The magnetic circuit has been a popular and powerful tool to analyze the magnetic field in electromagnetic devices for a long history. However, in the conventional magnetic circuit there is only one kind of component namely reluctance, which cannot analyze the phase shift or the amplitude attenuation of the alternating flux in electromagnetic devices. In this article, a new physical concept of magnetic-inductance is proposed, based on which the alternating-flux magnetic circuit theory including two kinds of components namely reluctance and magnetic-inductance has been developed. Furthermore, the virtual magnetic power is defined as the analogue of electric power, and the magnetoelectric power law is derived for magnetic circuits. Using the proposed magnetic circuit theory with magnetic-inductance, the relationship between the electric power and the virtual magnetic power is revealed and the long-lasting confusions in previous magnetic circuit methods, i.e., power calculation and phase shifts of magnetic variables, are clarified. By experiments, the magnetic-inductance and the magnetoelectric power law are validated, and their applications in eddy current loss analysis and B-H curve estimation in magnetic materials are demonstrated.

This paper summarizes the main results and contributions of the MagNet Challenge 2023, an open-source research initiative for data-driven modeling of power magnetic materials. The MagNet Challenge has (1) advanced the stateof-the-art in power magnetics modeling; (2) set up examples for fostering an open-source and transparent research community; (3) developed useful guidelines and practical rules for conducting data-driven research in power electronics; and (4) provided a fair performance benchmark leading to insights on the most promising future research directions. The competition yielded a collection of publicly disclosed software algorithms and tools designed to capture the distinct loss characteristics of power magnetic materials, which are mostly open-sourced. We have attempted to bridge power electronics domain knowledge with state-of-the-art advancements in artificial intelligence, machine learning, pattern recognition, and signal processing. The MagNet Challenge has greatly improved the accuracy and reduced the size of data-driven power magnetic material models. The models and tools created for various materials were meticulously documented and shared within the broader power electronics community.

Currently, some empirical formula methods, such as the Steinmetz equation, have been widely used in calculating high-frequency magnetic core loss. Although these methods may provide satisfactory accuracy under some certain conditions, they not only cannot present clear physical interpretation and fail to account for the origin and variation of losses, but also offer much lower accuracy for wide operation ranges. In this article, a new analytical model is proposed for the first time to predict core loss by the new vector magnetic circuit theory. In addition to reluctance, two new components, i.e., magductance and hysteretance are proposed in the vector magnetic circuit, which are used to describe the eddy-current loss and the hysteresis loss, respectively. Thus, the clear physical significance is available with the proposed loss model. Given the geometrical and physical parameters of cores, the loss can be predicted. Furthermore, the uneven distribution of magnetic flux inside the magnetic core is characterized by parallel vector magnetic circuits. By comparing with the available empirical formulas, it has been proven that the proposed analytical model not only offers clear physical concepts, but also has much higher accuracy.

In order to solve the problems of mesh node dynamic connection between the stator and rotor and the inability of single reluctance element to characterize the eddy current and hysteresis effects of ferromagnetic materials in the conventional equivalent magnetic network (EMN) model, this paper proposes an equivalent magnetic network model with three elements: magnetic flux source, reluctance and magductance (TEEMN). The "magnetic flux source" is arranged in the air gap mesh, whose magnitudes can be quickly determined by the analytical method. Changing the magnitudes of the magnetic flux source to imitate "virtual rotation" of the rotor solves the problem of mesh dynamic connection of the EMN model. At the same time, the "magductance L " element is introduced to characterize the influence of eddy current and hysteresis effects on the magnetic flux density. Further, considering the saturation effect of the magnetic circuit, a calculation method of the saturation factor of "effective magnetic impedance" is proposed to further improve the calculation accuracy of the TEEMN model. Taking a dual three-phase vernier permanent magnet machine as an example, the modeling process and analysis method of the TEEMN model is presented in detail, and verified by the finite element analysis results and experimental results.

This paper aims to study the calculation method of the bi-direction coupling of electromagnetic (EM) -thermal field, focusing on the data transfer method between different types of mesh elements in different physical fields. First, a complete EM-thermal field bi-directional coupling analysis model is established, based on which the changing rule between the EM losses of different components of the motor and their temperature rise curves is studied. Although the complete bi-direction EM-thermal field coupling analysis method is closest to the actual operation of the motor, this method is computationally intensive and takes a long time to calculate. For this reason, this paper also proposes an improved EM-thermal field bi-directional coupling calculation method based on the changing rule between the EM losses of different components of the motor and their temperature rise curves, significantly reducing the calculation time. The innovation of this paper is to realize the data transfer between different types of mesh elements in different physical fields, find the changing rule between EM loss and temperature rise curve, and establish a fast calculation method of bi-direction coupling of EM-thermal field. Finally, an experimental platform is built, and the experimental results verify the accuracy of the proposed methods.

Due to the presence of the new magnetic component of magductance (or magnetic-inductace), the traditional scalar magnetic circuit theory is evolved into the vector magnetic circuit theory. Further research is still required to determine whether the vector magnetic circuit theory and the current electromagnetic theory are compatible with one another. In this paper, the reluctance and magductance parameters of the magnetic circuit are derived using electromagnetic field theory, vector magnetic circuit theory, and electrical circuit theory by taking a laminated magnetic core as an example. Additionally, based on the derived general expressions for the magnetic circuit parameters, the law of magnetic circuit parameters changing with magnetic circuit frequency is plotted and summarized, and the compatibility of electromagnetic field theory, vector magnetic circuit theory, and electrical circuit theory is analyzed. Finally, combined with the magnetoelectric power law, the derived general expressions for the magnetic circuit parameters have been verified by the experiments with the Epstein frame.