Experimental Studies of the Processes of Stepped Torque Loads Parrying by Asynchronous Electric Drives and Interpretation of Experimental Results by Nonlinear Transfer Functions of Drives

Abstract

This article presents the results of experimental studies of asynchronous motors with a short-circuited rotor (induction motors—IM) with the most common frequency control methods: scalar; vector control; vector with speed control circuit; scalar control with dynamic compensation. The purpose of the experiments was to identify and show the features of the reaction of these control methods to the stepped sketches of the load on the asynchronous electric drive, as in a nonlinear electromechanical system. When selecting the parameters and settings of the “Schneider electric” frequency converter settings, standard instructions and techniques have been used, so the settings of the regulators were not optimal. The aim was not to determine the most effective structures and show fundamentally new solutions. Asynchronous electric motors are substantially nonlinear structures. In the formation of vector control theory, a number of simplifications and assumptions were used, the cost of which was not very clear and theoretically difficult to assess. This work is a step towards estimating the cost of these simplifications. This paper provides the results of experiments in which step-loading modes are presented by the maximum possible registered signals and the amplitude of the stator voltage, formed by various algorithms, the frequency and amplitude of the rotor current and the actual sliding and rotation speed of the engine rotor. This made it possible to maximally objectively assess the effectiveness of the interpretation of asynchronous electric drives and the methods of their regulation. The authors have conducted research in this area for about 15 years. In numerous articles on this subject over the past 25–30 years, the authors did not find such results. The vast majority of work devoted to the study of asynchronous electric drives with frequency control uses the notion of not too significant errors in the linearization of Park’s vector equations. In particular, the concepts of the sinusoidality of currents and voltages in AC motors and the accuracy of vector equations are almost always used, which are valid only at a constant frequency of the stator voltage.