Study on High Temperature Superconducting Power Device Due to Dynamic Control of Magnetic Shield Functions

从磁屏蔽功能动态控制的角度对高温超导故障限流器和超导功率器件进行了研究，在磁屏蔽型超导故障限流器的研究中，提出了一种将控制用磁场绕组环形缠绕在超导屏蔽管上，通过施加频率在几千赫兹左右的交流磁场来动态控制超导特性的主动控制方法。研制了具有这种主动控制线圈的故障电流限制器，并对其各种特性进行了实验和计算机仿真研究。结果表明，施加频率在几千赫兹左右的交流磁场会使磁通流电阻率显著提高，从而使限流阻抗变得比没有主动控制时大得多。这一事实表明，虽然到目前为止，磁通流电阻率被认为只受磁场和/或温度的控制，但它还将取决于交流磁场频率的大小。对于超导功率器件，利用由薄膜超导圆盘和闭路铁芯组成的装置，研究了铁芯中磁通的动态行为。结果表明，铁芯中的磁通将由薄膜的超导向正常导电转变所控制。

The high Tc superconducting fault current limiter and the superconducting power device were studied from a view point of dynamic control in the magnetic shielding functions.In the research on the magnetic shield type superconducting fault current limiter, an active control method in which the field winding for control is wound on the superconducting shield tube in a toroidal fashion and the superconducting properties will be controlled dynamically by applying the ac magnetic field of frequencies of around a few kHz to the one has been proposed. The fault corrent limiters with such an active control coil were fabricated and the various characteristics were studied experimentally and by computer simulation.It was made clear that the flux flow resistivity would be considerably increased by applying the ac magnetic fields of frequencies of around a few kHz and accordingly the current limiting impedance would become fairly large as compared with the case without an active control. This fact indicates that although the flux flow resistivity was thought to be controlled only by magnetic field and/or temperature so far, it will also depend on the magnitude of the frequency of ac magnetic field. The reason why the flux flow resistivity will be affected by the frequency of ac field is not clarified yet, but the phenomenon will be very useful for the improvement in performances of the fault corrent limiters.As for the superconducting power devices, the dynamic behaviors of magnetic flux in the iron core were investigated by using the device consisted of the thin film superconducting discs and the closed circuit iron core. It was clarified that the magnetic flux in the iron core would be controlled by the superconducting to normal conducting transition of the thin film.