Niroo Research InstituteElectromechanical Energy Conversion Systems2676-430X4220250901Machine Learning Ball-Bearing Fault Detection Methods Using Envelope Analysis and Power Spectral Density1722696310.30503/eecs.2025.488460.1064ENMohammad HatamiKakeshDepartment of Electrical Engineering, Shiraz University of TechnologyAkbarRahidehShiraz University of Technology0000-0001-5388-2199Gholam RezaAgahDepartment of Electrical Engineering, Shiraz University of TechnologyShahinHedayati KiaUniversité de Picardie JulesVerne, 80039 Amiens, FranceJournal Article20241112Ball-bearings are one of the most important components in rotating machinery. Due to practical importance of rotating machineries in industry, fault detection has become inevitable. Various techniques have been implemented for ball-bearing fault detection using vibration signals. In this research, vibration signal analysis methods are presented to extract suitable features for training some of the machine learning techniques in order to diagnose ball-bearing defects in different speeds. The purpose of this study is to obtain a highly accurate algorithm and compare its performance with that of other machine learning algorithms. To achieve this goal, Hilbert transform has been applied for envelope analysis to attenuate the frequencies that are not related to ball-bearing fault and perform power spectral density and descriptive statistics to extract features. Also comparison and evaluation of random forest, support vector machine, artificial neural network and k-nearest neighbour have been carried out for this study. For dataset with 1465 samples in various speed, random forest has achieved the accuracy above %97.https://eecs.nri.ac.ir/article_226963_5dd03de72cf4df899721911a56138c58.pdfNiroo Research InstituteElectromechanical Energy Conversion Systems2676-430X4220250901Magnetic Force Calculation Using Lorentz Force and Energy Conservation in Electrical Machines83422949710.30503/eecs.2025.488806.1065ENMohammad HoseinJavanmardidepartment of electrical and electronics engineering, Shiraz university of technology, Shiraz, IranAkbarRahidedepartment of electrical and electronics engineering, Shiraz university of technology, Shiraz, IranJafarRouzegardepartment of mechanical engineering, Shiraz university of technology, IranJournal Article20241114In many engineering textbooks, very simple algebraic relations are used for magnetic forces. The simplicity of the relations lies in the well-known magnetic circuit model from which they have been derived. However, some applications require more accuracy. One niche application is the calculation of magnetic forces in electrical machines due to slotting effect. The application is twofold: 1) vibration analysis which requires calculation of the net torque ripple (leading to cogging torque) and the oscillation of resultant normal force (attractions/repulsions). 2) deformation analysis which requires calculating the surface and volume force density distribution. Given the magnetic field distribution, the analyses can be furnished by leveraging advanced formulae of magnetic force. Thus in order to increase the accuracy, engineers would have to resort to 1) more advanced magnetic models that yield a precise two-dimensional magnetic field distribution and 2) a reliable method of magnetic force calculation. The latter is the subject of this paper. To be a reference for engineering community, this paper follows these objectives: 1) since not all engineers are accustomed with advanced physics topics; this paper aims to bring a handful of formulae from the outset. Additionally, two novel formulae are derived: surface force density and Maxwell couple stress tensor. 2) Revisiting the underlying theory and derivation of the related formulae for three purposes: 2-1) providing subjective foresight, 2-2) elucidating the limitation of the usage of the formulae and 2-3) to point out common mistaken interpretations. Two case-studies are investigated to verify the identity of all formulae.https://eecs.nri.ac.ir/article_229497_85c6508b22098e575b67b17297fa7fa7.pdfNiroo Research InstituteElectromechanical Energy Conversion Systems2676-430X4220250901Minimizing Position Errors in Helical Motion Resolvers Through Optimal Turn Function Design354122760610.30503/eecs.2025.494201.1067ENFatemeZareIsfahan University of TechnologyZahraNasiri GheidariSharif University of TechnologyJournal Article20241215As the demand for Two-Degree of Freedom (2-DoF) electrical machines continues to grow, the need for advanced sensors capable of detecting positions in multiple directions becomes increasingly critical. Compared to employing two separate sensors, using a single 2-DoF sensor offers significant advantages by reducing weight, volume, and complexity in control systems. This paper investigates a 2-DoF position sensor designed for helical motion detection. Given the significant impact of winding arrangements on resolver performance, determining the optimal winding configuration for helical motion is essential. To address the computational challenges associated with 3D Finite Element Analysis (3D-FEA), a numerical model based on the Winding Function (WF) method is developed to facilitate the optimization process. Subsequently, the Particle Swarm Optimization (PSO) algorithm is applied to refine the winding arrangement further and achieve greater accuracy. The results demonstrate that the resolver equipped with the optimized winding configuration significantly outperforms the one with the initial winding