Emad Dlala

Three-Dimensional Eddy-Current Analysis in Steel Laminations of Electrical Machines as a Contribution for Improved Iron Loss Modeling

A finite-element method to compute the 3-D eddy-current distribution in steel laminations of electrical machines is presented and applied to the loss estimation of an induction machine. Two different eddy-current formulations, the A-V and A-T formulations, are investigated. The 3-D model is excited by boundary conditions derived from a 2-D field solution. The obtained eddy-current losses serve as a validation basis for those from two simplified iron loss models. The first one is the traditional model based on the statistical loss theory. The second one is the so-called hybrid model, which is based on the evaluation of magnetization curves. Both models are found to produce reasonable results for low-frequency losses. The hybrid model is particularly suitable for the estimation of high-order harmonic losses. The results from the models are compared to measured no-load iron loss data.

Efficiency map simulations for an interior PM motor with experimental comparison and investigation of magnet size reduction

Reduction of permanent magnet materials in electric machines is of interest to many machine manufacturers and designers as cost of rare-earth materials is of increasing concern. The impact of changing a machine design parameter, such as the shape of the magnets, may have consequences such as a reduction in efficiency, or introduce a change in torque quality. In this paper, an efficiency map computation is compared with measurements for a permanent magnet synchronous machine, including the complete torque-speed operating region. The validated simulation model led to an investigation of reducing the permanent magnet size where 20% of magnet size reduction was achieved. The impact of the magnet size reduction on the efficiency and machine performance was quantified, and design changes were simulated which maintained the desired efficiency over the operating range.

Anisotropic Generalization of Vector Preisach Hysteresis Models for Nonoriented Steels

A Preisach-type vector hysteresis model is developed to represent anisotropic material characteristics under static and dynamic conditions. Bi- and uniaxial anisotropy are incorporated by generalizing the input projection of the vector model. Frequency-dependent eddy current and excess effects are considered by an additional field strength component. The model is applied to simulate the magnetic properties of weakly anisotropic nonoriented magnetic steel. The simulation results are successfully validated against measurements under alternating and circular flux carried out on a rotational single-sheet tester.

Combined FE and Particle Swarm algorithm for optimization of high speed PM synchronous machine

Purpose – The purpose of this paper is to optimize the stator slot geometry of a high-speed electrical machine, which is used as an assist for a turbocharger. Meanwhile, the suitability of the Particle Swarm algorithm for such a problem is to be tested. Design/methodology/approach – The starting point of the optimization is an existing design, for which the Particle Swarm algorithm is applied in conjunction with the transient time-stepping 2D finite element method. Findings – It is found that regardless of its stochastic nature, the Particle Swarm work well for the optimization of electrical machines. The optimized design resulted in an increase of the slot area and increase of the iron loss, which was compensated by a dramatic decrease in the Joule losses. Research limitations/implications – The optimization was concentrated on the stator design whereas the rotor dimensioning was carried out withing the compressor and turbine design. Originality/value – A turbocharger with electric assist is designed opt...

Improved model for the prediction of core loss in finite element analysis of electric machines

This paper presents an improved model for the prediction of core loss in numerical analysis of electromechanical devices. The model allows the coefficients of hysteresis and eddy current losses to vary with peak flux density and frequency based on physical observation of the loss dissipation. The coefficients are derived from the energy loss equation and extracted from specific power loss data typically provided by standard Epstein frame or single-sheet tests. The model was implemented in a 2-D finite-element code for the prediction of core losses in an induction motor where a close correlation between predicted and measured results was found.