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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 (30 June 2022) | Viewed by 13533

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Special Issue Editors

Dr. João Filipe Pereira Fernandes

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Guest Editor

Instituto de Engenharia Mecânica (IDMEC), Instituto Superior Técnico (IST), Universidade Lisboa (UL), Lisbon, Portugal
Interests: electrical machines design and optimization; core and coreless superconducting machines; alternative for rare-earth electrical machines; special materials to reduce saturation in the magnetic circuit core; electrical machines for aircraft and automotive applications
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Dr. Paulo Jose Da Costa Branco

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Guest Editor

Department of Electrical and Computer Engineering, Instituto Superior Técnico, University of Lisbon, 1649-004 Lisboa, Portugal
Interests: electrical machines and drives; photovoltaic systems; applications of superconductors for electric power systems
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

The interest for higher-performance electrical machines is a constant challenge among the research and industrial communities. This challenge has been enhanced with the emergent and even more critical electrification of modern transportation systems, as for example in the aircraft and in automobile industries, thus creating the need for new designs of electrical machines and to spread their current electromagnetic, thermal, and mechanical limits.

The development of new electromagnetic materials and the significant growth of computational resources have been key aspects contributing to overcoming this challenge. The Guest Editor is inviting submissions to a Special Issue of Energies on the subject area of “Electrical Machine Design 2021”. This Special Issue will deal with novel designs and optimization techniques and with the application of new electromagnetic materials for electrical machines. Topics of interest for publication include but are not limited to:

Techniques for electrical machines design and optimizations;
FEM, BEM, and analytical methods;
Multiphysic coupled simulation and optimization;
Electromagnetic, thermal, and mechanical simulations;
Application of new magnetic material and soft magnetic materials;
Novel machine configurations and topologies;
Electrical machines design for aircraft and automotive applications;
Alternative for rare-earth electrical machines.

Prof. Dr. João Filipe Pereira Fernandes
Prof. Dr. Paulo Jose Da Costa Branco
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 submissions that pass pre-check are 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 2600 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

techniques for electrical machines design and optimizations
FEM, BEM, and analytical methods
multiphysic coupled simulation and optimization
electromagnetic, thermal, and mechanical simulations
application of new magnetic material and soft magnetic materials
novel machine configurations and topologies
electrical machines design for aircraft and automotive applications
alternative for rare-earth electrical machines

Published Papers (6 papers)

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Research

18 pages, 5511 KiB

Open AccessArticle

A Numerical Study on the Energization of the Field Coils of a Full-Size Wind Turbine with Different Types of Flux Pumps

by Giacomo Russo and Antonio Morandi

Energies 2022, 15(15), 5392; https://0-doi-org.brum.beds.ac.uk/10.3390/en15155392 - 26 Jul 2022

Cited by 7 | Viewed by 1506

Abstract

High temperature superconductivity is emerging as a solution for lightweight, cost-effective and high-power wind generators. Current injection and maintainment/sustainment in the field winding are obtained by metal current leads which, due to persistent heat conduction and joule loss, are responsible for a large part of the total cryogenic heat load. Slip rings, which further reduce the overall performance and reliability of the system, are also required. In this paper we assess the viability of the HTS dynamo and the rectifier flux pumps for energizing the field coils of the EcoSwing 3.6 MW HTS wind generator. Both a “warm” solution, with the rectifier at room temperature, and a “cold” solution, in which the latter is integrated into the cryostat, are investigated with regard to the rectifier flux pump. A comparison with the actual, state-of-the-art, system of the EcoSwing machine is carried out in terms of the total required cooling power and the ability to charge the HTS field winding up to the rated current. It is found that the dynamo flux pump, beside avoiding the need of slip rings, allows the reduction in the required cooling by about 74% with respect to the conventional current-leads-based solution. Full article

(This article belongs to the Special Issue Electrical Machine Design 2021)

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21 pages, 6640 KiB

Open AccessArticle

Optimal Design of an Interior Permanent Magnet Synchronous Motor with Cobalt Iron Core

by Pedro P. C. Bhagubai, Luís F. D. Bucho, João F. P. Fernandes and P. J. Costa Branco

Energies 2022, 15(8), 2882; https://0-doi-org.brum.beds.ac.uk/10.3390/en15082882 - 14 Apr 2022

Cited by 6 | Viewed by 2109

Abstract

The use of a cobalt-iron (VaCoFe) core is investigated as an alternative to silicon-iron (FeSi) in the design of interior permanent magnet synchronous motors (IPMSM). Considering VaCoFe and FeSi cores, a spoke-type IPMSM geometry is optimized for a torque range up to 40 N·m, providing a general comparative analysis between materials. This is done considering the application of a four-motor competition vehicle’s powertrain. A genetic optimization algorithm is coupled to the motor’s electromagnetic and thermal hybrid analytical/finite-element model to provide sufficiently accurate results within a feasible time. VaCoFe allows an estimated increase of up to 64% in torque for the same efficiency level, or up to 5% in efficiency for the same torque. After optimization and using a detailed time-dependent model, a potential 3.2% increase in efficiency, a core weight reduction of 4.1%, and a decrease of 9.6% in the motor’s core volume were found for the VaCoFe at 20 N·m. In addition, for the same motor volume, the VaCoFe allows an increase of 51.9% in torque with an increase of 1.1% in efficiency when compared with FeSi. Full article

(This article belongs to the Special Issue Electrical Machine Design 2021)

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14 pages, 2062 KiB

Open AccessArticle

Sensorless Switched Reluctance Machine and Speed Control: A Study to Remove the Position Encoder at High Speed of Operation

by Jonathan Velasco Costa and Paulo J. C. Branco

Energies 2022, 15(5), 1716; https://0-doi-org.brum.beds.ac.uk/10.3390/en15051716 - 25 Feb 2022

