Method for controlling an electric motor

摘要

A method is disclosed for controlling the rotation speed of an electric motor, using a frequency converter. Command values for an amplitude value (Vla) of a primary voltage (terminal voltage) of the motor, and a phase difference between the primary voltage and an induced electromotive force, that is to say the internal phase angle ( delta ) are arithmetically determined on the basis of at least one primary frequency command ( omega *l) and a torque current command (I*lq) (or torque command). The output voltage of the frequency converter is controlled in accordance with these commands. The arithmetic determination of the internal phase angle ( delta ) is carried out separately by an approximation in accordance with delta = delta l - delta r, on the basis of a phase angle component ( delta r), using the resistance voltage loss and a phase angle component ( delta l) using a reactance voltage drop in the motor. In the arithmetic determination of the primary voltage amplitude (Vl) is carried out using the internal phase angle ( delta ).