An Improved Formula for Lamination Core Loss Calculations in Machines Operating with High Frequency and High Flux Density Excitation (original) (raw)
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IEEE Transactions on Industry Applications, 2012
To study the fundamental essence of core losses and to achieve an accurate core loss separation formula, a dynamic finite-element model for the nonlinear hysteresis loop of laminations has been established. In the model, Maxwell's equations are solved for the hysteresis character in the magnetic lamination, using the Galerkin finite-element method, where the hysteresis is represented by an energetic hysteresis model. Based on the simulation results, the magnetic characteristics, skin effect, time delay, and magnetic field distribution are discussed. Then, core losses, particularly excess losses, affected by the magnetic characteristics are carefully examined. It is concluded that excess current loss formula is only applicable for the cases where skin effect is negligible and the sum of hysteresis losses and eddy current losses can more generally represent total losses. Index Terms-Ferroelectric hysteresis, loss measurement, magnetic core losses.
A Novel Hysteresis Core Loss Model for Magnetic Laminations
IEEE Transactions on Energy Conversion, 2011
A general dynamic hysteresis core loss model has been developed. Experimental data for different lamination thicknesses have been measured and analyzed at various frequencies. Based on the analysis, a dynamic hysteresis finite element core loss model is established and validated by experiments. The developed dynamic hysteresis model is simple and efficient, and has been shown to be very accurate compared with the experiments. Moreover, the model can calculate core losses based on the input parameters obtained from experimental measurements at only one single frequency in a thin lamination. The model, to our best knowledge, is the first one that is capable of calculating core losses for different thicknesses of materials and different operating frequencies, without a massive experimental database. In addition, only the eddy current and hysteresis models are necessary for this calculation but with the important addition of the variation of the flux density within the lamination.
IEEE Transactions on Magnetics, 2000
This paper investigates the interdependence of hysteresis and eddy-current losses in magnetic cores. Based on the results of a numerical model developed for the analysis, the magnetodynamic loss phenomena are found to be distinctly interdependent. Because of the effects of eddy currents on the flux distribution in the lamination depth, hysteresis and excess losses show a dependence on eddy currents, and hence, on the excitation frequency. Eddy-current and excess losses, on the other hand, are affected by the magnetic characteristics of the material where hysteresis plays the role of a damper. An application of the model to a rotating electrical machine has showed that the interdependence between the losses is quite significant.
On the variation with flux and frequency of the core loss coefficients in electrical machines
IEEE Transactions on Industry Applications, 2000
A model of core losses, in which the hysteresis coefficients are variable with the frequency and induction (flux density) and the eddy-current and excess loss coefficients are variable only with the induction, is proposed. A procedure for identifying the model coefficients from multifrequency Epstein tests is described, and examples are provided for three typical grades of non-grain-oriented laminated steel suitable for electric motor manufacturing. Over a wide range of frequencies between 20-400 Hz and inductions from 0.05 to 2 T, the new model yielded much lower errors for the specific core losses than conventional models. The applicability of the model for electric machine analysis is also discussed, and examples from an interior permanent-magnet and an induction motor are included.
Computation of core losses in electrical sheets used in electrical machines
IET Electric Power Applications, 2019
One of the most important quantities for magnetic materials is energy loss, usually expressed in terms of loss per mass unit and one cycle. From an engineering point of view, it would be desirable to have an accurate and simple model of energy losses in electrical sheets. This study presents a new approach to describing core losses in electrical sheets. The proposed approach allowed one obtaining a new formula for total losses in the material, in which only basic material coefficients such as material conductivity and magnetic permeability expressed in the form of a magnetic hysteresis loop are needed. The expressions used so far are semi-empirical, whereas the proposed model clearly indicates how the material parameters affect the losses. This stays in contrary to the approach in which the hysteresis losses are obtained from measurements by extrapolation of the ratio of losses and frequency when the frequency tends to zero. The obtained expression for total losses in the material was compared with the commonly used expression proposed by Bertotti, and comparable approximation errors of prediction were obtained. The comparisons were made on the example of non-oriented electrical sheets.
IEEE Transactions on Magnetics, 2018
In this paper, the different temperature dependencies of hysteresis and eddy current losses of non-oriented Si-steel laminations are investigated. The measured iron loss results show that both the hysteresis and eddy current losses vary linearly with temperature between 40°C to 100°C, a typical temperature range of electrical machines. Varying rates of hysteresis and eddy current losses with the temperature are different and fluctuate with flux density and frequency. Based on this, an improved iron loss model which can consider temperature dependencies of hysteresis and eddy current losses separately is developed. Based on the improved iron loss model, the temperature influence on the iron loss can be fully considered by measuring iron losses at only two different temperatures. The investigation is experimentally validated by both the tests based on a ring specimen and an electrical machine.
IEEE Transactions on Industry Applications, 2012
This paper presents a new method for the separation of core loss components (hysteresis and eddy current) in laminations exposed to high frequency excitations. Accurate separation of core losses is achieved by calculating the hysteresis losses at each frequency taking into account the non-uniform flux distribution inside the lamination. The results highlight that the assumption of constant hysteresis energy loss per cycle is only valid at low frequencies, where skin effect is negligible. The developed model is then used to study the effect of the annealing process on core loss components in laminations exposed to high frequency excitations. Core loss measurements are performed on different laminations at several frequencies in the range of 20 Hz-4000 Hz. A comparison of the separated core loss components shows that a huge reduction in the hysteresis losses is achieved by annealing, while the annealing process increases the eddy current loss component at high frequencies and high flux densities. The results are then analyzed by comparing the separated eddy current loss with an analytical eddy current loss model that accounts for the non-uniform distribution of the magnetic field.
IET Electric Power Applications, 2017
This paper presents a comparative study on the accuracy of three iron loss prediction models. The models are based on the decomposition of core or iron losses into the hysteresis and the eddy current loss components. The time domain extensions of two frequency domain models have been used to predict the iron losses due to a number of non-sinusoidal waveforms with and without the presence of minor loops. A third model, by Boglietti, that has been proposed recently to predict core losses for non-sinusoidal and Pulse Width Modulated (PWM) waveforms has also been studied. The unknown coefficients of each model have been determined by data fitting iron losses obtained from Epstein frame experiments for induction levels and fundamental frequencies up to 1.6 Tesla and 2 kHz, respectively. Core losses due to PWM waveforms have been measured at various fundamental and switching frequencies in unipolar and bipolar modes. The experimentally measured iron losses have been compared to those predicted using the three models and the accuracy and applicability of each model have been discussed.
Calculation of eddy currents and associated losses in electrical steel laminations
1999
Starting from the well known analytical formula for the eddy current losses in electrical steel laminations, saturation and edge effects are studied by means of 1D and 2D finite element models of a single lamination. A novel method for directly including the laminated core energy dissipation in a time stepped 2D model of a complete (rotating) machine is proposed. By way of example the method is applied to a tooth model with enforced flux waveforms.