The Research Of Large Transformer's Stray Loss

In Large Power Transform,it is very large of magnetic flux leakage generated by load current.The magnetic flux leakage form closed loop with through the main insulation distanc and core clamping device?main column core or the tank,a lot of eddy current formed with the magnetic flux leakage through the ferromagnetic materials,the eddy current generated loss and heat.Whether the loss or heat,are not detrimental to the transformer,it will not only reduce the efficiency of the transformer,but also damage the transformer insulation,and the safe operation of the transformer will be affected,the life of the transf ormer will be shorten.The loss caused by the leakage flux in the metal structure of the transformer is called the stray loss,the eddy current loss of the tank is the main.It is inevitably of the Stray loss for transformer,and it grows with the increase of transformer power,the study on stray loss in engineering,On the one hand,it is to controll the leakage flux within the allowable range with the user's requirements;on the other hand,to control the leakage flux density for avoiding the local overheating,and ensure the safe operation of the transformer.By the research and experiment of experts and scholars,the most effective way to reduce the leakage flux of metal structures is to install the shield plate or make slots for flux leakage in the place where the flux density is dense.The structure of the l tank also has some influence on the stray loss.When the parameters of the transformer are not regular,the designer needs to analyze the leakage magnetic field of the metal structures and the tank to avoid local overheating.Based on the influence of the leakage magnetic field on the above problems,a comprehensive analysis is needed.This paper expounds the subject from the following aspects:Based on the basic theory of electromagnetic field,the ele ctromagnetic field equation is derived.The finite element method,modeling software Pro/ENGINEER and electromagnetic field simulation software Mag Net are introduced in this paper.The causes and effects of leakage magnetic field are also analyzed.Taking a SFP-410000/220 transformer as an example,the leakage magnetic field of the transformer is calculated by using Mag Net software.this paper come to the conclusion that there will not be a hot spot from analyzing the magnetic flux density and the stray loss density of the metal objects.In order to further explore the leakage magnetic effect caused by the change of the angle of the top of the tank,the leakage magnetic field is analyzed for the high voltage side with 35 degree tankcover and 45 degree tank cover in this paper.It is slightly greater that the stray loss effect and heat effect in 45 degree tank cover than in 35 degrees tank,and no hot spot has been formed.Finally,the test results were compared with the calculations and analysises above.