Search results

Several formulations have been developed solving 3D eddy current problems by the Finite element method based on vector quantities. Scalars, involving only one unknown per node of the mesh seem to be, however, more efficient. A particular scalar potential formulation has already been developed which is able to handle 3D magnetostatics,. This technique has been extended for cases involving eddy currents developed at low frequencies, where the skin effect can be neglected.

The leakage reactance end component is calculated by considering the net flux linking the stator end winding when both stator and rotor are excited with currents so that the net flux density in the airgap is zero. The stator and rotor end windings are assumed to consist of coils that close through the airgap by means of fictitious filaments and thus their respective current distributions are represented by systems of closed currents. Iron boundaries other than the end plate are neglected and the end plate is considered to be unsaturated and also a magnetic mirror, i.e. μ=∞, ό=0.

Some problems involve eddy currents developed in thin skin effect depths and a numerical analysis, based on the classical finite element method, is extremely laborious and expensive. Although such situations lead to operations concerning the linear part of the material characteristics, the related geometries are not, usually, simple enough to permit an analytical solution. The present work is based on a new type of element enabling efficient modeling in such cases. It combines the increased accuracy and speed of analytical solutions for large subdomains, a reduced number of unknowns and the advantages of functional minimization procedures.

The design of several electromagnetic devices, such as magnets and transformers, leads to a 3D magnetostatic field analysis. Although such problems can be solved by using vector potential formulations, scalar potential techniques seem to be more efficient because of the reduced number of unknowns they introduce. Even these methods, however, present certain drawbacks, depending on the way the scalar potential is defined: considerable cancellation errors in iron parts, difficulties to simulate multiply connected iron cores, a complicated way to compute a source field distribution.

Maximum axial and radial flux densities due to peripheral stator current The flux desnity, Bsper, is found by using the Biot‐Savart law expressed in cylindrical coordinates. Thus

The end winding current distribution of the squirrel cage rotor consists of (Fig.1) : a peripheral current flowing in the end ring of the cage placed at a distance ar from the end core plane, 2) an axial current flowing in the straight part of the

The purpose of this paper is to replace the end winding current distribution of the squirrel cage rotor of induction motors with appropriate current sheets of sinusoidal distribution and then determine analytically the flux density at any point on the end zone due to stator end winding currents (Fig.1).

The paper presents a procedure for the design of claw pole alternators for small scale wind power applications. The method involves a preliminary design stage by means of the classical magnetic circuit analysis and a detailed design stage involving a 3D finite element model. This technique has been implemented in the design of a multiple generation for a small scale gearless autonomous system. The developed model can be implemented for the optimization of the rotor claw geometry through a minimization algorithm.

To identify interactions existing between electromagnetic, electric and mechanical phenomena in variable speed permanent generator wind‐turbines and propose a methodology enabling oscillations analysis.

Evaluation of the accuracy of alternative approaches such as traditional fundamental and higher harmonic representation as well as coupled field, circuit and mechanical techniques based on the finite element method to represent such phenomena.

Low frequency oscillations observed experimentally necessitate strong coupling between electromagnetic, electrical and mechanical phenomena.

The techniques adopted are limited to two‐dimensional configurations, while possible three‐dimensional air‐gap eccentricity is not considered.

Special consideration should be paid by the wind turbine controller to attenuate the studied oscillations.

Development of an adequate modelling methodology enabling consideration of low frequency oscillations.

Gives introductory remarks about chapter 1 of this group of 31 papers, from ISEF 1999 Proceedings, in the methodologies for field analysis, in the electromagnetic community. Observes that computer package implementation theory contributes to clarification. Discusses the areas covered by some of the papers ‐ such as artificial intelligence using fuzzy logic. Includes applications such as permanent magnets and looks at eddy current problems. States the finite element method is currently the most popular method used for field computation. Closes by pointing out the amalgam of topics.