Currently, asynchronous electric drive on the basis of semiconductor frequency converters is widespread because of the relative simplicity and reliability of the design, the use of digital control systems, providing the accuracy and flexibility of process control, which allows for a significant increase in product quality, reduction in energy consumption and improvement of the enterprise profitability. In spite of these advantages, the problem of ensuring high energy efficiency of the drive in wide range of its operational modes is still not solved in full scale. The paper is devoted to the reduction of losses in the asynchronous drive on the basis of en-ergy-saving control algorithms that aim to ensure the desired mode of the driven mechanism while minimizing losses in copper and steel of the motor. On the basis of the motor model, taking into account magnetic losses, dependences of losses in the copper and steel, as well as the total loss from the absolute slip have been derived for different operating points of the drive. The optimal values of the absolute slip for different speeds of the rotor have been obtained for use in the con-trollers ensuring operation of the drive at maximum efficiency, highest power factor and minimum of the stator current. For minimizing the losses in the drive when changing the motor parameters it has been offered the combined method based on the method of loss model and iterative method of searching the minimum of power consumption. The effectiveness of the proposed control system using fuzzy logic is confirmed by comparing the graphs of losses and efficiency, obtained at using a traditional control law and the optimal control law.
In the face of energy lack and rising energy prices one of the priorities of current researches is to improve energy efficiency of electric drives, which are widely used in modern industrial plants. Existing methods of minimizing losses are mainly designed for stationary regimes. At the same time, the development of algorithms for reducing losses in transient and in particular starting conditions is given little attention. Due to the high complexity of the description of the multivari-ate dynamic processes determining the optimal control laws is advantageously to be carried out us-ing stochastic optimization methods. The work seeks to substantiate the optimal starting character-istics of an asynchronous drive based on a genetic algorithm. A feature of the proposed method of optimization is the use of multiple simulation experiments to find start-up characteristics which provide a minimum energy loss. Automation of the search is performed using the developed pro-gram, which includes a module of a genetic algorithm and a module for interfacing with the elec-tric model in the MATLAB/Simulink environment. The program allows choosing the parameters of the genetic algorithm along with controlling the process of optimization. Application of the proposed method allowed obtaining the optimal starting characteristics «voltage – frequency» in a tabular form with consequent linear approximation of the data. Increase in efficiency due to the proposed start up law has been confirmed by comparing the simulation re-sults under conditions of using a traditional linear characteristic and derived optimal law. The es-timation of losses reduction has been carried out at the drive load of different kind in a wide range of its variation.
The paper is dedicated to analyzing identification of turn to turn faults by digital differential protection relay of power transformers. Reliable algorithms of finding turn to turn faults from external faults and transformer inrush are described.
The paper is dedicated to analyzing the use of Kalman filtering theory for Application in digital differential protection relay of power transformers. The state variables for the fault identification and protection operation criteria are described. Comparison of operation times of differential protections, based on Kalman filtering theory and Fourier algorithm is presented.
The paper is dedicated to optimization of a pulse width modulation (PWM) in multilevel inverters with floating capacitors. Comparison of PWM techniques which satisfy the condition of a capacitor voltage balance is presented from the electromagnetic compatibility point of view for the case of a fan-loaded induction motor.
The paper presents the results of a computer modeling technology applied in the «Sevuralboxitruda» enterprise. The aim of the technology is to forecast geodynamical processes during mining works in tectonic-stressed zones of ore deposits. The impact degree on structural components of room-and-pillar mining method caused by active tectonic faults is estimated.
On the basis of comparative analysis of the mine main fan electric drive input voltage-current characteristics, a frequency-variable drive with pulse width modulation (PWM) rectifier and PWM inverter is shown to be the most competitive one because of its capability to independently implement the substation power factor correction and the mine air flow energy-saving control.
The paper is devoted to the experimental study of jaw crusher characteristics under condition that nonidentity of subsystems electro-mechanical parameters causes the distortion of the nominal mode of the jaw crusher operation. Experimental data obtained have confirmed basic statements of a self-synchronization theory. The initial phase shift of jaws oscillations is shown to result in a substantial decrease in the crusher productivity and a significant increase in the specific power consumption.
The paper is devoted to building up time series models to forecast the power consumption of a mine. The results discussed are obtained using various linear filter models and artificial neural network. The wavelet transform of the raw time series is shown to be an efficient technique to increase the forecasting accuracy.
The justification of parameters of technological chamber and heating mode as applied to the problem of preparation of gold-bearing sands for enrichment is given. On the basis of electrothermal-physical model of interaction of HF-electromagnetic field with imperfect dielectric the system of equations linking parameters of generator and technological chamber, rock feeding rate and its effective parameters, taking into account continuous phase transition, which degree of manifestation depends on the clay fraction content, is obtained.
Reliability and efficiency of electrical equipment depends on the quality of electrical energy in distribution networks. The key issue of power quality assurance is the problem of higher harmonics. The problem arose due to the widespread introduction of power electronics as the most effective means of ensuring the required modes of operation of electromechanical and electrotechnological complexes. In this paper the influence of higher harmonics on the power quality is analyzed by means of MATLAB Simulink system, the principle of parallel active filter based on the algorithm of direct current control is considered.
Features of ferroresonance oscillations and methods of their elimination are considered on the example of transformer-capacitor system of longitudinal and transverse compensation used in power circuits of powerful electric motors, in power supply systems of ore-thermal and arc steelmaking furnaces. Based on the solution of Duffing's equation, the influence of current amplitude and system attenuation coefficient on the operating mode of transformer-capacitor has been determined. The stability area of the basic type of oscillations has been evaluated. It was found the existence of subharmonic oscillations and the influence of not only the amplitude but also the source phase on the appearance of anomalous modes caused by the relay effect and the phenomenon of self-modulation was revealed. It is shown that the elimination of ferroresonant oscillations is connected with maintenance of a magnetic circuit mode close to linear and with a choice of a damping coefficient from the condition of the maximum permissible value of the active resistance introduced into a line.
In the article, the main directions of the 2000 research in the field of creating electrical complexes for mining oil gas industries are considered. They are: the application of non-contact regulated power drive with control algorithms for mining machines and mechanisms; ensuring higher productivity and energy saving development of electrical technologies and special technical means for mining operations development of automated electrical complexes and systems based on the introduction of microprocessor technology; design, development and implementation of computer technology and automated control of energy consumption and adaptation of new types of electrical equipment, ensuring increased reliability and efficiency of electrical complexes; development and implementation of the concept and algorithms of usage management in oil production complexes; development of automatic control system of multifunctional resonant angle transducers with motion of different frequency and amplitude; application of methods of direct electrotechnology, based on electromechanical transfer of electric field energy in the rock proper to obtain technological effect development of electrical complexes of automatic and automated systems, which can be designed and developed as autonomous systems of different purposes.
Одним из способов подготовки мерзлых пород к экскавации является оттаивание. Однако применение для этой цели традиционных методов нагрева нельзя признать удовлетворительным как из-за невысокого темпа оттайки, обусловленного низкой теплопроводностью мерзлых пород, так и вследствие отрицательного влияния источников нагрева на тепловой режим выработки ...
Поведение антенны в скважине с точки зрения ее входного сопротивления представляет интерес в связи с исследованием возможности расширения скважин в мерзлых породах до больших диаметров с применением СВЧ энергии ...