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.

Computer Models of Pem Fuel Cells for the Study of Transient Modes in Electrical Power Supply Complexes

Static and dynamic computer models of fuel cells are considered. A static model is determined that most ac-curately reproduces the current-voltage characteristic of a real fuel cell. A method for tuning it according to the experimental I - V characteristic by the least squares method is proposed. A method for its adjustment ac-cording to the experimental I - V characteristic by the method of gradient descent is proposed. A modified elec-trical equivalent circuit of a fuel cell has been developed, which simulates its dynamic response, taking into ac-count the damping effect of eddy currents during operation of a stack of fuel cells on a pulse voltage converter. A method is proposed for determining the parameters of the model from the experimental oscillograms of the current and voltage of the stack. A universal model of a stack of fuel cells in LTspice has been developed, which makes it possible to simulate a dynamic response and, if necessary, simulate a real static I – V characteristic of the stack.

Development of the Industrial Robot Electric Drive Model

Currently, the penetration of industrial robots into all sectors of the economy is increasing. However, there is an acute problem of conducting preliminary tests. The use of the digital twin as a replacement for the industrial robot is driven by high economic costs. In order to reduce the cost of the project, a solution is proposed to conduct preliminary tests on the developed model. The article developed a mathematical model of one of the drives of the industrial robot manipulator Yaskawa Motoman MH50-35. The model is suitable for researching the movement of the robot' tool. A mathematical description of a permanent magnet synchronous motor SGMJV-09A in a rotating coordinate system is given and a block diagram of the power part of the drive is made. A system for regulating the position of the robot's tool with a nonlinear position controller has been synthesized. Based on the results of modeling the operation of an electric drive in the Matlab Simulink environment, the degree of correspondence of the developed model to a real object was assessed and conclusions were drawn about the limits of its applicability for studying the operation of an electric drive of a robotic arm. The accuracy of working out the task for turning the wrist is 0.0001 rad, there is no overshoot in position, and the time for completing a full turn of the tool is 1.07 s.

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.