the pulse control stage 6 the two decoupler diodes 5 10 each takes care of the smaller modulation value of the rpm regulator 4 and the current regulator 9 respectively accordingly these elements assume the regulation of the modulation which corresponds to the functional mode of a so called two channel limitation control 34 foldbackcharacteristic 34 in accordance with the invention by tuning the motor characteristic to the adjustment parameters of the rpm regulator 4 and the current regulator 9 the drive of the motor passes through three different segments note fig1 in segment 1 below or to the left of m n the drive operates in a rpm controlled manner the rpm regulator controls the drive in segment 2 between m n and m limiting the drive operates along its natural characteristic curve that is the natural speed torque curve without speed control the the rpm regulator 4 is overcontrolled the triac 2 is completely modulated the maximum possible voltage is applied to the motor 1 corresponding to the voltage of the mains neither of the regulators 4 9 controls the drive when m limiting is reached or exceeded that is at i i limited the equilibrium between i ref and i act at the current regulator is reached accordingly current regulator 9 assumes the guidance and control of the drive in the reverse direction to prevent a further rise of the current the drop in the rpm connected therewith causes a drop of the current reference value through the reference value generator 11 whereby another reduction of the modulation is caused to the.