| 摘要 |
PURPOSE:To prevent the breakage of a switching element and the bad influence to other elements due to the breakage by installing at least one among an eddy-current detecting means for the switching elements connected in parallel and a means for observing the state between the current input and output terminals of the eddy-current detecting means and the switching elements. CONSTITUTION:When short-circuit breakage is generated between a drain electrode and a source electrode in a transistor Qm1, an eddy current flows in a block B1. Said eddy current is detected by an alarm type fuse F1, which is molten to output an alarm signal, and switch S1 is opened by the alarm signal, and spark erosion work is suspended, and the bad influence for others is prevented. When the short-circuit trouble is generated between the drain and the source of other transistor Qm2 or Qmn, similar operation is carried-out. Thus, the breakage of other transistors and the bad influences for other circuit elements can be eliminated. |
