| 摘要 |
PURPOSE:To prevent joule heat generation even if performance of a high temperature superconductor lowers by using a plurality of high temperature superconductors to take a normal temperature terminal out of each thereof to the outside of a heat insulating vacuum container and by providing a voltage measurement lead to each of the high temperature superconductors. CONSTITUTION:A superconductive coil 1 is excited with normal temperature side terminals 5 in parallel in connection with an excitation power supply in normal temperature environment. A voltage is not generated when a high temperature superconductor is in a superconductive state when energized but generated when it is in a normal conductive state. Therefore, if a voltage of both ends of the high temperature superconductor is measured by a voltmeter 15 connected to a voltage measurement instrumentation lead line 14, a lead 9b which is shifted to a normal conductive state with deteriorated performance containing water, etc., can be known. The lead 9b of a high temperature superconductive material which is shifted to a normal conductive state is cut off from the excitation power supply at a normal temperature side terminal 5 and the superconductive coil 1 is excited through the lead 9b of a sound high temperature superconductive material. |
