Quasistatic Approximation for Exposure Assessment of Wireless Power Transfer

Laakso, Ilkka; Shimamoto, Takuya; Hirata, Akimasa; Feliziani, M.

doi:10.1587/transcom.e98.b.1156

Cited by 11 publications

(7 citation statements)

References 19 publications

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“…3). In line with [34]- [36], the deviation of the results achieved using the MQS approximation in terms of induced E-field and SAR from that obtained by full-wave analysis by means of the finite-difference time-domain method is always <1 dB. The restrictions to MF-evaluations is justified, as the E-field and the SAR in the human body are principally induced by inductive coupling for WPT systems based on magnetic resonance technologies [35], [36].…”

Section: A Coupling Transformation Functions 1) Generic Gradient Sousupporting

confidence: 55%

“…It has been shown by comparison to the full-wave analysis that the MQS approximation is valid for localized exposures to WPT systems and at frequencies <10 MHz [34]- [36]. To confirm the applicability to WPT exposure, we performed an additional validation by evaluating a WPT phone charging system (see Fig.…”

Section: A Coupling Transformation Functions 1) Generic Gradient Soumentioning

confidence: 99%

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Novel Method and Procedure for Evaluating Compliance of Sources With Strong Gradient Magnetic Fields Such as Wireless Power Transfer Systems

Liorni

Lisewski

Capstick

et al. 2020

IEEE Trans. Electromagn. Compat.

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To date, the development of valid and globally universally accepted recognized methods for the accurate exposure assessment of wireless power transfer (WPT) technologies is lagging behind the rapid emergence of high power systems in the energy and automotive sectors. WPT systems based on inductive and magnetic resonance technologies generate strong but rapidly decaying magnetic fields, which often exceed reference levels (RL) in the immediate vicinity of the WPT coils by up to a factor of >100. Compliance testing of WPT systems with limits derived for homogeneous exposure can lead to estimations of exposure that exceed by up to 40 dB assessments of the fields induced in the human body, i.e., the basic restrictions (BR) defined by the international safety guidelines. Testing compliance with the BR is impractical for regulatory purposes due to the high costs of resources of determining the maximum exposure conditions. This paper presents a novel compliance testing method that mitigates the overestimation of the exposure while maintaining the simplicity of the testing procedure. This is achieved by using coupling transformation functions to correlate not only the amplitude and frequency but also the gradient of the incident field with the BR. These novel conservative coupling functions have been determined by means of a large scale numerical study in the frequency range 3 kHz-10 MHz supported by a physics-based approximation. The here proposed compliance testing method is still conservative in comparison to the compliance toward BR of localized sources. However, in comparison to today's practice of applying RL directly, the overestimation is strongly reduced for high gradient fields (G n > 50 T/m/T), e.g., by more than 3000 times for field gradients of about 200 T/m/T. We have validated the method by numerical analysis of human exposure to actual WPT sources. The adoption of the new method will help to accelerate the introduction of high-power wireless charging devices in the global market.

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Section: A Coupling Transformation Functions 1) Generic Gradient Sousupporting

confidence: 55%

Section: A Coupling Transformation Functions 1) Generic Gradient Soumentioning

confidence: 99%

Novel Method and Procedure for Evaluating Compliance of Sources With Strong Gradient Magnetic Fields Such as Wireless Power Transfer Systems

Liorni

Lisewski

Capstick

et al. 2020

IEEE Trans. Electromagn. Compat.

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“…The leakage of electromagnetic field from WPT systems should also comply with the related regulations to make the WPT technology safe and accessible. Studies have been carried out by researchers in different scenarios such as housing environments [ 5 , 6 ], electrical vehicles [ 7 , 8 , 9 , 10 , 11 , 12 ], and bio-implanted applications [ 13 , 14 , 15 , 16 , 17 , 18 , 19 , 20 ]. Human models of adults, children, and pregnant woman [ 21 , 22 , 23 , 24 , 25 , 26 , 27 , 28 , 29 ] have also been built to estimate possible biological threats.…”

Section: Introductionmentioning

confidence: 99%

Human Exposure to Electromagnetic Fields from Parallel Wireless Power Transfer Systems

Huang

2017

IJERPH

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The scenario of multiple wireless power transfer (WPT) systems working closely, synchronously or asynchronously with phase difference often occurs in power supply for household appliances and electric vehicles in parking lots. Magnetic field leakage from the WPT systems is also varied due to unpredictable asynchronous working conditions. In this study, the magnetic field leakage from parallel WPT systems working with phase difference is predicted, and the induced electric field and specific absorption rate (SAR) in a human body standing in the vicinity are also evaluated. Computational results are compared with the restrictions prescribed in the regulations established to limit human exposure to time-varying electromagnetic fields (EMFs). The results show that the middle region between the two WPT coils is safer for the two WPT systems working in-phase, and the peripheral regions are safer around the WPT systems working anti-phase. Thin metallic plates larger than the WPT coils can shield the magnetic field leakage well, while smaller ones may worsen the situation. The orientation of the human body will influence the maximum magnitude of induced electric field and its distribution within the human body. The induced electric field centralizes in the trunk, groin, and genitals with only one exception: when the human body is standing right at the middle of the two WPT coils working in-phase, the induced electric field focuses on lower limbs. The SAR value in the lungs always seems to be greater than in other organs, while the value in the liver is minimal. Human exposure to EMFs meets the guidelines of the International Committee on Non-Ionizing Radiation Protection (ICNIRP), specifically reference levels with respect to magnetic field and basic restrictions on induced electric fields and SAR, as the charging power is lower than 3.1 kW and 55.5 kW, respectively. These results are positive with respect to the safe applications of parallel WPT systems working simultaneously.

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“…For inductive charging, we assume a slowly time-varying current, which justifies using a magneto quasi-static approximation based on stationary currents. The maximum error of this approximation is roughly 15% in the specific absorption rate (SAR) [8], but the approximation decreases the computation time significantly. To improve the computation time even further in order to allow rapid prototyping and optimization, an analytic approximation of the magneto quasi-static equations can be used.…”

mentioning

confidence: 99%

An Approximate Electromagnetic Model for Optimizing Wireless Charging of Biomedical Implants

Oosterhout

Paulides

Pflug

et al. 2022

IEEE Trans. Biomed. Eng.

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Quasistatic Approximation for Exposure Assessment of Wireless Power Transfer

Cited by 11 publications

References 19 publications

Novel Method and Procedure for Evaluating Compliance of Sources With Strong Gradient Magnetic Fields Such as Wireless Power Transfer Systems

Novel Method and Procedure for Evaluating Compliance of Sources With Strong Gradient Magnetic Fields Such as Wireless Power Transfer Systems

Human Exposure to Electromagnetic Fields from Parallel Wireless Power Transfer Systems

An Approximate Electromagnetic Model for Optimizing Wireless Charging of Biomedical Implants

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