Eddy Current Losses In Windings Research Articles

Fast Calculation of Strand Eddy Current Loss in Inverter-Fed Electrical Machines

This paper investigates the complex the slot leakage magnetic field and the strand eddy current loss in windings of inverter-fed electrical machines. It shows that the magnetic saturation and the pulsewidth modulation (PWM) harmonics could have a significant influence on the slot leakage magnetic field, thus may influence the eddy current loss. To consider these effects while reducing the computation burden, a semi-analytical strand eddy current loss calculation method is proposed based on the slot leakage field calculation by 2D magnetostatic finite element method (FEM) and a 2-D analytical high-frequency eddy current loss expression. The frozen differential permeability method (FDPM) and the linear time-harmonics FEM are used to fast calculate the PWM-induced slot leakage field with the magnetic saturation considered. Besides, a conductor position model is used to extract the conductor coordinates and leakage field information for calculating the eddy current loss. The proposed method is implemented and experimentally validated on a surface-mounted permanent magnet (SPM) electro-mechanical actuator (EMA) fed by a PWM inverter for aircraft application. It shows high calculation accuracy and fast calculation speed, which is suitable for motor-inverter system design and optimization.

Computationally Efficient Strand Eddy Current Loss Calculation in Electric Machines

A fast finite element (FE) based method for the calculation of eddy current losses in the stator windings of randomly wound electric machines is presented in this paper. The method is particularly suitable for implementation in large-scale design optimization algorithms where a qualitative characterization of such losses at higher speeds is most beneficial for identification of the design solutions that exhibit the lowest overall losses including the ac losses in the stator windings. Unlike the common practice of assuming a constant slot fill factor s <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">f</sub> for all the design variations, the maximum s <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">f</sub> in the developed method is determined based on the individual slot structure/dimensions and strand wire specifications. Furthermore, in lieu of detailed modeling of the conductor strands in the initial FE model, which significantly adds to the complexity of the problem, an alternative rectangular coil modeling subject to a subsequent flux mapping technique for determination of the impinging flux on each individual strand is pursued. Rather than pursuing the precise estimation of ac conductor losses, the research focus of this paper is placed on the development of a computationally efficient technique for the derivation of strand eddy current losses applicable in design optimization, especially where both the electromagnetic and thermal machine behavior are accounted for. A fractional-slot concentrated winding permanent magnet synchronous machine is used for the purpose of this study due to the higher slot leakage flux and slot opening fringing flux of such machines, which are the major contributors to strand eddy current losses in the windings. The analysis is supplemented with an investigation on the influence of the electrical loading on ac winding loss effects for this machine design, a subject that has received less attention in the literature. Experimental ac loss measurements on a 12-slot 10-pole stator assembly will be discussed to verify the existing trends in the simulation results.

Temperature Rise Calculation of a Flux-Switching Permanent-Magnet Double-Rotor Machine Using Electromagnetic-Thermal Coupling Analysis

The flux-switching permanent-magnet double-rotor machine (FSPM-DRM) used for hybrid electric vehicles has attracted considerable attention due to the compact structure and high torque density. Compared with conventional machine, the FSPM-DRM suffers from more severe thermal problems in its inner rotor. This paper aims to make an accurate prediction of the performances and temperature distributions in the FSPM-DRM. First, the eddy current loss in windings with an improved analytical method is discussed and the results are validated by those from a 2-D finite-element (FE) model. With the obtained power losses, the lumped-parameter scheme considering end effect is compared with a 3-D FE thermal model to predict the temperature in each part of the FSPM-DRM at hybrid driving mode, in which both yield similar results. Then the maximum temperatures of different parts at the rated load and 160% load under various operational modes are simulated. Some experimental results are reported, validating the numerical and simulated results.

