Research On The Loss Influenced By The Mag Netic Shielding Mode Under Harmonic Excitation

In this paper,the safety operation of transformer is the engineering background,and the magnetic shielding is studied based on the TEAM Problem21benchmark family model.As more and more power electronic devices used in power system,the transformer is more and more work under complex conditions,in view of the transformer is likely to produce local overheating,it is necessary to analyze the harmonic of transformer magnetic shielding.magnetic shield is to add the silicon steel plate shielding layer between the box and winding,let the leakage flux through the silicon steel sheet without the box body.P21~c-M1 benchmark model is set in the transformer magnetic shielding problem,consisted of two coils of opposite excitation,magnetic steel and silicon steel laminated.That structure resulting in a large number of magnetic flux through the shielding layer,its loss characteristics has become the key problem.Compared the simulation result of four kinds magnetic shielding mode as unoriented flat type,orientation flat,unoriented vertical and vertical.The electromagnetic characteristics of the magnetic steel plate and the silicon steel sheet used in the experiment were measured by the Epstein coil.In this paper,we measured the magnetic steel plate Q235B,Non-oriented silicon steel sheet35ww300,oriented silicon steel sheet B30P105(0°).Through the electromagnetic simulation software MagNet can give the electromagnetic properties of the corresponding to the three dimensional model,and according to the structural characteristics of P21 magnetic shielding model simplified,greatly saves the computation time.Using the function of MagNet to solve the time-harmonic electromagnetic field.According to the simulation results,observe the distribution of magnetic flux density and current density distribution,and explain the distribution characteristics and differences of various magnetic shields.The causes of these phenomena are given from the aspects of material properties and stacking modes.Through the analysis of the formation mechanism of hysteresis loss and eddy current loss,it can be seen that the loss of ferromagnetic material is mainly related to the magnetic flux density.In this paper,the induced voltage is obtained by winding the copper wire in a specific position on the silicon steel sheet.Section flux,and thus calculate the peak flux density of the cross section.The classical Steinmetz loss model is based on the formation mechanism of ferromagnetic material loss.It is believed that the loss of the same material is mainly related to the frequency and magnetic flux density.Based on the original Steinmetz equation,we study the loss of the magnetic shield under harmonics by Bertotti classical trinomial and modified Steinmetz equation(MSE),and consider the Bertotti trinomial is suitable for analyzing the composition of loss so as to know the difference between different magnetic shields hysteresis loss and eddy current loss of the size and proportion of total loss,the flat magnetic shield is greater than the vertical magnetic shield,35WW300 non-oriented magnetic shield is larger than the oriented magnetic shield B30P105;non-oriented magnetic shield eddy current loss is greater than the oriented silicon steel sheet eddy current loss.When the harmonic content in the excitation changes,the modified Steinmetz equation(MSE)can continue to maintain a good fitting effect by replacing the equivalent frequency.