| 摘要 |
The load (M) may be a single-phase or polyphase motor fed from a three-phase network (U,V,W) via an electromechanical switch (20) and an inverse-parallel thyristor switch (30) operated by a controller (40), which energises the coil (53) of a shunt contactor (50) connected in series with a resistor or transformer (60) across the thyristor switch. The resistor or transformer establishes a DC voltage (V) across the thyristor switch when the contactor is closed. Its impedance is chosen such that the thyristor switch is rendered conductive when an overcurrent appears and closes the shunt. |
