Asynchronous Engines Research Articles

NASOS AGREGATLARIDA ASINXRON MOTORNING OʻTISH JARAYONLARIDAGI ENERGIYA TEJAMKORLIK MASALALARINI MATEMATIK MODEL ORQALI TADQIQ ETISH

The article scrutinizes the transients of asynchronous engines regulated by a frequency converter in pumping units used in water supply systems of industrial enterprises and settlements and presents the results of mathematical modeling of energy-efficient operating modes. Transients of asynchronous motors with frequency control and rational use of electricity during periods of shortage of energy were taken as the subject of the research; the actual goal of the sought-after solution was chosen by means of a fundamental mathematical analysis of the shortcomings observed in the subject of the study. The relevance of this work increases again if we take into account the fact that the work carried out in this area has been so far implemented mainly in reclamation pipeline systems with low static torque; however, the results and methods of application cannot always be directly applied to pipeline systems of industrial enterprises with high static torque. Being a research method, specific aspects of existing methods of control of pumping units were studied in practice. When constructing a mathematical model of the transient processes of an asynchronous motor, the Kramer method was used to account for the static resistance and the moment of friction created in the pipe. In the dynamic characteristic of an asynchronous motor, matrices are constructed with an account of the oscillatory process and brought to a final decision. The outcome of the work was a mathematical expression representing transients occurring in every phase of the asynchronous motor stator, taking account of the oscillatory state, and a graph of this function. The research findings will enable the use of the frequency correction method in pipeline systems with increased static pressure and pumping units with an energy consumption of less than 100 kW to increase their energy efficiency. According to the research findings, the energy indicators of asynchronous motors were determined by analyzing the parameters of electromechanical converters by means of frequency adjustment in the pipeline system with high static torque in industrial enterprises where the experiment took place.

Research of the Modes of Starting and Braking during Work of the Systems of Group Electric Drive of Mine Electric Locomotive with the Different Types of Electric Engines

In the article the results of research of work of mine electric locomotive are driven on condition of stability of the system "A wheel is a rail" on coupling of wheels of electric locomotive with rails. It is marked that work of mine electric locomotive transport is conditioned by the row of specific terms. It is indicated that for realization of the electromechanics systems of mine electric locomotives structures are used with the hauling electric engines of direct and variable current. During working as of mine electric locomotive an important question there is coupling of wheels of electric locomotive with rails. Investigation of worsening of coupling of wheel with a rail is an origin of processes of skidding in the mode of creation of tractive or юза force in the mode braking of electric locomotive, that influence negatively for other knots of hauling electromechanic. In turn stability of the system "A wheel is a rail" depends on the type of hauling electromechanic. At consideration condition of stability of electromechanic on coupling of wheels of electric locomotive with rails important is inflexibility of descriptions of hauling electric motors. What more inflexibility, the higher stability of the system "A wheel is a rail". More hard descriptions can be got in the system of electromechanic with hauling asynchronous engines that give an opportunity to use this fact for realization of proportional distribution of efforts between the wheelpairs of electric locomotive. The systems ticker-coil on speed allow to carry out distribution of hauling and brake efforts that is attached to the wheelpairs of electric locomotive, in accordance with distribution of efforts from these wheelpairs on rails, only after the beginning of processes of skidding or skidding. For the decision of this problem a sufficient condition there is a limit of currents of hauling electric motors on the set level. In this connection possibility of distribution of hauling and brake efforts appears at any moment to time. For the decision of task of rational distribution of efforts of electric locomotive, distribution of forces was analysed between his wheelpairs in the function of total force that pulls an electric locomotive on his coupling. On the basis of analysis an idea was got about the redistribution of loading on the axes of electric locomotive. This distribution is in direct ratio to his total tractive force and coupling height, and in inverse ratio to inflexibility of corps. As a result, in order that propelling and brake forces on the axes of electric locomotive corresponded to distribution of weight on rails on wheelpairs, it is necessary to support identical correlation of weight and efforts on the axes of electric locomotive. The design of transients was conducted in the system of group electric hauling drive of mine electric locomotive in the mode of starting and braking. A design is executed for the engine of direct-current with successive connection of poles and hauling asynchronous engine. The charts of transients in the system of group electric hauling drive of mine electric locomotive in the mode of starting and braking showed absence of processes of skidding and slipping at application of the offered principle for the control system.

