| 摘要 |
PURPOSE:To prevent overvoltage applied to a snubber capacitor, by a method wherein when charging voltage of the snubber capacitor rises to power source voltage or higher a capacitor is connected in parallel to a GTO thyristor. CONSTITUTION:If a GTO thyristor 4 is turned off, current flowing in the GTO thyristor 4 passes through a diode 8 and a capacitor 12 thereby rapid rising of voltage applied to the GTO thyristor 4 is prevented. When charging voltage of the capacitor 12 attains to charging voltage of a second capacitor 24, i.e., power source voltage, a diode 20 is rendered conductive and current flowing in the capacitor 12 only passes also through the second capacitor 24 thereby voltage rise rate is rapidly reduced.
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