the operation of an electromagnetic schaltungsanordnung betätigbaren, mechanical brake of an electric motor

摘要

Electric motors, in particular geared motors, are often equipped with electromagnetically actuated mechanical brakes. In order to ensure that an excitation coil (3) can be operated with alternating-current mains supplies of various voltages, it is proposed to generate a unipolar voltage that varies over time with a certain period by means of a voltage source (2), the output voltage of which is positive and different from zero in a first time segment of this voltage period and in this first time segment has a maximal value, and in a second segment of the voltage period is zero or approaches zero. To pass an excitation current from the voltage source (2) to the excitation coil (3), a current path (15) is provided that is opened substantially at the beginning of the first time segment. The current path (15) is blocked again at a certain point within the first time segment, this point being selected such that the excitation current does not exceed a predetermined maximal value. During a time span in which the excitation coil (3) is or should be permanently excited, the opening and blocking of the current path are repeated in each voltage period.