Modeling of Combined Metal Oxide Varistors and Ferrite Core Filters to Augment Avionic Safety during Lightning Transients

The performance of ferrite core filters to suppress lightning induced fast transients in the avionic environment is discussed in this article. A dynamic model of a ferrite core filter has been formulated by the combination of a rate independent hysteresis model based on the Preisach theory, and a linear electrical network. The dynamic model is numerically implemented by a finite difference scheme in the time domain. The model is parametric with respect to the geometrical dimension of the ferrite core, which is useful in the design process. The combination of a ferrite core filter with a metal oxide varistor is considered in order to study the practical effect in terms of protection level, size of the core, and the lifetime of varistor. The pin injection tests procedure, reported in the specific standards for avionic diagnostic is simulated, and the predicted results are experimentally verified.