Research of Load Unbalance of a Two- Motor Variable Frequency Dtive for Scraper Conveyor

The article analyzes the uneven loading of the scraper conveyor electric motors. The most common type of multi-motor conveyor is considered here: two-drive, with head and end drives connected through gearboxes and sprockets by an endless chain with scrapers. The simulation results are presented for three variants of com-binations of parameters of electric drives. It has been established that the use of a two-motor variable frequen-cy drive of a scraper conveyor powered by a single frequency converter inevitably entails uneven loading of the electric motors of the head and end drives. To eliminate this disadvantage, it is proposed to supply each electric motor from its own frequency converter. A system of automatic load balancing is proposed. The implementation and the result of the work of the load balancing system are carried out on a model in the Matlab / Simulink system.

Conceptual Directions of Creating Digital Twins for Electrotechnical Systems of Rolling Mill Facilities

This article considers the development of digital twins (DT) for the mechatronic facilities of the coiling machine group in a wide-strip hot rolling mill. The analysis of Russian and foreign sources confirmed that a lot of attention is paid to the economy digitalization. All of the leading metal plant equipment and electrical engineering system manufacturers are working on creating DTs. The analysis of the literature showed that the authors lack a uniform understanding of the conceptual directions in the creation of DTs and there are many definitions of this term. Therefore, the first part of the article deals with the analysis of the digital twin concepts according to their application at industrial companies. The authors substantiate the feasibility of the DT de-velopment for the electromechanical and mechatronic systems of the most complex metal production components, i.e., rolling mills. This initiative development is relevant due to the reconstruction of the 2500 wide-strip hot rolling mill at Magnitogorsk Iron and Steel Works PJSC (MMK PJSC) that involves the installation of unique equipment. Due to this, the development of DTs to implement the virtual commissioning of the equipment becomes a priority. The virtual adjustment of automation and process control systems is also required. This problem can be solved through the example of three coiling machines, each of which has electric and hydraulic auxiliary equipment. These coiling machines are used for rolling the heavy hot-rolled bar and they feature a unique design. Therefore, the development of DTs for mechatronic facilities is a novel scientific problem. The authors propose the methods for the development of DTs used in the virtual commissioning of process control systems. They present the structure of the coiling section automation system and the structure of the DT imple-mented on the basis of programmable logic controllers (PLC). The authors provide the specifications for the Siemens PLCs installed at each of the coiling machines and the coiling machine master controller. To develop the control systems for electric and hydraulic drives, it is recommended to use the Matlab Simulink software package. The authors provide temporal dependencies obtained using DTs and other similar oscillograph charts produced during the operation of the coiling machine that can help model the operation of the mechanisms in question. The results of their comparison show that the processes correspond to each other. Thus, the use of the developed DT to adjust the electrotechnical systems of rolling mills is reasoned. The accepted concept of making digital twins for the electrotechnical systems of rolling mill components is relevant and technically feasible

The State and Prospects of Development of Power Supply Systems of Metallurgical Enterprises with On-Site Power Plants

The article considers the features of design of industrial power supply system of metallurgical enterprises with on-site electrical power generation. The problems of increasing the efficiency of the main electrical equipment of on-site power plants are formulated. The analysis of development trends in the energy sector of Russian metallurgy is carried out, on the basis of which the importance of industrial on-site power plants is shown. The problem of choosing a generator automatic excitation control system of on-site power plants is con-sidered and possible ways of its solution are given. The task of regime optimization of industrial on-site power plants is considered and original optimization algorithms are presented. Methods of increasing the reliability of power supply of critical equipment and mechanisms involved in the technological process of thermal power plants are proposed. The urgency of the tasks of complex automation and digitalization in the industrial power supply systems is shown, while the special meaning of "digital twins" is noted. Possible prospects for the development of on-site power plants in the context of the decarbonization policy and the transition to alternative energy are considered.

Design of an Optimal Controller in a Voltage Regulation System When Powering Submersible Electromechanical Equipment

The paper addresses the issue of designing an optimal controller using the measured state variables of a nonlinear multi-dimensional object with transient disturbances – power supply of submersible electromechanical equipment with AC transmission via a cable power line. We present an approach to the design of an adjustable PI-controller enabling to determine its closed-form parameters with the linearized model of a complex control object. A numerical example for simulation of a power supply highlighting capability of the design algorithm for the optimal controller with the quadratic criteria is provided. The obtained results can be used to tackle problems of adaptive control of remotely powered electromechanical objects without sensors.

