| 摘要 |
Such a method for the exact control of the speed of a direct- current motor is carried out by changing the actuation current within a period. In these cases, a direct-current motor is used instead of an alternating-current motor with mechanical down-stepping. The direct- current shunt motor is connected via its excitation winding to a constant voltage; the magnetic flux is therefore also constant except for a small weakening due to the armature reaction. Even when loaded, the speed of the direct-current shunt motor is quite constant. For selected cases in which machines and devices are to be driven with machine parts which move backwards and forwards and themselves in turn control other elements, the usual control method by varying the actuation current is not adequate. A speed control method operating with the highest degree of accuracy consists in using the comparison value between actual and reference value according to determined negative or positive sign in the form of pulse pauses in each case between pulse sequences at the beginning of the period in order to switch off the pulsating actuation current with the duration of the difference between the actual and the reference value. The associated circuit arrangement uses a reference or actual value counter (Z1) with the predetermined counting value, a comparator (V1) and a pause timing counter timing (Z2), the pause timer counter (Z2) serving as interrupter for the motor actuating current and stipulating the timing value for the pause length. <IMAGE> |
