METHOD AND CONTROL UNIT FOR OPERATING A DRIVE TRAIN

The invention relates to a method for operating a drive train, in which the drive train (10) is designed in particular as a pump or a compressor, having a main drive (11) which is designed as an electric machine that can be operated at a constant rotational speed, having an auxiliary drive (12) which is designed as an electric machine that can be operated at a variable rotational speed, and a speed control gearbox (13) having a fixed mechanical transmission ratio is connected between the two drives (11, 12) and the drive train (10), i.e. for starting the drive train and for pulling the drive train (10) to a defined set rotational speed. The main drive (11) is started via a direct online start-up in which it is directly coupled to the supply network (15). In the case of an intermediate connection of a converter (14), in which the converter (14) is indirectly coupled to the supply network (15), the auxiliary drive (12) is activated simultaneously with the main drive (11) or at some pointbefore the main drive (1