With the soft start device SAE 3 a bi-directional power semi-conductor is integrated into one of the phases. By contolling its firing angle in a time-dependant manner only a small current flows into one of the phases. The current is steadily increased until the max. current flow angle is reached. In this way the max. torque is present which is sufficient enough to enable a save start even with drives having a large friction torque at standstill. The current rise time (running-up time) and the initial torque of the motor can be seperately set. The settingpotentiometers are accessible by removing the front cover. When the max. current flow angle is present after the settable starting time has elapsed a relay contact shortens the power semi-conductor, thus removing the starting electronics from the circuitry. Since only 1 phase is influenced, an asymmetric rotating field is generated which causes a higher thermal loss of the motor.