Circuit arrangement for operating a multi-phase synchronous motor in a direct voltage network

A circuit arrangement for operating a synchronous motor including a multi-phase armature winding in a direct voltage network, the arrangement comprising a switching device for the successive connection of the winding phases of the armature winding to a direct mains voltage, the switching device including a plurality of semiconductor switches that are associated with the individual winding phases, and a commutation device for the actuation in the proper sequence of the semiconductor switches by means of switching signals in conformance with the rotary position of the rotor of the synchronous motor, characterized in that each control input (G) of the semiconductor switches (14-16;

• 41-44) is preceded by an analog difference former (18-20;
• 51-56) which receives, on the one hand, the switching signal (S1-S3;
• S1-S6) associated with the semiconductor switch (14-16;
• 41-46) and, on the other hand, a reference signal derived from the phase sum current of the armature winding (10);
• and the actuation of the semiconductor switches (14-16;
• 41-46) is effected by the difference formers (18-20;
• 51-56) in such a manner that the semiconductor switches (14-16;
• 41-46) are fully energized as long as the amplitude of the switching signal (S1-S3;
• S1-S6) is greater than the amplitude of the reference signal.