Study On Thermal Characteristics Of Oil Based Magnetic Liquid Transformer

Oil immersed transformer is an indispensable and important component of the power system.With the increasing capacity and voltage level of the single power transformer,the problem of excessive loss and exceeding of raising temperature has become most considerable issues for engineers.At the same time,large capacity power transformers mainly use oil immersion cooling mode.In order to reduce operation cost,more than 80%uses natural oil circulating cooling mode.The power of natural oil circulation transformer is the thermal buoyancy,and its internal loss and oil properties are the key factors that affect hot spot temperature rise.Therefore,in order to improve the insulation characteristics of transformer oil and reduce the stray loss of clip and fuel tank,the temperature field analysis based on Fe₃O₄ nano modified oil immersed transformer is proposed.This paper has conducted in-depth analysis and systematic research in terms of loss modeling and calculation,and the calculation and research of the hotspot temperature rise.The main achievements and innovations are as follows:?1?The field circuit coupling method is used to calculate the three-dimensional nonlinear eddy current field of oil based magnetic liquid transformer and pure oil transformer?considering the nonlinear B-H curve of material?.The energy method is used to solve the short circuit impedance of the transformer.The accuracy of the calculation is verified by comparing the calculated short-circuit impedance with the short-circuit impedance given by the design value,and the calculated value of magnetic induction intensity is basically consistent with the design value.The distribution of magnetic flux leakage in the main air channel between the magnetic liquid with 200 Gauss,250 Gauss and 350 Gauss magnetic saturation and pure oil are analyzed respectively.The difference between magnetic leakage field and stray loss by using the magnetic fluid with the magnetic saturation of 350 Gauss and pure oil is compared.By analyzing the leakage magnetic field of transformer structure,the result shows that the magnetism and loss on the surface of the fuel tank and clamps have been significantly reduced after using the magnetic fluid.?2?Taking an oil immersed transformer as an example,a three-dimensional finite volume numerical analysis model for the calculation of transformer temperature rise is established.The temperature field and oil field of the transformer are calculated by CFX software.The temperature rise of the transformer is determined based on the multi-field coupling analysis method of electromagnetic field,oil field and temperature field.This method considers the influence of temperature on the material characteristics and the difference in temperature rise between the transformer of magnetic saturation350 Gauss of and pure oil transformer clip and fuel tank is compared.The calculated hot point temperature rise is basically consistent with the design value.It proves that the oil based magnetic liquid transformer has a better heat dissipation and provides an important reference for the heat design of the pressure transformer.?3?The oil based magnetic liquid transformer and the oil field of the oil transformer are compared and analyzed,and the difference of the hottest temperature rise and the flow velocity of the oil field in the high voltage winding area and the low voltage winding area is compared.The oil based magnetic fluid transformer has better heat dissipation performance because of the thermal magnetic convection.