Abstract
The paper presents studies of the system "induction generator-induction motor" with parametric asymmetry on a mathematical model to determine the quality of generated electricity in load operating modes. A mathematical model of the "induction generator-induction motor" system has been developed taking into account losses in steel and parametric asymmetry. The analysis of the transient characteristics of an induction generator when a motor load is connected in symmetrical and asymmetrical modes of operation is carried out. The results of changes in the main characteristics of an induction motor at various degrees of parametric asymmetry in the generator are presented. The quality of the generated electricity was analyzed based on the calculations of the unbalance coefficients for each of the operating modes. The assessment of the thermal state in steady-state conditions was carried out using an equivalent thermal equivalent circuit. Thermal transients were investigated when starting an induction motor from an autonomous energy source based on an induction generator. On a thermal mathematical model, the study of the effect of the output voltage asymmetry on the heating of the connected induction motor was carried out. It is shown that the asymmetry of the output voltage of an induction generator reaches 3–10 % and causes overheating of the windings in excess of the permissible values. A regression model has been developed for studying the operating conditions of an induction motor when powered by an induction generator with an asymmetry of the stator windings. The use of the obtained equations will make it possible to determine the most rational combination of factors affecting the heating of the stator windings of induction machines, in which they will not overheat above the maximum permissible temperature values of the corresponding insulation classes
Highlights
The development of agriculture leads to an increase in demand for autonomous power supplies (APS)
The following objectives were set: – development of a mathematical model of an autonomous induction generator with capacitor excitation, taking into account losses in steel and parametric asymmetry in the stator windings; – to analyze the electromechanical and starting characteristics of the motor when powered by an induction generator, taking into account the parametric asymmetry in the stator windings; – to develop a thermal model of the “induction generator-induction motor” system with asymmetry in the stator windings; – to develop a regression model that makes it possible to assess the influence of the asymmetry of the stator electrical circuit on the operation of induction machines
After excluding statistically insignificant coefficients, mathematical models of the second order in natural form, describing the dependence of the temperature rise of the induction motors (IM) stator winding (T) and the voltage unbalance factor (K2U) on the coefficients that take into account the asymmetry in the electric circuit of the stator of induction machines, will take the form: K2U = 55.9345 − 47.1848εA + 21.805ε2A −
Summary
The development of agriculture leads to an increase in demand for autonomous power supplies (APS). The operating modes of autonomous power supplies are characterized by sharply changing loads and require the use of specialized equipment This is especially true of cases when a direct start of induction squirrel-cage motors of comparable power is carried out from an autonomous source. Stable operation of consumers connected in parallel with induction motors (IM) of comparable power becomes impossible, and the electric motors that turn on accelerate very slowly or do not start at all. In this regard, the issue of using the IG as a source for powering the network, which includes the IM, is relevant. Harmonics of various orders appear in the field curve, which cause distortion of the shape of the torque curves and, with a significant proportion of the removed sections, can make it impossible to IM start
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