Verfahren und Einrichtung zur Drehzahlmessung eines getaktet angesteuerten elektrischen Motors

Verfahren zur Drehzahlmessung eines getaktet angesteuerten elektrischen Motors, wobei der Motor (M) in festzulegenden Zeitabständen (T1) für eine definierte Messzeit (T2) durch das für die Taktung vorgesehene Schaltelement (1) voll aufgesteuert und in dieser Zeit die der Motordrehzahl (n) proportionale Frequenz der Welligkeit im Strom gemessen wird. The procedure includes measurement of a voltage which is proportional to the current, associated with the switching element controlling the motor. The measured voltage is amplified and filtered, delivering a rectangular voltage signal for measurement. The procedure provides measurement of the speed of rotation of an electric motor which is entirely controlled, at intervals of time, by measuring over a period of time determined by a switching element, the frequency of oscillation of a current which is proportional to the speed of rotation of the motor. The circuit measures a voltage which is proportional to the current, associated with the switching element. This measurement is taken before application to an amplifier (5), a filter (3,4,6) and an evaluation circuit for the determining the frequency of oscillation of the current flowing within a measurement phase in which the motor (M) is completely controlled. The measured voltage, which is proportional to the current, is transformed after filtering out the direct current component into a rectangular voltage signal. This is achieved by use of a comparator (7).