OCTOBER 19-20, 2012 - YMCA University of Science & Technology

Proceedings of the National Conference on
Trends and Advances in Mechanical Engineering,
YMCA University of Science & Technology, Faridabad, Haryana, Oct 19-20, 2012
Fig. 7 Sensitivity Plot for Life
6.2 Identifying Optimum Diameter of Capacitor Lead
From the sensitivity analysis it has been concluded that life of capacitor is completely dependent on the radius of
leads with direct proportion. So in order to reduce the failure probability of capacitor, lead radius needs to be
increased. Hence to identify the optimum size of the capacitor leads number of iterations of FE model simulation
were carried out by varying the radius of the lead. Cumulative distribution curve for capacitor life is used to
obtain the optimum size of capacitor lead radius. This curve gives the failure probability of capacitor at a
particular lead radius. X-axis represents the number of minutes to fail and Y- axis represents the probability of
failure. Graph consists of three curves representing failure probability. Lower and upper curves quantify the
accuracy of probability results; center curve gives the probability (P) of life. Complement to this reliability is the
probability of failure, i.e. 1-P. It is the probability that the life exceeds the limit [8]. Optimized lead diameter is
one for which the failure probability is smaller. Details of FE model simulation iterations are given below;
Iteration 1: Simulation was carried out with lead radius of 0.3 mm + 0.1 mm, for expected life of 8 hours (480
minutes). Cumulative distribution plot of capacitor life in minutes for iteration 1 is shown in Fig.8.
From the graph it can be observed that there is about 95% failure probability of component, which is
unacceptable.
Fig. 8 Cumulative Distribution Plot of Life for Iteration1
Iteration 2: In this iteration lead radius was increased to 0.45 mm + 0.1 mm, simulation carried out with
increased lead radius, for expected life of 8 hours (480 minutes). Cumulative distribution plot of capacitor life in
minutes for iteration 2 is shown in Fig.9. From the graph it can be observed that there is about 65% failure
probability of component, which is also unacceptable.
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