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Hybrid excited synchronous machines (HESMs) combine permanent-magnet (PM) excitation and wound field (WF) excitation. The goal of hybrid excitation is to combine the advantages of PM excited machines and WF synchronous machines. HESM have been identified as one of the emerging technologies for modern energy conversion systems. They have been the subject of many review articles. The principle of hybrid excitation allows solving many drawbacks related to PM electric machines operation: flux weakening, energy efficiency, and PMs price fluctuation. It helps to introduce an additional degree of freedom in the design of synchronous machines, and allows therefore an easier adaptation of PM synchronous machines to a wider applications scope. To this additional degree corresponds the possibility of adjusting the contribution of the two magnetic field sources: PM and WF. The use of this technology for electric traction has been the subject of many scientific and technical contributions. In this contribution, the emphasis will be put on the use of these machines as generators in transportation applications and renewable energy applications. The design and operation of three particular structures will be presented. Two of them have been designed as generators for transportation applications, and the third one has been designed as generator for renewable energy conversion. All of them are flux switching hybrid excited synchronous machines (FSHESM). [ABSTRACT FROM AUTHOR]

The aim of this paper is to assess the efficacy of non-conformal meshing in mesh-based generated reluctance network modeling. A representative semi-numerical example is introduced to demonstrate the possibilities and accuracy offered by a non-conformal meshing. In a conformal mesh, two reluctance block elements share the same branch. This makes the computation faster and more accurate but is not convenient for motion processing or mesh relaxation and it does not solve the air-gap modeling problem (rotor/stator connectivity). To solve this, different approaches are used. The interpolation approach developed in this paper aims to render motion processing independent of discretization. This approach is also applied to couple different meshes (spatial discretization) and makes it possible to connect a lumped parameter model to a meshed one. The model is divided into independent zones that are connected via the interpolation coupling. Several reluctance network (RN) non-conformal meshes are presented and global quantities are compared to a fine-meshed finite-element model. Magnetic saturation is considered in the iron parts. Comparisons are provided under open-circuit and on-load configurations for flux linkage and force. The main advantage is to overcome the limitations of generic RN for which the movement modeling requires remeshing at each position. The drawbacks of the method are the increased number of variables (additional interface nodes) and a certain loss of accuracy due to the interpolation function order. [ABSTRACT FROM AUTHOR]

This aim of this paper is to assess the efficacy of mesh-based generated reluctance network (MGRN) modeling for the performance evaluation of a permanent magnet linear machine under load conditions. In the previous publications related to the use of this modeling technique, only approach implementation under an open-circuit performance has been assessed. The MGRN approach is based on the discretization of the geometry using elementary reluctance blocks (reluctance elements). This modeling technique has been implemented in a software tool that allows the automated processing of an arbitrary geometry providing a gain in model development durations. Validation of the MGRN model has been realized by comparison with a finite element analysis (FEA). Comparisons showed that both local and global quantities evaluated by MGRN and FEA are in excellent agreement. [ABSTRACT FROM AUTHOR]

The goal of this contribution is to show the capabilities of relatively fast computation techniques which can be advantageously used in design optimization procedures of electrical machines. The computation of cogging torque, for rotating machines, and force, for linear machines, being very sensitive to the accuracy of used models, its estimation is then used as an indicator for the efficacy and correctness of these techniques. A finite-element (FE) model will be used as a reference model. The first technique is based on a reluctance network (RN) generated from a mesh of studied structure. The second technique consists of coupling RNs obtained from a mesh of some parts of studied structure and an analytical model of magnetic field in other parts. These techniques are used for the modeling of a linear tubular flux-switching permanent magnet (LTFSPM) machine. LTFSPM machines are relatively complicated to model, and their modeling using these two techniques has never been reported yet in the scientific literature. The two models are both validated by comparisons with FE analyses. [ABSTRACT FROM AUTHOR]

This paper presents a summary of a vibrational behaviour investigation of a 27 slots/24 poles combination surface mounted synchronous electric motor. To achieve this investigation, first, an electromagnetic analysis is done using a quasi 3D finite element model allowing to consider the rotor skewing and to compute the machine magnetic quantities. Second, a modal analysis is done using a 3D FE structural model in order to compute the motor natural frequencies for two cases of contact (Prefect and Adjusted), which are correlated with the magnetic pressure harmonics to extract the possibly excited modes and to show the contact coefficients influence on the overall results. Third, a structural mechanical analysis under static magnetic loads is done, in which the vibrational response for each harmonic of the magnetic pressure is computed in order to determine which harmonic is responsible of high order displacements. Finally, a structural mechanical analysis under time varying magnetic loads is done to compute machine's vibrational response for a chosen operating speed using the corresponding local magnetic forces distribution. [ABSTRACT FROM AUTHOR]

