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A special issue of Energies (ISSN 1996-1073). This special issue belongs to the section "F: Electrical Engineering".

Deadline for manuscript submissions: closed (25 February 2025) | Viewed by 29139

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Dr. Dan-Cristian Popa

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Department of Electrical Machines and Drives, Technical University of Cluj-Napoca, 28 Memorandumului Street, 400114 Cluj-Napoca, Romania
Interests: design of electric machines; numerical and analytical analysis; transverse flux machines; induction machines; transformers
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Prof. Dr. Emil Cazacu

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Department of Electrotechnics, Faculty of Electrical Engineering, University “POLITEHNICA” of Bucharest, Splaiul Independentei 313, Sector 6, 060042 Bucharest, Romania
Interests: electromagnetic field computation; magnetic levitation; nonlinear circuits; measurement and interpretation of power quality parameters for low-voltage consumers that operates in distorted and/or unbalanced states
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Special Issue Information

Dear colleagues,

The need for the efficient and high density power electric machines has led to study of various new topologies and optimization of the classic ones. The use of numerical analysis has become a regular used tool for the evaluation of the performances of the electrical machines. Also, the employment of various analytical models represents an important tool for the above mentioned purpose. In this context, the studies on these topics are always of interest for the researchers in this domain.

This Special Issue aims to publish researches on different topologies of electrical machines, based mainly on, but not limited to Magnetic Field Computations and Energy Efficiency Studies. These analyses are challenging for the researchers as efficiency increases cannot be achieved without finding innovative solutions. Also, analytical and numerical analyses are always subject to approaches leading to remarkable progresses in the study of the electrical machines. Given the above considerations, topics of interest are:

Innovative design of rotary and linear machines, with or without permanent magnets
Techniques for optimization
Analytical and numerical electromagnetic analysis
Application of new magnetic materials
Thermal and mechanical simulations
Control strategies
Noise, vibration and heat analysis
Energy Efficiency Studies
Energetical Optimisation Analysis

Assoc. Prof. Dr. Dan-Cristian Popa
Prof. Dr. Emil Cazacu
Guest Editors

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Keywords

Transverse flux machines
Magnetic field
Numerical analysis
Novel topology
Optimized design
New magnetic materials
Losses calculations
Control algorithm
NVH (noise, vibration, and harshness)
Thermal field analysis
Energy efficiency
Otimisation study

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Related Special Issue

Magnetic Field Computations and Energy Efficiency Studies in Electrical Machines, 2nd Edition in Energies

Published Papers (13 papers)

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Research

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27 pages, 4210 KiB

Open AccessArticle

Magnetic Field Distribution and Energy Losses in a Permanent Magnet Linear Synchronous Motor Under Stick-Slip Friction

by Paweł Olejnik, Yared D. Desta and Marcin Mydłowski

Energies 2025, 18(1), 191; https://doi.org/10.3390/en18010191 - 4 Jan 2025

Cited by 1 | Viewed by 1356

Abstract

This study investigates the modeling and dynamic analysis of three coupled electromechanical systems, emphasizing interactions between a magnetic linear drive and frictional contact with flat springs. The experimental setup includes a table driven by a three-phase permanent magnet linear synchronous motor (PMLSM) using an LMCA4 inductor, LMCAS3 magnetic track, and Xenus XTL controller. Mechanical phenomena such as stick-slip friction and impulsive loads are observed, particularly due to the rapid buckling of flat springs. These springs transition between sliding friction and fixation, impacting the motor’s operation during reciprocating velocity trajectories and generating acoustic emissions. Numerical simulations using COMSOL Multiphysics evaluate the magnetic field and system geometry in two- and three-dimensional spaces. Key findings include mechanical stick-slip vibrations, numerical modeling of the linear drive, and comparative analysis of experimental and simulated inductor current variations. Additionally, energy loss mechanisms under irregular loading conditions are assessed. The results highlight the coupling between friction-induced current changes and magnetic field variations, elucidating their impact on motor efficiency, vibration propagation, and acoustic emissions. The study provides insights into optimizing the design and reliability of coreless linear motors for precision applications under discontinuous loading. Full article

(This article belongs to the Special Issue Magnetic Field Computations and Energy Efficiency Studies in Electrical Machines)

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14 pages, 9141 KiB

Open AccessArticle

End-Region Losses in High-Power Electrical Machines: Impact of Material Thickness on Eddy Current Losses in Clamping Structures

by Walid Mohand Oussaid, Abdelmounaïm Tounzi, Raphaël Romary, Abdelkader Benabou, Walid Boughanmi and Daniel Laloy

