Impact of a Strong AC Electromagnetic Field on a Conductor Mesh: Design Guidelines and Safety Assessment

Abstract

To design installation close to high-power AC electromagnetic device, a prediction of the electromagnetic coupling may be mandatory. The present device is composed of different high current multi-turn coils located near the installation, a conductor mesh. At first, the interactions between the different coils are assessed. The Maxwell-Ampère equation is solved through the magnetic vector potential formulation. Thanks to this potential, the magnetic induction field is deduced together with the induced current in the coils. Using a superposition principle, it is possible to build the coupling matrix which describes the self-inductance of each coil and the mutual inductances linking the different coils together. Then the Maxwell-Ampère equation is solved again using the same formulation but in a different configuration. As a first step, the magnetic induction field is deduced together with the induced current in the mesh. As a second step, the temperature within the mesh is computed in a time dependant simulation to predict the temperature rise in the mesh all along the coil working cycles. The simulations are run with COMSOL Multiphysics using a finite element method. Thanks to the computation results, local heating zones are identified: the mesh used in this topic is not fully periodic and some local mesh elements concentrate currents and heat. The heat in these areas is such that the mechanical properties of the mesh can be compromised notwithstanding the fatigue due to thermal dilatation cycles. As a result, design guidelines are established for similar installations located in the presence of high-power AC electromagnetic devices. The mesh should be as periodic as possible to spread the induced currents over the largest quantity of mesh elements. Moreover, a minimum distance between the installation and the coil should be respected. In the present installation, the use of simulation is of high importance to ensure the whole system integrity over the long run.