Electrical Engineering & Electromechanics

Numerical modeling of coupled electromagnetic and thermal processes in the zone induction heating system for metal billets

V. Yu. Grytsiuk, M. A. M. Yassin — Sun, 02 Mar 2025 00:00:00 +0200

Introduction. For many modern manufacturing processes, induction heating provides an attractive combination of speed, consistency and control. Multi-inductor (zone) systems with continuous billets feed are the most promising, which keep the billet cross sectional average temperature equal. It allows to avoid overheating at low throughputs and reduces the number of rejected billets. Problem. With zone induction heating systems for metal billets developing it is necessary, at the design stage, to perform a quantitative analysis of the main characteristics of the electrothermal process and provide recommendations for optimal parameters and heating modes selections. Accurate calculations for induction heating systems involve considering the distribution of the magnetic field, current density, and changes of material properties throughout volume of the heated billet. The goal of the work is to develop the numerical model and analyze the coupled electromagnetic and thermal processes in zone induction heating system for metal billets to determine the optimal power ratio of the inductors and choose rational heating modes for the billets. Methodology. The spatiotemporal distribution of the electromagnetic field and temperature throughout the volume of the billet during the induction heating process is described by the system of Maxwell and Fourier equations. For numerical calculations by the finite element method, the COMSOL Multiphysics 6.1 software package was used. All three methods of heat transfer are taken into account – conduction, convection, and radiation. Multiphysics couplings use electromagnetic power dissipation as a heat sources, and the billet material properties are specified by temperature functions. The operation of the inductors’ coils is modeled using the «Multi-Turn Coil» function, which uses a homogenized model. The translational motion of the billet is modeled by using the «Translational Motion» function. Results. The numerical 3D-model of coupled electromagnetic and thermal processes in the zone induction heating system for metal billets has been developed. Modeling was carried out for the design of a four-inductor system with the nominal capacity of 5000 kg/h. Data on the spatial distribution of the electromagnetic and temperature fields in the moving heated steel billet were obtained. Originality. Three-dimensional graphs of electrical conductivity and relative magnetic permeability change inside the moving heated steel billet are presented. Results of the temperature distribution calculations along the length of the steel billet for different inductors power ratios are provided. It is shown how the change in the power distribution of the inductors affects the billet heating parameters. Practical value. Analysis of the obtained data allows to determinate the necessary inductors powers to ensure the required heating mode. The results make it possible to reduce the time and resources required for the development, optimization of the design and improvement of the technological process of zone induction heating for metal billets. References 20, table 1, figures 13.

Online detection of phase resistance of switched reluctance motor by sinusoidal signal injection

Y. Lee — Sun, 02 Mar 2025 00:00:00 +0200

Introduction. Switched reluctance motors (SRMs) are widely used in various applications due to their simplicity, robustness, and cost-effectiveness. However, the performance of SRMs can be significantly influenced by variations in their phase resistance, especially under high current and saturated conditions. Accurate knowledge of this parameter is crucial for optimal control and efficient operation. Problem. During operation, SRM parameters, particularly phase resistance, can vary considerably. These variations pose challenges to control strategies that rely on precise parameter values, leading to potential inefficiencies and degraded performance. There is a need for an effective method to monitor and identify these changes in real-time. Goal. This paper aims to develop and validate a method for the online detection and identification of phase resistance in SRMs. The method should work under varying operational conditions without requiring additional hardware, thereby maintaining the system's simplicity and cost-effectiveness. Methodology. The proposed method injects a sinusoidal signal into the inactive phase of the SRM using Sinusoidal Pulse Width Modulation (SPWM) via the main converter. The phasor method is then applied to determine the impedance of the phase circuit, from which the phase resistance can be identified. This approach eliminates the need for extra circuits, making it an efficient solution. Results. Simulations were conducted to evaluate the proposed method. The results demonstrate that the method can accurately track the variation in phase resistance under different operational conditions, validating its effectiveness. Originality. The originality of this work lies in its innovative use of the phasor method combined with SPWM for online phase resistance detection in SRMs, without the need for additional hardware components. Practical value. This method provides a practical solution for real-time phase resistance identification in SRMs, enhancing the reliability and performance of control strategies in various industrial applications. References 17, table 1, figures 6.

