Identification of internal parameters of asynchronous electric motor

Abstract

An important practical problem which solution is necessary in the operation of variable frequency asynchronous electric drives with vector control in installations used in industry and agriculture is the constant identification of the instantaneous value of the generalized rotor flux-coupling vector, its modulus, phase angle, harmonic functions or projections of this vector on the orthogonal coordinate axes which are stationary relative to the machine stator. The values of these parameters of the asynchronous electric drive are used to determine the energy modes of operation and to calculate the mechanical and electromechanical characteristics of the electric drive, including equivalent schemes. The modern approach to asynchronous electric drive regulation through solving the problem of indirect identification of internal parameters of the induction machine mainly consists in realization of this identification without installation of rotating mechanical sensors of position and rotor speed on the machine shaft. This approach simplifies the technological manufacturing of the induction machine and does not require its execution with two output ends of the shaft. The paper analyzes the methods used to identify the operating mode parameters of frequency-controlled asynchronous AC electric drive used in industrial plants and agricultural equipment. Universal algorithms of identification of projection of generalized vector of rotor flux-coupling, speed and other parameters of frequency-controlled machine mode at supply from frequency converters with pulse-width modulation are developed. The accuracy of regulation of the developed algorithms for the frequency-controlled asynchronous electric drive is determined by the accuracy of measurements of stator voltages and currents of the induction motor and is especially high when the motor is used on mechanical characteristics up to the critical slip in the range well described by the refined Kloss equation. The developed and proposed algorithms of identification of internal parameters of induction motor have a number of important features including those that allow determining with their help all the necessary parameters of energy modes of frequency-controlled AC electric drive.