rotor 20 acting in the closing direction of the throttle valve 10 is applied to the three phase winding 18 a rotary field frequency f 20 hz is for instance selected for this which at the squirrel cage rotor 20 generates a torque that is approximately on the order of magnitude of the breakdown torque of the asynchronous motor 17 once the closing position of the throttle valve 10 is attained the rotary field frequency is returned to zero again if certain applications also require a high opening speed of the throttle valve 10 then in the same way first a high rotary field frequency can be applied to the three phase winding 18 and this frequency is then reduced far enough that the desired opening angle of the throttle valve 10 is established to this end the set point value is first raised far enough that a rotary field frequency of f 20 hz for instance is specified by the microcomputer 40 and then the set point value is reduced far enough that the rotary field frequency f 2 for instance is applied if the rotational angle u03c6 2 of the throttle valve 10 is to be established in order to increase the adjusting force at the throttle valve shaft 14 at a specified drive moment of the asynchronous motor 17 or conversely to enable reducing the drive moment of the asynchronous motor 17 if the adjusting force at the throttle valve shaft 14 remains constant a step up gear can also be disposed between the drive shaft 15 and the throttle valve shaft 14 the invention is not restricted to the exemplary embodiment described for instance the short circuit rotor can also be embodied as a simple solid rotor of electrically conductive material such as iron or copper.