Numerical-field analysis of differential leakage reactance of stator winding in three-phase induction motors

V. I. Milykh — Sun, 02 Mar 2025 00:00:00 +0200

Introduction. The differential leakage reactance (DLR) of the stator winding of three-phase induction motors (TIM) is considered. It is known that DLR is the sum of the self-induction resistances of the winding from all harmonics of its magnetic field, excluding the first one, and its analytical definition is too complicated. But this reactance is a mandatory design element, including for calculating a number of other parameters and characteristics of such motors. Problem. Because of this, in the current classical design methods, the DLR are determined by a simplified formula with the addition of a number of coefficients, tabular and graphical dependencies. As a result, not only the physical and mathematical meaning of DLR is lost, but even the accuracy of its calculation is difficult to assess. Goal. The purpose of the paper consists in the comparative verification of the classical design calculation of the DLR of the TIM stator winding by numerical-field analysis of the harmonic composition of the EMF of self-inductions in this winding and by the determination of the considered DLR on such a basis. Methodology. Harmonic analysis is performed by obtaining the angular and time discrete functions of the magnetic flux linkage (MFL) of the stator winding with their formation in two ways: single-position calculation of the magnetic field and conditional rotation of the phase zones of the winding, or multi-position calculations of the rotating magnetic field and determination of the MFL of stationary phase zones. Results. Computational analysis is performed for nine common variants of TIM, designed according to a single classical method with variation of their power and the number of poles. Originality. A comparison of the results of the classical and numerical-field calculations of the DLR using the FEMM program showed their large discrepancy, which is attributed to the indicated inadequacy of the first one, since the second option is devoid of the shortcomings of the first one due to the fact that it takes into account the dimensions of the TIM structures, the saturation of the magnetic circuit and the physical and mathematical essence of the parameters and values under consideration. Practical value. The presented method of numerical-field analysis and the obtained results of calculating the DLR of the TIM stator winding are recommended as a basis for improving the system of their design. At the same time, a similar approach can be applied to the DLR of the TIM rotor winding, but taking into account its features. References 27, tables 13, figures 7.

Method for reduction of magnetic field of uncertain extended technical objects based on their multyspheroidal model and compensating magnetic dipoles

Sun, 02 Mar 2025 00:00:00 +0200

Problem. The implementation of strict requirements for magnetic silence of elongated energy-saturated objects such as naval vessel and submarines is an important scientific and technical problem of magnetism of technical objects. Purpose. Development of method for reduction of magnetic field of uncertain extended technical objects based on their multyspheroidal model and optimization of parameters of compensating dipoles for compensate of spheroidal harmonics of external magnetic field of technical object. Methodology. Number, coordinates of spatial arrangement and magnitudes of spherical harmonics of compensating dipole of magnetic field sources calculated as magnetostatics geometric inverse problems solution in the form of nonlinear minimax optimization problem based on multyspheroidal model of magnetic field of extended technical objects. Nonlinear objective function calculated as the weighted sum of squared of resulting magnetic field COMSOL Multiphysics software package used. Nonlinear minimax optimization problems solutions calculated based on particle swarm nonlinear optimization algorithms. Results. The results of reduction of the initial magnetic field of extended technical objects based on their multyspheroidal model and optimization of parameters of compensating magnetic dipoles for compensate of spheroidal harmonics of external magnetic field of technical object using multyspheroidal model of the magnetic field in the form of spatial prolate spheroidal harmonics in the prolate spheroidal coordinate system and taking into account the uncertainty of the magnetic characteristics of extended technical objects. Originality. For the first time the method for reduction of magnetic field of uncertain extended technical objects based on their multyspheroidal model and optimization of parameters of compensating magnetic dipoles for compensate of spheroidal harmonics of external magnetic field of technical object using multyspheroidal model of the magnetic field developed. Unlike known methods, the developed method makes it possible to increase the efficiency of magnetic field reduction of uncertain extended technical objects. Practical value. It is theoretically shown the possibility to reduce by almost 100 times of modulus of induction and horizontal component of the induction of the original magnetic field of uncertain extended technical objects based on optimization of parameters of compensating magnetic dipoles for compensate of spheroidal harmonics of external magnetic field of technical object using multyspheroidal model of the magnetic field. References 48, figures 6.

