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Special Issue "Future Electrical Machines"

A special issue of Energies (ISSN 1996-1073). This special issue belongs to the section "A6: Electric Vehicles".

Deadline for manuscript submissions: closed (30 September 2021).

Special Issue Editors

Prof. Dr. Carlos Platero
E-Mail Website1 Website2
Guest Editor
Department of Automatic Control, Electrical and Electronic Engineering and Industrial Informatics, Universidad Politécnica de Madrid, 28006 Madrid, Spain
Interests: Integration of renewable energy in power systems, Energy efficiency, Protections, condition monitoring and diagnosis of electrical machines, especially large synchronous generators
Special Issues, Collections and Topics in MDPI journals
Dr. Konstantinos N. Gyftakis
E-Mail Website
Guest Editor
School of Engineering, The University of Edinburgh, Edinburg EH8 9YL, UK
Interests: condition monitoring of electrical machines; fault diagnosis of electrical machines. fault prognosis of electrical machines; design of electrical machines; electromagnetic analysis of electrical machines; insulation degradation

Special Issue Information

Dear Colleagues

Electrical machines play a crucial role in all industry fields and power generation, as well as final energy use and domestic applications. In this modern reality and under the global need for CO2 emission reduction, electric motors, transformers and generators are continuously evolving, aiming for higher efficiencies simultaneously with more reliable operation.

In the field of energy generation and consumption, great changes are taking place. An increasing number of electrical machines are working together with power electronics, while a significant portion of the generated power is covered by renewable energy harvesting. A large number of multiterminal HVDCs are planned in the transmission systems, with new transformers specially designed for them. Moreover, regarding the end use of electric power, there are many developments, such as high-efficiency motors, motors for electric vehicles, aircraft drives, and new technologies such as reluctance, permanent magnets, and superconducting machines.

The electrical machine operation and condition monitoring in the era of the industry 4.0 will be equally innovative. New techniques for signal processing, artificial intelligence, big data analysis, new sensors, and wireless and real time monitoring devices, among others, will be used for the control and supervision of electrical machines.

This Special Issue will focus on all the new advances related to electrical machines, such as novel designs, new applications, condition monitoring, etc. Papers related to modern advances in electrical machines which will shape the future in this field are most welcome.

Prof. Dr. Carlos Platero
Dr. Konstantinos N. Gyftakis
Guest Editors

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All papers will be peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Energies is an international peer-reviewed open access semimonthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2200 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • Electrical machines
  • Permanent magnet synchronous machines and drives
  • Reluctance synchronous machines and drives
  • High-efficiency electric motors
  • Superconducting electrical machines
  • Reluctance machines
  • Electrical machine condition monitoring
  • Electric motors for vehicle and rail applications
  • Aircraft electric drives
  • Artificial-intelligence-based electrical machines and drives

Published Papers (7 papers)