Dynamic interaction between clustered liquid propellant rocket engines under their asynchronous start-ups

A nonlinear mathematical model of the low-frequency dynamics of the clustered multi-engine rocket propulsion system has been developed and the computations of the engine transient processes during the start-ups of the four-engine propulsion system with a shared feed system have been made applied. Based on propulsion system start-up modeling the influence of the connectivity of engines in a cluster on the starting characteristics of individual engines is shown. In particular, an advanced nonlinear mathematical model of the pump cavitation phenomena is a distinctive feature of the mathematical model. The computation results showed that the asynchronous engines start-ups during rocket lift-off lead to severely nonlinear engine transients and clustered engine thrust misbalance. The influence of the rocket engines asynchronous start-ups on the clustered feed system transients depends on many factors, mainly on from the clustered feed system low-frequency dynamics, the magnitude of the disturbance and the phase difference between disturbances acting on different branches of the feed system. The deep lingering dips in the flow rate and pressure transients are possible due to the nonlinear dynamic interaction of the engines. In case of great pressure dips at the pump inlet (up to the pressure of saturated vapors during significant periods of start-up time) the cavitation breakdowns of the pumps of one or more engines from the cluster are possible. This can disrupt the operation of the entire propulsion system and leads to the failure of the launch vehicle mission.

STUDY OF PHYSICAL PROCESSES IN THE DIRECT CURRENT LINK OF THE LOADING-BACK SCHEME OF ASYNCHRONOUS MACHINES

The article notes the tendency of introducing asynchronous engines, entailing the necessity to introduce the equipment which is intended to carry out maintenance, repair and acceptance check-outs. The general part of test circuits for asynchronous motors by the loading-back method with two controlled inverters is emphasized. The mathematical model of similar schemes’ functioning is shown. The article gives the results obtained by mathematic simulation of physical processes in the direct current link in the loading-back scheme for asynchronous machines Significant ripple voltage of constant voltage and DC in these circuits is noted. The issue of measuring power in the DC link passing through one inverter to the test engine and through another inverter from the load generator is considered. The authors carried out calculation of the capacities mentioned in the steady state modes for asynchronous machines with nominal power of 0.37 kW, 5.5 kW and 250 kW at different values of capacitor capacitance included in the DC link. Basing on the results of calculations, the authors found the dependence between the relative value of the procedural error in determining power in the DC link by the product of the current values of pulsed voltages and current. The current value from the product of instantaneous values of voltage and current at some time interval was taken as the true value of power. It is shown that at the capacitor capacity above some critical value this procedural error does not exceed 0.9% at the nominal power of the test engines 0.37 kW; 0.3% – at the power of 5.5 kW; 0.2% – at the power of 250 kW. This error increases dramatically when capacitor capacitance decreases. It is shown that the value of the capacitance corresponding to the inflection of the considered dependence approximately corresponds to the value necessary for limiting ripple voltage in the DC link of up to 600 V.

METHOD OF ASYNCHRONOUS ENGINES EQUIVALENCY FOR CALCULATING SHORT CIRCUIT CURRENT IN A SYSTEM OF BALANCE-OF-PLANT NEEDS

In short-circuiting in power plants of balance-of-power plant needs three-phase asynchronous motors with a short-closed rotor have a significant influence on the nature of the process and the magnitude of the short circuit current. In the system of balance-of-plant needs it is necessary to take into account the components of short circuit current from asynchronous motors when selecting and checking switches, as well as when selecting and checking current-carrying parts (cables, complete current wires, etc.) not only at the initial moment of the short circuit, but at the time of its shutdown as well. The methods for calculating short circuit current taking into account the influence of asynchronous motors continue to be improved; there is a search for new methods that simplify calculations as much as possible while maintaining the credibility of the results. In doing so, some issues require further study and research, such as the possibility of asynchronous motors equivalency. Power plants have to take into account the components of the short circuit current from a large number of asynchronous engines, which is not only time-consuming, but sometimes impossible due to the absence of full information on engines and mechanisms of balance-of-plant needs. To improve the efficiency and accuracy of calculations for power plant design tasks, it is advisable to replace asynchronous engine groups with equivalents. The relevance of improving the method of equivalency of asynchronous engines at power plants increases along with increasing requirements to enhance the reliability of electrical installations of balance-of-power plant needs and to reduce the costs of technical inventory due to calculation errors. The article considers the method for equivalencing the group of low-voltage asynchronous motors on the example of the balance-of-plant needs system at TPP № 1 located in the town of Dushanbe of the Republic of Tajikistan. Modeling the electromechanical processes caused by short circuits of different electrical remoteness was carried out using ETAP software complex (OTI, USA).

