Contemporary industrial equipment is increasingly developing towards complexity. In order to ensure the high reliability and sustainability of industrial equipment, more flexible maintenance strategies have attracted extensive attention. In view of this, this paper aims to summarize the current situation of existing maintenance strategies, so as to enable colleagues in the industry to choose or formulate more efficient maintenance strategies. Firstly, the characteristics, application potential and limitations of single component maintenance strategies, such as corrective maintenance, preventive maintenance and predictive maintenance, are described in detail from the perspective of maintenance time. On the basis of single component maintenance and the dependency between multiple components, the advantages and disadvantages of multicomponent maintenance strategies, such as batch maintenance, opportunity maintenance and group maintenance, are summarized, and suggestions for the future maintenance of industrial equipment are proposed. Based on this, industries can select the appropriate maintenance strategy according to their equipment characteristics, or improve their existing maintenance strategies based on actual needs.

The study presented in this paper contributes to quantification of the correlations between resistance degradation and Al metallization layer reconstruction observed in high-power insulated gate bipolar transistor (IGBT) modules during power cycling. The microstructure evolution that occurs in the Al metallization layer during power cycling was investigated via electron and ion microscopy, and the surface roughness was measured and used to characterize the Al metallization degradation. An electrical four-point probe method was used to examine the change in the electrical parameter (resistance) of the Al metallization layer in the IGBT modules. The effect of Al metallization layer reconstruction on its electrical performance was investigated by experimental observation and finite element analysis (FEA). The results show that both the Al metallization layer surface morphology and cracks propagating across the Al metallization layer thickness significantly affect the metallization resistance. In the initial and mid-point stages of power cycling, the increase in the Al metallization layer resistance is consistent with the surface roughness evolution. Near the ultimate lifetime of the IGBT module, the change in the resistance strongly depends on the crack density.

Health state estimation can quantitatively evaluate the current degradation state of equipment, and remaining life prediction can quantitatively predict the remaining service time of equipment. These two technologies can provide a basis for condition-based maintenance and predictive maintenance of equipment, respectively. In recent years, a large amount of research has been implemented in these two technologies. However, there is not any systematic review that covers these two technologies, and their engineering applications, comprehensively. To fill the gap, this paper makes a comparative analysis of existing health state estimation and remaining life prediction methods, and details the characteristics and limitations of various methods. The engineering applications of these two methods are summarized, and their applicable objects are briefly given. Finally, these two methods are summarized, and their feasibility for engineering application is discussed. This work provides guidance for the selection of industrial equipment health assessment and remaining life prediction methods.

Health state estimation can evaluate the current degradation state of equipment, and the evaluation results can provide a basis for formulating equipment maintenance strategies. At present, in the research on health state estimation, only one level of indicators of the equipment is usually considered, meaning incomplete estimation results. In addition, the current evaluation methods rarely consider the impact of data noise on the evaluation results, which can easily lead to abnormal evaluation results. To solve the above two problems, this paper first introduces the state indicators such as ripple voltage and output voltage, as well as the ratio of theoretical use time into the evaluation indicators. Furthermore, a health state estimation method combining grey clustering and fuzzy comprehensive evaluation methods is established. This method can consider the characteristics of multiple data groups at the same time, thus the impact of data noise on the evaluation results can be reduced. During the evaluation, the grey clustering method is used to evaluate the clustering coefficient vector of the power supply under a single group of data. After that, the clustering coefficient vector of multiple groups of data is used as the membership vector of fuzzy comprehensive evaluation, and the fuzzy comprehensive evaluation method is used to evaluate the health state of a power supply under multiple groups of data. An example shows that this method is effective in estimating the health state of a normally degraded power supply.

This study quantifies the correlations between crack evolution and electrical performance degradation of the Al metallization in insulated gate bipolar transistor (IGBT) modules. The resistance of the Al metallization under different power cycling times was measured by the four-point probe method. The cracks that occur in the Al metallization were investigated by measuring crack geometric parameters, e.g., shape, geometric size and density. Simplified analytical models containing different crack geometric parameters were established by the finite element method (FEM). The influences of crack evolution on the resistance and current density of the Al metallization were quantitatively analyzed. The results indicate that the crack depth has the largest effect on the Al metallization resistance compared with the crack length and width. At the later stage of power cycling, increasing the crack depth plays a critical role in metallization resistance degradation. In addition, cracks affect the current flow direction and the maximum current density in the Al metallization. With increasing crack depth and length, the maximum current density in the crack vicinity increases continuously. However, increasing the crack width reduces the maximum current density.