12/03/2014
Human Exposure to Close-Range Resonant Wireless Power Transfer Systems as a Function of Design Parameters
Xi Lin Chen, Aghuinyue Umenei, David Baarman, Nicolas Chavannes, Valerio De Santis, Juan Mosig, and Niels Kuster, IEEE Transactions on Electromagnetic Compatibility, Volume PP, Issue 99, pp. 1-8, online March 12, 2014
In this study, we investigated human exposure to close-range wireless power transfer (WPT) systems with coil diameters of up to 150 mm operating in the frequency range 0.1 – 10 MHz. We propose the use of approximation formulae for making conservative estimates of human exposure with respect to the most stringent exposure guidelines. The approximation has been verified for two pre-commercial prototype WPT systems, the first of which, a 5 W system operating at 100 kHz, was evaluated as part of this study. The second system to be verified, which operates at 6.78 MHz with a nominal current of 5.4 Arms was reported in a separate study.
The scientific and technical impact of this study can be summarized as:
- Approximation formulae – including scaling factors derived from numerical simulations that take variations of complex human anatomies into consideration – are proposed for making conservative estimates of human exposure with respect to the most stringent exposure guidelines.
- Comparisons of human body exposure from WPT systems operating at very different frequency bands have been performed.
- Based on the results obtained, the optimal operational frequency range for WPT with respect to compliance with exposure safety guidelines is between 1 and 2.5 MHz.