Study On Magnetic Field Distribution And Magnetic Flux Leakage Analysis Of Core Winding Structures

Under normal operating conditions, the additional loss caused by the leakage magnetic field will directly affect the efficiency and life of the transformer. In addition, the leakage magnetic field generated by the transient short-circuit current will produce mechanical force, which has an influence on transformer insulation and mechanical structure, So it is necessary to analyze the transformer leakage magnetic field, research the magnetic field distribution of the internal parts, find the concentration leakage, and provide the basis for magnetic flux leakage testing transformer. In this paper based on the basic theory of electromagnetism,we use 35kV oil immersed power transformer (S13-12500/35) as the simulation object, build simulation model, simulate and analyse the two dimensional of oil immersed transformer and two,three-dimensional transient field by Maxwell software. This paper mainly studies the electromagnetic field distribution of oil-immersed transformer load, no-load operation state. The main contents are as follows:(1) Based on the of Maxwell’s equations, we introduce the scalar magnetic potential and the magnetic vector potential, and load boundary,establishes the mathematical model of electromagnetic field in order to calculate the internal magnetic field size for transformer. The mathematical model consists of 2D transformer leakage magnetic field and 2D,3D transient field. So the mathematical model have 2D leakage magnetic field,2D transient field and 3D transient field.(2) According to the electromagnetic theory, we combine with the S13-12500/35-type transformer structure parameters, use the Maxwell electromagnetic simulation software to build a two-dimensional side model, a two-dimensional model of the leakage magnetic field, a three-dimensional transient field model. It analyses the distribution of magnetic field analysis of the above model in the no load condition. The magnetic field lines are mainly concentrated in the main magnetic field, the leakage magnetic field lines are mainly concentrated in the two sides of high-low voltage winding empty hang; Under the two-dimensional transient the magnetic flux density at the corner of the iron core and the iron yoke is maximum; at ωt= 180°magnetic flux density is maximum, it is about 2.91T; Under the three-dimensional transient the magnetic flux density at the corner of the iron core and the iron yoke is maximum; at magnetic flux density is maximum, it is about 7.31T.(3) Load has access to the low voltage side. We use Maxwell electromagnetic simulation software to simulate two-dimensional side and forward model, the 2D leakage magnetic field model, the 3D transient field model. Then we analyse the magnetic field distribution of the above models under the state of loading. The dense leakage magnetic field of the two sides of high-low voltage winding and fuel tank area is the most at two-dimensional side model. The magnetic flux leakage accounts for 3.72% and 49.6% respectively in the vertical and horizontal distribution of the leakage magnetic. The positive cutting leakage magnetic component accounts for 2.43%.Under the two-dimensional transient, the position of maximum flux density is basically the B column, the corner of the core and the iron yoke. At ωt= 180° the flux density is the strongest. The maximum magnetic flux density is approximately 2.75T.Under the three-dimensional instantaneous condition; the position of maximum flux density is basically the B column, the corner of the core and the iron yoke. At ωt= 90° the flux density is the strongest. The maximum magnetic flux density is approximately 4.74T.