Most materials exhibit different tensile and compressive strains given the same stress applied in tension or compression. These materials are known as bimodular materials. An important model of bimodular materials is the criterion of positive-negative signs of principal stress proposed by Ambartsumyan. This model is mainly applicable to isotropic materials and deals with the principal stress state in a point. However, due to the inherent complexity of the constitutive relation, FEM based on iterative strategy and analytical methods based on a simplified mechanical model are required. In this paper, we review the basic assumptions of this model and its development, several innovative computational methods, and some important engineering applications. We also discuss the sequent key problems in this field.

No abstract

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.

In this paper, according to the parameters of the dry type air core smoothing reactor, the stress-sound field and fluid-temperature field coupling simulation model is established, the detailed temperature field and sound field distribution are obtained, and the influence law of sound arrester on the sound pressure level and temperature rise are analyzed. It can be found that the temperature rise of encapsulation coils are significantly increased when adding the sound arrester, and the reasons are given by analyzing the fluid velocity in the air ducts. Meanwhile, the optimization design method about sound arrester is proposed based on the orthogonal experiment design and finite element method. The influence curve and contribution rate of sound arrester on the pressure level and temperature rise are analyzed, and the optimal structural parameters of the sound arrester are obtained. The results show that the optimization method can significantly reduce the temperature rise and sound pressure level simultaneously, and improving the operational reliability of the smoothing reactor.

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.

In this paper, a fluid-thermal coupled finite element model is established based on the design parameters of dry-type core reactor, the detailed temperature distribution results are given, and the heat transfer process of the layer coils was analyzed. Meanwhile, the electromagnetic characteristics of core reactor have been analyzed, it shows that the structure parameters adjustment of layer coils have little effect on the inductance of reactor. Taking the metal conductor usage of coils as the optimization object, the heat dissipation process between the layer coils and air ducts is equivalent to the vertical pipe, the calculation method of temperature rise is given, and the thermal efficiency optimization method of dry-type core reactor is proposed based on the particle swarm optimization algorithm, which can obtain the optimal structure parameters of coils. According to the optimization design results, the metal conductor usage of coils is only 80% compared with the initial parameters, and the correctness is verified by the simulation results. Thus, the optimization method can significantly improve the thermal efficiency and reduce the metal conductor usage of core reactor.

No abstract