Energies 2024, 17(22), 5684; https://doi.org/10.3390/en17225684 - 14 Nov 2024

Cited by 1 | Viewed by 797

Abstract

High-power electrical machines often utilize clamping structures composed of various materials with specific geometric dimensions to secure the stator laminations. These structures are exposed to end-region magnetic flux, which induces eddy currents, leading to significant power losses that reduce the machine’s efficiency. This study systematically investigates the impact of clamping plate thickness on eddy current losses across different materials and operating frequencies. A simplified experimental configuration was established to validate the numerical model developed using 3D Finite Element Method (FEM). This model was used to calculate the eddy current losses and analyze the influence of plate thickness under various conditions. A comprehensive parametric analysis was performed, revealing critical insights into the relationship between material properties, plate thickness, and loss generation. The findings indicate that while thinner plates exhibit higher current density, thicker plates provide a larger volume for current flow, resulting in varying loss patterns depending on the material’s electrical and magnetic properties. The study’s results offer valuable guidance for optimizing clamping structure designs in high-power electrical machines by selecting materials and thicknesses that minimize losses while maintaining mechanical integrity. Full article

(This article belongs to the Special Issue Magnetic Field Computations and Energy Efficiency Studies in Electrical Machines)

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15 pages, 7151 KiB

Open AccessFeature PaperArticle

Application of the Salp Swarm Algorithm to Optimal Design of Tuned Inductive Choke

by Łukasz Knypiński, Milena Kurzawa, Rafał Wojciechowski and Michał Gwóźdź

Energies 2024, 17(20), 5129; https://doi.org/10.3390/en17205129 - 15 Oct 2024

Cited by 3 | Viewed by 748

Abstract

The article presents an algorithm and optimization software designed for the optimal configuration of a tuned inductive choke. The optimization software consists of two main parts: an optimization procedure and a mathematical model for the designed electromagnetic devices. A lumped-parameters model of a tuned inductive choke was developed, with the device’s structure described by three design variables. As an optimality criterion, the multi-objective compromise function was adopted. The objective function merges the total inductances of the electromagnetic device under different operation states. The optimized structure was analyzed using the finite element method. The developed lumped-parameters model is characterized by good accuracy and can be successfully applied to optimize tuned inductive chokes for various rated parameters. The optimization procedure was adapted to the tuned inductive choke model by appropriately selecting the characteristic coefficient of the salp swarm algorithm. The reliability of the optimization software was verified through experimental measurements. Full article

(This article belongs to the Special Issue Magnetic Field Computations and Energy Efficiency Studies in Electrical Machines)

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21 pages, 6983 KiB

Open AccessArticle

Sensorless Detection of Mechanical Unbalance in Servodrive with Elastic Coupling

by Pawel Ewert, Tomasz Pajchrowski and Bartlomiej Wicher

Energies 2024, 17(19), 4859; https://doi.org/10.3390/en17194859 - 27 Sep 2024

Viewed by 787

Abstract

The article focusses on detecting the unbalance of a mechanical component in the electric drive system of a two-mass servomechanism with a permanent magnet synchronous motor (PMSM), which is connected to the load via a long, flexible shaft. In the example analysed, the degree of unbalance was determined using the reference current signal from the speed controller of the field-orientated control (FOC) system. The authors presented a two-mass model with an unbalanced mechanical system. The short-time Fourier transform (STFT) transform was used to analyse the symptoms of unbalance, and an artificial neural network multi-layer perceptron (MLP) was used for system state inference. The effectiveness of the presented analysis, based on the reference current signal from the sensor embedded in the control system, was experimentally confirmed. Full article

(This article belongs to the Special Issue Magnetic Field Computations and Energy Efficiency Studies in Electrical Machines)