The paper describes an analytical technique which has been developed to predict the armature reaction field of tubular modular permanent magnet (PM) machines in which the fundamental of the stator magnetomotive force (mmf) has fewer poles than that of the permanent magnet armature, the thrust force being developed by the interaction between a higher-order mmf harmonic with the permanent magnet field. The analytical solution also allows the prediction of the self- and mutual-winding inductances of a tubular modular machine in closed forms and facilitates dynamic modeling, as well as the evaluation of any partial irreversible demagnetization of the magnets which might occur under various operating conditions. The utility and accuracy of the developed technique are demonstrated by extensive finite element analyses and measurements on a nine-slot/ten-pole tubular modular PM machine. [ABSTRACT FROM AUTHOR]

The aim of this paper is, first, to extend the application of the hybrid analytical modeling (HAM) approach for the analysis of tubular linear machines (TLPM), something that has never been reported yet in the scientific literature. The HAM consists of a strong coupling between the reluctance network and the Fourier series solution of magnetic scalar potential. In order to assess the merits and capabilities of the HAM, it is applied to the study of the cogging force in linear machines and compared with finite element analyses (FEA). The cogging force is a global quantity, which is very sensitive to magnetic field computation accuracy and constitutes, therefore, a good measure of the accuracy of the HAM as compared with FEA. The HAM should require less computation time as compared with FEA, and is then more suitable for predesign stage. Three different structures are analyzed: a flat linear machine, a TLPM with internal mobile armature, and, finally, a TLPM with external mobile armature. The analyses are conducted, considering the effect of magnetic saturation. [ABSTRACT FROM PUBLISHER]

The aim of this paper is to highlight the capabilities of a new hybrid analytical modeling (HAM) approach for the analysis and design of various electromagnetic structures. After an introduction, where the aim of the development of this modeling approach is presented, the modeling approach is described. The new HAM is based on a strong coupling of the magnetic equivalent circuits method and analytical models (AMs). The AM, based on the formal solution of Maxwell’s equations, is established thanks to the separation of variables method. The HAM is applied to different permanent magnet electric machine structures, and the results are validated extensively by comparison with the finite-element analyses. [ABSTRACT FROM AUTHOR]

This paper describes an analytical technique for prediction of open circuit eddy-current loss in armature windings and permanent magnets (PM) of series double excitation synchronous machines. First, a 2-D exact analytical solution of open circuit magnetic field distribution in idealized geometry of series double excitation synchronous machine is established. It involves solving Maxwell's equations in stator slots, air gap, PM region, and rotor slots. Then, magnetic vector potential solutions in the stator slots and PM regions are respectively used for prediction of resistance limited eddy currents in armature windings and permanent magnets. This analytical model is then used to estimate eddy-current loss in armature windings and permanent magnets. The validity of the developed model, which is also applicable to conventional designs of permanent-magnet machine, is verified by time-stepped transient finite-element analysis (FEA). The developed model is then used to quantify the effectiveness of segmenting the magnets and armature windings in reducing the eddy-current loss. [ABSTRACT FROM PUBLISHER]

This paper presents 3-D finite-element analysis of a new double excitation synchronous machine. It is shown that the machine has true field regulation capability. The principle of operation and design aspects of this new machine are presented in the paper. Comparison of 3-D FEA with an experimental study done on a prototype having a different rotor structure is also investigated. [ABSTRACT FROM PUBLISHER]

We present an exact 2-D analytical model for predicting the magnetic field in idealized structures of surface mounted permanent-magnet tubular linear machines that account for the stator slotting effect. The open-circuit and armature reaction magnetic field distributions are analytically derived and compared to finite-element analyses. The on-load magnetic field calculation is based on the superposition of the component fields due to permanent magnets and armature field reaction. Our model can be advantageously used for the analysis and design of a class of linear tubular machines. [ABSTRACT FROM PUBLISHER]

We describe an exact 2-D analytical model for predicting the open circuit magnetic field in idealized structures of wound field and series hybrid excitation permanent-magnet synchronous machines. This technique can be used for either internal or external rotor radial-field machine topologies. It involves analytical solution of Maxwell's equations in stator and rotor slots and annular air-gap/magnet regions. We compare results from this analytical model to corresponding finite-element analyses. We then use it to estimate the cogging torque, induced back-electromotive force, and to study the effects of rotor skewing. [ABSTRACT FROM PUBLISHER]

The paper describes two techniques for reducing the cogging force associated with the finite length of the ferromagnetic armature core of a tubular permanent-magnet machine. Analytical expressions for predicting the cogging force which is associated with armature cores having skewed or stepped end faces are established, and a cogging-force-minimisation technique is employed to determine an optimal armature-core length. The validity of the analytical cogging-force predictions and the effectiveness of the cogging-force-reduction techniques are verified by three-dimensional finite-element analyses and experimental measurements. [ABSTRACT FROM AUTHOR]