| 摘要 |
PURPOSE:To suppress the reverse recovery transient voltage at turning OFF time of a thyristor by connecting a series circuit of a diode of the same polarity, a diode and a capacitor in an anti-parallel with the thyristor. CONSTITUTION:A diode 20 is connected in the same polarity as a thyristor 10, a series circuit of a diode 34 and a capacitor 32 is connected in parallel with the diode 30, a discharging resistor 36 is connected with the capacitor 32, and a time constant is largely set. If a switch SW22 is closed when a load current I0 is flowed through a commutation reactor 20, the diode 30 and the thyristor 10, a thyristor current (i) starts reducing to eventually flow reversely. When the diode 30 is turned OFF, the difference of the current (i) and the current flowed to the diode 30 is flowed to the capacitor 32 and the diode 34, the capacitor 32 is charged in the polarity as shown, and the voltage vc of the capacitor 32 becomes vcapprox.=E. Thus, the reverse recovery transient voltage when the thyristor is turned OFF is suppressed by the voltage vc. |
