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This paper presents the results of an analysis of a low-power Wireless Power Transfer (WPT) system. The system consists of periodically distributed planar spiral coils that form the transmitting and receiving planes. An analytical and numerical analysis of the WPT system, over the frequency range from 100 to 1000 kHz, was carried out. A simpler and faster solution is the proposed use of an equivalent circuit represented by a single WPT cell. The influence of coil resistance changes on the power and efficiency of the WPT system was studied. This was obtained by changing the diameter of the wire from which the coils were wound. In addition, the size of the coil, the number of turns, and the distance between the two planes have changed. After a detailed analysis, the results showed that the highest efficiency values were obtained for a wire diameter of 200 μm, which means the lowest coil resistance. However, the lowest efficiency values were obtained for the smallest wire diameter, i.e., 100 µm, which means the highest coil resistance. In this case, the efficiency decreased by more than 40%. Based on the calculation results, it was also shown that it was better to accept the skin effect (efficiency decreased below 7%) than to reduce the wire diameter to eliminate it. [ABSTRACT FROM AUTHOR]

Wireless power transfer (WPT) technology has been popularized due to its convenience, safety, and unmanned nature. To improve the transmission performance of couplers and reduce the magnetic field, the designers of such couplers often adopt a combination of coils and substrates: however, the non-ferromagnetic substrate often leads to the enhancement of coil equivalent resistance and the decrease of the efficiency of a WPT system. In the present work, the effect of a substrate on coil equivalent resistance is evaluated by finite element simulation. The effects of the distance between a substrate and a coil and the number of turns of coil on the equivalent resistance of coils are studied. Based on the calculation method of alternating current resistance for Litz-wire, the equivalent resistance reduction method involving use of a coil with substrates is proposed to significantly reduce equivalent resistance of the coil with its substrate. A high-power-density coupler is designed based on the above method. The power densities of a transmitting coil and a receiving coil are only 0.542 W/cm 3 and 0.81 W/cm 3 respectively. When the transmission distance is 200 mm, a power transmission of 3.61 kW is realized, and the efficiency of the coupler and system reaches 94.61% and 92.56%, respectively. • The more coil turns, the greater effect of non-ferromagnetic substrate on resistance. • The change of substrate size will significantly affect the coil equivalent resistance. • The mutual inductance of coupler with substrate hardly affects the coil equivalent resistance. • Increasing strand number of Litz wire significantly reduce coil resistance with NFMS. • The proposed coupler structure achieves high power density and high efficiency. [ABSTRACT FROM AUTHOR]

This paper presents the results of an analysis of a low-power Wireless Power Transfer (WPT) system. The system consists of periodically distributed planar spiral coils that form the transmitting and receiving planes. An analytical and numerical analysis of the WPT system, over the frequency range from 100 to 1000 kHz, was carried out. A simpler and faster solution is the proposed use of an equivalent circuit represented by a single WPT cell. The influence of coil resistance changes on the power and efficiency of the WPT system was studied. This was obtained by changing the diameter of the wire from which the coils were wound. In addition, the size of the coil, the number of turns, and the distance between the two planes have changed. After a detailed analysis, the results showed that the highest efficiency values were obtained for a wire diameter of 200 μm, which means the lowest coil resistance. However, the lowest efficiency values were obtained for the smallest wire diameter, i.e., 100 µm, which means the highest coil resistance. In this case, the efficiency decreased by more than 40%. Based on the calculation results, it was also shown that it was better to accept the skin effect (efficiency decreased below 7%) than to reduce the wire diameter to eliminate it.

