Engineering methods for calculating the operating modes of asynchronous electric drives with a weakened main magnetic flux

This article discusses engineering methods for calculating the operating modes of asynchronous electric drives with frequency control and with a reduced main magnetic flux. Magnetization currents and rotor currents are calculated by methods based on simplified equivalent circuits for induction motors and vector diagrams. The conditions for the minimum stator current are given and it is proved that this state corresponds to the equality of the amplitudes of the magnetizing current and the rotor current (reactive and active currents, respectively). This provision makes it possible to estimate the current of the rotor of an asynchronous electric motor when the main magnetic flux is weakened. The calculation of the rotor and magnetization currents is carried out according to experimental data. The proposed calculation methods are necessary for optimizing the operating modes of asynchronous electric drives operating with a load less than the nominal one. This optimization consists in reducing the maximum amplitude of the stator voltage. The proposed methods make it possible to evaluate the decrease in the magnetization current and the increase in the rotor current, which may be excessive.