A.C. loss contributions of the transport current and transverse field caused by combined action in a multifilamentary wire

A.c. losses caused by an a.c. transport current and a transverse a.c. magnetic field during simultaneous action were measured. The loss contributions have been obtained separately. The measurements were performed on a NbTi multifilamentary wire having a CuNi matrix of low conductivity in order to prevent eddy currents. The test configuration is presented and measurement results as well as theoretical confirmation are dealt with

A fast operating magnetically controlled switch for 1 kA

The power of fully superconducting rectifiers can be improved by increasing either the operating frequency or the transformer primary inductance [1]. The frequency is usually limited by the recovery time of thermally controlled switches. In order to achieve a higher switching speed, magnetically controlled switches are preferable [1,2]. This paper describes a magnetically controlled switch which can be used for currents up to 500 A at 25 Hz. The switch element, consisting of several Nb1%Zr multifilamentary superconductors, is placed between two concentric solenoids which generate the necessary magnetic field. The Nb1%Zr superconductor is well suited for this purpose because of its relatively low critical field (¿ 0.75 T) and high maximum current density (about 5.109A/m2below 0.3 T)

A new test setup to measure the AC losses of the conductors for NET

A description is given of a new test system currently under construction. The system will be used to measure the AC losses of subcables from Next European Torus (NET) conductors. A special feature of the test arrangement is that the losses will be determined while the sample carries a transport current and is at the same time subjected to a changing magnetic field in the transverse and longitudinal directions. Several aspects of the design, such as magnetic field, forces, and losses, are discusse

A high-power magnetically switched superconducting rectifier operating at 5 Hz

Above a certain current level, the use of a superconducting rectifier as a cryogenic current source offers advantages compared to the use of a power supply at room temperature which requires large current feed-throughs into the cryostat. In some cases, the power of such a rectifier is immaterial, for example if it is to be used as a current supply for short test samples with low inductances. Usually, however, a rectifier is intended to energize large superconducting magnets, so the maximum power available becomes an important parameter since it determines the loading time. One method of increasing the power of a rectifier is to raise the operating frequency. In this respect, magnetically controlled switches with very fast switching times are preferable to thermally controlled ones. This paper reports on the design, as well as the experimental results of a magnetically switched full-wave superconducting rectifier. Once this rectifier is brought to its design frequency of 5 Hz, the average power delivered to the cryogenic load will be 500 W

Experimental results of thermally controlled superconducting switches for high frequency operation

As part of a study to develop thermally controlled switches for use in superconducting rectifiers operating at a few hertz and 1 kA, a theoretical model is presented of the thermal behavior of such a switch. The calculations are compared with experimental results of several switches having recovery times between 40 and 200 ms. A discussion is given of the maximum temperature T/sub N/ that occurs in the normal regions when the switch is in the resistive state. Once T/sub N/ is known, it is possible to predict the recovery time, activation energy, stationary dissipation and minimum propagation current. The calculated and measured results, in good agreement, show that T/sub N/ is approximately 12 K and largely independent of the thickness or material of the insulation layer. Mention is made of some problems, related to the room-temperature equipment which drives the rectifier, that so far have prevented the rectifiers from being used at their design specifications

Hepatitis in a patient with SLE: Is it autoimmune hepatitis?

In a patient with systemic lupus erythematosus (SLE), we considered the diagnosis of autoimmune hepatitis (AIH) in view of raised serum aminotransferases, hypergammaglobulinaemia, antinuclear antibodies (titre 1:10240), seronegative of markers for viral hepatitis and absence of recent hepatotoxic drug usage. The diagnosis of AIH was supported by using the scoring system, recently developed by the International Autoimmune Hepatitis Group and the excellent response to treatment with prednisone. Liver histology, however, showed no characteristic features of AIH. The relevance of liver histology and scoring for AIH in SLE with hepatic involvement is discussed