| 摘要 |
PURPOSE:To make it possible to predict the disconnection of a water cooled cable, by a method wherein the change in the cross area of the water cooled cable is detected when a comparison value with impedance at a normal time exceeds a predetermined value because the change in the cross area of said cable appears largest at the change in DC resistance to output a signal to an alarm circuit. CONSTITUTION:The ratio of the voltage drop VK of a water cooled cable 2 detected by a voltage drop detector 6 and the voltage Vo of a main circuit detected by a transformer 5 for a measuring instrument, that is, the ratio V= VK/VO is compared by a first comparator 7 and this value V appears as the change in the impedance of the water cooled cable 2. Therefore, it is compared to the impedance ZR of the water cooled cable 2 as a new one from a reference signal input terminal 8 by a second comparator 9 and, when a V/VR value exceeds a predetermined value, a signal is outputted to an alarm circuit. As mentioned above, by detecting the impedance change by converting the same to voltage change, the change in the cross area of the water cooled cable 2 can be detected in good sensitivity. |
