A Comparative Analysis of Transient Processes in an Asynchronous Motor

Abstract

The results of an investigation of an asynchronous motor in the modes of direct starting and load changing obtained with mathematical modeling using a block of nonlinear systems of Lookup Table type and functional block F_cn of the MATLAB/Simulink software package. Introducing the above-mentioned elements into the model makes it possible to simply take into account changes in the parameters of an electrical machine caused by saturation of the magnetic circuit and the effect of current displacement in the rotor bars in transient modes. The saturation of the magnetic system when passing the main magnetic flux and leakage fluxes is taken into account using functional dependences, which are specified in the blocks by tabular methods, which provides model simplicity and clarity of the modeling process. Unlike a model created based on a standard block of an electric motor of Asynchronous Machine type, the proposed variant makes it possible to observe the changes of any variables of asynchronous machine during the transition process and creates good preconditions for various investigations of electric drives. Using the developed model. the comparative analysis was done of dynamic characteristics, which revealed that the transient processes in the asynchronous motor under direct starting, taking into account the saturation of the magnetic circuit and the effect of current displacement in the rotor flow that is 1.5 times faster than in the ideal machine. In addition, the first maximum of torque is 1.6 times greater than in a simplified motor model. Under a load surge, the differences in the curves of changes of torques and angular velocities are insignificant. If to neglect the effect of current displacement in the rotor bars, the transient processes do not coincide only when starting. The most essential differences are observed between the transient characteristics of the developed model and the model composed of the standard MATLAB Simulink blocks. The obtained results make it possible to draw a conclusion as to the effectiveness of applying the developed motor model when investigation of dynamical modes, selecting a starting and protective equipment of asynchronous electric drives.