Conference Papers

1) ICEM 2022

Title: Rotor deformation impact on operating characteristics of IPM Motor under High-Speed conditions

Authors: Georgios K. Sakkas and Antonios G. Kladas

Abstract: This paper investigates effects on permanent magnet motor characteristics of the non-uniform air-gap caused by rotor deformations under high-speed conditions. Particularly, changes in the spatial flux density harmonics, in the flux linkage variations with stator windings and in the electromagnetic torque ripple are evaluated and discussed in the case of a V-type interior permanent magnet synchronous motor. The rotor deformations created by centrifugal forces are analyzed by using static mechanical FEA. The motor electromagnetic behavior is simulated through an appropriate weak coupling of a 2D FEA with an EM-FDTD numerical scheme. The results enable consideration of interaction amongst electromagnetic and mechanical small time scale phenomena and can be easily implemented in design optimization algorithms.

Total Number of Pages: 6 p.

Continue reading:  Published Paper

2) CEFC 2022

Title: Particular Model for Efficient Switching Frequency Loss consideration in Surface Mounted Permanent Magnets

Authors: Georgios K. Sakkas and Antonios G. Kladas

Abstract: The paper proposes a particular modeling procedure for efficient switching frequency loss consideration in surface mounted permanent magnet rotors in cases of PWM supply. The model is based on 2D finite element analysis combined with circuit equations in the permanent magnet regions enabling end effects consideration associated with the switching frequency, which is responsible for the major part of eddy current losses in the magnets. The model’s accuracy is validated through measurements in a magnetic circuit. Comparison between measured and simulation losses by implementing a traditional loss separation analysis has illustrated the relative dominance of switching frequency eddy current losses in permanent magnets and the feasibility of the proposed methodology.

Total Number of Pages: 2 p.

Continue reading:  Published Paper

 3) Intermag 2023

Title: Robust Design of Permanent Magnet Motors for Electric Traction Applications

Authors: Georgios K. Sakkas and Antonios G. Kladas

Abstract: This paper presents a methodology enabling robust design of permanent magnet motors constituting a favored choice in electric traction applications, particularly promising in high speed ranges. Appropriate permanent magnet grade and configuration selection ensuring satisfaction of standard design criteria such as high efficiency and high power density over a wide range of operating conditions are considered in conjunction with fault risk avoidance offering enhanced robustness and drive viability. Higher harmonic phenomena introduce increased stray losses in high speeds such as eddy current losses in surface mounted permanent magnets and are taken into consideration through an appropriate coupled field and circuit approach. The proposed modeling techniques are validated by measurements in prototype linear machine experimental set-up.

Total Number of Pages: 2 p.

Continue reading:  Published Paper

4) Intermag 2023

Title: 3D-printed Magnetic Iron Material Modeling for High Speed Actuators

Authors: Maria Sofia C. Pechlivanidou and Antonios G. Kladas

Abstract: This paper presents the modeling procedure of a particular 3D printed iron material appropriate for low cost production of cores of actuators, a trend which is recently popular in the research community, with direct interest for the relevant industry. The characteristics of cores manufactured by a commercially available magnetic iron polylactic acid filament with low mass and cost are determined by considering a magnetic circuit of toroidal core geometry. A permanent magnet actuator prototype is then constructed by using equally 3D printing procedure to manufacture also the machine’s casing and other individual parts by using a polyethylene terephthalate material. The motor’s behavior is evaluated through finite element analysis in conjunction with equivalent surface impedance technique to account for the supply higher harmonic losses and the obtained results are validated by measurements.

Total Number of Pages: 2 p.