Solenoid valves represent indispensable elements in various engineering systems. Their failure can lead to unexpected problems. This failure may be caused by fluctuations in the coil resistance of the electromagnetic solenoid (EMS) which actuates these solenoid valves. Hence the need to monitor this parameter for a preventive maintenance of these actuators. The proposed method consists to use supervised machine learning to monitor coil resistance of the EMS valve. The EMS valve is coupled to an optical fiber squeezer which, acts as a force sensor. The solenoid armature applies a mechanical force to the optical fiber and changes the polarization state of the light that travels through the optical fiber and then this force infects the power of the light. A Simulink model is used to determine the open loop system step response. The identification of the system allows obtaining its transfer function, which depends on the parameters of the EMS and in particular on its coil resistance. By varying the coil resistance while fixing the other physical parameters of the EMS, we generate a database whose elements are the coefficients of the transfer function of the solenoid open loop and the electrical resistance of its coil. The generated database is used for training several supervised machine learning models whose predictors are the elements of the transfer function; the response is the coil resistance. The Gaussian process for regression allows to predict the variations of the coil resistance with the smallest relative error although it takes a relatively long time for the training compared to the other models used. [ABSTRACT FROM AUTHOR]

The reverse conducting‐IGBT (RC‐IGBT) is a well suited device for soft switching applications, that is, zero voltage switching (ZVS). However, standard RC‐IGBTs are optimised for hard switching, which shows different switching waveforms compared with soft switching. In this study, the optimisation of the RC‐IGBT is described for soft switching applications using the example of an induction cooker. The investigated induction cooker is implemented by using the single‐ended quasi‐resonant topology. Simulations show that main losses of the induction cooker occur in the induction coil and the RC‐IGBT (power switch). The performance of the coil can be improved mainly by minimising the coil resistance. The IGBT‐optimisation is based on the reduction of tail current in the soft switching mode. The IGBT thickness is decreased and the local lifetime is used to achieve lower tail current. A reduction of the overall losses by 30% is achievable. As a result, the cooling system of the IGBT can be smaller and cheaper. [ABSTRACT FROM AUTHOR]

Abstract: Eddy current sensors, as one of nondestructive testing and evaluation instruments, have been widely used in displacement measurement as well as defect characterization. However, in eddy current displacement measurement, the test not only depends on the displacement between the coil and samples, but also relates to the electrical and magnetic properties (such as electrical conductivity and magnetic permeability) of samples. So, the eddy current sensor is limited to test one sample after one calibration. In order to make eddy current sensors compatible with more samples after one calibration without testing error, this paper designed a new eddy current displacement instrument extended from the previous theoretical analysis and experiment study investigating the relationship of the coil resistance and inductance. A series of experiments indicate that the designed new eddy current displacement instrument can eliminate the influence of the samples'' electromagnetic properties effectively. [Copyright &y& Elsevier]

Radiofrequency (RF) transmitter and receiver coils in magnetic resonance imaging systems are used, respectively, to excite the nuclei in the object to be imaged and to pick up the signals emitted by the nuclei. The quality of obtained images strongly depends upon the correct choice of the coils geometry and typology. For low-field magnetic resonance imaging systems, the dominant power dissipation mechanisms are mainly due to conductor losses and the coils performance are affected by cross-sectional shape of RF coil conductors. This work proposes a method for the estimation of the different skin effects contribution to the total conductor resistance for coil built using strip conductor. The evaluation of coil resistance was performed at different tuning frequencies usually used in clinical scanner (21-128 MHz). © 2012 Wiley Periodicals, Inc. Concepts Magn Reson Part B (Magn Reson Engineering) 41B: 57-61, 2012 [ABSTRACT FROM AUTHOR]

Wireless power transfer (WPT) technology has been widely used in many fields. Nevertheless, in the field of high power transmission, such as the WPT system of electric vehicles, the power transmission efficiency of WPT system lags behind that of wired charging due to losses brought by substrate shielding materials. In this regard, the conduction resistance of Litz-wire coils without substrate is analyzed first in this paper. Secondly, the induction resistance of the coil with single-layer and double-layer substrate materials is modeled. Then, through the establishment of a coil simulation and experimental platform with a single-layer substrate, a contrastive analysis of the variation trend of coil equivalent series resistance (coil ESR) at changing thickness and area and constant volume of the substrate is carried out in combination with the theory. The variation law of coil ESR at changing thickness and area and constant volume of double-layer substrate is also explored at the end of this paper. This is expected to contribute to the reduction of coil losses in the WPT system through a systematic study of the influence of substrate size changes on the coil resistance of the WPT system. [ABSTRACT FROM AUTHOR]