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Research

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Article
Design and Characteristic Analysis of a Homopolar Synchronous Machine Using a NI HTS Field Coil
Energies 2021, 14(18), 5658; https://doi.org/10.3390/en14185658 - 08 Sep 2021
Viewed by 413
Abstract
This paper deals with a homopolar synchronous machine (HSM) applying high-temperature superconducting (HTS) field coils. Superconductors, especially high-temperature superconductors, have high potential as advanced materials for next-generation electrical machines due to their high critical current density and excellent mechanical strength. However, coils made [...] Read more.
This paper deals with a homopolar synchronous machine (HSM) applying high-temperature superconducting (HTS) field coils. Superconductors, especially high-temperature superconductors, have high potential as advanced materials for next-generation electrical machines due to their high critical current density and excellent mechanical strength. However, coils made with high-temperature superconductors have a high risk of being damaged in the event of a quench due to the intrinsic low normal zone propagation velocity (NZPV). Therefore, the coil protection issue has been regarded as one of the most important research fields in HTS coil applications. Currently, the most actively studied method for quench protection of the HTS coils is the no-insulation (NI) winding technique. The NI winding technique is a method of winding an HTS coil without inserting an insulating material between turns. This method can automatically bypass the current to the adjacent turn when a local quench occurs inside the HTS coil, greatly improving the operating stability of the HTS coils. Accordingly, many institutions are conducting research to develop advanced electrical machines using NI HTS coils. However, the NI HTS coil has its intrinsic charge/discharge delay problem, which makes it difficult to successfully develop electrical machines using the NI HTS coil. In this study, we investigated how this charging/discharging problem appeared when the NI HTS coil was used in an HTS homopolar synchronous machine (HSM) which is one of the electrical machines with a high possibility of applying the HTS coil in the future because it has a stationary field coil structure. For this, the characteristic resistances of HTS coils were experimentally obtained and applied to the simulation model. Full article
(This article belongs to the Special Issue Future Electrical Machines)
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Article
Asymmetrical Rotor Skewing Optimization in Switched Reluctance Machines Using Differential Evolutionary Algorithm
Energies 2021, 14(11), 3194; https://doi.org/10.3390/en14113194 - 29 May 2021
Viewed by 771
Abstract
Minimizing torque ripple in electrical machines for a given application is not a straightforward task, especially when the application imposes certain constraints. There are many techniques to improve torque ripple, either design-based or control-based. In this paper, a new geometry for switched reluctance [...] Read more.
Minimizing torque ripple in electrical machines for a given application is not a straightforward task, especially when the application imposes certain constraints. There are many techniques to improve torque ripple, either design-based or control-based. In this paper, a new geometry for switched reluctance machines based on rotor poles skewing is proposed to minimize torque ripple. This paper describes a methodology to design an asymmetrical skew rotor—switched reluctance machine using a multi-objective differential evolutionary algorithm. The main parameters of the optimization process are defined, as is the optimization methodology to obtain an improved design with less torque ripple than a conventional one. Moreover, the analytical formulas used in the optimization method, as well as the optimization technique, are deduced and explained in detail. The mathematical model used to simulate the electrical machine and the power converter are also described. Two-dimensional and three-dimensional finite element analyses were also conducted to assess whether 3D effects (end-effect and axial fringing field) affected the results. Finally, a particular case of a high-voltage direct current-controlled generator in the base of the More Electric Aircraft (MEA) concept or an energy storage system as an electrical machine was analyzed, and the results for the improved configuration were compared with those for the conventional one. Full article
(This article belongs to the Special Issue Future Electrical Machines)
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Article
Electric Drivetrain Optimization for a Commercial Fleet with Different Degrees of Electrical Machine Commonality
Energies 2021, 14(11), 2989; https://doi.org/10.3390/en14112989 - 21 May 2021
Viewed by 757
Abstract
At present, the prevalence of electric vehicles is increasing continuously. In particular, there are promising applications for commercial vehicles transferring from conventional to full electric, due to lower operating costs and stricter emission regulations. Thus, cost analysis from the fleet perspective becomes important. [...] Read more.
At present, the prevalence of electric vehicles is increasing continuously. In particular, there are promising applications for commercial vehicles transferring from conventional to full electric, due to lower operating costs and stricter emission regulations. Thus, cost analysis from the fleet perspective becomes important. The study of cost competitiveness of different drivetrain designs is necessary to evaluate the fleet cost variance for different degrees of electrical machine commonality. This paper presents a methodology to find a preliminary powertrain design that minimizes the Total Cost of Ownership (TCO) for an entire fleet of electric commercial vehicles while fulfilling the performance requirements of each vehicle type. This methodology is based on scalable electric machine models, and particle swarm is used as the main optimization algorithm. The results show that the total cost penalty incurred when sharing the same electrical machine is small, therefore, there is a cost saving potential in higher degrees of electrical machine commonality. Full article
(This article belongs to the Special Issue Future Electrical Machines)
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Article
AC Magnetic Loss Reduction of SLM Processed Fe-Si for Additive Manufacturing of Electrical Machines
Energies 2021, 14(5), 1241; https://doi.org/10.3390/en14051241 - 24 Feb 2021
Cited by 2 | Viewed by 1323
Abstract
Additively manufactured soft magnetic Fe-3.7%w.t.Si toroidal samples with solid and novel partitioned cross-sectional geometries are characterized through magnetic measurements. This study focuses on the effect of air gaps and annealing temperature on AC core losses at the 50 Hz frequency. In addition, DC [...] Read more.
Additively manufactured soft magnetic Fe-3.7%w.t.Si toroidal samples with solid and novel partitioned cross-sectional geometries are characterized through magnetic measurements. This study focuses on the effect of air gaps and annealing temperature on AC core losses at the 50 Hz frequency. In addition, DC electromagnetic material properties are presented, showing comparable results to conventional and other 3D-printed, high-grade, soft magnetic materials. The magnetization of 1.5 T was achieved at 1800 A/m, exhibiting a maximum relative permeability of 28,900 and hysteresis losses of 0.61 (1 T) and 1.7 (1.5 T) W/kg. A clear trend of total core loss reduction at 50 Hz was observed in relation to the segregation of the specimen cross-sectional topology. The lowest 50 Hz total core losses were measured for the toroidal specimen with four internal air gaps annealed at 1200 °C, exhibiting a total core loss of 1.2 (1 T) and 5.5 (1.5 T) W/kg. This is equal to an 860% total core loss reduction at 1 T and a 510% loss reduction at 1.5 T magnetization compared to solid bulk-printed material. Based on the findings, the advantages and disadvantages of printed air-gapped material internal structures are discussed in detail. Full article
(This article belongs to the Special Issue Future Electrical Machines)
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Article
Time-Frequency Analysis Based on Minimum-Norm Spectral Estimation to Detect Induction Motor Faults
Energies 2020, 13(16), 4102; https://doi.org/10.3390/en13164102 - 07 Aug 2020
Cited by 2 | Viewed by 868
Abstract
In this work, a new time-frequency tool based on minimum-norm spectral estimation is introduced for multiple fault detection in induction motors. Several diagnostic techniques are available to identify certain faults in induction machines; however, they generally give acceptable results only for machines operating [...] Read more.
In this work, a new time-frequency tool based on minimum-norm spectral estimation is introduced for multiple fault detection in induction motors. Several diagnostic techniques are available to identify certain faults in induction machines; however, they generally give acceptable results only for machines operating under stationary conditions. Induction motors rarely operate under stationary conditions as they are constantly affected by load oscillations, speed waves, unbalanced voltages, and other external conditions. To overcome this issue, different time-frequency analysis techniques have been proposed for fault detection in induction motors under non-stationary regimes. However, most of them have low-resolution, low-accuracy or both. The proposed method employs the minimum-norm spectral estimation to provide high frequency resolution and accuracy in the time-frequency domain. This technique exploits the advantages of non-stationary conditions, where mechanical and electrical stresses in the machine are higher than in stationary conditions, improving the detectability of fault components. Numerical simulation and experimental results are provided to validate the effectiveness of the method in starting current analysis of induction motors. Full article
(This article belongs to the Special Issue Future Electrical Machines)
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Review

