Study On Vibration And Noise Of Power Transformer Under Different Stresses And DC Bias

With the increasing demand for power in China,electric equipment such as power transformers plays an increasingly important role in the power system.However,during the operation of power transformer,electromagnetic vibration will be produced due to the magnetostriction of iron core silicon steel sheet,when this vibration travels through the air to the outside world,it causes continuous noise.This will not only affect people’s physical and mental health,but also cause damage to equipment.When the power transformer is working,the iron core will be subjected to the force of the clamp,which will change the vibration and noise generated by the power transformer.At the same time,DC bias will also occur in the winding due to the inflow of DC,which will not only aggravate the vibration and noise of power transformer,but also threaten the safe operation of the whole power grid.In order to analyze more accurately and find effective vibration and noise reduction measures,it is of great significance to study the vibration and noise of power transformer under different stress and DC magnetic bias.The main research contents are as follows:（1）Based on a set of standard magnetostrictive measurement system for silicon steel sheet,the magnetization curve,relative permeability curve,loss curve and magnetostriction curve of oriented silicon steel sheet 27SQGD090 under natural state,different stress,different DC bias,different harmonics and different angles are measured and analyzed respectively.It lays the foundation for the finite element analysis of power transformer noise.（2）Through the given basic parameters of power transformer,the electromagnetic part of a 10 k V/0.4k V,100 k VA dry-type power transformer is designed and studied,the design process and specific data of core,winding and short-circuit parameters are given.It lays a foundation for the finite element analysis of power transformer.（3）The vibration characteristics of power transformer are studied based on ANSYS finite element simulation software.The finite element method calculates the model under three different parameters,and considers the free constraints and fixed constraints,obtained the natural frequency and modal mode shape of each stage of the core of the power transformer,and its analysis shows that the iron core is prone to resonance bands,it provide effective data support for power transformer to effectively avoid resonance state.（4）The three-dimensional finite element model of power transformer is established by using COMSOL finite element software,through the calculation of electromagnetic field,structural force field and acoustic field multiphysics coupling,the magnetic density map,vibration displacement map,stress cloud map and noise distribution map under normal operation and clamping pressure stress of 2MPa,4MPa,6MPa and DC bias of 1V,2V are obtained,the effects of the compressive stress of the clamp and the DC bias on the vibration and noise of the power transformer are obtained by comparative analysis.