Prediction Of Eddy Current Loss Research Articles

Finite‐element analysis combined with an ensemble Gaussian process regression to predict the damper eddy current losses in a large turbo‐generator

A method combining the finite-element method (FEM) numerical calculation with machine learning is developed and used to calculate the eddy current losses of the rotor damping slot wedge of generator with different structures and electromagnetic properties. FEM simulation data is used as the input, and the stacking method is used to build the ensemble Gaussian process regression model for eddy current loss prediction to predict and analyse the calculation results. The error is tiny. The FEM results are highly consistent with the prediction data. As demonstrated by comparison experiments, the prediction accuracy of the stacking Gaussian process regression (SGPR) model is greater than that of other models. Therefore, the SGPR model provides a new auxiliary design method for large generators that can help improve generator design efficiency.

Prediction of Eddy Current Losses in Cooling Tubes of Direct Cooled Windings in Electric Machines

The direct coil cooling method is one of the existing cooling techniques for electric machines with concentrated windings, in which cooling tubes of conductive material are inserted between the windings. In such cases, eddy current losses are induced in those cooling tubes because of the time variant magnetic field. To compute the cooling tubes losses, either a transient finite element simulation (mostly based on commercial software), or a full analytical method, which is more complex to be constructed, is required. Instead, this paper proposes a simple and an accurate combined semi-analytical-finite element method to calculate the losses of electric machines having cooling tubes. The 2D magnetostatic solution of the magnetic field is obtained e.g., using the free package “FEMM”. Then, the eddy current losses in the tubes are computed using simple analytical equations. In addition, the iron core losses could be obtained. In order to validate the proposed method, two cases are investigated. In Case 1, a six-toothed stator of a switched reluctance machine (SRM), without rotor, is employed in which six cooling tubes are used while in Case 2 a complete rotating SRM is studied. The proposed method is validated by a 2D transient simulation in the commercial software “ANSYS Maxwell” and also by experimental measurements. Evidently, the proposed method is simple and fast to be constructed and it is almost free of cost.

Experimental Validation of 3-D Magnet Eddy Current Loss Prediction in Surface-Mounted Permanent Magnet Machines

This paper presents the experimental validation of three-dimensional (3-D) Fourier method employed for predicting magnet eddy current loss in surface-mounted permanent magnet (SPM) machines. The magnet loss is measured for a 12-slot 14-pole SPM machine from experimental tests when the machine is operated with inverter under locked rotor conditions by repeating tests with two rotors, one with magnets and one without. The eddy current loss associated with each significant harmonic in the captured armature currents is predicted separately employing the developed method and the total magnet loss is evaluated by applying the principle of superposition. The magnet loss at real operating conditions of the machine is predicted from the method using the phase current captured when the SPM is operating at its maximum speed conditions. The result is used as an example to devise an effective means of further reduction in the total magnet loss.

Computationally Efficient 3-D Eddy Current Loss Prediction in Magnets of Interior Permanent Magnet Machines

This paper proposes a computationally efficient method based on imaging technique, for accurate prediction of 3-D eddy current loss in the rotor magnets of interior permanent magnet (IPM) machines. The 2-D time-stepped finite-element analysis (FEA) is employed to generate the radial and the tangential 2-D magnetic field information within the magnet for the application of the 3-D imaging technique. The method is validated with 3-D time-stepped FEA for an 8 pole, 18 slot IPM machine evaluating its resistance limited magnet loss with the increase in axial and tangential segmentation. Magnet loss considering eddy current reaction at high frequencies is evaluated from the proposed method by employing the diffusion of the 2-D magnetic field variation along the axial plane. The loss associated with all the frequencies together in the armature currents is evaluated by considering each of the harmonics separately in the proposed method employing the frozen permeability to account for magnetic saturation. The results obtained are verified with 3-D FEA evaluating the magnet loss at fundamental, 10 and 20 kHz time harmonics in armature currents.

3D analysis of eddy current loss in the permanent magnet coupling.

This paper first presents a 3D analytical model for analyzing the radial air-gap magnetic field between the inner and outer magnetic rotors of the permanent magnet couplings by using the Amperian current model. Based on the air-gap field analysis, the eddy current loss in the isolation cover is predicted according to the Maxwell's equations. A 3D finite element analysis model is constructed to analyze the magnetic field spatial distributions and vector eddy currents, and then the simulation results obtained are analyzed and compared with the analytical method. Finally, the current losses of two types of practical magnet couplings are measured in the experiment to compare with the theoretical results. It is concluded that the 3D analytical method of eddy current loss in the magnet coupling is viable and could be used for the eddy current loss prediction of magnet couplings.

