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.
An assessment of self-(Cold-) supported SMES systems
Abstract The perceived long-range application of Superconducting Magnetic Energy Storage (SMES) has been for large-scale applications. Since SMES is highly efficient and has a rapid response time, it has a significant technical advantage over other storage technologies. Though the cost per unit of stored energy, $/kWh, for several major components, such as the superconductor and the cryostat, decrease as plant size increases, the amount of structural support that is required to withstand the electromagnetic force is directly proportional to the stored energy. Recognition of this fact led to the proposal of warm- or external-supported SMES, which has been the primary technology researched for the past 20 years. Recently, a team led by Bechtel suggested that cold or self support would be cost effective for SMES plants of intermediate size, i.e., from a few to several hundred MWh. This paper evaluates the cold- or self-supported SMES design to determine if it has sufficient material to withstand the electromagnetic forces. The design is shown to meet a criterion derived from the virial equation. Earlier work, which predicted that larger quantities of material are required, is reviewed.
Development of a thermally switched superconducting rectifier for 100 kA
A full-wave superconducting rectifier for 100 kA has been developed. Typical design values of this device are: a secondary current of 100 kA, a primary amplitude of 20 A, an operating frequency of 0.5 Hz, and an average power on the order of 100 W. The rectification is achieved by means of thermally controlled superconducting switches with recovery times of 150 to 300 ms. A description of the rectifier system is given. The first experiments, in which the rectifier was tested at up to 25 kA demonstrate reliable and fail-safe operation of the rectifier at lower current levels. It was, for example, successfully used to load and unload a 25-kA coil at a rectifier frequency of 0.4 Hz and an average power of 30 W. During tests without any load, it was found that the secondary circuit of the transformer quenches at about 60 kA. Therefore, it is unlikely that the rectifier in its present configuration will attain 100 kA.