A Global Approach to the Design of Insulation Systems for Aerospace Electrical Assets: Focus on Printed Circuit Board

The evolution of power electronics in aerospace and, in general, electrified transportation assets, is centered on the development of MV power electronics converters, which maximize power density and efficiency. This turns into a high-field and temperature design, ultrafast switching, and high-frequency modulation. Such conditions may pose significant and unpreceded electrothermal stresses on insulation systems of electrical asset components, such as printed circuit boards (PCBs). The magnitude, profile, and time behavior of stresses, as well as their effect on intrinsic and extrinsic aging mechanisms, have to be known, being the basis of a highly reliable electrothermal insulation design able to provide a specified life at specified failure probability. This article introduces an innovative criterion to optimize the design of the insulation system of MV PCB, according to the new "three-leg" approach that consists of interlacing electric field simulation, life and discharge modeling, and partial discharge testing. The essence of such an approach is to design an insulation system, as regards bulk and surface subcomponents, by a global view, where aging processes rule design rather than macroscopic failure risk. Accordingly, life and reliability are determined by appropriate models, accounting for intrinsic aging, and, in addition, the design ensures that operation stresses do not trigger extrinsic accelerated aging mechanisms, as those associated with partial discharges. It is shown in this article that the proposed approach can lead to an innovative and effective design, delivering the specified life and ensuring that the electrical field on the surface (and in the bulk) is limited to values below the threshold for partial discharge inception. This can question, in principle, the use of creepage and clearance tools, since the new design procedure will be related to the minimization of the likelihood of partial discharge inception, rather than to avoiding the risk of macroscopic surface discharges.