The electrical behavior of the ITER central solenoid model coil (CSMC) exposed to the voltage rise occurring during a safety discharge initiated by a counter acting current switch has been studied. A detailed network model has been set up to determine the transient overvoltages inside the windings of the CSMC when the coil is subjected to transient voltages. The analysis takes into account the frequency-dependent resistance of the conductor in case of high-frequency oscillations, and considers the influence of the extensive instrumentation cables of the coil. The model's accuracy is demonstrated over a frequency range up to 30 Khz. The total inductance and capacitance of the coil model are in very good agreement with previously obtained measurements and design values. The discharge circuit has also been modeled in order to accurately simulate the discharge process. It was found that the terminal voltage generated during a safety discharge causes transient oscillations inside the windings. However, they do not cause overvoltages exceeding the maximum acceptable insulation stress. The influence of several parameters of the discharge circuit on the rise time and shape of the resulting terminal voltage was investigated. Controlling these values might be a measure to prevent excessive internal oscillations for larger coils with lower natural frequencies than the CSMC.

This paper presents an FE modelling approach for the calculation of transient eddy currents in thin conductive layers, where the complexity of the geometry prohibits both a detailed FE modelling and the use of analytical tools. The method allows an estimation of the maximum values of eddy currents at a highly reduced modelling effort and the use of a commercial FE software package. A prerequisite is a slowly varying magnetic field that can be assumed to be unaffected by the eddy currents. It is shown that neither the source of the magnetic field nor the insulating environment has to be modelled. The model is built up exclusively from 2D elements and is excited via the magnetic vector potential. The spatial distribution of the latter is calculated separately in a magnetostatic calculation based on Biot–Savart's law. It is then applied in time‐varying form as a dynamic boundary condition at every node of the model. The method was applied to a simple problem for which the results of a detailed FE calculation were available, to document its validity. Further numerical results are presented for the plasma vessel and the heat radiation shield of the Wendelstein 7‐X fusion experiment in the case of an emergency discharge. © 1998 John Wiley & Sons, Ltd.

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Magnet coils wound from superconducting multistrand cables exhibit a reduced current carrying capability during non-steady-state operation. This may be caused by a nonuniform current distribution in the cable. The extent of this nonuniformity depends on the design of the coil. Hence, measurements of the actual current distribution can not be performed on short cable samples. In order to be able to estimate the performance of a cable for a given coil geometry already during the design phase of the magnet, lumped network models have been developed for a numerical investigation based on geometrical and material data of the coil and the cable. This work focuses on cable-in-conduit conductors (CICCs). Actual conductor designs have been modeled and the influence of the interstrand conductance and the geometrical accuracy of the cable was investigated.

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