Content

• 1. Relevance of the topic
• 2. The aims and tasks of the research
• 3. The planned practical result
• 4. Review of the literature on the subject
• 5. Existing methods and means of technical diagnostics of electric motors
• 6. Conclusion
• 7. List of sources

Relevance of the topic

About 40% of the electricity produced in the world is consumed by the electric drive, the main type of which is the asynchronous motor (AM) with squirrel-cage rotor (SCR). This breadth of distribution explained by the simplicity of production and operation, as well as the following advantages:

• approximately constant speed for different loads;
• the possibility of short-term mechanical overload;
• simplicity of design;
• Start simple and easy to automation.

However, the main problem of asynchronous motors is their high damage of which, according to statistics, distributed as follows:

• damage to stator elements – 38%;
• damage to the elements of the rotor – 10%;
• damage to the bearing elements – 40%;
• other damage – 12% [1].

The sudden failure of the engine can cause accidents and lengthy downtime of production, which in turn turn leads to direct financial losses that are caused by a violation of the process and the cost of restoration and repair of motor. In this regard, the issue is highly relevant diagnostic BP. The process of automation of technological processes through the use of technical diagnostics condition of the equipment in the operating conditions to minimize the damage from these effects by detect defects at an early stage of development.

At present, special attention were paid to the control equipment as, but not in the system regular preventive maintenance. This is made possible through the use of methods and means of control and analysis of the current technical condition. The advantage of this approach lies in the fact that repair only for the equipment to which it is required, assessment of the state is in the process operation, without any squabbles and revisions based on the monitoring and analysis of relevant parameters. Also, this approach is a significant source of competitiveness, profitability and profitability. This contributes to the development of microprocessor and computer technology. Costs maintenance of electric motors is reduced by 50-75% compared to the maintenance of the system regular preventive maintenance [2].

For the introduction of technology services as required complete diagnosis of the object, and it is desirable to identify all defects that affect the life, long before the failure to prepare for the repair.

Thus, from all of the above visible urgency of developing and improving methods and means of diagnosing the technical condition of motor control parameters based on the operating modes.

The aims and tasks of the research

The aim of work is to develop methods of technical diagnostics, allowing early identification defects in the motor operating conditions and providing an opportunity to establish probable cause developing damage.

Tasks of the research, in accordance with the purpose of the work are as follows:

1. Analyze the results of physical and mathematical modeling of the operating modes with AD CDR in the event of various types of defects.
2. Develop a method for technical diagnosis, to identify the defects produced in the early stages their development and possible causes of their development.
3. To assess the cost-effectiveness in the implementation of the developed method of technical diagnostics asynchronous motor with squirrel cage rotor.

The object of research is the state and the parameters of the operating mode of AD with CDR in the event of defects stator and rotor windings.

The subject of research is a diagnosis of technical condition of AD with CDR-based recognition sources of asymmetry parameters of the operating mode.

The projected practical result

It is planned to test the developed method of diagnosing AD with CDR on a laboratory model to evaluate check the reliability of the method and accuracy of diagnostic parameters.

Review of the literature on the subject

Investigation of the influence of defects on the electrical machines their parameters and characteristics of the papers M.A. Hashimov, M.Z. Dudnik, I.P. Kopylov, D.V. Polkovnichenko, V.F. Sivokobylenko, M.P. Kostenko and other authors.

Results of studies show that the faults of stator and rotor windings in varying degrees broken symmetry and sinusoidal currents and voltages in phases, a decrease energy performance and a deterioration in performance, there are vibrations, changes in noise, etc.

Review of existing methods of technical diagnostics of electric motors has shown that currently There is no unified concept of diagnosing and monitoring the technical condition is mainly done during scheduled maintenance, which does not allow to detect defects at an early stage of development and prevent significant damage to motors or their complete failure. but more effective and convenient to use a diagnosis in the operating mode, ie without a break electrical equipment. By this method of diagnosis and the need to move to improve the resource and reliability of electrical equipment, reduce costs associated with repairs and downtime.

Existing methods and means of technical diagnostics of electric motors

The most common method of diagnosis of electric motors is now the vibration diagnostics, based on the measurement and analysis of vibration of the motor housing. The complex is virtually vibration parameters completely characterizes the technical condition of the operating unit and to predict the occurrence of malfunctions and accidents induction motors and electromechanical equipment. The criteria by which the estimated efficacy of various methods of vibration diagnostics, as well as the most common groups of methods vibrodiagnostics induction motors are given in [7].

