This talk introduces the concept of electromagnetic resilience, which is a new discipline of risk management that must be applied to electronic devices that are subjected to electromagnetic interference. The problem is that any electronic device, whether it be a flat-screen television or a hospital life-support machine, consists of thousands of electronic components than could potentially be affected by electromagnetic disturbances. And here we are not talking about an electromagnetic pulse that occurs when lightning strikes, but the much lower, let’s call them “everyday incidences”, like when an ordinary mobile phone is in use.
As recently as 2 Oct 2022, the simple act of making a phone call has been the cause of an unexpected close-down of one of the main nuclear reactors in Belgium for two full weeks. The reason being that the system was not sufficiently resilient to that particular form of electromagnetic disturbances, under those circumstances, at that time.
This is the type of problem this talk wants to address: how can we make electronic devices, many of which are vital to our everyday lives, resilient in environments that are impossible to predict? The talk will given insight in the latest research on several different aspects of resilience so that a future device can self-adjust the way that it functions, before, during, or after it encounters electromagnetic interference, while being able to maintain at least its key capabilities under these conditions. In other words, with electromagnetic resilience we acknowledge that the electromagnetic environment is never completely knowable, and although we can make a device robust against electromagnetic interference that we know it will encounter during its lifecycle, we must also make the device resilient to cope with any unforeseen electromagnetic disturbances that just might come its way.
The 3D formulations using magnetic and electric scalar potentials, and vector A, T potentials will be discussed for electromagnetic fields at low frequency. The focus will be on the Finite Difference Method (FDM), Finite Integration Technique (FIT) and Finite Element Method (FEM) using nodal and edge elements. Multi-Branch Electric and Magnetic Network Models (MBNM) will also be considered. It has been shown that the FDM, FIT and FEM equations may be described in a form similar to the circuit equations of MBNM. The difference is only in the formulas that define the coefficients of discussed equations and in the distribution of network nodes. In the discussion on the equivalence of considered methods it was noted that the equations usually obtained via a variational approach may be more conveniently derived using integral methods employing a geometrical description of the interpolating functions of edge and facet finite elements. A language of circuit theory will be used to explain FDM, FIT, FEM and MBNM. For the vector potential A, T formulations the equations of FEM, FIT and FDM represent the loop (mesh) equations of MBNM for loops around the element edges. However, for the scalar potentials these equations are analogous to the nodal equations of equivalent MBNM.
Equivalent MBNM models allow to create a new, effective procedures in computational electromagnetics. Using this models a description of multiply connected windings in the finite element space using edge values of the vector potential T0 may be explain as the classical mmf distribution formulation. Well before the advent of edge element formulation a version of this approach was already common in FDM and often referred to as ‘current linkage distributions’ created by the electrical machine windings. Equivalent MBNM help to form the procedures of electromagnetic force and torque calculation using FEM, FIT, FDM. It will be shown that the analogies between FEM, FIT, FDM and Multi-Branch Electric and Magnetic Network Models have been found very helpful in teaching, especially if students are already familiar with one of the methods; this will be particularly important when field methods are introduced to students already conversant with circuit theory.
In the presentation the selected comparisons will be made between the results obtained using the different methods for both scalar and vector potential formulations. The results of force and torque calculations will be discussed.
The Time Reversal technique, which has found numerous applications, is based on the time-reversal invariance of many physical laws.
In this talk, a very simple example is used to illustrate the main ideas behind the application of the time reversal technique. Electromagnetic Time Reversal is then introduced and studies are described on the applicability of the technique to the location of lightning discharges.