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The increasing use of power electronic equipment and the importance of their continuous and correct operation have attracted remarkable attention to the condition monitoring of power electronic converters. Since capacitors are the leading cause of power electronic converters failure, this article attempts to attain a solution to monitor the condition of the dc-link capacitor in a three-phase back-to-back converter using the stimulated measurable transients. The proposed method works based on the temporary change of switching logic and the measurement of the dc-link voltage and converter input phase current transients. By processing the measured signals, the capacitance of the capacitor is calculated as an indicator of its degradation. The results of simulations and experimental studies are presented to verify the proficiency of the proposed method. Based on the results, the calculated capacitance is consistent with the value measured by an LCR meter with an estimation error of less than 1%.

In this paper, various temperature distributions on a thin resistant interphase layer bonded between two different materials were studied. The numerical finite element analysis for heat-conduction problems is considered for two cases: namely, a temperature-dependent source or sink and non-uniform temperature distributions at the surfaces and non-uniform source distributions into the intermediate layer. The finite element analysis shows good performance for thin heat conducting adhesive layers.

Fiber/matrix adhesions are most likely to control the overall mechanical behavior of fiber-reinforced composite materials. In this work, non-linear mechanical behaviors have been evaluated for a thin intermediate layer for plane stress case, which can be considered to be the adhesive elasto-plastic epoxy matrix. The adhesive which is the intermediate layer situated between two carbon fibers is assumed to be very small in thickness in comparison with those of the surrounding materials. Verification with the numerical simulation based on finite element method (FEM) has shown high accuracy of the derived formulations.

The imperialist competitive algorithm (ICA) that was recently introduced has shown good performance in optimization problems. This present study aims to establish on optimal design method of thin adhesive structure under non-monotonic heat source. The optimization results of ICA are compared with finite element method (FEM) and genetic algorithm (GA). Comparison shows the success of ICA for design of adhesive joints in materials.

In this paper a novel evolutionary universal search strategy called colonial competitive algorithm (CCA) is applied to establish an optimal imperfect transmission condition for a thin epoxy intermediate interphase layer which is bonded between two dissimilar strips of materials. The recently introduced CCA has demonstrated excellent capabilities such as faster convergence and better global optimum achievement. Finally the results of CCA are compared with finite element method (FEM) and genetic algorithm (GA). In application, compression shows the success of CCA for design of adhesive joints in the composite materials.