Substantiation of engineering methods for identifying optimization modes of asynchronous electric drives

Variable-frequency drive is widely applied in the different industries. Classic methods of operating mode analysis of asynchronous electric drives are the equivalent circuits and vector diagrams. The result of their application is not most often visual and effective. Often the simplifications required for visual clarity are too great. This is the case with the interpretation of the popular optimization of power consumption by reducing the amplitude of the stator voltage. The article proposes a rationale for the modified equivalent circuits and vector diagrams, which makes it possible to evaluate how this optimization affects the entire complex of parameters and variables that characterize the mode of operation of an asynchronous electric drive - changes in rotation speed, slip and rotor current. Simplified vector diagrams and equivalent circuits are proposed, which allow estimating the active and reactive power flows in the electric drive and their changes while optimizing the stator voltage amplitude. Based on the proposed equivalent schemes, calculations were carried out showing the nature of the change in the rotor and stator currents with variations in the stator voltage. The proposed calculation methods made it possible to carry out a comprehensive assessment of the control method for asynchronous electric drives with the main magnetic flux, determined by the ratio of the amplitude of the voltage applied to the motor stator to its frequency, which is significantly lower than the nominal value.