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Improvement of protection devices for three-phase asynchronous motors used for agricultural purposes


Author: Şapovalov Veaceslav
Degree:doctor of engineering
Speciality: 05.20.01 - Agricultural Engineering
Year:2020
Scientific adviser: Liviu Volconovici
doctor habilitat, professor, Agrarian State University of Moldova
Institution: Agrarian State University of Moldova

Status

The thesis was presented on the 27 December, 2019
Approved by NCAA on the 28 February, 2020

Abstract

Adobe PDF document – 1.46 Mb / in romanian
Adobe PDF document – 1.40 Mb / in russian

Thesis

CZU 621.313.333

Adobe PDF document 4.22 Mb / in russian
190 pages

Keywords

protection of asynchronous motors, reliability of asynchronous motors, mathematical model of an induction motor

Summary

Thesis structure includes: the introduction, three chapters, general conclusions and recommendations, a bibliography of 176 sources, 9 annexes, and 120 pages of the basic text, 39 figures and 68 tables, research results are published in 19 scientific papers. Key words: protection of asynchronous motors, reliability of asynchronous motors, mathematical model of an induction motor.

The purpose of research: to develop a universal device for the protection of asynchronous three-phase electric motors according to the main reserve regimes.

The objectives of research: to develop a structural and conceptual scheme of the protective device based on the performed research and the proposed mathematical model. The methodology of scientific research includes the methods of analysis, synthesis, modeling and hypothetical method used.

Scientific novelty and originality of the research consist in identifying the essence of the appearance of high harmonic voltage in the zero-phase cable of an asynchronous motor. The important scientific problem solved in the researched field. It was reached a theoretical argumentation justifying the appearance of high harmonic voltage in the zero-phase cable of an asynchronous motor and there were determined the factors that influence the magnitude of this voltage and the limits of its change.

The scientific significance of research consists in justifying the structural scheme and the required parameters for all types of protection devices, the operation of which is based on the appearance of high harmonic voltage in the zero-phase cable when interrupting power supply.

The applicative value of research consists in the fact that the obtained experimental characteristics of an asynchronous motor have served as a basis for substantiating and developing concrete task for designing a universal protective device, i.e. bringing it to the level of an engineering problem.

The implementation of scientific results. Analytical and experimental researches were used to develop the universal protection device, the experimental samples of which were implemented in a range of agricultural farms from the Republic of Moldova (the poultry farm located in Volontirovca village, Stefan-Voda district) and Russia (defense enterprises nr. 107078 and nr. 125833 from Moscow)