Dielectric parameters of phase and belt paper impregnated insulation of power cables

G. V. Bezprozvannych, Y. S. Moskvitin, I. O. Kostiukov, O. M. Grechko — Sun, 02 Mar 2025 00:00:00 +0200

Introduction. Medium voltage power cables with paper impregnated insulation remain an important component of power networks. The reliability and efficiency of such cables have been confirmed by their long service life also at nuclear power plants. Problem. It is not possible to directly determine the dielectric parameters of phase and belt paper insulation of power cables. Effective electrical diagnostic systems are required to assess the technical condition of such types of power cable insulation. The aim of the work is to substantiate the methodology for determining the dielectric properties of phase and belt paper impregnated insulation based on cumulative measurements of the electrical capacitance and the tangent of the dielectric loss angle of power cables of nuclear power plants and power networks. Methodology. The developed methodology is based on the solution of a system of linear algebraic equations of the sixth order for determining the dielectric properties of types of paper impregnated insulation of power three-core cables in a metal sheath. Scientific novelty. The differences in the structure of the probing electric field in phase and belt paper insulation depending on the inspection scheme of three-core power cables with sector cores in a metal sheath have been established. The shares of electric energy in the types of insulation under different probing electric field schemes have been determined, which allows determining the tangent of the dielectric loss angle of phase and belt paper insulation. Practical significance. The results of the practical implementation of the developed methodology for assessing the differences in the properties of phase and belt insulation of power cables of nuclear power plants and power network cables during spatial scanning of electrical insulation by frequency and voltage, respectively, are presented. References 41, figures 4, table 6.

Complex physicochemical analysis of transformer oil parameters using the inductively coupled plasma mass spectrometry technique

T. K. Nurubeyli, A. M. Hashimov, N. E. Imamverdiyev, G. N. Mammadova — Sun, 02 Mar 2025 00:00:00 +0200

Introduction. Transformers are crucial and expensive components of power systems, experiencing electrical, thermal, and chemical stresses. Transformer oil analysis is important for diagnosing transformer faults and assessing its remaining service life. The oil used in transformers degrades over time due to its interaction with electrical loads and heat from the core and windings. The oil degrades into low-molecular gases and carbon particles, which affect its dielectric properties and indicate potential problems. Analysis of dissolved gases in oil allows early detection of defects such as corona or arc discharges, as well as overheating. In addition, analysis of metal content in oil helps to clarify the type and location of the fault identified by gas analysis. Novelty of the proposed work lies in the study of the relationship between transformer oil parameters and its quality, as well as the effect of dissolved gases. The article proposes a method for determining how changes in these parameters affect each other. The obtained data are compared with the results of mass spectrometric analysis for a more accurate assessment of the transformer condition. The purpose of this paper is to explore the connection between the chemical properties of transformer oil and the elemental composition determined through inductively coupled plasma mass spectrometry (ICP-MS). Methods. The solution to the problem was carried out using the inductively coupled plasma mass spectrometry method from Agilent Technologies 7700e (USA) to measure the concentration of metals in transformer oil. Results. An inverse correlation has been identified between the acidity of transformer oil and its furfural content. Experimental evidence has shown that the water content has the most significant impact on decreasing the breakdown voltage of dielectric oil. It was found that CO gas has the greatest influence on the formation of furfural. It has been established that gaseous C₂H₂ plays an important role in the formation of acidic components. Correlations were found between the oil acidity and the concentrations of copper and iron and between the breakdown voltage and the amount of lead and aluminium in the transformer oil. A high concentration of copper in the oil indicates potential issues with the transformer windings, as well as in any bronze or brass components, and the concentration of iron in significant quantities indicates problems with the transformer core and tank. Moreover, as the breakdown voltage of the oil decreases, there is a marked increase in the concentrations of lead and aluminum. This suggests that significant amounts of lead are found in the transformer solder joints, while aluminum is present in the windings and ceramic bushings. Practical value. The advantage of the mass spectrometric method for detecting metals in transformer oils is the ability to accurately determine the type of fault and diagnose transformer problems. Research shows that this method allows early detection of potential problems and predicts the condition of the transformer. References 21, table 2, figures 8.

