Albert Foggia

Influence of Magnetic Materials on Claw Pole Machines Behavior

This paper presents a study on magnetic materials for claw pole machines which are widely used nowadays in the automobile industry for their simple manufacturing and cost reasons. The finite element analysis with the loss surface model is used to evaluate the iron losses for three categories of material: M800-50A, M330-35A, and AFK502. Comparisons are made in terms of output current, efficiency, as well as iron loss as main characteristics of the machine. On the other hand, the experimental method of loss separation provides a clear idea of the loss distribution in the machines, from which the iron loss can be deduced. A qualitative comparison is made between the two methods, which proves to be coherent.

Coupling electric circuit and 2D-FEM model with Dommel's approach for transient analysis [of EM devices]

Dommels approach applied to simulate the electrical parameters in a transient analysis of electromagnetic devices, such as electrical machines and transformers, is presented in this paper. Equations of electric circuit and equations of magnetic fields are taken into account by simultaneously coupling nodal analysis and 2D FEM. The inductances and capacitances are treated like one-dimensional finite elements leading to a symmetrical matrix solved by a step-by-step technique. The formulation was validated by comparing numerical results and experimental data.

Numerical solution of eddy currents problems including moving conducting parts

In the study of transient or steady-state eddy current effects, a general diffusion equation derived from Maxwells equations is solved by a classical finite element method for the spatial problem with time discretization. The moving part of the system is taken into account by a mesh distortion where the mesh points associated with this part have to follow the displacement. This technique can be used when the movement is time harmonic and displacement limited in order to obtain a few distorted mesh. It is applied to an axisymmetric apparatus and eddy current losses calculations are compared with experimental results.

A 3D finite-element computation of eddy currents and losses in the stator end laminations of large synchronous machines

Eddy current losses due to axial fluxes are computed in the stator end laminations of a salient-pole synchronous machine under open-circuit operating conditions. The calculation is carried out with the aid of a 3D finite-element package which uses a linear T-/spl phi/ formulation. The domain spans a full pole pitch of the machine. The flux densities computed in the end region at points outside the stator core are compared with experimental measurements. The results and the limitations of the model are discussed.

Electromagnetic field formulation for eddy current calculations in nondestructive testing systems

The authors present the most practical configuration for detecting cracks in material, by applying an electromagnetic field along the largest dimension of the crack. An electromagnetic field formulation of the system equation is proposed using Maxwells relations and separating the magnetic field into externally applied field and reaction field. The system equation is solved by using two classical methods : finite element technic for spatial problem and finite difference for time discretisation. So two dimensional eddy currents can be calculated immediately and related to the excitation characteristics for impedance calculation. Eddy currents lines in material for different cracks and sensor positions are presented. Theoretical results show important impedance changes.

Optimal magnetic sensor location for spherical harmonic identification applied to radiated electrical devices

This paper deals with the use of spherical harmonic representation to identify the magnetic multipolar sources associated to a given item, by measuring the near field around it. If the model presents many advantages, its use in an inverse problem approach requires special caution to critical points like the choice of sensor number and location. A method is presented that makes it possible, from a high number of information, to reduce the sensor number to a minimum and to optimize their location with respect to robustness. The robustness issue is solved by using an original method based on a genetic algorithm. A simple but didactic example illustrates the difficulties that can be met and our strategy to overcome them

Performance analysis of windings configuration on fractional-slots PMSM performance

During the first steps of machines design, engineers have to choose the topology the most appropriate to the specifications. The topology includes the number of stators slots, the number of rotors poles and the winding associated. Traditionally, designers choose one of the common used topology in the industry and consequently, a lot of solutions are not studied. In fact, the performances of the machines are strongly linked to this choice that has to be fully justified. Then, in this paper, a method from the star of slots is presented and also the way to determine the different winding configuration that could exist for each slots/poles combination. An approach to rapidly evaluate the overall performance of Permanent Magnet Synchronous Machines (PMSM) is also used. Thus, designers can perform better choice of the PMSMs topology regarding the specifications.