ROTATIONAL SPEED CONTROL DEVICE FOR AN ELECTRIC MOTOR

摘要

The invention concerns a rotational speed control device for an electric motor (11) fed by a direct voltage source (13). The device has a controlled switch device (23) by means of which the motor voltage is alternately switched on and off under the control of a modulated switch pulse sequence. The switching frequency is higher than the frequency corresponding to the time constant of the electric motor (11). The switched motor voltage is regulated to a voltage set value corresponding to a desired rotational speed of the motor by influencing the modulated switch pulse sequence.