Showing papers by "L.J.M. van de Klundert published in 1981"
TL;DR: In the past twenty years, a large variety of mechanically or electrically driven devices have been proposed and successfully operated and the basic principle of operation of each class of devices is shown and specific material problems and limitations are reported as mentioned in this paper.
131 citations
TL;DR: In this paper, full and half wave superconducting transformer rectifiers are analyzed and modes of operation and loss mechanisms are detailed and a comparison between the behaviour of dynamos and rectifiers is presented.
58 citations
TL;DR: In this article, results on three experimental superconducting rectifiers are reported, two of them are 1 kA low frequency flux pumps, one thermally and magnetically switched.
11 citations
TL;DR: In this article, a thermally switched 9 kA full wave rectifier-fluxpump is presented, which consists of a current step up transformer, two reliable thermally activated switches and a dummy load inductor.
Abstract: The feasibility of superconducting rectifier-fluxpumps has to be demonstrated at current levels of 10 - 100 kA, where is asked for in the superconducting devices now being planned. An intensive program has been started at the low temperature division of the University of Twente to construct such high current rectifiers. A thermally switched 9 kA full wave rectifier-fluxpump will be presented. The s.c. rectifier consists of a current step up transformer, two reliable thermally activated switches and a dummy load inductor. Both, load coil and rectifier are fully protected against failure modes. The rectifier is now (March, 1981) under test and has energized yet the load coil to a level of 4.5 kJ at 9 kA within 150 seconds, frequency 0.11 Hz, mean power 30 W, the efficiency of the energy conversion is 99,1%.
10 citations
TL;DR: In this article, a numerical method is presented which allows the calculation of the a.c. response of type II superconductors under quasi-static conditions for arbitrary jc (B,x), Ben (Ba), and Bex (Ba) relations.
Abstract: A numerical method is presented which allows the calculation of the a.c. response of type II superconductors under quasi-static conditions for arbitrary jc (B,x), Ben (Ba) and Bex (Ba) relations. Flux distributions, induced voltage waveforms, hysteresis loops and a.c. losses have been calculated. Deviations between experimental results and earlier calculations with respect to a minimum in the a.c. losses are explained by taking into account the finite thickness of the sample and realistic Ben (Ba) and Bex (Ba) relations.
7 citations
TL;DR: In this paper, the authors present an inductive technique which makes it possible to determine the critical current density, surface screening currents, and flux conductivity of type II superconductors separately.
7 citations
TL;DR: In this article, the development of thermal instabilities in a single niobium crystal has been studied experimentally under various external conditions and the observed flux jump behaviour cannot be explained in terms of existing theoretical models.
4 citations
TL;DR: In this paper, a method is presented to determine the conductivity and its magnetic induction dependence from the decay of the induced voltage during periods of constant field, and the correctness of the analysis is confirmed by the close agreement between the complete experimental and theoretical voltage waveforms.
Abstract: The inductive response of normal metals to trapezoidal a.c. fields is studied theoretically as well as experimentally. A method is presented to determine the conductivity and its magnetic induction dependence from the decay of the induced voltage during periods of constant field. The correctness of the analysis is confirmed by the close agreement between the complete experimental and theoretical voltage waveforms.
1 citations
TL;DR: Within the scope of a research program of superconducting rectifiers software is being developed to take care of the control of such systems, but because the reliability of computersystems is unsatisfactory an additional hardware protection system still handles the most important alarms.
Abstract: Within the scope of a research program of superconducting rectifiers software is being developed to take care of the control of such systems. The hard-ware architecture which interferes with the in and output signals is based on a LSI-11/2 microprocessor with sufficient mass storage for data logging, console and printer. The flexibility inherent to this hardware configuration is desired for optimalisation of the rectifier concerning maximum current, power, efficiency and quench stability. The paper describes the structure of the program and the interaction between both computer hardware and software and the superconducting rectifier. However, because the reliability of computersystems is unsatisfactory an additional hardware protection system still handles the most important alarms.
1 citations