Influence of contact resistance on shielding efficiency of shielding gutters for HV cables

in Proceedings of the 14th Biennial IEEE Conference on Electromagnetic Field Computation (CEFC2010) (2010, May)

Shielding of buried three phase high voltage cables can be done by placing the cables in conducting ferromagnetic U- shaped gutters covered by plates. In case of a perfect electrical contact between ... [more ▼]

Shielding of buried three phase high voltage cables can be done by placing the cables in conducting ferromagnetic U- shaped gutters covered by plates. In case of a perfect electrical contact between adjacent gutters and between adjacent cover plates, the induced currents in the shield efficiently reduce the field generated in the vicinity of the cables. However, as a perfect contact cannot be guaranteed, it is useful to quantify the effect of a bad electrical contact on the shielding performance. From 2D FEM, 3D FEM and experiments, it is observed that a bad contact does not influence significantly the shielding if the axial length of the plates is relatively long compared to their other dimensions. [less ▲]

Finite-Element Analysis of a Shielded Pulsed-Current Induction Heater -- Experimental Validation of a Time-Domain Thin-Shell Approach

in COMPEL (2010), 29(6), 1585-1595

Purpose – The aim of this paper is the experimental validation of an original time-domain thin-shell formulation. The numerical results of a three-dimensional thin-shell model are compared with the ... [more ▼]

Purpose – The aim of this paper is the experimental validation of an original time-domain thin-shell formulation. The numerical results of a three-dimensional thin-shell model are compared with the measurements performed on a heating device at different working frequencies. Design/methodology/approach – A time-domain extension of the classical frequency-domain thin-shell approach is used for the finite-element analysis of a shielded pulse-current induction heater. The time-domain interface conditions at the shell surface are expressed in terms of the average flux density vector in the shell, as well as in terms of a limited number of higher-order components. Findings – A very good agreement between measurements and simulations is observed. A clear advantage of the proposed thin-shell approach is that the mesh of the computation domain does not depend on the working frequency anymore. It provides a good compromise between computational cost and accuracy. Indeed, adding a sufficient number of induction components, a very high accuracy can be achieved. Originality/value – The method is based on the coupling of a time-domain 1D thin-shell model with a magnetic vector potential formulation via the surface integral term. A limited number of additional unknowns for the magnetic flux density are incorporated on the shell boundary. [less ▲]

Analysis of perforated magnetic shields for electric power applications

in IET Electric Power Applications (2009), 3(2), 123-132

The shielding performance of perforated magnetic shields for electric power applications is described. The shielding of an axisymmetric induction heating device is studied as a function of frequency ... [more ▼]

The shielding performance of perforated magnetic shields for electric power applications is described. The shielding of an axisymmetric induction heating device is studied as a function of frequency, number of perforations and dimensions of the perforations. From the numerical point of view, the perforations cause the numerical model to be 3D. A numerical optimisation is carried out to find the optimal geometry with respect to the shielding factor and the volume of the shield. For the optimisation, two approaches are presented. The first approach is fast and easy-to-implement, but has limited accuracy. It uses a classical 2D axisymmetric model where the perforations are approximated by ‘axisymmetric air gaps’ resulting in a segmented shield. It is shown how to modify the 2D model to obtain results that are similar to the ones of a 3D model. The second approach is more accurate although quite fast, but more difficult to implement. It combines a 3D thin- shell finite element model with the unmodified 2D model in a space mapping optimisation algorithm. The validation of both models is based on experimental work for an unperforated shield and for the optimised perforated shield. [less ▲]

Fast multipole accelerated finite element-boundary element analysis of shielded induction heaters

in IEEE Transactions on Magnetics (2006), 42(4), 1407-1410

This paper deals with the analysis of a shielded induction heater by means of a fast multipole accelerated hybrid finite-element boundary-element model. It concerns an experimental setup with passive and ... [more ▼]

This paper deals with the analysis of a shielded induction heater by means of a fast multipole accelerated hybrid finite-element boundary-element model. It concerns an experimental setup with passive and active shielding for mitigating the stray field in the surrounding area. Numerical results of the magnetodynamic model are compared with measurements. Further, various aspects of the numerical scheme are discussed and its efficiency is evidenced. [less ▲]