Procedures for Automotive Industry
The Swedish partners are Department of Signals and Systems, Chalmers, Yngve Hamnerius, Volvo Cars, Kjell Attback and Torptronics, Tomas Nilsson.
We are performing experimental evaluation of exposure scenarios within cars. We have developed methods for measurements of transients.
For complex signals, with several frequency components, the directive gives rules for a summation of the frequency components. This summation leads to an overestimation of the fields in many cases. We have developed measurement methods that avoids this overestimation,
We are studying the compliance for inhomogeneous fields by calculating the induced electric field strength in the body. These calculations show how much the action value can be exceeded, before the limits are violated. We analyze real cases, building on measurement of fields from conventional, hybrid and electric cars.
Figure: Example of a measurement of the starter motor current in a car.