Method and system for limiting the current output by a speed controller operating according to a U/F control law

System for limiting the current output by a speed controller for three-phase asynchronous electric motor (M), said controller (V) comprising an inverter of PWM type whose electronic switches are commanded by a microcontroller circuit (Mc) operating according to a voltage control law (LC) of pure U/F type in which the voltage (Vqref) applied to the terminals of the stator of the motor is proportional to the frequency of the stator (Wstat) in accordance with a determined constant (k), said system being characterized in that it comprises means (LIC) for:

• comparing, on the basis of the measurements of the phase currents of the motor (M), the modulus of the vector of these phase currents (ModI) with a limit value (Ilim) so as to obtain a limitation error,
• calculating, as a function of this limitation error, a correction voltage (dV),
• calculating, when the modulus of the vector of the phase currents (ModI) is greater than said limit value (Ilim), a correction value for the frequency of the stator (Wstat) by multiplying said correction voltage (dv) by the inverse of said determined constant (k),
• applying this correction value for the frequency of the stator (Wstat) in the voltage control law (LC) of U/F type so as to obtain a corrected frequency of the stator (Wstatc),
• calculating the product of the corrected frequency of the stator (Wstatc) with said determined constant (k) so as to obtain the control voltage (Vqref) applied to the motor (M).