Brushless DC motor drive with optimal fractional-order sliding-mode control based on a genetic algorithm

I. I. Alnaib, A. N. Alsammak, K. K. Mohammed — Sun, 02 Mar 2025 00:00:00 +0200

Introduction. Brushless DC (BLDC) motor is a type of permanent magnet synchronous motor that operates without brushes employed in many applications owing to its efficiency and control in electric cars. One of the main reasons BLDC motors are better than brushed DC motors is that they employ an electronic commutation circuit instead of a mechanical one. The fractional order sliding mode controller (FOSMC) was used, which is characterized by high durability and is not affected by the disturbances that the motor is exposed to during operation, as well as overcoming the chattering phenomenon present in the conventional sliding mode controller (CSMC). The novelty of the proposed work consists of to use FOSMC by genetic algorithm (GA) to mitigate the chattering phenomena in sliding mode control (SMC) for optimal response for speed control and regeneration braking control in BLDC motor by using single stage by voltage source inverter and decrease energy use during motor starting. Purpose. Improvement FOSMC techniques for the regulation of BLDC motor’s driving control system. Methods. Employing the GA to optimize the parameters of FOSMC to mitigate the chattering phenomenon in SMC to regulate BLDC motor’s driving control system. Results. A comparison was made between two types of sliding controllers to obtain the best performance of the control system in speed control operations and motor braking operations, the FOSMC, through parameter optimization via the GA, surpasses the CSMC in achieving optimal performance in driving the BLDC motor. Practical value. FOSMC exhibits superiority over the CSMC, as indicated by the reduced integral time absolute error in motor speed tracking and regenerative brake control, with values of (0.028, 0.046, and 0.075) for the FOSMC, in contrast to (2.72, 1.56, and 0.17) for the CSMC, the overshoot for FOSMC is (0, 0, and 11.4), but for CSMC it is (60.4, 43.7, and 11.2). During braking mode for FOSMC, the power recovery from the motor to the battery was (1.96, 9, and 17.76), but in CSMC, it was (0.99, 4.49, and 11.98). Moreover, the braking length was expedited, and the battery’s initial power consumption diminished at the outset. References 32, tables 5, figures 6.

Ensuring service continuity in electric vehicles with vector control and linear quadratic regulator for dual star induction motors

Z. Darsouni, S. E. Rezgui, H. Benalla, F. Rebahi, M. A. M. Boumendjel — Sun, 02 Mar 2025 00:00:00 +0200

Introduction. In this paper, the use of a Linear Quadratic Regulator (LQR) to control a Dual Star Induction Motor (DSIM) powered by dual three-level neutral point clamped inverters in electric vehicle (EV) propulsion systems is explored. Purpose. Ensuring both high performance against parameter sensitivity and service continuity in the event of faults is challenging in EV propulsion systems. The aim is to maximize both system performance and service continuity through the optimal design of the controller. Methods. DSIM is controlled by a LQR, which is replaced the traditional PI controller in the field-oriented control (FOC) system for speed regulation. Starting with FOC the optimal regulator is designed by introducing a minimization criterion into the Ricatti equation. The LQR control law is then employed as a speed regulator to ensure precise regulation and optimize DSIM operation under various load and speed conditions. The avoidance of linearization of the DSIM facilitates the exploitation of its true nonlinear dynamics. Novelty. Three tests are conducted to evaluate system performance. A precision test by varying the reference speed and analyzing speed response, settling time, precision and overshoot, a robustness test against parameter variations, assessing system robustness against changes in stator and rotor resistances and moment of inertia, and a fault robustness test evaluating system robustness against faults such as phase faults while maintaining load torque. The results show that this approach can keep the motor running smoothly even under parameter variations or degraded conditions. The precision and adaptability of the LQR technique enhance the overall efficiency and stability of the DSIM, making it a highly viable solution for modern EVs. This robust performance against parameter variations and loads is essential in ensuring the reliability and longevity of EV propulsion systems. Practical value. This approach holds significant potential for advancing EV technology, promising improved performance and reliability in real-world applications. References 44, tables 2, figures 15.