Methods for Evaluating the Influence of Non-Sinusidal Voltage on Capacitor Units in Power Supply Systems

The problems of evaluating the EMC for capacitor units (CU) in power supply systems are considered. The admissible value of the current non-sinusoidal component for the CU was found, it corresponds to the actual standards. The dynamic model of the «supply line – CU» circuit has been substantiated. An equivalent circuit is given. A non-sinusoidal signal is considered as the sum of a sinusoidal and non-sinusoidal component. As a non-sinusoidal component, a voltage pulse noise model with oppositely polar periodic rectangular pulses and pauses was used. Two approaches to determine the useful signal are considered. A physically substantiated interpretation of the concept of non-sinusoidal voltage is proposed for impulse noise. Expressions are given to determine the current noise of the CU. An example of the practical calculation of voltage and current distortion is given. The graphs of the voltage impulse noise and the resulting current noise are shown. An algorithm has been developed to evaluate the effectiveness of means for reducing impulse noise.

Control of an Asynchronous Electric Drive Based on Forecasting Its State

Variants of constructing control systems with a lagging argument for the positioning problem of an asyn-chronous electric motor (IM) and the problem of energy-saving AM control are considered. Variants of control of an asynchronous electric drive with IM on the basis of predicting its state are considered. The analytical de-sign of the predictor (ADP) is an asynchronous motor control algorithm based on the mathematical theory of optimal control (L.S. Pontryagin's maximum principle). The control algorithm (ADP) ensures the achievement of the minimum value of the target functional, which (functional), in contrast to the structure of the classical pre-dictive control system (Model Predictive Control - MPC), is clearly not part of the ADP. Calculations of the movements of an electric drive with an IM in the control modes of its state, taking into account delays along the channels for assessing its state and control, as well as using predictors, are given. The effectiveness of the in-troduction of predictors to improve the stability and quality of control of an electric drive with an IM has been established.

Optimization Problem of a Linear Induction Generator with a Liquid Working Fluid

We present the problem of optimization of cylindrical linear induction generators. The stator winding is located on the inner and outer cores of the magnetic system. The working fluid is a well-conducting liquid moving at a constant speed along the length of the channel. Since the generator is one of the elements of a complex installation the problem of optimizing it should be coordinated with a similar problem for the installation as a whole. This is done with the help the parameters common to all installation elements. Such parameters are the speed and flow rate of the working fluid. We describe the calculation algorithm with the use of computer technology. The efficiency and specific gravity of the generator are accepted as optimality criteria. The calculation results for a generator with the power of 20 MW are presented.

Synthesis of a Scalar Automatic Control System of a Valve Engine with Field Control for a Rowing Electric Installation with an Azipod Propulsion and Steering System

The article deals with the main trends in the development of marine automatic AC electric drive systems. A variant of the implementation of an electric drive using an electromechanical converter of a synchronous machine with electromagnetic field excitation is presented. A promising electric drive system with a valve engine for the icebreaker's with the Azipod propulsion and steering system is proposed. The aim of the work is to eliminate the structural complexity and expand the functional capabilities of the electric drive by using a scalar automatic control system of the frequency of rotation in the two-zone control of the valve motor of the EPS. The novelty lies in the use of the approach and representation of the control object-a valve motor as an analog of a DC collector motor controlled by an armature and by a field. The analysis of control processes is directly related to the processes of electromechanical energy conversion occurring in a synchronous machine.

Apparent and True Charges in the Partial Discharge Model at Different Defective Domain Sizes

A model of the partial discharges in a sample of solid insulation with air cavity is presented. The material of the insulation is cross-linked polyethylene. The model is based on an active-capacitive equivalent circuit, in which the resistance of the air cavity at the instant of a partial discharge ignition is shunted by the active resistance of the spark. The model takes into consideration the delay of the discharge development. The evaluation of the diagnostic value of the apparent and true charges is carried out. The results of the apparent and true charges relationship with the dimensions and proportions of the air cavity are presented. It is shown that the same magnitude of both true and apparent charges can correspond to the different volumes and shapes of the air cavities in the insulation.

An Approach to the Use of an External Magnetic Field As a Diagnostic Sign of an Asynchronous Motor Malfunction

The article deals with the issues related to the possibility of diagnosing the technical condition of an asyn-chronous electric motor by an external magnetic field. The justification of the problems associated with the di-agnosis of electric motors is given. The difficulties that arise when measuring the external magnetic field of electric motors, as well as the devices with which it is possible to carry out measurements, are described. The re-lationship between the EMF of the sensor and the external magnetic field is shown. The results of processing the EMF waveforms induced by an external magnetic field in an inductive sensor for various electric motors are presented. The processing was carried out by the fast Fourier transform method. The external magnetic field contains the first harmonic and various harmonics that are multiples of the combination of the stator teeth, or the sum of the stator and rotor teeth that fall on one pair of poles. The ratio of the amplitudes of the first and tooth harmonics is affected by the measurement location and the orientation of the sensor. Diagrams showing the ratio of the main and tooth harmonics at different points of the motor body are constructed. The depend-ences of the harmonic amplitudes on the magnitude of the magnetizing current of the stator are given. Changes in the amplitudes and spectrum of harmonics in the presence and absence of an inter-turn short circuit in the stator winding are shown. Diagrams of the circular external magnetic field for the main and higher harmonics are constructed. The study shows the possibility of using an external magnetic field to detect inter-turn short circuits of the stator winding.