NbTi foil thermally controlled switches for superconducting converters with operation frequency up to 50 Hz.: Part 1: Experiment
The increase of the operation frequency of superconducting converters up to 50 Hz opens new ways to improve their parameters. Thermally controlled switches using NbTi foil are able to operate at industrial frequency with reasonable efficiency and dynamic parameters. Such switches have been developed and tested. The paper presents experimental results of static and dynamic behavior of the switches. The rectification mode was tested with different shapes of the applied voltage, with currents from 150 to 450 A, voltages from 10 mV to 2.5 V and recovery times between 1 and 10 ms. The switches presented here have experimentally demonstrated superior dynamic parameters at higher efficiency than the ones reported in literature up to now.
NbTi thermally controlled switches for superconducting converters with operation frequency up to 50 Hz. Part 2: Theory and analysis
A review is given of several known thermally controlled switches developed for superconducting converters. It shows their rather low frequency of operation (up to a few Hz) which strongly differs from the industrial frequency. This is not only due to the long recovery times of the switches, but also to the fact that the efficiency drops as the frequency increases. To develop switches suitable for 50 Hz, having reasonable efficiency, a theoretical model of the switch is necessary. Such a model is presented here, and illustrated for 50 Hz switches made from NbTi foil.
Investigations of dielectric gratings using electrodynamic models based on volume integral equations
Eigenmodes of planar and cylindrical dielectric gratings (DGs) and electromagnetic wave scattering from multiplayer DGs are investigated. The DG characteristics are calculated using numerical-analytical solution of integral equations (IEs).