3-D Numerical Hybrid Method for PM Eddy-Current Losses Calculation: Application to Axial-Flux PMSMs

International audienceThis paper describes a 3-D numerical hybrid method (NHM) of the permanent-magnet (PM) eddy-current losses in axial-flux PM synchronous machines (PMSMs). The PM magnetic flux density is determined using the multi-static 3-D finite-element method (FEM) at resistance-limited (i.e., without eddy-current reaction field). Based on the predicted flux density distribution, the eddy-currents induced in the PMs and the 3-D PM eddy-current losses are calculated by 3-D finite-difference method (FDM) considering a large mesh. Therefore, this 3-D NHM is based on a coupling between the multi-static 3-D FEM and the 3-D FDM. Two 24-slots/16-poles (i.e., fractional-slot number) axial-flux PMSMs having a non-overlapping winding (all teeth wound type) with stator double-sided structure are studied: 1) surface-PM (SPM) and 2) interior-PM (IPM) To evaluate the reliability of the proposed technique, the 3-D PM eddy-current losses are determined and compared with transient 3-D FEM (i.e., magneto-dynamical 3-D FEM). The same nonlinear properties of the laminations have been applied for multi-static/transient 3-D FEM. The computation time can be divided by 25 with a difference less than 12%

Computationally efficient 3D analytical magnet loss prediction in surface mounted permanent magnet machines

This study proposes a computationally efficient analytical method, for accurate prediction of three-dimensional (3D) eddy current loss in the rotor magnets of surface mounted permanent magnet (SPM) machines considering slotting effect. Subdomain model incorporating stator tooth tips is employed to generate the information on radial and tangential time-derivatives of 2D magnetic field (eddy current sources) within the magnet. The distribution of the eddy current sources in 3D is established for the magnets by applying the eddy current boundary conditions and the Coulomb gauge imposed on the current vector potential. The 3D eddy current distributions in magnets are derived analytically by employing the method of variable separation and the total eddy current loss in the magnets are subsequently established. The method is validated by 3D time-stepped finite element analysis for 18-slot, 8-pole and 12-slot, 8-pole permanent magnet machines. The eddy current loss variations in the rotor magnets with axial and circumferential number of segmentations are studied. The reduction of magnet eddy current loss is investigated with respect to harmonic wavelength of the source components to suggest a suitable segmentation for the rotor magnets in SPM machines

Stator iron loss of tubular permanent-magnet machines

While methods of determining the iron loss in rotating permanent-magnet (PM) machines have been investigated extensively, the study of iron loss in linear machines is relatively poorly documented. This paper describes a simple analytical method to predict flux density waveforms in discrete regions of the laminated stator of a tubular PM machine, and employs an established iron loss model to determine the iron loss components, on both no load and on load. Analytical predictions are compared with the iron loss deduced from finite-element analyses for two tubular PM machine designs, and it is shown that if a machine has a relatively high electrical loading, the on-load iron loss can be significantly higher than the no-load value

Study of innovative electric machines for high efficiency vehicular traction applications

This thesis collects some of the work accomplished during the PhD research activity focused on the study of special electric machines for vehicle traction applications. The work is divided into due parts. The rst part is mainly technological and covers some studies and experimental activities concerning new technical solutions to solve some common issues in operation of electric motors for automotive use, namely ux weakening and cogging torque. The second part has a more theoretical nature and focuses on some methods for electric machine modeling and analysis which has been developed to facilitate the study and design optimizations carried out during the PhD research work. The chapters in the rst part address the following topics: 1. Development and testing of an interior-permanent-magnet motor prototype fully conceived, designed and manufactured at the University of Trieste to implement a new concept of flux weakening system at high speeds. The concept has been also protected through a pending patent. 2. Multi-objective design optimization of an interior permanent magnet reluctance-assisted synchronous motor for the automotive industry. The design optimization was meant to support an industrial development project which is still in progress so no prototype has been built yet. 3. Study of a new optimized magnetic wedge design capable of reducing cogging torque in automotive propulsion motors having open stator slots. The second part proposes some analytical and numerical results that have been worked out to approach the modeling and optimization of various kinds of permanent magnet synchronous motors. The main problem to which these chapters try to answer is to nd suciently fast but accurate methods for permanent magnet analysis without time-consuming finite-element transient analysis. The proposed methods have been successfully integrated into design optimization programs used in the industrial environment in the development of innovative electric machines not only for the automotive industry

Computationally Efficient 3D Eddy Current Loss Prediction in Magnets of Interior Permanent Magnet Machines

This paper proposes a computationally efficient method based on imaging technique, for accurate prediction of 3- dimensional (3D) eddy current loss in the rotor magnets of interior permanent magnet (IPM) machines. 2D time-stepped finite element analysis is employed to generate the radial and the tangential 2D magnetic field information within the magnet for application of the 3D imaging technique. The method is validated with 3D time-stepped finite element analysis (FEA) for an 8 pole-18 slot IPM machine evaluating its resistance limited magnet loss with increase in axial and tangential segmentation. Magnet loss considering eddy current reaction at high frequencies is evaluated from the proposed method by employing the diffusion of the 2D magnetic field variation along the axial plane. The loss associated with all the frequencies together in the armature currents is evaluated by considering each of the harmonics separately in the proposed method employing the frozen permeability to account for magnetic saturation. The results obtained are verified with 3D FEA evaluating the magnet loss at fundamental, 10 and 20 kHz time harmonics in armature currents

Mathematical Models for the Design of Electrical Machines

This book is a comprehensive set of articles reflecting the latest advances and developments in mathematical modeling and the design of electrical machines for different applications. The main models discussed are based on the: i) Maxwell–Fourier method (i.e., the formal resolution of Maxwell’s equations by using the separation of variables method and the Fourier’s series in 2-D or 3-D with a quasi-Cartesian or polar coordinate system); ii) electrical, thermal and magnetic equivalent circuit; iii) hybrid model. In these different papers, the numerical method and the experimental tests have been used as comparisons or validations

Design and Application of Electrical Machines

Electrical machines are one of the most important components of the industrial world. They are at the heart of the new industrial revolution, brought forth by the development of electromobility and renewable energy systems. Electric motors must meet the most stringent requirements of reliability, availability, and high efficiency in order, among other things, to match the useful lifetime of power electronics in complex system applications and compete in the market under ever-increasing pressure to deliver the highest performance criteria. Today, thanks to the application of highly efficient numerical algorithms running on high-performance computers, it is possible to design electric machines and very complex drive systems faster and at a lower cost. At the same time, progress in the field of material science and technology enables the development of increasingly complex motor designs and topologies. The purpose of this Special Issue is to contribute to this development of electric machines. The publication of this collection of scientific articles, dedicated to the topic of electric machine design and application, contributes to the dissemination of the above information among professionals dealing with electrical machines