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.
New 50 Hz Superconductin Power Supply for a 2 kA DC 2 agnet
A new superconducting power supply able to operate directly from the mains voltage at a frequency of 50- 60 Hz is under development in our institutes. It will be applied to power a separator magnet for iron ore recycling. The supply consists of a full wave superconducting converter, a 'cold' protection system, and control and measuring units. Typical design values of the device are: output current of 1-2kA, voltage of 1-0.5 V; input current of 7 A, voltage of 220 V and frequency of 50 Hz; an efficiency better than 96%. The high current part of the supply finally will be placed in the same cryostat as the separator magnet. The basic concept of the device is presented in the paper.
Efficiency aspects in superconducting rectifiers
The subject of this paper is the overall efficiency of thermally and magnetically controlled superconducting rectifiers. Such devices can be used to energize high-current superconducting loads, or alternatively, to make up the loss in a load which has been energized previously by means of (demountable) current leads. Both applications can result in a considerable saving of helium consumption. An analysis is made of the losses occurring in the rectifier components. The presented formulae are useful when designing a high-efficiency rectifier. Also, for an existing rectifier, the influence of parameters such as primary waveform, the primary amplitude, the frequency and the fraction of pumping time can be studied. To illustrate the theory, it is used to determine the overall efficiency of two experimental rectifiers constructed at the University of Twente.