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This paper deals with the problem of internal overvoltages within large coils due to fast‐rising surges. Numerical simulations are performed on a lumped‐parameter equivalent circuit, representing a coil of the magnetic system of a thermo‐nuclear fusion experiment. Inductances and capacitances are computed through numerical methods which ensure a good precision even with complex geometries. The effect of the conductive painting on the outer surface of the coil is also taken into account. The simulation results are compared with a number of measurements on a full‐size prototype coil. Turn‐to‐earth, as well as inter‐turn overvoltages, are both computed and measured in many grounding conditions. The experimental results fit well with computation and theoretical prediction.

The equivalent currents method has proven to be particularly effective in the identification of plasma boundary in Tokamak fusion devices. Anyway, the ill‐posedness of the mathematical model to be inverted calls for the adoption of suitable regularization techniques to be adopted, in particular to reduce the influence of the measurement errors. In this paper the equivalent currents method is illustrated, together with some details on its application to the plasma identification. In addition, two algorithms for the optimal choice of the representation basis are presented, together with a discussion about the obtained numerical results.

The eddy current method of non‐destructive testing uses an alternating current excitation to induce secondary currents in a specimen under test. Flaws within the specimen affect the induced currents, causing changes in the impedance of a test coil. In this paper we present a method for obtaining a solution of inverse problems, in which the parameters of defects are unknown and the excitation function and the eddy current system response are given. The method is based on the use of artificial neural networks, which are trained using measurements. Illustrative examples are given.