arrangement in terms of accuracy.https://eecs.nri.ac.ir/article_227606_e948636780a19c7017e3e128008a2838.pdfNiroo Research InstituteElectromechanical Energy Conversion Systems2676-430X4220250901Geomagnetically Induced Current Impact on Power Transformer and Neutral Protection Methods425522770710.30503/eecs.2025.498142.1070ENJawadFaizSchool of Electrical and Computer Engineering, College of Engineering, University of Tehran0000-0003-0844-8523HadisHosseinpourSchool of Electrical and Computer Engineering, College of Engineering, University of TehranJournal Article20250105Geomagnetically induced current (GIC) is a geomagnetic phenomenon. Inducing this current in power grid can cause damage the transformers by creating hot spots, increases the losses of power system and causes some problems in the electrical energy transmission process to the consumers. GIC can make the transformer to operate in its magnetic saturation region and therefore to increase the reactive power and harmonics by the transformer. This paper introduces the GIC and its impacts on the power systems and power transformers. Moreover, several methods to confront this destructive phenomenon are investigated and their merits and drawbacks are proposed using computer simulations of a power system in the presence of GIC. Increasing the sensitivity of the neutral wire leads to faster changes in the power system when a problem occurs in the neutral wire. So, system operation in normal case and in the presence of the GIC must be realized and all these involve a comprehensive control of power system.https://eecs.nri.ac.ir/article_227707_38d04f724b352778f02c80461bf80714.pdfNiroo Research InstituteElectromechanical Energy Conversion Systems2676-430X4220250901Strategies for Minimizing Stray Losses in Power Transformers: Effects of Shield Material and Placement566523078610.30503/eecs.2025.498188.1071ENMahsaTaghilouAmirkabir University of Technology0009-0001-0622-9936MojtabaMirsalimAmirkabir University of Technology0000-0003-0219-7081Journal Article20250105A transformer is a vital component of the power grid infrastructure as it facilitates efficient transmission, distribution, and utilization of electrical energy, and ensures reliable and uninterrupted power supply to consumers. As the demand for electricity in a power grid increases, additional transformers with higher ratings may be required to handle the increased load. Therefore, the reduction of losses in power transformers is essential for optimizing energy efficiency, reducing costs, and maintaining a reliable power grid. Stray loss which is 20-25% of the total load loss of the transformer, can affect power quality by introducing harmonics into the power grid. Stray losses also increase the temperature, and cooling requirement for the transformer. In addition to the power grid’s cost and performance, the transformer’s lifetime is also important, which ultimately depends on the amount of losses. Therefore, to compromise between the cost and performance and guarantee losses, it should be reduced. In reducing stray losses, shielding is an effective technique that generates opposing fields to the stray flux or establishes a path with lower reluctance. In this study, the three-dimensional finite element method (FEM) is employed to accurately assess the stray losses in the structural components of a 250 MVA power transformer. Various factors, including the choice of materials (ferromagnetic and copper) and the strategic placement of shields, are considered to minimize energy losses and enhance the overall efficiency of the transformer.https://eecs.nri.ac.ir/article_230786_2614e26f4ee5acb582f06dc3944cf3f9.pdfNiroo Research InstituteElectromechanical Energy Conversion Systems2676-430X4220250901Torque Ripple Reduction in a Modular Drive of Twelve-Phase, Non-Sinusoidal PMSM with Double Stator Windings based on an Ultra-local model and Extended State Observers (ESO)667522983210.30503/eecs.2025.504836.1072ENAbolfazlHalvaei NiasarFaculty of Electrical and Computer Engineering,
University of Kashan0000-0003-4265-5120DavoodMalekiFaculty of Electrical and Computer Engineering,
University of Kashan,
Ravand Road, Kashan, IranJournal Article20250205In the electric drive systems of marine propulsion, particularly in submarines, multiphase permanent magnet synchronous motors (PMSMs) have garnered significant attention due to their enhanced reliability in high-power applications. This paper investigates a twelve-phase non-sinusoidal PMSM with double stator windings, where each stator phase's windings are symmetrically positioned relative to the stator centre. Each winding is powered by a single-phase H-bridge inverter, with both inverters of each phase controlled by a dedicated microcontroller. Given the independent control system for each phase, conventional dq-axis modeling and control methods are not applicable. Instead, the system is modeled in a stationary 12-phase reference frame. Furthermore, due to the non-sinusoidal back-EMF voltage waveforms, harmonic current injection is independently applied to each phase to mitigate torque ripple. For harmonic reference current regulation, a state feedback controller based on an ultra-local model is employed, replacing traditional PI or hysteresis controllers. Additionally, extended state observers (ESOs) are designed to estimate uncertainties and parameter mismatches. Simulation results validate the superiority of the proposed control approach.https://eecs.nri.ac.ir/article_229832_44ae6e48a1193aafcdb2ad15baeebb1c.pdf