In this paper, in accordance with the breaker requirements of a parallel-type circuit breaker based on a high-coupling split reactor, the structure of a coupling reactor is proposed, and the influences of the inner radius, encapsulation height, air ducts width and encapsulation number of the reactor on coupling factor are analyzed. The reactor design is optimized to minimize metal conductor usage, and the initial design parameters of the coupling reactor are selected based on equal height and heat flux of the coaxial encapsulations. Meanwhile, combined thermal and electromagnetic optimization method and heat load optimization are adopted considering a single-arm limiting current and two-arm flow current working conditions. The optimization results show that the metal conductor usage of the coupling reactor is only 63% compared to a design based on the initial design parameters, and the correctness of the optimization is verified by simulation results.

In this paper, according to the design parameters of oil-immersed iron core reactor, the thermal network model of windings is established by the thermo-electric analogy method, and the temperature distribution of the windings can be obtained. Meanwhile, a fluid-thermal coupled finite element model is established, the temperature and fluid velocity distribution are extracted, and the simulation results show that the error coefficient of temperature is less than 3% compared with the thermal network model, so the correctness of thermal network model has been verified. Taking the metal conductor usage and loss of windings as the optimization objects, the optimization method based on the particle swarm algorithm and thermal network model is proposed, and the Pareto optimal solutions between the metal conductor usage and loss of windings are given. The optimization results show that the metal conductor usage is reduced by 23.05%, and the loss is reduced by 20.25% compared with the initial design parameters, and the maximum temperature of winding does not exceed the expected value. Thus, the objects of low metal conductor usage and loss of windings are conflicted and cannot be optimized simultaneously; the optimization method has an important guiding significance for the design of oil-immersed iron core.

Inverse hysteresis model with magnetic flux density and magnetic field intensity as input and output respectively is more preferred, compared with the forward one, for resolving the electromagnetic issues of electrical equipment in terms of magnetic vector potential or with voltage sources. And an inverse hysteresis model with high accuracy and high computation speed both has broader range of applications. However, the well known classical Preisach hysteresis model is formulated with the forward form, and has the double integration of its distribution function, making it inconvenient and unpractical in the electrical engineering. In this paper, an analytical inverse Preisach model is proposed for the first time. Firstly, the analytical expressions of permeability of initial magnetization curve, descending and ascending branches of the hysteresis loop are derived using one closed form of Everett integral function. Subsequently the analytical inverse Preisach model is derived by the difference method, considering the reversible magnetization component that classical Preisach model cannot simulate with an odd function analytically. The experiment of one grain oriented silicon steel sample and one non-oriented silicon steel sample, under different magnetic excitation levels is conducted, and the accuracy and efficiency of the proposed analytical inverse Preisach model are confirmed by comparing its simulated hysteresis loops with the experimental ones and that computed with the widely used inverse Jiles-Atherton hysteresis model.

In this paper, the basic structure and design parameters of an oil-immersed air core coupling reactor were given according to the interruption requirement of the 160 kV mechanical direct current circuit breaker, and a field-circuit coupled finite element model was established based on the ANSOFT simulation platform. The prototype test results verified the correctness of the simulation calculation method. The coupling reactor design was optimized to minimize the total volume, taking equal height and heat flux design parameters as the optimization object, and the influence of the insulation distance between the oil tank and encapsulations on the secondary current of the coupling reactor were analyzed. Meanwhile, a combined optimization method about the reactor body and oil tank was proposed, and the optimization contour surface was plotted, which described the relationship between the total volume of the coupling reactor and structure parameters of the reactor body and oil tank. According to the optimization design results, the total volume was only 89% compared with the initial design parameters, and the correctness was verified by the simulation results.

Clutter filtering according to distinct Doppler echoes is a major measure to deal with the interference in radar signals caused by the rotating blades of nearby wind turbines. For the problem that the traditional simulation method of scattering point superposition model could not simulate the continuity of induced current on the blade's complex surface, the authors proposed a new simulation method of Doppler echoes based on scattered electric field calculation and expounded the basic principle and implementation steps of the method. First, they found the correspondence between the electric field's complex amplitude vector and the echo signal by deducing the equations of echo signal and scattering electric field; second, they used the quasi‐static technique, the hybrid algorithm of physical optics and method of moment to achieve an accurate solution of the scattered electric field sequence; finally, the authors used the short‐time Fourier transform to obtain the time–frequency domain data of blades Doppler echoes. The result was compared with data obtained from the scattering point superposition model and in‐field experiments, and the accuracy of the proposed method was verified.