| 摘要 |
PURPOSE:To reduce current running in a protective circuit when a magnet is being excited and to reduce the Joule loss by a method wherein a protective circuit, in which a low resistor and a permanent current switch are series-connected, is parallel- connected to a magnet coil, the permanent current switch is maintained in a normal conductive state when a magnet is excited, and the permanent current switch is maintained in a superconductive state after said excitation is finished. CONSTITUTION:The current loss generating in a protective circuit is indicated by the quantity of heat W1=V<2>/(R+r) when the resistance value of a permanent current switch (PCS) 4 is set at (r). Accordingly, if the PCS 4 is maintained in the normal conductive state and allows the resistance (r) in that state when a magnet is excited, the resistance of the protective circuit is brought to (R+r), which is larger than before, and the value of W1 is reduced. Also, in the mode of permanent current, a magnet coil and the PCS 2 can be protected by the desired protective resistor 3 by having the PCS 4 in the superconductive state of r=0 in the same manner as the PCS 2 of a magnet. The permanent current switch usually has the structure wherein an electric heater is wound on a superconductive wire, electric resistance is generated on the superconductive wire or its resistance in brought to zero by turning ON or OFF the heater. This well known switch can be the PCS 4. |
