Frequency response analysis of a toroidal field coil of the divertor tokamak test facility

The magnet system of the Divertor Tokamak Test (DTT) facility is mainly made up with superconducting coils. During the operation of the DTT machine, high voltages will appear across each Toroidal Field Coil (TFC) when fast current will ramp down; the reason why, a reliable electrical insulation is required for the operation of the TFC system. With the aim of checking the correct sizing and implementation of the electrical insulation, different DC and AC electrical tests will be performed during all the coil manufacturing process. Among these, the impedance spectrum test, or rather the complex impedance measurement over several decades of frequency range, can be used to analyze the frequency response of the coil. The variations of the resonance frequency (f0), during its electrical acceptance test, can be useful to make predictions about the detectability of internal failure conditions in a coil. This paper focuses on analysis of the frequency response of a TFC, using a numerical simulation approach. The goal is to assess the impedance spectrum of a TFC within a fixed frequency band by a frequency-dependent lumped network. Starting from the TFC layout, a WP with the casing has been modeled by a complex network of lumped parameters in Ansys 2021/R2 environment. The data (amplitude and phase angle vs frequency) obtained have been used to study the f0 variation during the different manufacturing stage of the WP. This model will be able to make predictions about the detectability of internal short-circuit in a TFC.