Despite the development of technical means and methods of measurement of vibration analysis, vibration diagnostics is number of deficiencies caused by contact sensors to the attachment object. For more information the technical state of the object can be obtained from measurements of the temporal and spectral characteristics phase currents and stray fields that exist outside the motor housing. These diagnostic methods are proximity, which is an undoubted advantage over their vibration monitoring.

With the development of computer technology came the development of automatic and automated systems diagnosis of electric motors (eg, Figure 1). At the same time to implement them as diagnostic parameters are various operating parameters of the motor [3].

In [8] separately allocated to diagnosis of electric motors, which are characterized by frequent switching on and supply voltage is removed. The necessity of diagnosing such engines in the transitional modes of operation. The paper considers the automated measuring system, with which the measurements of diagnostic parameters of the object of research. The complex includes: personal computer, a specialized data acquisition board, placed in the socket system host computer, inductive type sensors for measuring the phase currents and stray fields of the electric motor, software.

In[9] the method of diagnosis of induction motors based on the average power acceptance testing. Developed and implemented on a computer mathematical model for calculating specific values of the quality of induction motors based on the results of acceptance tests, the use of which is possible in the process of manufacturing of induction motors. Also in this study developed a mathematical model for finding out the causes of quality indicators for limits and the program for data analysis of reasons for a computer, set up the influence of a diagnostic algorithm input parameters on the quality of performance.

Work [10] devoted to diagnosis ekstsentrisisteta rotor induction motors according to the harmonic composition of the stator current. It based on the results of mathematical modeling and physical experiment first established the relationship of the amplitudes of harmonic components of the spectrum consumed current for some types of induction motors with the magnitude of the eccentricity, which allows to estimate the marginal parameters eccentricity of the rotor in the motor is running. Also we propose an improved Mathematical model of induction motor with rotor eccentricity on the basis of the analytical expression values of mutual inductance, which characterizes the influence of rotor eccentricity on the harmonic of the stator current, which differs from the known fact that allows using standard programs used for simulation of induction motors for various types of induction motors with error of not more than 10% expect the value of the order and the stator current harmonics generated eccentricity. According to the results obtained in the data it is concluded that the diagnosis eccentricity of the rotor induction motor with portable devices should be used spectral analysis of the current only one phase, whereas in the diagnosis of high-power induction motors and responsible in the food chain which current sensors are installed in three phases of power, it is advisable to use the analysis of the spectral composition generalized vector of the stator current in order to identify not only the eccentricity of the rotor, but also other damage to the induction motor. It should be noted in this paper the proposed method of automatic control the eccentricity of the rotor induction motors, which differs from the existing order that a comparison of the harmonics of the stator current, derived from the spectral analysis is carried out with the given values of current harmonics on the characteristic frequencies. The proposed method can improve the reliability and selectivity of the recognition ekstsentrisisteta at an early stage of its development. Microprocessor control device eccentricity Rotor designed for performance, allows to detect unacceptable level of eccentricity rotor induction motors of more than 30% of the nominal value of the air gap.

Analytical method of calculation of currents and moments when one defect rod cells are short-circuited rotor is given in[11]. In this method, used the concept of representing vectors introduced in functional relations characteristic of the magnetization of the magnetic circuit of the machine and take into account the electromagnetic coupling MDS of different sequences of the rotor with the stator winding. Also in this study developed a method of symmetrical components with respect to electric cars. It is shown that every sequence rotor currents MDS creates a number of periods and the rotation direction of which depends on the order of the sequence. The studies of induction motors with symmetric and asymmetric cell rotor in continuous operation under the the load. At constant shaft power determined the temperature rise of stator winding and rotor shown that due to the breakage of one of the rod cells of the rotor temperature rise of stator and rotor may increase by several degrees.

In[4] is proposed to determine the efficiency of induction motors by their functional state. This state is represented by three variants - two functional (nominal and Unrated) and one non-functional - and characterized by such indicators as the net power at shaft motor and the speed of the resource costs of the stator winding. It was determined that the cost of speed change resource under the conditions of constant power to the motor shaft due to the occurrence of damage in its nodes. The relationship between changes of active power losses and changes the functional state of the induction motor, based on which a new method of diagnosis, which makes it possible to monitor the efficiency of the engine in a production operation and locate the damaged sites.

In [2] developed a method for diagnosing stator and rotor induction motor squirrel-cage rotor according to the control of the instantaneous phase currents and voltages in the working modes, which differs from the known methods by the fact that to evaluate the technical condition A comprehensive motor serviceability criterion based on the use of symmetric components of the stator current and the angle of inclination of the mechanical characteristics of induction motors in working slips. To account for the influence of voltage unbalance on the results of the diagnostic method is developed, based on comparing values of the motor phase resistance, which are calculated according to control the instantaneous values of phase currents and voltages. A generalized dependence of the complex serviceability criterion for asynchronous motors with a CDR of different types for different types of defects in stator and rotor windings, are used to define the boundary values of this criterion.