Global maximum power point tracking method for photovoltaic systems using Takagi-Sugeno fuzzy models and ANFIS approach

N. Hadjidj, M. Benbrahim, D. Ounnas, L. H. Mouss — Sun, 02 Mar 2025 00:00:00 +0200

Introduction. A new global maximum power point tracking (GMPPT) control strategy for a solar photovoltaic (PV) system, based on the combination of Takagi-Sugeno (T-S) fuzzy models and an ANFIS, is presented. The novelty of this paper lies in the integration of T-S fuzzy models and the ANFIS approach to develop an efficient GMPPT controller for a PV system operating under partial shading conditions. Purpose. The new GMPPT control strategy aims to extract maximum power from the PV system under varying weather conditions or partial shading. Methods. An ANFIS algorithm is used to determine the maximum voltage, which corresponds to the actual maximum power point, based on PV voltage and current. Next, the nonlinear model of the PV system is employed to design the T-S fuzzy controller. A reference model is then derived based on the maximum voltage. Finally, a tracking controller is developed using the reference model and the T-S fuzzy controller. The stability of the overall system is evaluated using Lyapunov’s method and is represented through linear matrix inequalities expressions. The results clearly demonstrate the advantages of the proposed GMPPT-based fuzzy control strategy, showcasing its high performance in effectively reducing oscillations in various steady states of the PV system, ensuring minimal overshoot and a faster response time. In addition, a comparative analysis of the proposed GMPPT controller against conventional algorithms, such as Incremental Conductance, Perturb & Observe and Particle Swarm Optimization, shows that it offers a fast dynamic response in finding the maximum power with significantly less oscillation around the maximum power point. References 20, tables 3, figures 14.

Integrating dual active bridge DC-DC converters: a novel energy management approach for hybrid renewable energy systems

K. Sabhi, M. Talea, H. Bahri, S. Dani — Sun, 02 Mar 2025 00:00:00 +0200

Introduction. Hybrid renewable energy systems, which integrate wind turbines, solar PV panels, and battery storage, are essential for sustainable energy solutions. However, managing the energy flow in these systems, especially under varying load demands and climatic conditions, remains a challenge. The novelty of this paper is introduces a hybrid renewable energy system structure using Dual Active Bridge (DAB) DC-DC converters and an energy management strategy (EMS) to control power flow more effectively. The approach includes a dump load mechanism to handle excess energy, offering a more efficient and flexible system operation. The purpose of this study is to develop a novel approach to managing and controlling hybrid renewable energy systems, specifically through the use of a DAB DC-DC converter. Unlike traditional methods that may struggle with efficiency and flexibility, our approach introduces an innovative EMS that leverages a reduced neural network block for real-time optimal power tracking and a sophisticated control system to adapt to dynamic conditions. This approach aims to improve the flexibility of the system, enhance energy utilization, and address the limitations of existing methods by ensuring rapid and efficient responses to changes in load and climatic conditions. The primary goal of this study is to improve the performance and reliability of hybrid renewable energy systems by optimizing energy distribution and battery management. The strategy aims to ensure continuous energy availability, enhance battery lifespan, and improve system response to dynamic changes. Methods. The proposed EMS was developed and tested using MATLAB/Simulink. The system’s control mechanism prioritizes battery charging when renewable energy output exceeds demand and redirects excess energy to a dump load when necessary. Simulations were conducted under various load and climatic conditions to assess system performance. Results. The simulation results demonstrate that the proposed strategy effectively manages energy flow, ensuring optimal power distribution, quick adaptation to load changes, and maintaining the battery’s state of charge within safe limits. Practical value. The system showed improved stability and efficiency, validating the effectiveness of the control strategy in enhancing the overall performance of hybrid renewable energy systems. References 33, tables 3, figures 13.