Particular aspects of determining reliability indicators of thermoelectric generator modules using experimental data

Abstract

Resource tests allowed finding that the relative degradation of output power and efficiency of thermoelectric generator modules is not subject to linear law. This means that the distribution law for the failure time of such modules does not «copy» the distribution of their initial parameters, i.e. is neither normal nor logarithmically normal. Therefore, the aim of this paper is to find or select from among the existing such a failure time distribution law, which would clearly take into account the scattering of the rates of relative degradation of the parameters of thermoelectric generator modules. The paper substantiates the need to use diffusion-nonmonotonic failure time distribution for processing the results of resource tests of thermoelectric generator modules in order to determine their standardized reliability indicators and relative errors of the obtained values. It is proposed to determine the point estimates of the parameters of the law, namely the average failure time and the parameter of variation of the rate of degradation processes not by formulas obtained by the method of maximum likelihood, but by smoothing the probability of failure-free operation obtained by tests. The least squares method and Newton's method are used. Estimates obtained by the method of maximum likelihood serve as an initial approximation for Newton's method. This allows achieving significantly less error in determining standardized reliability indicators than when using the method of maximum likelihood.

Keywords

• reliability
• thermoelectric module
• failure time
• diffusion-nonmonotonic distribution
• maximum likelihood method
• least squares method
• relative error