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15 pages, 8528 KiB

Open AccessFeature PaperArticle

Numerical Modeling and Optimization of a Quasi-Resonant Inverter-Based Induction Heating Process of a Magnetic Gear

by Tamás Orosz, Miklós Csizmadia and Balázs Nagy

Energies 2024, 17(16), 4130; https://doi.org/10.3390/en17164130 - 19 Aug 2024

Viewed by 1043

Abstract

Induction heating is a clear, cheap, and highly effective technology used for many industrial and commercial applications. Generally, a time-varying magnetic field produces the required heat in the workpiece with a specially designed coil. The efficiency of the heating process depends highly on the coil design and the geometrical arrangement. A detailed and accurate finite element analysis of the induction heating process usually needs to resolve a coupled thermoelastic–magnetic problem, whose parameters values depend on the solution of another field. The paper deals with a shrink-fitting process design problem: a gear should be assembled with an axe. The interesting part of this case study is given the prescribed low limits for critical stress, the temperature of the gear material, and the heat-treated wearing surfaces. A coupled finite-element-based model and a genetic algorithm-based parameter determination methodology were presented. A thermal imaging-based measurement validated the presented numerical model and parameter determination task. The results show that the proposed methodology can be used to calibrate and validate the numerical model and optimize an induction heating process. Full article

(This article belongs to the Special Issue Magnetic Field Computations and Energy Efficiency Studies in Electrical Machines)

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24 pages, 11017 KiB

Open AccessArticle

Accelerated 3D FEA of an Axial Flux Machine by Exclusively Using the Magnetic Scalar Potential

by Adrian Schäfer, Urs Pecha, Benedikt Kaiser, Martin Schmid and Nejila Parspour

Energies 2023, 16(18), 6596; https://doi.org/10.3390/en16186596 - 13 Sep 2023

Cited by 2 | Viewed by 2081

Abstract

This article focuses on increasing the computational efficiency of 3D multi-static magnetic finite element analysis (FEA) for electrical machines (EMs), which have a magnetic field evolving in 3D space. Although 3D FEA is crucial for analyzing these machines and their operational behavior, it is computationally expensive. A novel approach is proposed in order to solve the magnetic field equations by exclusively using the magnetic scalar potential. For this purpose, virtual variable permanent magnets (vPMs) are introduced to model the impact of the machine’s coils. The effect on which this approach is based is derived from and explained by Maxwell’s equations. To validate the new approach, an axial flux machine (AFM) is simulated using both 2D and 3D FEA with the magnetic vector potential and current-carrying coils as a reference. The results demonstrate a high level of agreement between the new approach and the reference simulations as well as an acceleration of the computation by a factor of 15 or even more. Additionally, the research provides valuable insights into meshing techniques and torque calculation for EMs in FEA. Full article

(This article belongs to the Special Issue Magnetic Field Computations and Energy Efficiency Studies in Electrical Machines)

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12 pages, 2322 KiB

Open AccessArticle

Digital Twin as a Virtual Sensor for Wind Turbine Applications

by Mahmoud Ibrahim, Anton Rassõlkin, Toomas Vaimann, Ants Kallaste, Janis Zakis, Van Khang Hyunh and Raimondas Pomarnacki

Energies 2023, 16(17), 6246; https://doi.org/10.3390/en16176246 - 28 Aug 2023

Cited by 8 | Viewed by 3088

Abstract

Digital twins (DTs) have been implemented in various applications, including wind turbine generators (WTGs). They are used to create virtual replicas of physical turbines, which can be used to monitor and optimize their performance. By simulating the behavior of physical turbines in real time, DTs enable operators to predict potential failures and optimize maintenance schedules, resulting in increased reliability, safety, and efficiency. WTGs rely on accurate wind speed measurements for safe and efficient operation. However, physical wind speed sensors are prone to inaccuracies and failures due to environmental factors or inherent issues, resulting in partial or missing measurements that can affect the turbine’s performance. This paper proposes a DT-based sensing methodology to overcome these limitations by augmenting the physical sensor platform with virtual sensor arrays. A test bench of a direct drive WTG based on a permanent magnet synchronous generator (PMSG) was prepared, and its mathematical model was derived. MATLAB/Simulink was used to develop the WTG virtual model based on its mathematical model. A data acquisition system (DAS) equipped with an ActiveX server was used to facilitate real-time data exchange between the virtual and physical models. The virtual sensor was then validated and tuned using real sensory data from the physical turbine model. The results from the developed DT model showed the power of the DT as a virtual sensor in estimating wind speed according to the generated power. Full article

(This article belongs to the Special Issue Magnetic Field Computations and Energy Efficiency Studies in Electrical Machines)

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20 pages, 7435 KiB

Open AccessArticle

Numerical Aspects of a Two-Way Coupling for Electro-Mechanical Interactions—A Wind Energy Perspective

by Fiona Dominique Lüdecke, Martin Schmid, Eva Rehe, Sangamithra Panneer Selvam, Nejila Parspour and Po Wen Cheng

