A Mutual Inductance Measurement Method for the Wireless Power Transfer System

Abstract

The characteristic of the Magnetic Resonance Wireless Power Transfer (MR-WPT) system is related on the coupling coefficients between coils, so it is very important to accurately measure mutual inductance. The method of measuring mutual inductance using the primary current and the secondary voltage, when the secondary circuit is opened, is commonly used and most reliable. However, a standard sine wave generator and a linear power amplifier are needed for measuring the mutual inductance. Due to the high frequency inverter of WPT system may be has distortion, it is not recommended to be as the sine wave generator for measuring the mutual inductance. The proposed method demonstrate that, although the output current waveform of the high frequency inverter and the voltage waveform on the secondary coil are highly distorted in PWM (Pulse Width Modulation) control mode, the base component’s amplitudes of these waveforms are investigated by FFT (Fast Fourier Transform), and then, the mutual inductance is calculated by using these values. According to the above contents, the experimental platform is built, and then the experiments on the different duty cycle ratio and the different frequencies, that is, including the different quantities of its high-frequency harmonics, has been done. In addition, the same operation as above is repeated on the different distances, and the results are compared with the theoretical calculation values. Consequently, the results show that the method is very close to the theoretical value, and it is very stable in whole distance range.

Calculation of Mutual Inductance between Two Planar Coils with Custom Specifications and Positions Using a Machine Learning Approach

“…The relative error of the calculations was assessed compared to finite element simulation results, with a maximum value of 3.55%. Sokhui and colleagues (Sokhui et al, 2019) introduced a novel method for measuring mutual inductance using the Fast Fourier Transform, which matches the experimental results. They also assumed both coil axes to be parallel in all calculations and disregarded angular misalignments.…”

Mutual Inductance Measurement in Wireless Power Transfer Systems Operating in the MHz Range

“…Since the first mutual inductance modeling study [21], many results have been achieved both in modeling and measuring the mutual inductance of an inductive link [1], [12], [22]- [26]. Limiting ourselves to measurement techniques, and neglecting methods employed either in primary metrology (e.g., threevoltmeter technique [27]) or that need ad-hoc circuits (e.g., a compensation network in [28] or a whole resonant circuit in [29], [30]), the approaches known in the literature can be grouped into two main classes, according to the required measurement instrument: a) approaches based on VNA and on the scattering matrix evaluation [19], [20], [31]; b) approaches based on LCR meter such as the seriesantiseries technique [32], [33] (and the dual parallelantiparallel one [32], not considered here due to space reasons), the direct measurement technique [34] and the one relying on the Z-matrix evaluation [35]. In the following, we detail these methodologies with the help of a reference case.…”