Abstract: An asynchronous motor is supplied with power from an AC line voltage via a variable speed drive including a rectifier bridge connected to the AC line voltage, a DC voltage intermediate circuit including a capacitor, and an inverter including switches controlled by a control circuit and connected to the phase windings of the motor. A cascade regulation structure includes a frequency regulator, a current limiter and a current regulator driving the control circuit. The frequency regulator input is connected to a ramp generator supplying the motor start speed and the frequency regulator output is connected to the current limiter. The output of the current limiter is connected to the current regulator. The cascade regulation structure is associated with the intermediate circuit to limit the DC voltage at the capacitor by means of the current limiter.

Abstract: An adjustment and dialogue device, more particularly for speed variators comprises potentiometers for adjusting the operating parameters of the variator, a unit displaying these parameters, an advance knob for successively displaying these parameters, a processor whose inputs are connected to the advance knobn and to the potentiometers via a converter and whose outputs are connected to the display unit, and a support being one part of a printed circuit control card located in a casing whose front face has a removable part which can be opened by the user.