| 摘要 |
<p>To have better control of the short circuit problem occurring in connection with the reversal of direction of rotation of controllable three-phase asynchronous motors, and thus to be able to change the direction of rotation without prior decrease in the speed of rotation, the reversal circuit (30) is associated with a blocking device (43) which allows reversal only after the inverter switching elements arranged in series have been extinguished. In addition, the frequency of the frequency generator (9) is kept proportional to the regulated direct voltage (U1). There is no destruction of the switching elements since the reversal process in each case virtually coincides with an extinction process. <IMAGE></p> |
