Numerical assessment of EMF exposure of a cow to a wireless power transfer system for dairy cattle

In this paper, we assessed the exposure of a cow to the electromagnetic fields (EMFs) induced by a wireless power transfer (WPT) system working at 92 kHz in a dairy barn. Cow exposure to the radiated EMFs was evaluated and compared to safety guidelines. We modeled a realistic WPT system for dairy cows in Sim4Life, a 3D electromagnetic simulation tool. We validated the model with electric field measurements; simulated fields deviated on average 6% from measured fields. We used the proposed WPT model to evaluate the stimulation and thermal effects based on the internal electric field and the specific absorption rate (SAR), respectively. Results showed that the exposure mainly varied with the distance of the transmitter to the body: variation of 5 dB of the induced electric field when the transmitter was set at 20 cm and 10 cm from the body. The distance of the receiver to the body influenced the exposure less (10%). We also compared the exposure with the limits provided by the International Commission on Non-Ionizing Radiation Protection (ICNIRP). The internal electric fields were more conservative than SAR, which showed values far below exposure limits

Exposure and neuronal excitation by wireless power transfer for auricular vagus nerve stimulation

Inductive wireless power transfer (WPT) can be used to power implanted as well as wearable medical devices, such as a percutaneous auricular vagus nerve stimulation device. This device is placed on the neck of the patient and is connected to needle electrodes in the auricle. With regard to WPT, limitations on exposure to electric and magnetic fields should not be exceeded. Furthermore, these fields should not interfere with the therapeutic goal of stimulation, i.e., with unintended peripheral nerve stimulation in the auricle. These effects are investigated by numerical simulation of induced internal fields in the head and neck and, for the first time, subsequent neuronal simulations, quantifying the potential of neuronal excitation by the fields in the auricle in particular. Internal electric field values were in the range of 1\%-5\% of the ICNIRP 2010 basic restrictions, and current densities were in the range of 30\%-45\% of the ICNIRP 1998 basic restrictions, indicating that all tested configurations are conform the guidelines. Basic restrictions on heating of tissue turned out not to be of relevance for this application. Thresholds for neuronal stimulation were two orders of magnitude higher than the induced fields, suggesting that there is almost no risk for unintended stimulation