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Rare-Earth-Free Permanent Magnet Motors and Generators for Use in Electric...
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Rare-Earth-Free Permanent Magnet Motors and Generators for Use in Electric Vehicles and Wind Turbines

A special issue of Magnetism (ISSN 2673-8724).

Deadline for manuscript submissions: 31 August 2025 | Viewed by 2162

Special Issue Editors

Prof. Dr. Yang-Ki Hong

E-Mail Website
Guest Editor
Department of Electrical and Computer Engineering, The University of Alabama, Tuscaloosa, AL 35487, USA
Interests: computational materials science; electromagnetics; magnetism; nanocrystalline soft magnets; rare-earth-free permanent magnets; permanent magnet synchronous motors; 5G/6G antennas; CubeSat and UAV antennas
Dr. Shuhui Li

E-Mail Website
Guest Editor
Department of Electrical and Computer Engineering, The University of Alabama, Tuscaloosa, AL 35487, USA
Interests: artificial intelligence; power electronics; power systems; renewable energy systems; electric machines and drives; smart grid
Special Issues, Collections and Topics in MDPI journals
Dr. Vandana Rallabandi

E-Mail Website
Guest Editor
Oak Ridge National Laboratory, Oak Ridge, TN 37830, USA
Interests: electric machines; power electronics drives; renewable energy devices and systems; energy storage; power systems

Special Issue Information

Dear Colleagues,

The energy and transportation industries focus on combating climate change and conserving energy. There have been significant advancements in electric vehicle and wind turbine technologies to speed up their efforts. However, the widespread adoption of electric machines requires affordable and high-energy efficient electric motors and generators. Additionally, there is a need for stable supply chains of rare-earth (RE) minerals, which are used to produce permanent magnets. In response to the growing demand for electric mobility, permanent magnet synchronous motors (PMSM) and permanent magnet-assisted synchronous reluctance motors (PMASyncRM) have been developed.

The use of RE magnets in electric motors for electric vehicles (EVs) and in the generators of wind turbines is widespread. However, the unstable supply chain of RE minerals results in high costs for RE magnets, geopolitical complications, and significant environmental and health risks associated with mining these minerals. These issues require urgent attention.

This Special Issue will cover recent and innovative research trends in electric machines designed based on RE-free permanent magnets, addressing the urgent issues mentioned above. We encourage authors to submit original research and review articles focusing on theoretical and experimental electric machine design and interpretation of the machine’s performance.

This special issue is relevant to one of Magnetism Journal’s scopes: Electrical Machines and Power Transformers and Inductors.

Topics of interest for publication include, but are not limited to:

  • Rare-earth (RE)-free permanent and soft magnets for electric machine applications.
  • Working principles of permanent magnet synchronous motor (PMSM).
  • AI-based design of high-torque density and low-torque ripple RE-free PMSM.
  • AI-based design of RE-free permanent magnet-assisted synchronous reluctance machine (PMASynRM).
  • AI-based design of energy-shifting PMSM.
  • Electromagnetic characteristics of spoke-type PMSM.
  • Copper and iron losses in spoke-type PMSM and PMASyncRM.
  • Consumption of magnetic materials for rotor of spoke-type PMSM and PMASynRM.
  • Motor controllers and control circuitry for PMSM.
  • Control of back-electromotive force of PMSM.
  • Finite element analysis (FEA) or method (FEM) for electromagnetic analysis of permanent magnet synchronous motors (PMSM).
  • Factors that determine the energy efficiency map of PMSM.
  • Power and torque densities.
  • Torque ripple control mechanisms.
  • Copper loss.
  • Pros and Cons of PMSM.
  • Review of spoke-type RE-free-permanent magnet synchronous motors (PMSM).
  • Review of RE-free-permanent magnet-assisted SynRM (PMASynRM).

We look forward to receiving your manuscripts.

