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.
Right coronary artery stenosis associated with tricuspid valve ring annuloplasty
A 70-year-old man with severe symptomatic functional mitral valve regurgitation underwent successful mitral valve repair combined with tricuspid valve ring annuloplasty. Pre-operative coronary angiography (CAG) showed no significant stenosis. One-and-a-half years later, the patient presented with an acute exacerbation of heart failure. Repeat CAG demonstrated tight stenosis in the right coronary artery (RCA) with arterial kinking that corresponded to the same point as the stenosis where the RCA is the closest to the tricuspid valve ring. The new lesion probably occurred as a consequence of the tricuspid valve ring annuloplasty.