Investigation Of The Flux Distribution And Iron Loss Inside Magnetic Shielding Under Non-sinusoidal Excitation Environment

Power transformer is a kind of indispensable electrical equipment of electric power system.Magnetic shielding and electric shielding are widely distributed in the inner structure of transformer,such as oil tank and iron core and other metal structure parts,whose main effect is to reduce the loss and the temperature rise due to the flux leakage.Meanwhile,the harmonic components of non-sinusoidal excitation environment greatly increases the stray loss of these parts,leading to local heating of the equipment,and endangering the safe and stable operation of the power system.Moreover,the materials of magnetic shielding under different external magnetic field excitation show different electromagnetic properties.Thus,this paper focuses on the following contents:an improved loss model is presented based on loss model proposed by scholar Bertotti,taking the implications of non-sinusoidal multivariate conditions on iron loss.And curve-fitting and error analysis are carried out by using the Non-Linear Least Squares Method under 1st Opt programming environment.Based on the P21~c-M1 model and the Mag Net electromagnetic simulation software,this paper further reduce the error of stray loss determined by measurement combined with simulation method,and then loss characteristics of magnetic shielding component under non-sinusoidal excitation are simulated and verified using the improved loss model.The main research content of this article is as follows:1)Introducing the correction factors of iron loss components to the Bertotti loss model,an improved loss model is proposed to consider the effect of harmonic content,order and phase of non-sinusoidal excitation environment on the iron loss of magnetic materials.2)The magnetic performance testing platform under non-sinusoidal multivariate excitation was set up to measure the loss characteristics of oriented electrical steel sheets(B30P105)under harmonic excitation.The loss data measured by Epstein Square under non-sinusoidal excitation environment can be fitted by the Non-Linear Least Squares Method,and the influence of harmonic multivariate condition on the correction factor and loss components is studied simultaneously.3)The methods for determining stray loss of magnetic shielding components in common use and their limitations are briefly analyzed,and a method of combining measurement and fine modeling is proposed.Based on P21-M1 simplified model,the validity of this method is verified under sinusoidal excitation and harmonic multivariate excitation.4)Based on the simplified P21-M1 model,an improved loss model(represent the relationship between the effective value of flux density and the iron loss),and the simulation software Mag Net are used to indirectly calculate stray loss of shielding.The method of using model to calculate stray loss,which need deal with a large amount of data,but it can accurately calculate the loss of shielding and solve the difficult problem of stray loss separation of components under non-sinusoidal excitation environment.5)Based on P21~C-M1 and its simplified model,the magnetic flux distribution and stray loss of two different structures of shielding under harmonic multivariate excitation are investigated,as well as the additional eddy current loss and stray loss of different laminated layers.