Analysis of self-starting of own needs of heat power plants

This article presents the results of the analysis of self-start of asynchronous engines of the existing power plant, it`s based on the research conducted at the Department of Power Plants and Electric Power Systems of Siberian Federal University.

FEATURES OF IMPROVING ASYNCHRONOUS ENGINES IN THE CONTEXT OF TRAINING FUTURE TEACHERS OF TECHNOLOGY

The article covers issues related to the ways of improvement an asynchronous engine. The features of modernization of asynchronous motors aimed at increasing their energy efficiency are considered. The reasons for the low average load of this engine in the electric drive, especially the traditional and the newest approaches to the calculation of such engines, are analyzed. A new method of executing a stator winding (combined windings) of an electric motor, which has a significant economic effect, is characterized. It is noted that this method of performing the stator winding provides: the ability to adjust the speed at a constant current frequency by gradually changing the voltage throughout the speed range; soft and stable mechanical characteristics; consumption of smaller starting currents and increase of a twisting moment; improvement of vibration and noise characteristics. The importance and peculiarities of studying the methods of increasing the energy efficiency of asynchronous engines by future teachers is substantiated. In this context, the study of improving the efficiency of electrical installations, in particular induction motors, is important in the formation of professional competencies of teachers related to the ability to analyze and evaluate objects of the technological environment and the ability to organize research activities of students in the process of working on educational projects. . The main methods of forming these competencies are the method of specific situations (case method), as well as the method of algorithm for solving inventive problems. Key words: asynchronous engine, energy efficiency, technological processes, electric drive, combined windings, future teachers of technology, the method of specific situations (case method), the method of algorithm for solving inventive problems (the Innovation Algorithm).

INVESTIGATION OF THE HEATING PROCESSES AND TEMPERATURE FIELD OF THE FREQUENCY-CONTROLLED ASYNCHRONOUS ENGINE BASED ON MATHEMATICAL MODELS

The study of the temperature field of the engine for non-stationary modes is done. A numerical simulation of a non-stationary thermal process using dynamic EHD, the characteristic of the rate of rise of temperatures is done. An increase in the temperature of individual parts in the idle interval, when the power of heat release is significantly reduced, is established, and the reverse of the heat flow through the air gap is established. It is shown that the EHD method, in contrast to the FEM, is self-sufficient, which determines its practical value. In various parts of the speed control range in the implementation of various laws of regulation. At the same time, the main electrical, magnetic and additional losses associated with the fundamental voltage harmonics (FVH), and mechanical losses, as well as additional electrical and magnetic losses associated with the higher voltage harmonics, change. When using serial asynchronous engines as frequency-controlled. Permissible under the conditions of heating power is significantly reduced by the power of serial engines. Depending on the synchronous speed, the reduction is from 10 % to 20 %. Given the additional overheating due to higher voltage harmonics, as well as the deterioration of the cooling conditions when adjusting the rotational speed "down" from the nominal, it seems very relevant.

Automated system for processing diagnostic parameters of asynchronous motors for poultry house ventilation systems

The most common electric motor to drive working machines is an asynchronous one with a short-circuited rotor. It has a fairly large resource, provided proper operation. When analysing faults, it was found that the most common cause of failure is increased wear of bearings. The diagnostic parameter of this fault is an increase in the eccentricity of the rotor, to identify which we have developed a diagnostic method that allows us to evaluate the technical condition of the engine using an indirect indicator, the rotor speed. To make a diagnosis, it is necessary to process the data on the dynamics of change in the rotor speed of the engine and predict its operation for the forthcoming period. To simplify data processing, a program has been developed that is an automated system for analysing diagnostic parameters and can significantly reduce the laboriousness and time of diagnosis, eliminating the influence of the human factor. The developed programme was used to analyse the operation of asynchronous engines in poultry house ventilation systems, to predict their failure, as well as to plan maintenance and repair.

Математическое моделирование асинхронных тяговых электродвигателей локомотивов с короткозамкнутым ротором

Objective: To analyze processes in asynchronous engines in case of failure occurrence in rotor winding. Methods: Mathematical model of asynchronous locomotive propulsion engine with cage rotor (AD) was applied. Model calculations applied for the solution of the differential equation system by means of numerical integration were given. Results: The presented AD mathematical model makes it possible to assess the influence of engine’s parameters and load on transient behavior of motor start, as well as to conduct the research in an asynchronous engine in case of balanced and unbalanced operation modes in a three-phase system of coordinates. The latter allow for an adequate description of physics in stator windings in case of failures of rotor bar windings of AD locomotives. Basic equations for the locomotive propulsion engine stator and rotor of different coordinate systems were presented. A structural computational scheme of a three-phase asynchronous engine with a squirrel-cage rotor was developed, making it possible to calculate AD transients. The mathematical model was implemented with MATLAB Simulink software package. Practical importance: The results obtained by means of locomotive asynchronous engine simulation in case of failures of rotor bar windings, as well as AD twisting moment alteration in time demonstrated the possibility of using such a model in order to detect the specific features of failure occurrence in AD.

