| 摘要 |
<p>In rectifiers, or frequency converters with a d.c. intermediate stage, feeding inductive loads transient high voltages may arise. These are sensed by a level detecting element (VD) connected to the common point of a RC element (R1, C2) across the d.c. supply. The level detector output triggers a thyristor (Th) in series with a limiting resistor (Rb), also across the d.c. The thyristor is shunted by an LC element (L, C1). When the voltage level on the first capacitor (C2) rises due to a voltage transient to a predetermined level the detector (VD) responds and excites the thyristor gate, thus applying a controlled short circuit across the d.c. lines. The detector is typically a four layer semiconductor device.</p> |
