| 摘要 |
PURPOSE:To effectively suppress surge and to prevent the breakdown of elements by a method wherein the dv/dt at the time of turn off is suppressed and the peak value is suppressed as well. CONSTITUTION:Surge absorbing circuits consisting of capacitors Cu, Cx-resistors- Ru, Rx-diodes du, dx are connected in parallel with the terminals of each gate turn off thyristors Su, Sx which composes a bridge inverter and dv/dt at the time of turn off is suppressed and di/dt at the time of turn off is also suppressed by reactors Lu, Lx at positive and negative sides. And, furthermore, surge absorbing circuits consisting of diodes D10, D20 are respectively connected in parallel with a reactor Lu at positive side and that Lx at negative side in each arm and the peak value of dv/dt at the time of turn off is controlled. In this way, the suppression of dv/dt and the peak value are isolated for control. Therefore, the most effective surge suppression can be done and the breakdown of elements caused by switching loss or the like can be prevented. |