Systems mutual loadings of traction asynchronous cars

The review of methods of post-repair tests of traction asynchronous motors under conditions of locomotive depot is carried out.The necessity of introducing special stands for post-repair tests is shown in order to improve their quality, reduce the number of failures of service equipment, improve safety of the railway transport. Let’s consider a question of power supply of the research asynchronous engine in wide frequency range and also a possibility of creation of the universal stand for testing important asynchronous engines of the electrorolling stock. Survey of possible versions of the scheme mutual loadings of asynchronous electrical machines which can be used for testing traction asynchronous engines of the rolling stock is executed. Such systems can be constructed both with use of the static converter of frequency, and without it. The given short characteristic of each alternative, certain advantages and shortcomings of each of system options. It is shown that systems with use of static converters of frequency differ in high power efficiency, allow to carry out tests in the wide frequency range of power supply, however have higher prime cost. Schemes without converters of frequency differ in smaller power efficiency, impossibility to carry out tests in the wide range of frequency of power supply, high level of consumption of reactive power . The results of the carried-out analysis can be used when choosing rational option of a system mutual loadings of asynchronous electric motors which will differ in higher functionality and power efficiency. Use of such systems will allow to lower capital expenditure for creation new and modernization of traction electrical machines that exist at the station for test.

Emergency Control Systems in the Uninterrupted Traction Power Supply of Subways

Traction dc power supply systems with a traditional feed voltage of 825 V are part of the basic transport infrastructure of metropolitan cities. The development of electrified railroads has resulted in the mainstream use of these systems. There are many works about their strengths and weaknesses; however, modern circumstances make it necessary to operate and upgrade these systems, maintain their usability, and improve their efficiency. New rolling stock with asynchronous engines is being launched for subway service with increased loads and travel speeds. In these conditions, one of the main features of maintaining the course of transportation is to guarantee uninterrupted power supply of electric rolling stock. This can be made possible through appropriate and timely responses by maintenance personnel, power dispatchers, automation and emergency control systems. The microprocessor systems used at the modern level of technological development have been embodied in intelligent terminals of feeder lines of electric traction networks used in subway service. Their algorithmic part must be improved and upgraded for compliance with the current realities of subway service by integrating emergency control equipment algorithms, full-scale analysis of analog processes in the electric traction network, discrete signals of automatic controls and telemechanics, and states and switches of cross-connect equipment, which must facilitate increased automation of the traction substation and make it completely unattended.

NUMERICAL WITHOUT ITERATION METHOD OF MODELING OF ELECTROMECHANICAL PROCESSES IN ASYNCHRONOUS ENGINES

Purpose. Development of calculation of electromagnetic and electromechanic transients is in asynchronous engines without iterations.Methodology. Numeral methods of integration of usual differential equations, programming. Findings. As the system of equations, describing the dynamics of asynchronous engine, contents the products of rotor and stator currents and product of rotation frequency of rotor and currents, so this system is nonlinear one. The numeral solution of nonlinear differential equations supposes an iteration process on every step of integration. Time-continuing and badly converging iteration process may be the reason of calculation slowing. The improvement of numeral method by the way of an iteration process removing is offered. As result the modeling time is reduced. The improved numeral method is applied for integration of differential equations, describing the dynamics of asynchronous engine.Originality. The improvement of numeral method allowing to execute numeral integrations of differential equations containing product of functions is offered, that allows to avoid an iteration process on every step of integration and shorten modeling time.Practical value. On the basis of the offered methodology the universal program of modeling of electromechanics processes in asynchronous engines could be developed as taking advantage on fast-acting.