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Review
Alternating Current Loss of Superconductors Applied to Superconducting Electrical Machines
Energies 2021, 14(8), 2234; https://doi.org/10.3390/en14082234 - 16 Apr 2021
Cited by 2 | Viewed by 1041
Abstract
Superconductor technology has recently attracted increasing attention in power-generation- and electrical-propulsion-related domains, as it provides a solution to the limited power density seen by the core component, electrical machines. Superconducting machines, characterized by both high power density and high efficiency, can effectively reduce [...] Read more.
Superconductor technology has recently attracted increasing attention in power-generation- and electrical-propulsion-related domains, as it provides a solution to the limited power density seen by the core component, electrical machines. Superconducting machines, characterized by both high power density and high efficiency, can effectively reduce the size and mass compared to conventional machine designs. This opens the way to large-scale purely electrical applications, e.g., all-electrical aircrafts. The alternating current (AC) loss of superconductors caused by time-varying transport currents or magnetic fields (or both) has impaired the efficiency and reliability of superconducting machines, bringing severe challenges to the cryogenic systems, too. Although much research has been conducted in terms of the qualitative and quantitative analysis of AC loss and its reduction methods, AC loss remains a crucial problem for the design of highly efficient superconducting machines, especially for those operating at high speeds for future aviation. Given that a critical review on the research advancement regarding the AC loss of superconductors has not been reported during the last dozen years, especially combined with electrical machines, this paper aims to clarify its research status and provide a useful reference for researchers working on superconducting machines. The adopted superconducting materials, analytical formulae, modelling methods, measurement approaches, as well as reduction techniques for AC loss of low-temperature superconductors (LTSs) and high-temperature superconductors (HTSs) in both low- and high-frequency fields have been systematically analyzed and summarized. Based on the authors’ previous research on the AC loss characteristics of HTS coated conductors (CCs), stacks, and coils at high frequencies, the challenges for the existing AC loss quantification methods have been elucidated, and multiple suggestions with respect to the AC loss reduction in superconducting machines have been put forward. This article systematically reviews the qualitative and quantitative analysis methods of AC loss as well as its reduction techniques in superconductors applied to electrical machines for the first time. It is believed to help deepen the understanding of AC loss and deliver a helpful guideline for the future development of superconducting machines and applied superconductivity. Full article
(This article belongs to the Special Issue Future Electrical Machines)
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Review
A Review on Additive Manufacturing Possibilities for Electrical Machines
Energies 2021, 14(7), 1940; https://doi.org/10.3390/en14071940 - 31 Mar 2021
Cited by 4 | Viewed by 936
Abstract
This paper presents current research trends and prospects of utilizing additive manufacturing (AM) techniques to manufacture electrical machines. Modern-day machine applications require extraordinary performance parameters such as high power-density, integrated functionalities, improved thermal, mechanical & electromagnetic properties. AM offers a higher degree of [...] Read more.
This paper presents current research trends and prospects of utilizing additive manufacturing (AM) techniques to manufacture electrical machines. Modern-day machine applications require extraordinary performance parameters such as high power-density, integrated functionalities, improved thermal, mechanical & electromagnetic properties. AM offers a higher degree of design flexibility to achieve these performance parameters, which is impossible to realize through conventional manufacturing techniques. AM has a lot to offer in every aspect of machine fabrication, such that from size/weight reduction to the realization of complex geometric designs. However, some practical limitations of existing AM techniques restrict their utilization in large scale production industry. The introduction of three-dimensional asymmetry in machine design is an aspect that can be exploited most with the prevalent level of research in AM. In order to take one step further towards the enablement of large-scale production of AM-built electrical machines, this paper also discusses some machine types which can best utilize existing developments in the field of AM. Full article
(This article belongs to the Special Issue Future Electrical Machines)
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