| 摘要 |
PURPOSE:To protect a wire from break by practicing a forced electric discharge when there exists a pseudo-shortcircuit or a pseudo-arc, and if normal condition is not recovered after a certain period of time, electric current is reduced. CONSTITUTION:Voltage Vg between two electrodes and reference voltage V1 are compared at a voltage between two electrodes detecting circuit 20 which consists of a comparator in which an operational amplifier is used. When the voltage Vg between the two electrodes decreases, output ''eo''of the comparator 20 turns to be negative, and a condencer Co is charged. After a certain period of time, output of another comparator 21 reaches nil. Then ''off'' time of a switching element 16 in a charging circuit is extended, thus reducing electric current required for machining. |
