Search results

Two complementary 3D finite element formulations, with either the magnetic field or the magnetic vector potential as unknowns, are developed to deal with the modeling of eddy currents in electrical steel laminations. The magnetic flux through the flux gates of the conducting region is imposed via the boundary terms of the weak formulations, in a natural way thanks to the use of edge finite elements. The two formulations are applied to a simple 1D eddy current problem with analytical solution. As a practical 3D application example, a T‐joint region of an electrical steel lamination is considered.

The influence of overlap joints in transformer cores on the local flux and eddy current distribution and on overall transformer characteristics is studied by means of two‐dimensional finite element (2D FE) models. A simplified 2D FE model of a single overlap joint is used for estimating the resulting increased magnetomotive force and increased eddy current losses. Both effects can be accounted for in a 2D FE model of the complete transformer by locally adopting modified material characteristics (viz. BH‐curve and electrical conductivity) in the cross‐section of the core. This novel method is demonstrated and validated by applying it to a three phase transformer. The calculated no‐load currents and losses are compared to the measured ones.

Vibrations and acoustic noise are some of the fundamental problems in the design and exploitation of switched reluctance motors (SRMs). Adequate experimental and analysis methods may help to resolve these problems. This paper presents a theoretical analysis of the magnetic force distribution in SRM and a procedure for calculating the magnetic forces and the resulting vibrations based on the 2D finite element method. Magnetic field and force computations and a structural analysis of the stator have been carried out in order to compute the frequency spectrum of the generalized forces and displacements of the most relevant vibration modes. It is shown that for these vibration modes, the frequency spectrum can be predicted analytically. The theoretical and the numerical analyses have been applied to a 6/4 SRM and an experimental validation is presented.

This paper deals with the magnetic vector and scalar potential formulation for two‐dimensional (2D) finite element (FE) calculations including a vector hysteresis model, namely a vectorized Jiles‐Atherton model. The particular case of a current‐free FE model with imposed fluxes and magnetomotive forces is studied. The non‐linear equations are solved by means of the Newton‐Raphson method, which leads to the use of the differential reluctivity and permeability tensor. The proposed method is applied to a simple 2D model exhibiting rotational flux, viz the T‐joint of a three‐phase transformer.

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.

This paper deals with the numerical modelling of electromagnetic losses in electrical machines, using electromagnetic field computations, combined with advanced material characterisations. The paper gradually proceeds to the actual reasons why the building factor, defined as the ratio of the measured iron losses in the machine and the losses obtained under standard conditions, exceeds the value of 1.

This paper deals with the modelling of transformer supply in the two‐dimensional (2D) finite element (FE) simulation of rotating electrical machines. Three different transformer models are compared. The reference one is based on two 2D FE models, considering a cross‐section either parallel or perpendicular to the laminations of the magnetic core. The parameters of the two other transformer models, a magnetic equivalent circuit and an electrical equivalent circuit, can be derived from the reference model. Particular attention is paid to some common features of the transformer models, e.g. with regard to the inclusion of iron losses. The three models are used in the 2D FE simulation of the steady‐state load operation and the starting from stand‐still of an induction motor.

The aim is to develop a nonlinear transformer model to achieve an accurate model to obtain the frequency components of the magnetizing current based on the harmonic voltages at the primary and secondary side. So, it can easily be implemented in a harmonic load‐flow program.

The transformer model is based on the harmonic balance method. The electric and magnetic equations of the transformer are derived from the electric and magnetic equivalent circuits.

The transformer model can be easily implemented in a harmonic load‐flow program. The accuracy of the model has been shown by comparing it with a finite element simulation. The transformer model can be used with asymmetrical supply voltages, because different saturation levels of the phases can occur. There is a coupling between the phases which can be concluded out of the asymmetrical currents in the transformer under symmetrical supply voltages.

The transformer model does not consider the iron losses and the interharmonics. In future work the transformer model will be used to study the harmonic losses in distribution networks, so the transformer losses due to these harmonics have to be considered. This can be achieved with a postcalculation process where the magnetic flux density is used to calculate the eddy current losses and the magnetic field intensity will be applied in a static Preisach model to quantify the hysteresis losses.

The model can be used in a harmonic load‐flow program in order to obtain more accurate simulations for the power system analysis and design.

The model presented in this paper is more detailed than similar papers found in literature (saturation of the yokes, coupling between the phases, interaction between different harmonics) and still it takes a brief simulation time.

The purpose of this paper is to analyze the performance of a new direct torque control (DTC) strategy dedicated to four‐switch three‐phase inverter (FSTPI)‐fed induction motor drives with extended speed range.

The approach is based on the synthesis of a suitable vector selection table in order to reduce torque ripple. The performance analysis is carried out based on three criteria: the total harmonic distortion; the switching loss factor; and the quality factor.

It has been clearly shown that the introduced DTC strategy offers high performance during both transient and steady‐state operations of the FSTPI‐fed induction motor drive, which are almost the same as those yielded by the Takahashi DTC strategy implemented in the same motor fed by a conventional six‐switch three‐phase inverter (SSTPI).

The work should be extended by an experimental validation of the simulation results.

The established results open up crucial benefits from the point of view of cost‐effectiveness and volume‐compactness of induction motor drives especially in large‐scale industries such as the automotive, where electric and hybrid propulsion systems are currently regarded as an interesting alternative to substitute or to assist the thermal propulsion systems.

The paper presents the implementation of a dedicated DTC strategy in FSTPI‐fed induction motor drives with extended speed range. The proposed DTC strategy offers interesting performance compared with that yielded by the Takahashi DTC strategy implemented in the same motor fed by an SSTPI.

This paper seeks to investigate the performance of a DTC strategy dedicated to the control of four‐switch three‐phase (B4) inverter fed induction motor drives. The major advantage of the B4 inverter is the reduced number of the involved power switches which opens up crucial cost benefits.

The principle of operation of the B4 inverter fed induction motor drive is recalled in a first step. Then, the basis of the proposed DTC strategy is presented. Following this, the synthesis of the corresponding vector selection table is carried out considering a subdivision of the space vector plan into sixteen sectors.

It has been found experimentally that the B4 inverter fed induction motor drive offers, under the proposed control strategy, interesting performance.

This work should be extended considering a comparison between the performance of B4 inverter fed induction motor drive under the proposed DTC strategy and those of the B6 inverter fed induction motor drive under the popular Takahashi DTC strategy.

The paper proposes a new DTC strategy dedicated to induction motor drives fed by B4 inverter. This reduced structure inverter is of great interest for large‐scale production industries such as the automotive one as far as cost‐effectiveness is concerned.