Energies 2022, 15(3), 1178; https://doi.org/10.3390/en15031178 - 5 Feb 2022

Cited by 2 | Viewed by 2531

Abstract

Generators in wind turbines are the key components to convert mechanical into electrical power. They are subject to electrical and mechanical excitation at the same time, which can cause electro-mechanical interactions. To avoid unwanted interactions, standard design approaches use conservative, stiff designs that lead to heavy generators of several hundred tons. New wind turbine designs, beyond 10 MW, need to revisit the conservative design approach as the tower top mass needs to be limited. To reduce the generator’s mass without large deformation that can damage the wind turbine, a better understanding of electro-mechanical interactions is key. This requires a detailed model including both the mechanical and the magnetic forces. This work presents a numerical setup of a coupled electromagnetic-structural multi-body model. While existing couplings are application-specific; the presented coupling is independent of the actual use case and allows for transient dynamic two-way coupled analyses. For validation, an experimental setup with basic components is introduced. The results show the applicability of the developed coupling for detailed analysis of general electro-mechanical interactions. Full article

(This article belongs to the Special Issue Magnetic Field Computations and Energy Efficiency Studies in Electrical Machines)

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17 pages, 7631 KiB

Open AccessArticle

High-Efficient Brushless Wound Rotor Synchronous Machine Topology Based on Sub-Harmonic Field-Excitation Technique

by Syed Sabir Hussain Bukhari, Qasim Ali, Jesús Doval-Gandoy and Jong-Suk Ro

Energies 2021, 14(15), 4427; https://doi.org/10.3390/en14154427 - 22 Jul 2021

Cited by 15 | Viewed by 3179

Abstract

This paper presents a new high-efficient three-phase brushless wound rotor synchronous machine (BL-WRSM) based on a sub-harmonic field excitation technique. In the proposed machine topology, the stator is equipped with two different three-phase windings: (1) main armature winding, and (2) additional armature winding. The main armature winding is based on a 4-pole winding configuration, whereas the additional armature winding is based on a 2-pole winding configuration. Both windings are supplied current from two different inverters, i.e., inverter-1, inverter-2, and simultaneously. Inverter-1 provides the regular input current to the main armature winding, whereas inverter-2 provides a three-phase current of low magnitude to the 2-pole additional armature winding. This generates an additional sub-harmonic component of MMF in the airgap beside the fundamental MMF. On the other side, the rotor is equipped with (1) harmonic, and (2) field windings. These windings are electrically coupled via a rectifier. The fundamental component of MMF produces the main rotating magnetic field, whereas the sub-harmonic MMF gets induced in the harmonic winding to produce harmonic current. This current is rectified to give DC to the rotor field winding to attain brushless operation. To authenticate the operation and analyze its performance, the proposed BL-WRSM topology is supported using 2-D finite element analysis (FEA) in JMAG-Designer. Later on, the performance of the proposed brushless topology is compared with the customary BL-WRSM topology to verify its high efficiency, high output torque, low torque ripple, and low unbalanced radial force on the rotor. Full article

(This article belongs to the Special Issue Magnetic Field Computations and Energy Efficiency Studies in Electrical Machines)

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Review

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25 pages, 1058 KiB

Open AccessReview

Model Order Reduction Methods for Rotating Electrical Machines: A Review

by Kristóf Levente Kiss and Tamás Orosz

Energies 2024, 17(20), 5145; https://doi.org/10.3390/en17205145 - 16 Oct 2024

Viewed by 1533

Abstract

Due to the rise of e-mobility applications, there is an increased demand to create more accurate control methods, which can reduce the loss in an e-drive system. The accurate modeling of the rotating machines needs to resolve a partial differential equation system that describes the thermal and mechanical behavior of the different parts in addition to the electromagnetic design. Due to these models’ limited resources and high computation demand, they cannot be used directly for real-time control. Model order reduction methods have been of growing interest in the past decades and offer solutions for this problem. According to the processed literature, many model order reduction-based methods are used for a wide range of problems. However, a paper has not been published that discusses a model order reduction-based real-time control model that is actually used in the industry. This paper aims to summarize and systematically review the model order reduction methods developed for rotating electrical machines in the last two decades and examine the possible usage of these methods for a real-time control problem. Full article

(This article belongs to the Special Issue Magnetic Field Computations and Energy Efficiency Studies in Electrical Machines)

