Characteristic Modeling And Further Studies On Anomalous Loss Of Soft Magnetic Materials In Electrical Engineering

Soft magnetic materials are widely applied in electrical engineering field,such as the most critical core components of the power transformers and electrical machines,which directly impact on the electrical properties of electrical equipments.To improve the performance,operational efficiency of electrical equipments,the most effective approach is solving the problem about the inner magnetic losses of core materials,which is also the cutting-edge,hotspot and thorny issue in the field of international electrical engineering.According to the requirements of the key project supported by the National Natural Science Foundation of China,comprehensive study for the theoretical calculation models of core losses and its component anomalous loss under the conditions of alternating and rotating excitations is focused in this paper,as regard to the widely used soft magnetic materials in electrical engineering.Then,investigation and analysis of the models are carried out by considering a variety of working conditions,such as high frequency and high order harmonics,high flux density and non-sinusoidal excitation,etc.Next,the anomalous loss properties of typical soft magnetic materials in electrical engineering are more accurately modeled and verified on the basis of the experimental data and novel losses separation methods of the total core losses.Moreover,further research on some specific issues encountered in the study process,such as skin effect and eddy current loss,etc.,are implemented.Achievements of this paper will provide a powerful reference to the database establishment of the losses characteristics.Also,experimental measurement and separation technology of the total core losses can promote the investigation and development of the 2-D and 3-D magnetic properties measurements for soft magnetic material in electrical engineering.The main research contents are as follows:1.On the basis of damping principle of vibration,the micro domain wall processes and losses are investigated and modeled at low-to-medium frequencies inside the soft magnetic materials in electrical engineering.Then,the coupled Landau-Lifshitz-Gilbert(LLG)and Maxwell electromagnetic field diffusion equations are therefore considered to describe the high-frequency characteristics.In combination with the calculation of classical eddy current loss,the overall core losses are thus deduced.Moreover,macro-physical interpretation of this energy losses behavior is analyzed in depth.2.The novel calculation model of total core losses is analyzed and compared with the alternating core losses original data of electrical steel sheets and the broadband rotating experimental core losses of electrical steel sheets and soft magnetic composites(SMCs)which are carried out by using a 3-D magnetic properties testing system.Under acceptable errors range,the separation of mean micro-vortex current losses is worked out at the same time.Meanwhile,the pure anomalous loss is applied to study the characteristics of the loss coefficients and prediction.3.A statistical calculation model of anomalous loss in soft magnetic materials is built based on the production and separation of dynamic losses and domain wall motion.Then,a testing method to determine the micro-statistical characteristic parameters is proposed due to the pure anomalous loss obtained by the separation of total alternating experimental core losses in electrical steel sheets.Moreover,the separated and predicted values of alternating and 3-D rotating anomalous losses are analyzed and compared,respectively.The validity of the calculation model is verified according to the results.4.Based on Fourier analysis,the finite element model of electrical steel sheets is simulated by adopting time-stepping method.Then,a calculation formula of rotating anomalous loss in electrical steel sheets is deducd indirectly by considering the influence of skin effect to loss coefficients and combining experimental measurement at low-to-medium frequencies under the condition of elliptical rotation excitation.Meanwhile,the broadband core losses and the components of an electrical steel laminated specimen under rotating and alternating excitations are analyzed and compared quantitatively.The results show that it is necessary to take the influences of harmonics,skin effect and rotating excitation to the materials properties into account seriously.5.By adopting the time-stepping finite element method,3-D rotating core losses considering harmonics of the bulk SMCs are modeled.The rotating loss coefficients taking into account skin effect are determined.Then,the variable loss coefficient and indirect orthogonal decomposition calculation models of rotating anomalous losses are built.Meanwhile,a separation of total 3-D rotating experimental core losses is worked out and three different methods are analyzed and compared qualitatively.Be noted that the two novel calculation models can be more effectively presented the anomalous loss features.6.An improved core losses calculation formula considering the impacts of frequency and flux density on the loss coefficients at high frequency and high flux density is proposed.According to the original and experimental data of core losses over wide range of excitation frequencies of electrical steel steels,the influences of skin effect and dynamic hysteresis loop to loss coefficients are investigated by employing the improved calculation formula.Then,new curves of core losses are achieved and compared with the measured data.The results show that the proposed formulae can improve the computation accuracy obviously.Moreover,the validity and feasibility of the novel calculation formula is validated.7.The skin effect in electrical steel sheet by applying an alternating excitation field is analyzed based on Maxwell electromagnetic field theory.Non-dimensionalized treatment for the electromagnetic field diffusion equation is produced and eddy current loss is calculated with and without considering skin effect,respectively.Meanwhile,experimental measurement and separation of broadband rotating core losses of steel sheet are obtained to bring to light the emergence of skin effect under rotating excitation.The simplification of magnetic constitutive equation is proposed and introduced into the diffusion equation.Therefore,an approximate expression of rotating eddy current loss component taking into account skin effect is eventually written.