Prof. Dr. Yang-Ki Hong
Dr. Shuhui Li
Dr. Vandana Rallabandi
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. Magnetism is an international peer-reviewed open access quarterly 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 1000 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

  • electromagnetics
  • rare-earth-free permanent magnets
  • permanent magnet synchronous motor
  • motor controller

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Published Papers (2 papers)

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Research

26 pages, 3464 KiB  
Article
A Model-Based Method Applying Sliding Mode Methodology for SynRM Sensorless Control
by Vasilios C. Ilioudis
Magnetism 2025, 5(1), 4; https://doi.org/10.3390/magnetism5010004 - 4 Feb 2025
Cited by 1 | Viewed by 647
Abstract
In this paper, a new sensorless approach is proposed to address the speed and position estimation of the Synchronous Reluctance Machine (SynRM). The design of the sensorless control algorithm is developed on the basis of the modified SynRM mathematical model employing a simple [...] Read more.
In this paper, a new sensorless approach is proposed to address the speed and position estimation of the Synchronous Reluctance Machine (SynRM). The design of the sensorless control algorithm is developed on the basis of the modified SynRM mathematical model employing a simple sliding mode observer (SMO) and a modified EMF observer that are connected in series. All variables of the modified SynRM model are expressed in the arbitrary rotating frame, which is the so-called estimated γδ reference frame. The derived modified rotor flux terms contain angle error information in the form of trigonometric functions. Initially, the modified rotor flux is expressed as a function of saliency and the stator current id, including the angular deviation between the dq and γδ reference frames, which are rotating at synchronous and estimated speeds, respectively. A suitably designed SMO is utilized to estimate the modified stator flux components in the γδ reference frame. Once the SMO operates in sliding mode, the derived equivalent control inputs of the flux/current observer are used to obtain the required angular position and speed information of rotor by means of the modified EMF and Speed/Position observer. Only measures of stator voltages and currents are required for the speed and position estimation. In addition, Lyapunov Candidate Functions (LCFs) have been applied to determine the sliding mode existence conditions and the gains of the modified EMF observer. The SynRM observer–controller system is tested and evaluated in a wide speed range, even at very low speeds, in the presence of torque load disturbances. Simulation results demonstrate the overall efficacy and robustness of the proposed sensorless approach. Moreover, simulation tests verify the fast convergence and high performance of the modified EMF/speed/angle observer. Full article
(This article belongs to the Special Issue Rare-Earth-Free Permanent Magnet Motors and Generators for Use in Electric Vehicles and Wind Turbines)
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16 pages, 5848 KiB  
Article
Recovery of Neodymium from Spent Hard Disk Drivers by Microwave Treatment and Magnesium Liquid Extraction
by Sabina Andreea Fironda, Ioana Cristina Badea, Marian Burada, Radu-Robert Piticescu and Lidia Licu
Magnetism 2025, 5(1), 3; https://doi.org/10.3390/magnetism5010003 - 30 Jan 2025
Viewed by 1034
Abstract
Rare earth elements (REEs) possess unique physical and chemical properties that render them indispensable in various industries, including electronics, energy production and storage, hybrid and electric vehicles, metallurgy, and petro-chemical processing. The criticality of REE underscores the need to enhance the efficiency of [...] Read more.
Rare earth elements (REEs) possess unique physical and chemical properties that render them indispensable in various industries, including electronics, energy production and storage, hybrid and electric vehicles, metallurgy, and petro-chemical processing. The criticality of REE underscores the need to enhance the efficiency of primary resource extraction and promote circularity through increased recycling from secondary sources. This paper provides a brief overview of REE recovery from secondary sources, particularly waste from electronic and electric equipment (WEEE). The discussion encompasses direct reuse of magnets, short-loop recycling (direct recycling), hydro- and pyrometallurgical processes, highlighting microwave (MW) technology. Original results are presented, focusing on the recovery of neodymium (Nd) from permanent magnet scraps from hard disk drives (HDD-PC) using microwave-assisted liquid metal extraction (LME) with magnesium (Mg) as the extractant. The subsequent separation of Nd from the Mg-Nd alloy via vacuum Mg distillation that is reused in the process is described. The experimental study demonstrates that the LME process, conducted in a microwave furnace, is a viable method for recovering Nd from permanent magnet scraps, which are essential for reducing the environmental impact of REE extraction and promoting a circular economy. By separating Nd from the alloy through vacuum distillation (450–550 mmHg), at temperatures of 850–900 °C for 8 h, a Nd sponge with a content of 95–98 wt.% Nd was obtained. The extracted content of Nd in the Mg alloy increases with increasing temperature and holding time. It was found that ≈ 97% of the Nd in the scrap was extracted from 2 to 5 mm crushed scrap at 800 °C for 8 h, using a LiF-LiCl-MgF2 protecting flux in a furnace Ar atmosphere. Full article
(This article belongs to the Special Issue Rare-Earth-Free Permanent Magnet Motors and Generators for Use in Electric Vehicles and Wind Turbines)
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