Continue reading:  Published Paper

5) Compumag 2023

Title: Coupled Field and Circuit Permanent Magnet Model including Eddy Current Losses due to PWM inverter supply

Authors: Georgios K. Sakkas and Antonios G. Kladas

Abstract: In this paper, a particular methodology is presented based on coupled field and circuit approach for representing permanent magnets in electrical machines including eddy current losses due to the switching frequency of PWM inverter supply. The governing equation is diffusion equation expressed in Cartesian two dimensional configuration in terms of magnetic vector potential while the gradient of the scalar electric potential term enables end effects consideration of permanent magnets. A particular segmentation of permanent magnets enables efficient consideration of eddy currents flowing in well defined paths of the magnet end regions even under dissymmetrical field conditions through appropriate equivalent circuit coupling. Comparison between 3D FEA and this particular model results in a C-Core setup has illustrated the accuracy and the feasibility of the proposed methodology.

Total Number of Pages: 2 p.

Continue reading:  Published Paper

6) CEFC 2024 (Under Review)

Title: Efficient Digital Twin of SPM based on FEA enabling Drive Current Harmonics Elimination

Authors: Antonios V. Sideris, Georgios K. Sakkas and Antonios G. Kladas

Abstract: The paper proposes an efficient methodology for digital twin construction of surface mounted synchronous permanent magnet motors enabling current harmonics elimination under PWM inverter supply. The method is based on finite element analysis of various motor operating conditions and determination of appropriate variable lumped parameter motor dynamic model. Both space harmonics and armature reaction impact on local saturation are taken into consideration. This technique achieves substantial torque ripple reduction and losses decrease. The method introduced has been validated by measurements on a manufactured prototype motor drive system.

Total Number of Pages: 2 p.

Continue reading:(Review Pending)

Journal Articles

1) IEEE Transactions on Magnetics (2023)

Title: Particular Model for Efficient Switching Frequency Loss consideration in Surface Mounted Permanent Magnets

Authors: Georgios K. Sakkas and Antonios G. Kladas

Abstract: The paper proposes a particular modeling procedure for efficient switching frequency loss consideration in surface mounted permanent magnet rotors in cases of PWM supply. The model is based on 2D finite element analysis combined with circuit equations in the permanent magnet regions enabling end effects consideration associated with the switching frequency, which is responsible for the major part of eddy current losses in the magnets. The model’s accuracy is validated through measurements in a magnetic circuit. Comparison between measured and simulation losses by implementing a traditional loss separation analysis has illustrated the relative dominance of switching frequency eddy current losses in permanent magnets and the feasibility of the proposed methodology.

Total Number of Pages: 5 p.

Continue reading:  Published Paper

2) IEEE Transactions on Magnetics (2023)

Title: Advanced Design of PWM Inverter Fed Permanent Magnet Motors

Authors: Georgios K. Sakkas, Charalambos–Rafail C. Vasilopoulos, Konstantinos G. Bourchas and Antonios G. Kladas

Abstract: This article presents a methodology enabling advanced design of permanent magnet motors constituting a favored choice in electric traction applications, particularly promising in high-speed ranges. Appropriate permanent magnet grade and configuration selection ensuring satisfaction of standard design criteria such as high efficiency and high-power density over a wide range of operating conditions are considered in conjunction with fault risk avoidance offering enhanced robustness and drive viability. Higher harmonic phenomena introduce increased stray losses in high speeds such as eddy current losses in surface-mounted permanent magnets and are taken into consideration through an appropriate coupled field and circuit approach. The proposed modeling techniques are validated by measurements in a prototype linear machine experimental setup.

Total Number of Pages: 11 p.

Continue reading:  Published Paper

3) IEEE Transactions on Magnetics (2023)

Title: Coupled Field and Circuit Permanent Magnet Model for High Speed Motor Analysis

Authors: Georgios K. Sakkas and Antonios G. Kladas

Abstract: In this paper, a particular methodology is introduced based on a coupled 2D FEA and circuit approach for the representation of permanent magnets in electrical machines including eddy current losses due to slot harmonics and switching frequency of PWM inverter supplies. The governing equation is diffusion equation expressed in Cartesian two dimensional configuration in terms of magnetic vector potential while the gradient of the electric scalar potential term enables end effects consideration of eddy currents developed in the permanent magnets. Accurate representation of eddy currents flowing in well defined paths in the permanent magnets has been achieved under dissymmetrical field conditions by introducing a particular segmentation of the magnet end regions through appropriate equivalent circuit coupling. Comparison of the results obtained by 3D FEA and the introduced coupled 2D model in a C-core magnetic circuit has illustrated the accuracy and the feasibility of the proposed methodology.

