Research On The Effect Of Stress On Core Vibration

Laminated core products such as power transformers and reactors play a very important role in the power transmission system,but the vibration and noise generated by their operation will not only affect the environment,but also shorten the service life of the equipment and reduce the reliability of the grid operation.Because the core of the power transformer is clamped by the windings and clamps,it is necessary to consider vibration under stress conditions.In addition,in the gap iron core reactor,due to its own structure,the iron core is subject to the tension of the rod.The tightening action makes the iron core cake of the gap iron core reactor under compressive stress in both natural and working conditions.In order to study the electromagnetic vibration of transformer and reactor cores,and to more accurately analyze and find effective noise reduction measures,this paper considers the stress factor,measures the magnetic characteristics of silicon steel sheets,considers the magnetostrictive effect of the core,and affects the transformer and reactor cores.Numerical analysis and experimental research of electromagnetic-mechanical coupling were carried out.The research contents of this paper are as follows:(1)In order to accurately obtain the magnetic characteristic parameters of the core under different stresses,the SST and magnetostrictive measurement system MST500 in accordance with the IEC standard were used in this paper.The magnetization and magnetostrictive characteristics of silicon steel sheets under tensile and compressive stress conditions were measured and analyzed.The effects of stress conditions on the magnetization and magnetostrictive properties of silicon steel sheets are described.(2)In order to accurately calculate the vibration of the three-phase transformer under the influence of electromagnetic force and magnetostrictive force,the magnetization and magnetostrictive curves under stress are first extended to a three-dimensional characteristic surface to represent the magnetic characteristic data under continuous stress.Analyze and calculate the vibration under stress and without stress,and compare the calculation result with the measured value of three-phase transformer vibration.The results show that considering the stress can improve the accuracy of the numerical calculation of electromagnetic vibration,which is conducive to the accuracy of noise assessment..(3)Based on the measurement data of the magnetization and magnetostrictive characteristics of various types of core silicon steel under different stresses,the electromagnetic vibration of the gap core reactor prototype was analyzed and calculated.Firstly,the magnetostrictive measurement system was improved,and the magnetization and magnetostrictive characteristics of three typical silicon steels for reactors at Shougang were measured under different stresses,especially compressive stress.The magnetostrictive effect of the core was considered.The magnetic field,mechanical field and sound field under different tightening forces were analyzed and calculated.The core magnetic flux density,stress,sound field distribution,and stress,vibration displacement and noise at different points in the core were calculated.The research results of this paper can provide different silicon steel magnetic characteristics data and theoretical analysis methods for the design of low-noise gap core reactors.