Abstract: The invention relates to a device and a method for estimating the rotational speed ? of an electric motor when freewheeling, the method being carried out in a variable speed drive for controlling the motor by generating reference alternating voltages Va, Vb. The method comprises a step for measuring the measured flux and torque currents Id and Iq of the motor in an orthogonal two-phase marker d, q, a step for determining said reference voltages Va, Vb, by carrying out a current regulation on the basis of said measured currents, and on the basis of zero reference currents Idref and Iqref in said marker d, q, and a step for calculating the rotational speed ? by evaluating the angle of rotation of the voltage vector, the components of which are said voltages Va, Vb in a fixed orthogonal two-phase marker a, b.

Abstract: The invention relates to a device and a method for estimating the rotational speed ? of an electric motor when freewheeling, the method being carried out in a variable speed drive for controlling the motor by generating reference alternating voltages Va, Vb. The method comprises a step for measuring the measured flux and torque currents Id and Iq of the motor in an orthogonal two-phase marker d,q, a step for determining said reference voltages Va, Vb, by carrying out a current regulation on the basis of said measured currents, and on the basis of zero reference currents Idref and Iqref in said marker d,q, and a step for calculating the rotational speed ? by evaluating the angle of rotation of the voltage vector, the components of which are said voltages Va, Vb in a fixed orthogonal two-phase marker a,b.

Abstract: A method and system for managing the voltage of a DC bus of a speed controller for an AC electric motor linked to a current distribution network. The method includes comparing a value of the voltage measured on the DC bus with a determined limit value, when the value of the voltage measured on the DC bus becomes greater than the limit value, forcing the slope of an internal ramp to a zero value so as to confer a constant frequency on the stator, and when the value of the voltage measured on the DC bus again becomes less than the limit value, progressively increasing the value of the slope of the internal ramp.

Abstract: The present invention relates to a method for limiting the current output by a speed controller (V) for three-phase asynchronous electric motor (M), said controller (V) operating according to a control law (LC) of pure U/F type. Said method is characterized in that it consists in calculating with the aid of a limitation function a correction value for the frequency of the stator (Wstat) then in applying thereto, so as to obtain, in the voltage control law (LC) of U/F type, a corrected frequency of the stator (Wstatc). According to the voltage control law of U/F type, the method thereafter consists on the basis of this corrected frequency of the stator (Wstatc) in obtaining the control voltage (Vqref) applied to the motor. The invention also relates to a system for limiting the current able to implement said method.

Abstract: The present invention refers to a method and to a system for managing the voltage (Vbus) of the DC bus of a speed controller for an AC electric motor (M) linked to a current distribution network (Rd). The method is characterized in that it consists in: comparing a value of the voltage (Vbus) measured on the DC bus with a determined limit value (Vlim), when the value of the voltage (Vbus) measured on the DC bus becomes greater than the limit value (Vlim), forcing the slope of an internal ramp (R) to a zero value so as to confer a constant frequency (Wstat) on the stator, when the value of the voltage (Vbus) measured on the DC bus again becomes less than the limit value (Vlim), progressively increasing the value of the slope of the internal ramp (R).

Abstract: This invention relates to a system for limitation of the output current from a speed controller for three-phase asynchronous electric motors, comprising a PWM type converter in which the electronic switches are controlled by a microcontroller circuit (Mc), characterized by the fact that the microcontroller circuit comprises means (LIC) of calculating the modulus of the current vector using motor phase current measurements, and comparing it with a limitation set value in order to obtain a limitation error (y) and to calculate a correction voltage (&Dgr;V) that is added to the control voltage (V) applied to the motor.

Abstract: This invention relates to a system for limitation of the output current from a speed controller for three-phase asynchronous electric motors, comprising a PWM type converter in which the electronic switches are controlled by a microcontroller circuit (Mc), characterized by the fact that the microcontroller circuit comprises means (LIC) of calculating the modulus of the current vector using motor phase current measurements, and comparing it with a limitation set value in order to obtain a limitation error (y) and to calculate a correction voltage (&Dgr;V) that is added to the control voltage (V) applied to the motor.

Abstract: A frequency converter for an asynchronous motor including a voltage converter (O) equipped with switches (Sa, Sb, Sc) controlled by a control circuit (CC) and powered by a DC bus (B) on which a shunt (Sh) is installed to measure a DC current passing through the bus, wherein, when at least one of two components of an output voltage vector Vs is less than a predetermined value TMIN, the frequency converter includes a device which calculates firstly a vector Vs' each of two components thereof being at least equal to the predetermined value TMIN, and secondly a vector Vs" such that vectorial average of Vs' and Vs" is equal to the output vector Vs.