Total Number of Pages: 5 p.

Continue reading:  Published Paper

4) IEEE Transactions on Magnetics (2023)

Title: Three-Dimensional-Printed Magnetic Iron Material Modeling for High Speed Actuators

Authors: Maria Sofia C. Pechlivanidou and Antonios G. Kladas

Abstract: This article presents the modeling procedure of a particular 3-D-printed iron material appropriate for low-cost production of cores of actuators, a trend which is recently popular in the research community, with direct interest for the relevant industry. At first, the characteristics of cores manufactured by a commercially available magnetic iron polylactic acid (PLA) filament with low mass and cost are determined by considering a simple magnetic circuit of toroidal core geometry. Next, a permanent magnet actuator prototype is constructed by using equally 3-D printing procedure to manufacture also the machine’s casing and other individual parts by using a polyethylene terephthalate material. The motor’s behavior is evaluated through finite element analysis (FEA) in conjunction with equivalent surface impedance technique, enabling efficient consideration of eddy current losses in high frequencies, and the obtained results are validated by measurements.

Total Number of Pages: 5 p.

Continue reading:  Published Paper

5) IEEE Transactions on Industry Applications – IEEE IAS (2024)  (under Review)

Title: Rotor deformation impact on operating characteristics of IPM Motor under High-Speed conditions

Authors: Georgios K. Sakkas, Charalambos–Rafail C. Vasilopoulos, Konstantinos G. Bourchas and Antonios G. Kladas

Abstract: This paper investigates effects on permanent magnet motor characteristics of the non-uniform air-gap caused by rotor deformations under high-speed conditions. Particularly, changes in the spatial flux density harmonics, in the flux linkage variations with stator windings and in the electromagnetic torque ripple are evaluated and discussed in the case of a V-type interior permanent magnet synchronous motor. The rotor deformations created by centrifugal forces are analyzed by using static mechanical FEA. The motor electromagnetic behavior is simulated through an appropriate weak coupling of a 2D FEA with an EM-FDTD numerical scheme. The proposed methodology is validated by experimental measurements and enables consideration of interaction amongst electromagnetic and mechanical small time scale phenomena while it can be easily incorporated in design optimization algorithms.

Total Number of Pages: 11 p.

Continue reading:  (Review Pending)

6) MDPI – Energies (2024)  (Accepted,  Manuscript in preparation)

Title: Overview on permanent magnet motor trends and developments

Authors: Vasileios I. Vlachou, Georgios K. Sakkas, Fotios P. Xintaropoulos, Maria Sofia C. Pechlivanidou, Themistoklis D. Kefalas, Marina A. Tsili and Antonios G. Kladas

Abstract: The extreme environmental issues and the resulting needs to save energy have turned the attention to electrification of energy applications. One of the key components involved in energy efficiency improvements is the appropriate conception and manufacturing of electric machines. This paper overviews the electromagnetic analysis governing the behavior of permanent magnets that enabled substantial efficiency gains in recent electric machine developments. Particular emphasis is given to model the properties and losses developed in permanent magnets in the emerging high speed applications. In addition, the investigation of properties and harmonic losses related to ferro-magnetic materials constituting the machine magnetic circuits are equally analyzed and discussed. The experimental validation of the implemented methodologies and developed models with respect to the obtained precision is reported. The introduction of mixed numerical techniques based on the finite element method intended to appropriately represent the different physical phenomena en-countered is outlined and discussed. Finally, fast and accurate simulation techniques including ag-gregated lumped parameter models considering harmonic losses associated with inverter supplies are commented.

Total Number of Pages: 49 p.

Continue reading: Preprint Version