Nadine Lahoud

Electrical Aging of the Insulation of Low-Voltage Machines: Model Definition and Test With the Design of Experiments

The aim of this paper is to present a method for modeling the life span of insulation materials in a partial discharge regime. Based on the design of experiments, it has many advantages: It reduces the number of time-consuming experiments, increases the accuracy of the results, and allows life span modeling under various stress conditions, including coupling effects between the factors. Accelerated aging tests are carried out to determine the life span of these materials. The resulting model presents an original relationship between the logarithm of the insulation life span and that of electrically applied stress and an exponential form of the temperature. Results show that the most influential factors can be identified according to their effects on the insulation life span. Moreover, the life span model validity is tested either with additional points which have not been used for modeling or through statistical tests. Finally, it is shown that fractional plans are not suitable to reduce the number of experiments. This application of the experimental design is best used during the initial phase, before the final drive has been built and any online diagnosis.

Using the design of experiments (DoE) method to elaborate an electrical ageing model for the insulation of low voltage rotating machines fed by inverters

A large amount of parameters related to both operating conditions and material design affects the electrical ageing of the low voltage rotating machine insulation. Accelerated ageing tests are usually undertaken in order to develop a theory to describe the electrical ageing process and to determine a lifetime model of these materials. However, to the best of our knowledge, there is no complete model allowing the prediction of an insulation lifetime from accelerated ageing tests, since there are many possible failure mechanisms and various synergetic effects between them. Another problem with accelerated ageing tests is that results of the tests tend to have a great deal of scatter. In the present work, we propose the use of the design of experiments (DoE) method, which is a useful statistical approach that would lead to a reliable and significant interpretation of the different ordering parameters of the insulation ageing process. Using the DoE method, the analysis of accelerated ageing test results allows identifying the factors that most influence the results, and those that do not, as well as details such as the existence of interactions and synergies between these factors. In the following, results from accelerated ageing tests on PEI varnishes, largely used in rotating machines insulation, are presented and analyzed with the DoE method.

Electrical ageing modeling of the insulation of low voltage rotating machines fed by inverters with the design of experiments (DoE) method

In the context of more electric aircrafts, the reliability of the low voltage insulation systems in rotating machines is an important issue. But, modeling and understanding their electrical ageing is a complex phenomenon especially when they are fed by PWM inverter. They involve a large amount of parameters related to both operating conditions and material design, which act together. Accelerated ageing tests are usually run in order to describe the electrical ageing process and to determine the lifetime of these materials. Nevertheless, full ageing tests with all the various parameters for different samples become rapidly time consuming. Moreover, there is not any complete model for insulation lifetime prediction under accelerated ageing tests. In this paper work, we propose a method based on the design of experiments (DoE) method, which is a useful statistical approach that would lead to a reliable and significant interpretation of the different ordering parameters of the insulation ageing process. Moreover, this method will help to reduce the number of required experimental or numerical trials and will, take into account the possible failure mechanisms and the various synergetic effects between them. Using the (DoE) method, a preliminary model of the insulation “lifetime” is presented with respect to the most important parameters at play and interactions between them.

Electrical ageing of the insulation of low voltage rotating machines fed by inverters: The use of the design of experiments (DoE)

The electrical ageing of the low voltage rotating machine insulation involves complex phenomena since a large amount of parameters related to both operating conditions and material design are acting together. Accelerated ageing tests are usually undertaken in order to develop a theory to describe the electrical ageing process and to determine the lifetime of these materials. To the best of our knowledge, yet there is no complete model allowing the prediction of an insulation lifetime from accelerated ageing tests, since there are many possible failure mechanisms and various synergetic effects between them. Indeed, if one intends to perform a complete ageing test taking into account the various parameters for different samples, the operation becomes financially intolerable and extremely time consuming. In the present work, we propose the use of the design of experiments (DoE) method, which is a useful statistical approach that would lead to a reliable and significant interpretation of the different ordering parameters of the insulation ageing process. Moreover, this method will help to reduce the number of required experimental or numerical trials. Using the (DoE) method, a preliminary model of the insulation “lifetime” is presented with respect to the most important parameters at play and interactions between them.