Voltages across magnetic components of power converters are generally pulse width modulation (PWM) waveforms, whereas the parameters of present magnetic core loss models are often tested under sinusoidal excitation by most magnetic material manufacturers. This leads to a significant difference with a PWM excitation and then impacts the testing accuracy of inductor losses. A testing device, based on DC law, has been designed to generate different kinds of PWM waveforms, and a corresponding testing scheme is proposed to accurately measure total inductor losses of different inductances with high frequency PWM excitations. Finally, experiments have been conducted to verify the effectiveness and correctness of the proposed scheme. The results show that the proposed testing scheme can accurately test the total inductor loss. Moreover, the proposed loss model of the testing device is in exact agreement with the actual device's loss with the fitting error within 1%, ensuring the accuracy of the proposed testing scheme.

With high power density and high-frequency power electronics technologies, parasitic capacitances of inductors and transformers have been widely discussed, in which parasitic capacitance may lead to electromagnetic interference (EMI) and efficiency performance degradation. Therefore, it is significant to analyze and model the parasitic capacitance of the inductors and transformers. This paper proposes a new parasitic capacitance calculated model of multilayer windings inductors and transformers. Based on the electromagnetic field theory, it can fully consider the edge effect of multilayer inductor windings, including the edge effect between adjacent and non-adjacent layers. Finally, the accuracy of the model is validated by simulation and experiment. Compared with the traditional parasitic capacitance calculated method, the proposed model can calculate the parasitic capacitance more accurately, and the maximum error between calculations and simulations is less than 8%.

Capacitive power transfer (CPT) technique uses coupled metal plates for energy transmission, which has the advantages of negligible eddy-current loss and low weight. To achieve efficient power transfer, CPT system often adopts circuit resonance and impedance compensation, which are generally realized by integer-order components, such as inductors and capacitors. However, it remains a fundamental challenge to create a CPT system whose transfer efficiency and output power are robust against the variation of resonant frequency and the coupled plates’ relative position. Therefore, this paper proposes a robust fractional-order autonomous CPT system containing a fractional-order inductor. Theoretical analysis shows that the transfer efficiency and output power of the proposed fractional-order CPT system are inherently robust not only to the variation of the coupled plates’ relative position but also to the resonant frequency. In contrast, the transfer efficiency and output power of traditional integer-order CPT systems are sensitive to the resonant frequency. The available experimental results verify the effectiveness of the proposed system.

Circular planar spiral coils are wildly used for the magnetic coupling system in a high-frequency wireless power transfer system. The loss of the magnetic coupling system usually takes dominance in the whole system. This paper built the calculation model of magnetic field strength and coil loss, the proposed calculation model can effectively consider the mutual influence between the transmitter and receiver coil and accurately calculated the AC loss of WPT coils. Then, the effect of turn spacing on the AC resistance of coil is analyzed. It reveals that the proximity effect loss is greater when the coil is tightly wound, and the AC loss can be optimized by designing the turn spacing. Based on the above analysis, a double-layer coil method is proposed. This method can reduce the AC loss and improve the quality factor (Q) without changing the mutual inductance and footprint of coil at high frequency. The AC resistance of the double-layer coil method can be greatly reduced compared with the general method through simulation and experiment. The work efficiency of WPT system is increased by 4.3%, which verifies the accuracy and flexibility of theoretical analysis.

High-power inductors are fundamental components in high-power DC–DC converters, with their performance being a crucial metric of converter efficiency. This paper presents an in-depth analysis of a novel calculation method for the air gap length in such inductors. Taking into account the effects of air gap diffusion and the winding magnetic field, an expression for the air gap diffusion radius is derived, focusing on a distributed air gap structure. Furthermore, models for calculating the air gap and winding reluctance are developed, grounded in electromagnetic field theory. An equivalent magnetic circuit model, formulated based on Kirchhoff's second law, facilitates the proposed method for air gap length calculation. This study also involves the development of 3D models for both discrete and decoupled integrated inductors. The comparison between simulation outcomes and calculated air gap lengths indicates a maximum error of less than 8%, with the minimum error being as low as − 0.79%. Compared with traditional methods, the calculation method proposed in this paper has significant advantages. Additionally, the discrepancy between calculated values and experimental measurements is found to be 1.11%. These results validate the accuracy and applicability of the theoretical analysis and calculation method, underscoring their significance in the design and optimization of high-power DC–DC converters.

The magnetic core is an important part of the magnetic coupling system in wireless power transmission (WPT) for EVs. It helps to increase the coupling coefficient and reduce magnetic field leakage. However, it also brings additional core loss. While the traditional core loss model cannot be used directly due to the uneven distribution of the magnetic flux density, this paper focuses on the flux density distribution in the disk core of a WPT system. Based on a finite element analysis (FEA) simulation and a theoretical magnetic flux density distribution analysis, a mathematical model of magnetic flux density distribution is built, which is regarded as a quadratic function. Through this model, the flux density distribution can be calculated by the electrical and mechanical specifications of the magnetic coupling system. Combining the model of flux density distribution, the disk core loss model of the WPT system is proposed—the idea of which is dividing the disk core into several circle sheets firstly, and then summing the core loss of all circle sheets. Finally, the FEA simulation results verify the proposed model as being correct and flexible.