PURPOSE: To stabilize arc discharge by providing a discharge length detection circuit between electrodes and/or a pulse group period detection circuit and comparing a discharge length and a pulse group period with set values respectively and correcting the rated output time and output period of pulse current groups according to respective deviation quantities.
CONSTITUTION: An inverter circuit part 10 to output the plural pulse current groups to the discharge electrodes is provided and a control circuit part 999 provided with a discharge length detector 12 between the electrodes, a pulse group period detector 514A, a discharge length setter 14 and a pulse group period setter 514B is arranged. The discharge length detector 12 compares the detected discharge length with the set value via voltage measurement between the discharge electrodes and the rated output time of the pulse current groups is corrected according to its deviation. At the starting point and the finishing point of the discharge, the rated output period is corrected according to deviation between the detected pulse group period and the set value. By this method, the arc length during discharging is always maintained uniform and the arc discharge is stabilized.
EGURI SHIGEO
UEDA YOSHIHIRO