Counter switching-on braking of asynchronous engines with induction rheostat and condenser in the rotary circuit

Counter switching-on braking of asynchronous engines with induction rheostat and condenser in the rotary circuit

Оценка влияния несинусоидальности питающего напряжения на напряжения смятия зубцов асинхронных двигателей

Оценка влияния несинусоидальности питающего напряжения на напряжения смятия зубцов асинхронных двигателей

Построение ряда энергосберегающих асинхронных электроприводов на основе унифицированного трансформаторно-транзисторного модуля

The paper considers a new unified construction of the transformer and transistor module executed on the minimum structure at one power transistor placed in the transformer common for all phases of the circuit allowing to minimize the number of power semiconductor keys. This unified module belongs to the converting equipment applied in AC adjustable electric drives for the smooth amplitude start-up, countercurrent braking, and also for implementation of the asynchronous engines positioning mode. Making a row of asynchronous electric drives on the basis of the unified transformer and transistor module allows one to meet the energy sa­ving requirements imposed on asynchronous electric drives during their operation. The ways for reduction of mass-dimensional indices of the booster transformer which forms a structural basis of the offered device by the modulation elimination of a network low frequency tension component in its primary winding are shown. The solution efficiency is confirmed by the analysis of the direct and smooth start-up experimental diagrams, braking, and also by the mode of the asynchronous engine positioning in the computer program MATLAB/Simulink. Energy consumption lowering at start-up, braking and positioning of the asynchronous engine, when using of the unified transformer and transistor module as a basic element of the electric drive mana­gement system, is proven by the experimental diagrams obtained in the computer program MATLAB/Simulink.

Electromagnetic and electromechanical processes in the variable electric drive of a circulating pump with double-speed asynchronous engines

Electric drives with gradually varied rotational speed used for regulation of the main circulating pumps (MCPs) of nuclear power stations maintain reliable operation of the reactor plant at different operational modes, including partial load levels of power generating units. The use of powerful asynchronous engines with short-circuited rotor and primary voltage of 6000 V in such electrical drives has made it necessary to use average voltage with a variable output frequency in order to produce the rotational speed of control converters. One effective technical solution that maintains reliable operation and safety of the reactor plant is use of the main first contour circulating pumps of an asynchronous engine with two independent windings on the stator: the main one of 6000 V connected to the converter and an additional low-voltage winding connected to the emergency supply circuit under “de-energization” conditions of auxiliary power needs, formed by the diesel-generator unit. Implementation of the circulating pump with double-speed asynchronous engine in the variable electric drive determined it necessary to carry out investigations of electromagnetic and electromechanical processes at control modes of the main and additional stator windings. Those modes were modeled on the basis of mathematical models and on a full-scale hydraulic test stand intended for testing circulating pumps. The main results concerning investigation of electromagnetic and electromechanical processes in an electrical drive with a double-speed asynchronous engine of 5000 kW and 6 kV used for operating control of the main circulating pumps of the reactor unit of an 800-MW power unit are given in the article.

Models of operating asynchronous engines at poor-quality electricity

В статье рассмотрены вопросы работы асинхронных двигателей с короткозамкнутым ротором в условиях некачественной электроэнергии. Проанализированы существующие математические модели асинхронного двигателя, работающего в указанных условиях, приведены их достоинства и недостатки. Выявлены модели, которые отражают влияние отдельных показателей качества питающего напряжения на работу электромеханического преобразователя.

Пускорегулирующие устройства для асинхронного электропривода на диодно-транзисторных модулях

New construction of the device, for implementation of the smooth amplitude start-up of asynchronous engines, allowing to minimize quantity of force semiconductor keys and to meet requirements to electromagnetic compatibility is considered. Ways of reduction of mass-dimensional indexes of the booster transformer which is a constructive basis of the offered device by the drive elimination of a network low frequency component of tension in its primary winding are shown. Efficiency of this decision is confirmed with the analysis of a magnetic status of the core of the transformer in the starting mode taking into account a hysteresis and the subsequent comparing of patterns of direct and smooth start-up of the asynchronous engine in the computer program Matlab/Simulink.

Losses of power in asynchronous traction engines of prospective electric rolling stock

Powered by autonomous voltage inverters, asynchronous traction engines of prospective electric rolling stock show signs of deterioration in current and voltage, which decreases the efficiency and power factors of these engines compared with corresponding indicators for engines powered by sine voltage power generators. As a result of harmonic analysis of curves of output voltage and current of two-level autonomous voltage inverters with amplitude pulse-width output voltage modulation, performed in the MatLab/Simulink and Mathcad software package, it was found out that the use of pulse-width modulation of autonomous inverter output voltage in a DTA-1200A prospective asynchronous traction engine leads to only a minor impairment of its energy indicators. At the same time, the use of multilevel autonomous voltage inverters, which require more complex and expensive converter electric equipment, is currently hardly justified.