Sub-Domain Model of Eddy Current Loss in Windings for Flux-Switching Permanent Magnet Machine under Open-Circuit Condition

This article shows a two-dimensional analysis model for predicting eddy current loss in a winding flux-switching permanent magnet under an open-circuit. The finite-element method is used for electrical machine design; however, this numerical method is always time consuming. Depending on the geometry, the mesh quality of the finite-element method should be high, and thus the finite-element method is more time consuming for special electrical machines. To solve this problem, a sub-domain model using Fourier analysis is improved for a flux-switching permanent magnet machine. It is obtained by solving Poisson and Laplace equations in polar coordinates for each domain, i.e., the magnet, air gap, rotor and stator slots, as well as external region. The model accounts for the influence of interaction between the stator slots and air gap, as well as rotor slots and air gap. Magnetic field distribution, flux linkage, back-electromotive force, cogging torque, and eddy current loss waveforms are derived from the analytical method and verified by finite-element analysis. To the best knowledge of the authors, such an analysis has not been carried out previously.

Analytical Model of Eddy Current Loss in Windings of Permanent-Magnet Machines Accounting for Load

This paper presents an analytical model for predicting open-circuit, armature reaction and on-load resistance limited eddy current losses in the conductors of surface-mounted permanent-magnet machines, based on the subdomain field model accounting for tooth-tips. The analytical model can be applied to machines having single-layer, two-radial-layer, or two-circumferential-layer windings. The interaction between spatial harmonics is accurately accounted for in the calculation of the AC copper loss. The investigation shows that neglecting the interaction in the analytical model has negligible influence on the prediction of total AC copper loss but results in significant error in the predicted loss distribution among conductors. The influence of tooth-tip dimension, conductor segmentation, and current on the AC copper loss is also investigated by the analytical model. The finite element analysis has verified the validity of the developed analytical model.

Frequency‐domain homogenization for periodic electromagnetic structure

PurposeThe purpose of this paper is to propose a general approach for the frequency‐domain homogenization of electromagnetic periodic structures. The method allows calculating macroscopic equivalent properties including local effects. It is based on the equivalence of active and reactive electromagnetic powers on an elementary cell. This work is applied to the modelling of eddy current losses in windings, by the use of the finite element method in 2D and 3D.Design/methodology/approachThe approach is based on an homogenization technique, allowing describing local properties (permeability and conductivity) and local effects (eddy currents) of periodical structures, through macroscopic homogenized behaviour laws.FindingsIt was found that the presence of local loops of eddy currents at the local scale implies that the average values of the electric and magnetic field are different from the macroscopic fields. This implies some precautions to implement the homogenization. Furthermore, the question of the coupling of the macroscopic laws has been clarified.Research limitations/implicationsThe proposed method is limited to the frequency domain. Some additional work is necessary to extend the researches in the time domain.Practical implicationsThe proposed methodology is applied for determining losses in coils with the finite element method. The major interest of the method is that it allows taking into account local effects (losses in particular), with a reduced computational time.Originality/valueThe method proposed in this paper is general and clarifies the principle of homogenization in the case of periodical structure in presence of local eddy currents (local loops of current).

Homogenization for Periodical Electromagnetic Structure: Which Formulation?

This paper proposes a general finite element approach for the frequency-domain homogenization of electromagnetic periodical structures. Based on local finite element resolutions on a cell, the method allows taking into account the local effects at the macroscopic level through the determination of equivalent macroscopic permeability and conductivity laws. Examples of the modeling of eddy current losses in windings are presented.

Temperature Rise Analysis of Switched Reluctance Motors Due to Electromagnetic Losses

<para xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> We present a finite-element analysis of the temperature rise of switched reluctance motors (SRM) due to electromagnetic losses. We estimate the various components of electromagnetic losses, including core loss in the lamination as well as copper and eddy-current losses in windings, and then predict the temperature rise within the motor due to these losses. We present simulation results for an 8/6 SRM and discuss various aspects of thermal design of SRMs. To validate the procedure for the estimation of electromagnetic losses, we compare predicted and measured losses. </para>