Circuit arrangement for controlling the starting and braking of three-phase asynchronous motors and method for operating such a circuit arrangement

摘要

In a circuit arrangement for controlling the starting and braking of three-phase asynchronous motors, at least one phase of the motor current leads (u, v, w) being used for phase control and each phase control device having at least one thyristor, controlled by a control device, a connecting lead being provided between the motor current leads (T1, T2) of two phases (u and/or v and/or w) after at least two phase control devices (11, 12), in which connecting lead there is arranged a switchable semiconductor component having a rectifier effect, in order to achieve a high positioning accuracy it is provided that a speed detecting device (34) has an integration device (40), acting as an actual distance transmitter, connected downstream from it, the output (41) of the latter being connected to a difference- forming device (42), the other input of the difference-forming device (42) being connected to a preset device (43) for presetting the nominal positioning distance after reaching a proximity switch (2), that the output of the difference-forming device (42) producing an actual residual-distance signal has connected downstream from it a preset device (44) for the nominal speed (n) as a function of the residual distance (s), and that the output (45) of this preset device (44) is connected to the input (46) of the speed regulator (37). IMAGE