New criteria for energy efficiency of induction motors with squirrel-cage rotor winding

Despite the great attention paid by Russian and foreign authors to the problem of timely fault detection in the squirrel-cage rotor windings of high-voltage induction motors, the papers published by them pay little attention to issues related to substantiating the need for carrying out the relevant studies. However, this is especially important for high-voltage electric motors used in power plant auxiliaries. The aim of the study is to assess the consequences from failure of induction motors used in power plant auxiliaries caused by a break of the rotor winding bars. Assessment of the failure consequences is an important component of the transition to risk-oriented management of induction motors operation. The main components of the failure consequences and the resulting economic damage are identified. It is shown that failures of high-voltage induction motors caused by broken rotor bars can lead to economic damage of several million rubles. It has been found, based on computer simulation results, that during operation of induction motors with broken rotor bars, their magnetic and electrical losses increase significantly. The study results have shown that the economic damage may also be significant during long-term operation of a large number of induction motors with this type of failure. The accomplished assessment of the failure consequences in money terms confirms the relevance and necessity to perform functional monitoring of the state of the rotor windings of high-voltage induction motors used in the system of power plant auxiliaries.

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Mathematical modelling of starting modes of induction motors with squirrel-cage rotor

Electrical Engineering & Electromechanics ◽

10.20998/2074-272x.2021.2.02 ◽

2021 ◽

pp. 9-15

Author(s):

V. S. Malyar ◽

O. Ye. Hamola ◽

V. S. Maday ◽

I. I. Vasylchyshyn

Keyword(s):

Mathematical Modelling ◽

Induction Motors ◽

Static Characteristics ◽

Coordinate Systems ◽

Two Phase ◽

Electric Drives ◽

Squirrel Cage ◽

Three Phase ◽

Rotor Winding ◽

Cage Rotor

Purpose. Development of methods and algorithms for calculation of starting modes of the induction motors with the squirrel-cage rotor. Methodology. Mathematical modelling of starting modes of asynchronous electric drives in various coordinate systems with the use of numerical methods for solving boundary problems for systems of differential equations and nonlinear systems of final equations and calculation with their use of static characteristics. Results. Methods and algorithms for numerical analysis of the starting modes of asynchronous electric drive have been developed, which make it possible to calculate the static characteristics and transients in fixed three-phase and orthogonal two-phase coordinate systems. Academic novelty. Known in the literature methods of calculation of starting modes have in their basis classical equivalent circuits with different approximate methods of calculating the parameters taking into account the saturation of a magnetic core and current displacement in a rotor winding. This approach requires a special solution of the adequacy problem for each problem. The methods described in the article for the saturation accounting use real magnetization characteristics of the main magnetic flux and leakage fluxes separately, and the skin effect phenomenon is taken into account by representing the squirrel-cage rotor winding as multilayer. Such mathematical model of the motor is universal and makes it possible to take into account the saturation and current displacement in any dynamic mode, including the start-up process. Mathematical models developed on the basis of the proposed methods provide the adequacy of results with a minimum amount of calculations and make it possible to perform optimization calculations. Practical value. Created on the basis of developed algorithms calculation programs allow to carry out with high reliability calculation of starting modes both in three-phase and two-phase axes of coordinates that gives the chance to analyze not only symmetric, but also asymmetric modes and to predict special features of functioning of system of the electric drive in the set technological conditions of operation and to form requirements to development and adjustment of starting systems with the purpose of maintenance of power effective and reliable operation of system of asynchronous electric drives.

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