Abstract: The machine comprises an electric driving motor, a speed reducer having at least two mechanical ratios coupled to the output shaft of the motor, a device for changing the mechanical ratio and a speed variator of the electric motor. The machine further comprises devices (7, 35, 36, 41) for selecting and displaying the speeds of rotation of the electric motor coupled to the device for changing the mechanical ratio.

Abstract: The variator comprises a triggerable silicon-controlled rectifier component for connection in series with the a.c. motor to the a.c. source, and a phase-shifting circuit connected to the terminals of the rectifier component and comprising a capacitive branch and a resistive branch which has a regulating potentiometer. The junction between these two branches is connected to the control electrode of the rectifier component. A unidirectional semiconductor component responsive to voltage is connected in parallel with the capacitive branch and a part of the resistive branch in which the potentiometer is inserted. The resistive branch comprises connected in parallel a first branch comprising a first resistor and the potentiometer and a second branch comprising a second resistor and a third resistor. The junction between the second and third resistors is connected to the slide of the potentiometer and the unidirectional component is connected to the junction between the potentiometer and the first resistor.

Abstract: A device for limiting the current in an a.c.motor having a commutator adapted to be supplied with current by a single-phase current source. The device comprising a triggerable silicon-controlled rectifier component connected in series with the motor and in parallel with an RC phase-shifting circuit furnishing the control voltage of the rectifier component. The capacitive branch of the RC circuit is connected in parallel with a shunt circuit which shunts a certain quantity of the charging current of the branch for modifying the trigger instants of the rectifier component. The shunt circuit comprises two transistors of opposed conductivity types which are connected with a common emitter configuration, the collector-emitter circuits of the transistors being connected in parallel with the capacitive branch. The limiting device further comprises a control circuit furnishing two d.c.