Determination of the number of revolutions of electrical machines

Zur Drehzahlerfassung (n) bei elektrischen Maschinen (3) wird ein dem elektrischen Moment (i) und den auftretenden Laststörungen (L^) proportionales Signal mit einer der Zeitkonstante (T?) der Maschine (3) proportionalen Zeitkonstante T^?) integriert und als errechneter Drehzahlistwert (n^) benutzt. Die Laststörungen (L^) werden durch Vergleich der Frequenz eines mit der Maschine (3) gekuppelten elektrischen Pulsgebers (4) mit einer dem errechneten Drehzahlistwert (n^) proportionalen Sollfrequenz ermittelt. 1. A device for producing a signal which corresponds to the actual rate of rotation of an electrical machine, with a pulse generator (4) coupled to the machine (3) to produce a pulse sequence having a pulse repetition frequency proportional to the rate of rotation of the machine, characterized by the following features : (a) means for the production of a signal (i) proportional to the electrical moment of the machine, (b) a correcting circuit which serves to superimpose on the signal (i), proportional to the electrical moment, a correcting signal proportional to the load moment (Le which acts upon the machine, (c) an integrator (51) which produces the rate of rotation actual value (n) by integrating the output signal of the correcting circuit with a time constant (Te ) proportional to the time constant (Te ) of the machine, and (d) a comparator circuit (53-56; 58, 59) which obtains the correcting signal by forming the difference between the pulse repetition frequency and the actual rate of rotation and integrating the difference signal.