New Approach for Accurate Prediction of Eddy Current Losses in Laminated Material in the Presence of Skin Effect With 2-D FEA

Two-dimensional finite element (FE) models normally assume the laminated core as a non-conductive material, and therefore, the damping effect of the eddy currents is ignored in the field solution. Besides, the use of integrated iron loss models in FE software could result in overestimated eddy current losses at high frequencies if the skin effect is ignored. This paper presents a simple way to accurately predict eddy current losses in laminations with FE analysis. An experimental setup along with the simulation models is used to demonstrate the validity of the method. The utility of this method in loss separation and identification of loss coefficients in the presence of skin effect is also illustrated. This method is also applied to a synchronous permanent magnet (PM) machine with sinusoidal current.

Air gap MMF based prediction of eddy current loss in the PMs of concentrated winding brushless machines

Purpose – The purpose of this paper is to an analytical approach-based prediction of the eddy current loss in the PMs of a concentrated winding machine equipped with 12 slots in the stator and ten poles in the rotor. Design/methodology/approach – The investigation of the PM eddy current loss has been carried out using an analytical model and a 2D time-stepped transient finite element analysis (FEA). Findings – It has been found, in the case of the treated machine, that just the subharmonic of rank 1 and the harmonic of rank 7 have significant contributions to the eddy current loss in the PMs. Research limitations/implications – A shift between the results yielded by the developed analytical model and those computed by FEA has been noticed. This limitation is mainly due to the slotting effect which has been omitted in the analytical model. Practical implications – Fractional slot PM machines are currently given an increasing attention in automotive applications. The prediction of their iron loss in an attempt to rethink their design represents a crucial efficiency benefit. Originality/value – The analytical prediction of the eddy current loss in each PM then in all PMs and their validation by FEA represent the major contribution of this work.

Magnetization Process in Thin Laminations up to 1 GHz

Amorphous and nanocrystalline ribbons with transverse anisotropy have been characterized by magneto-optical, fluxmetric, and transmission line techniques from DC to 1 GHz. The contributions of domain wall displacements and magnetization rotations to the magnetization process, singled out by direct domain observations, consistently fit with the observed dependence of complex permeability and energy losses on frequency. With the domain wall motion suffering progressive hindering with increasing frequency and falling into full relaxation on reaching the MHz range, the magnetization process becomes amenable to a classical description, the concept of loss decomposition being secured. For this description, the conventional rate-independent constitutive relation for the magnetic material proves, however, inadequate. The diffusion equation for the electromagnetic field is therefore coupled with the Landau-Lifshitz-Gilbert equation, taken as a dynamic constitutive magnetic equation, and a solution is worked out by a numerical procedure. Magnetization and eddy-current field are thus obtained versus time at any point of the lamination, account being taken of the exchange field and its restraining action on the skin effect. The so calculated magnetic loss behavior turns out to correctly describe the high-frequency results, while coalescing with the classical eddy-current loss prediction at low frequencies.

Eddy-Current Loss Prediction in the Rotor Magnets of a Permanent Magnet Synchronous Generator With Modular Winding Feeding a Rectifier Load

In a permanent magnet synchronous generator (PMSG) with modular winding, significant eddy current may be induced in the rotor magnets due to asynchronous rotating stator magneto-motive forces (MMFs), and a rectifier load may signify the situation further. The eddy-current loss prediction in the rotor magnets of a PMSG with modular winding feeding a rectifier load is described. An analytical method considering the stator current harmonics and stator MMF spatial harmonics and a time-stepping, coupled-circuit, 2-D finite-element method (FEM) are adopted. The predicted losses obtained from these two methods are compared and investigated.

Analytical Prediction of Eddy-Current Loss in Armature Windings of Permanent Magnet Brushless AC Machines

This paper presents an analytical model for prediction of eddy current loss in armature windings of permanent magnet brushless AC machines. The developed model can either be used in the case of internal or external rotor radial-field machines topologies. First, a 2-D exact analytical solution of magnetic field distribution in an actual geometry of slotted surface mounted PM radial flux synchronous machines is established. It involves solution of Maxwell's equations in slots, airgap and PM's region. Then, magnetic vector potential solution in the slots is used for prediction of resistance limited eddy current in armature windings. Finally, results from this analytical model are compared to corresponding finite element analyses.