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20 pages, 1611 KiB

Open AccessReview

Application of Low-Resolution Hall Position Sensor in Control and Position Estimation of PMSM—A Review

by Milad Akrami, Ehsan Jamshidpour, Lotfi Baghli and Vincent Frick

Energies 2024, 17(17), 4216; https://doi.org/10.3390/en17174216 - 23 Aug 2024

Cited by 6 | Viewed by 1732

Abstract

This paper reviews the application of Hall position sensors in control and position estimation of permanent magnet synchronous motors (PMSMs). Accurate rotor position and motor speed data are essential for the high-efficiency control of PMSMs in modern industry. Rotor position and motor speed can be measured by mechanical position sensors, which are costly and less reliable, or by rotor position observers, which are sensitive to system models and changes in motor parameters. This paper examines the benefits, limitations, challenges, and uses of low-resolution Hall position sensors in PMSM drives, presenting them as a cost-effective solution for achieving a balance between performance and expense. In addition, the paper discusses recent solutions to issues related to misplaced Hall position sensors and fault-tolerant control algorithms, and gives an outlook to future developments in this area. Full article

(This article belongs to the Special Issue Magnetic Field Computations and Energy Efficiency Studies in Electrical Machines)

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27 pages, 6618 KiB

Open AccessReview

Iron Loss Calculation Methods for Numerical Analysis of 3D-Printed Rotating Machines: A Review

by Tamás Orosz, Tamás Horváth, Balázs Tóth, Miklós Kuczmann and Bence Kocsis

Energies 2023, 16(18), 6547; https://doi.org/10.3390/en16186547 - 12 Sep 2023

Cited by 4 | Viewed by 3344

Abstract

Three-dimensional printing is a promising technology that offers increased freedom to create topologically optimised electrical machine designs with a much smaller layer thickness achievable with the current, laminated steel-sheet-based technology. These composite materials have promising magnetic behaviour, which can be competitive with the current magnetic materials. Accurately calculating the iron losses is challenging due to magnetic steels’ highly nonlinear hysteretic behaviour. Many numerical methodologies have been developed and applied in FEM-based simulations from the first introduced Steinmetz formulae. However, these old curve-fitting-based iron loss models are still actively used in modern finite-element solvers due to their simplicity and high computational demand for more-accurate mathematical methods, such as Preisach- or Jiles–Atherton-model-based calculations. In the case of 3D-printed electrical machines, where the printed material can have a strongly anisotropic behaviour and it is hard to define a standardised measurement, the applicability of the curve-fitting-based iron loss methodologies is limited. The following paper proposes an overview of the current problems and solutions for iron loss calculation and measurement methodologies and discusses their applicability in designing and optimising 3D-printed electrical machines. Full article

(This article belongs to the Special Issue Magnetic Field Computations and Energy Efficiency Studies in Electrical Machines)

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41 pages, 5818 KiB

Open AccessReview

Inverter-Fed Motor Drive System: A Systematic Analysis of Condition Monitoring and Practical Diagnostic Techniques

by Muhammad Usman Sardar, Toomas Vaimann, Lauri Kütt, Ants Kallaste, Bilal Asad, Siddique Akbar and Karolina Kudelina

Energies 2023, 16(15), 5628; https://doi.org/10.3390/en16155628 - 26 Jul 2023

Cited by 16 | Viewed by 4400

Abstract

Due to their efficiency and control capabilities, induction motors fed with inverters have become prevalent in various industrial applications. However, ensuring the reliable operation of the motor and diagnosing faults on time are crucial for preventing unexpected failures and minimizing downtime. This paper systematically analyzes condition monitoring and practical diagnostic techniques for inverter-fed motor drive systems. This study encompasses a thorough evaluation of different methods used for condition monitoring and diagnostics of induction motors, with the most crucial faults in their stator, rotor, bearings, eccentricity, shaft currents, and partial discharges. It also includes an assessment of their applicability. The presented analysis includes a focus on the challenges associated with inverter-fed systems, such as high-frequency harmonics, common-mode voltages causing the bearing currents, and high voltage gradients (dv/dt) due to fast switching frequency, which can impact the motor operation, as well as its faults analysis. Furthermore, this research explores the usefulness and efficiency of various available diagnostic methods, such as motor current signature analysis and other useful analyses using advanced signal processing techniques. This study aims to present findings that provide valuable insights for developing comprehensive condition monitoring strategies, and practical diagnostic techniques that enable proactive maintenance, enhanced system performance, and improved operational reliability of inverter-fed motor drive systems. Full article

(This article belongs to the Special Issue Magnetic Field Computations and Energy Efficiency Studies in Electrical Machines)

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