| 摘要 |
PURPOSE:To shorten the starting time while to prevent deterioration of flux by providing a roughly wound section near the auxiliary electrode of an outside coil wound over an inside coil for holding the electron emission substance thereby promotion arc discharge between main and auxiliary electrodes. CONSTITUTION:A roughly wound section 10a is provided in the outside coil 10 near an auxiliary electrode 3 to expose the inside coil 9 having electron emission substance thus to exist electron emission substance near the auxiliary electrode 3. Consequently, an arc spot is formed at the section 10a concentrically to promote arc discharge between main and auxiliary electrodes 2a, 3 while to retard glow discharge between main electrodes. Consequently, the starting time of arc discharge is shortened to reduce the ion impact between main electrodes due to glow discharge resulting in improvement of flux deterioration. |
