摘要 |
If the supplying converter (3, 4) of a rotating-field machine (2) is controlled with a desired frequency f* which corresponds to the sum of a desired slip-frequency value fs* and a rotor rotation speed /f1/ which is deacted only in terms of its magnitude, an opposing torque which acts on the rotor and moves the rotor against the desired rotation direction can lead to false frequency control. In order in these cases to be able to estimate negatively the rotor rotation speed, which is detected in terms of its magnitude, the actual flux value ( psi ) is calculated and is compared with a desired flux value ( psi *) which is determined by the control variables of the converter (comparison element 18). In the event of false frequency control, a changeover command is determined from the deviation between the two flux values, by means of which command the rotor rotation speed, which is deacted in terms of its magnitude, is estimated negatively in the formation of the sum (changeover switch 19) (Fig.1). <IMAGE> |