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.

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 is 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. INDEX TERMS Parallel-type circuit breaker, coupling reactor, metal conductor usage, combined thermal and electromagnetic optimization, heat load optimization.

A fluid-thermal coupled analysis based on FEM is conducted. The inner structure of the coils is built with consideration of both the structural details and the simplicity; thus, the detailed heat conduction process is coupled with the computational fluid dynamics in the thermal computation of air-core reactors. According to the simulation results, 2D temperature distribution results are given and proved by the thermal test results of a prototype. Then the temperature results are used to calculate the heat flux to predict the detailed heat transfer process in the packages of the reactors. The study in this paper may be useful in the design optimization in air-core reactors.

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