Figure 2 shows the change in dependency i1(t) = f[i2(t)] for different types of damage.

In [5] developed methods and devices not only determine a fact in the working circuit turns mode of induction motor, but also allow the detection of indiscriminately damaged section of the motor stator windings, to identify eccentricity of the rotor to the engine is running. In addition, the protection of the induction motor has been added blocks, allowing Identify the prolonged start-up, rollover, locked rotor.

Description of MFP security and operational diagnostics of asynchronous and synchronous motors is given in [6]. Set of features and protective devices depends on the diagnostic degree of responsibility of the unit with an electric motor in the process, the type of motor construction of stator and rotor windings, rated power and voltage. In particular, a device for Responsible single-speed induction motor voltages above 1 kV up to 2000 kW must respond to the short-circuit the stator winding, including the closure of turns of one phase winding ground fault stator, balanced and unbalanced overload, decrease the insulation resistance of stator winding, cliff rotor bars, and the failed launches of the protracted, locked rotor induction motor is running, the aging isolation, detection of bearing damage, rotor eccentricity, wry axis rotor induction motor and mechanism, remote connection between the induction motor and mechanism. Despite the obvious advantages of the described devices, the lack of should recognize that its implementation requires to make changes to the design of the motor.

Conclusion

Current methods of diagnosis of induction motors are outdated and ineffective because it failed to detect damage and defects in components of the electric motor in the early stages of their and require the shutdown of the equipment for the inspection. This leads to an unexpected exit engine failure and leads to losses associated with downtime of equipment, a violation manufacturing process and the cost of repair or replacement of equipment.

The developed method will allow diagnosis of electric motors to turn it off without using the control currents and voltages in the operating mode. Using the method should lead to higher cost-effectiveness and profitability of the enterprise on which it will be used.

List of sources

1. Сайт магистра ДонНТУ Шевцова А. В. [Электронный ресурс]. – Режим доступа: http://masters.donntu.ru/2009/eltf....
2. Полковниченко Дмитрий Викторович. Совершенствование диагностирования обмоток короткозамкнутых асинхронных электродвигателей на основе контроля параметров рабочего режима: Дис... канд. техн. наук: 05.09.01 / Донецкий национальный технический ун-т. – Донецк, 2003. – 202л. – Библиогр.: л. 136-148.
3. Сайт магистра ДонНТУ Маруневича А. И. [Электронный ресурс]. – Режим доступа: http://www.masters.donntu.ru/2006/eltf....
4. Вовк Александр Юрьевич. Эксплуатационный контроль работоспособности асинхронных электродвигателей по их функциональному состоянию: Дис... канд. техн. наук: 05.09.16 / Таврическая гос. агротехническая академия. – Мелитополь, 2003. – 172л. – Библиогр.: л. 128-140.
5. Ляткер И.И., Мордкович А.Г., Несвижский А.М. Система непрерывного контроля и диагностики синхронных машин // Электротехника. – 1996. – № 3. – С. 44-47.
6. Мануковский А.В. Совершенствование защит асинхронных двигателей от внутренних повреждений: Автореф. дис... канд.техн.наук. Павлодар, 1995.
7. Браташ О. В., Калинов А. П., Кременчугский государственный университет имени Михаила Остроградского, статья Анализ методов вибродиагностики асинхронных двигателей [Электронный ресурс]. – Режим доступа: http://www.nbuv.gov.ua/portal/natural....
8. Чернов, Дмитрий Владимирович Функциональная диагностика асинхронных электродвигателей в переходных режимах работы: автореферат дис. ... кандидата технических наук: 05.11.01 / Ульян. гос. техн. ун-т
9. Молодых, Павел Анатольевич Диагностика асинхронных двигателей средней мощности по результатам приемо-сдаточных испытаний: автореферат дис. ... кандидата технических наук: 05.09.01
10. Рогачев, Вячеслав Анатольевич Диагностирование эксцентриситета ротора асинхронных электродвигателей по гармоническому составу тока статора: диссертация ... кандидата технических наук: 05.09.01 / Рогачев Вячеслав Анатольевич; [Место защиты: Юж.-Рос. гос. техн. ун-т (Новочеркас. политехн. ин-т)
11. Саада Гургес Исследование влияния повреждений короткозамкнутого ротора на работу асинхронного двигателя: автореферат дис. ... кандидата технических наук: 05.09.01

At a writing of the given author's abstract master’s work is not completed. The final version of work can be received at the author or the supervisor of studies after December, 2012.