Étude des processus ondulatoires et des surtensions dans les moteurs asynchrones alimentés par des convertisseurs à semi-conducteurs

Mohand Tahar Belassel, University of Tizi Ouzou, Algeria

Abstract

This work concerns the survey of undulatory processes and over voltages in the asynchronous machines fed by semiconductor frequency converters which are controlled by PWM strategy type. It includes the different stages of usual calculation of electric machines, with explanation of certain construction particularities of the asynchronous machine fed by frequency converters. It emphasises the calculation of the undulatory parameters and the undulatory voltage determination in any point of the asynchronous machine winding for different time periods. The calculation of the undulatory parameters with the geometric method requires the knowledge of the machine geometric measurements and the development of equivalent schematic diagram while considering a simplifying hypothesis set and taking in account all the physical phenomena that intervene in an undulatory process. To analyze the physical phenomena that take place in drivers, in iron, and in the insulation during the undulatory process (UP), we replace the non-stationary phenomena that take place on the forehead of the wave by a high equivalent frequency. In this case, to take into account the manufacture in sheet of the sheet metal packet, the permeability of the iron ìr is replaced by a fictional environment with a relative complex magnetic permeability ìfeui and the dielectric losses in the insulation are valued by the admittance G. The undulatory voltage calculation is achieved by using FOURIER analytic method to solve the partial derivative differential equation (called telegraphic) of undulatory processes. To take into account the frequency dependence of R, L, and G parameters, iterative method will be used. The comparison of calculation results and experimental tests allowed us to conclude that the calculation modelling is adequate.