| 摘要 |
PROBLEM TO BE SOLVED: To solve a problem that it is difficult to determine whether a three-phase interrupting element is in disorder. SOLUTION: The electron beam generating device is provided with an electron gun generating electron beams, an accelerating voltage detecting circuit detecting an accelerating voltage of the electron gun, an emission current detecting circuit detecting an emission current of the electron gun, and a determination circuit determining discharge of the electron gun based on an accelerating voltage detecting signal and an emission current detecting signal. In the case the accelerating voltage detecting signal is lower than a given accelerating voltage set value and the emission current detecting signal is higher than a given emission current set value, the electron gun is determined to be discharging, and a current supplied to the electron gun is interrupted by the interruption circuit. COPYRIGHT: (C)2008,JPO&INPIT
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