




Optimum Life Test Plans of Electrical Insulation
for Thermal Stress








H. Hirose, T. Sakumura, N. Tabuchi, and T. Kiyosue








The 2014 IAENG International Conference on Electrical Engineering
(ICEE'14), pp.668672, March 1214, 2014, Hong Kong.






We
search for the optimum life test plans of electrical insulation
for thermal stress
assuming that the Arrhenius law holds between the thermal stress
and the lifetime, and that the logarithmic lifetime follows some
consistent probability distributions at a constant stress.
The optimization target is to find the optimum number of test specimens
at each test stress level, and we consider the case of the number
of stress level is three.
The criterion for optimality is measured by the root mean squared
error for the lifetime in use condition.
To take into account the reality, we used the parameter values in
a real experimental case.
Comparing the optimum results with those using the conventional test
method where test specimens are equally allocated to each test stress
level,
we have found that the confidence interval for the predicted value
in the optimum case becomes around 8085% of that in the conventional
test.
However, there is only a small difference between the optimum test
result and the conventional test result if linearity of the Arrhenius
plot is required.
It would be useful to know the semioptimum test plan in which the
efficiency is close to that in the optimum one and the test condition
is simple.
In that sense, we have found that we may regard the conventional
test plan as one of the semioptimum test plans. 




optimum
test plan, thermal deterioration, Arrhenius law, method of
least squares, maximum likelihood estimation method









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