AUTHORS' ABSTRACT: Zhang et al. 2017 (IEEE #6850): To avoid the electromagnetic hazard (EMH) that exists in wireless power transfer (WPT) systems and ensure human safety, this paper proposes a normalization method of delimiting the EMH region (EMHR) of WPT systems. The analytic expression of electromagnetic field intensity near a WPT system is deduced and verified. It is determined that the electromagnetic field generated by an electrified coil is related to the coil radius, turns, current and resonance frequency. Based on the study of the electromagnetic field intensity of a reference coil, normalization factors are introduced to evaluate the corresponding value of other coils immediately. According to the international safety guideline, the normalization method of delimiting the EMHR is proposed. First, the EMHR of the reference coil is obtained and simplified as a cylinder. Second, according to the relation of the electromagnetic field between the reference coil and other electrified coils, the EMHR of other electrified coils can be deduced based on normalization factors. Finally, the EMHR of the WPT systems is synthesized by EMHR of the primary and secondary coils. The normalization method is verified with finite element analysis software. It is convenient to delimit the EMHR of the WPT system by using the normalization method.
AUTHORS' ABSTRACT: Dai et al. 2017 (IEEE #6851): As battery-powered mobile devices become more popular and energy hungry, wireless power transfer technology, which allows the power to be transferred from a charger to ambient devices wirelessly, receives intensive interests. Existing schemes mainly focus on the power transfer efficiency but overlook the health impairments caused by RF exposure. In this paper, we study the safe charging problem (SCP) of scheduling power chargers so that more energy can be received while no location in the field has electromagnetic radiation (EMR) exceeding a given threshold Rt. We show that SCP is NP-hard and propose a solution, which provably outperforms the optimal solution to SCP with a relaxed EMR threshold (1-µ)Rt. Testbed results based on 8 Powercast TX91501 chargers validate our results. Extensive simulation results show that the gap between our solution and the optimal one is only 6.7% when µ = 0.1, while a naive greedy algorithm is 34.6% below our solution.