Cited by 1 | Viewed by 1879

Abstract

High-speed electrical machines have been of great research interest because of their excellent efficiency and high storage capacity. In the case of switched reluctance machines (SRMs), position feedback is required for effective operation. The installation of this sensor in a high-speed flywheel is difficult and expensive. This paper proposes and analyses a methodology to estimate the position of a SRM and remove the position encoder to apply the machine as a flywheel at 50,000 rpm. The machine is modeled with non-linear characteristics, and is simulated under single-pulse operation due to the high-speed. Two configurations of the sensorless method are presented: Robust Method and Sequential Method. The robust configuration identifies the firing angles position only, while the sequential setup can track any position. Both configurations present advantages and disadvantages in relation to the error of estimation and to the number of estimations. The methods are tested in closed-loop speed control. In the two cases, the position estimation supports satisfactory results for simulating operation of the machine at high speed. Full article

(This article belongs to the Special Issue Electrical Machine Design 2021)

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16 pages, 5740 KiB

Open AccessArticle

An Electromagnetic Design of a Fully Superconducting Generator for Wind Application

by Yingzhen Liu, Francesco Grilli, Jiwei Cao, Liyi Li, Chengming Zhang, Mingyi Wang, Fengyu Xu, Jingbo Lin and Mathias Noe

Energies 2021, 14(22), 7811; https://0-doi-org.brum.beds.ac.uk/10.3390/en14227811 - 22 Nov 2021

Cited by 7 | Viewed by 2258

Abstract

A fully superconducting wind generator employs superconductors in stator and rotor to enable high torque density and low weight, that is, enable an ultra-light electric machine for wind application. However, the level of the AC loss of the stator armature coils is a critical issue, which lacks investigations in the design of the fully superconducting generators. In this paper, an in-house model was developed to analyze the potential of a fully superconducting generator by integrating the electromagnetic design with the AC loss estimation. The electromagnetic model was made through analytical equations, which take into consideration the geometry, the magnetic properties of iron, and the nonlinear E–J constitutive law of superconductors. Since the permeability of iron materials and the critical current of the superconductors depend on the magnetic field, an iteration process was proposed to find their operating points for every electromagnetic design. The AC loss estimation was carried out through finite element software based on the T–A formulation of Maxwell’s equations instead of analytical equations, due to the complexity of magnetic fields, currents and rotation. The results demonstrate that the design approach is viable and efficient, and is therefore useful for the preliminary design of the generator. In addition, it is found that smaller tape width, larger distance between the superconducting coils in the same slot, smaller coil number in one slot and lower working temperature can reduce the AC loss of the stator coils, but the reduction of the AC loss needs careful design to achieve an optimum solution. Full article

(This article belongs to the Special Issue Electrical Machine Design 2021)

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22 pages, 8707 KiB

Open AccessArticle

Influence of Equivalent Circuit Resistances on Operating Parameters on Three-Phase Induction Motors with Powers up to 50 kW

by Marcel Torrent and Balduí Blanqué

Energies 2021, 14(21), 7130; https://0-doi-org.brum.beds.ac.uk/10.3390/en14217130 - 01 Nov 2021

Cited by 3 | Viewed by 1843

Abstract

This work shows the results obtained from studying the influence of equivalent circuit resistances on three-phase induction motors. The stator resistance, rotor resistance, and iron losses resistance affect the different motor operating variables (output power, current, speed, power factor, starting ratios, and maximum torque). These influences have been quantified, paying particular attention to the losses affected and their impact on efficiency. The study carried out does not apply optimization techniques. It evaluates the different influences of the equivalent circuit’s different resistances on its operation by evaluating applicable constructive modifications concerning available motors. The work has been limited to three-phase induction motors up to 50 kW and low voltage, with the nominal powers of the selected motors being 0.25 kW, 1.5 kW, 7.5 kW, 22 kW, and 45 kW. The tools used to carry out the study are analyzing the equivalent circuit and the simulation of the electromagnetic structure using a finite-element program. The variations proposed in each resistance for all the motors studied is not purely theoretical, as it is based on applying feasible constructive modifications, appropriately analyzed and simulated. These modifications are the variation of the conductor diameter in the stator coils, the change of the section of the rotor cage, and the selection of different ferromagnetic steel types. Full article

(This article belongs to the Special Issue Electrical Machine Design 2021)

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12 pages, 3084 KiB

Open AccessArticle

Torque Analysis for Rotational Devices with Nonmagnetic Rotor Driven by Magnetic Fluid Filled in Air Gap

by Gui-Hwan Kim and Hong-Soon Choi

Energies 2021, 14(15), 4669; https://0-doi-org.brum.beds.ac.uk/10.3390/en14154669 - 01 Aug 2021

Viewed by 1643

Abstract

In magnetomechanical applications, it is necessary to calculate the magnetic force or torque of specific objects. If the magnetic fluid is involved, the force and torque also include the effect of pressure caused by the fluid. The standard method is to solve the Navier–Stokes equation. However, obtaining magnetic body force density is still under controversy. To resolve this problem, this paper shows that the calculation of the torque of these applications should not only use the magnetic force calculation method, but also consider the mechanical pressure using an indirect approach, such as the virtual work principle. To illustrate this, we use an experimental motor made of a nonmagnetic rotor immersed in a magnetic fluid. Then, we show that the virtual work principle in appropriate approach can calculate the output torque of the nonmagnetic rotor due to pressure of the magnetic fluid. Numerical analysis and experimental results show the validity of this approach. In addition, we also explain how the magnetic fluid transmits its magnetic force to the stator and rotor, respectively. Full article

(This article belongs to the Special Issue Electrical Machine Design 2021)

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