Multi-Field Coupling Analysis and Suppression for Biased Magnetic Noise in Transformer

In view of the noise problem when the transformer is subject to DC disturbance, the existing scholars have carried out preliminary research on this problem, but have not deeply explored the internal correlation of electromagnetic, vibration and acoustic wave cooperative coupling propagation evolution when the transformer is subject to DC magnetic bias. Based on the coupling of multiple physical fields, this paper focuses on the DC bias noise characteristics of transformer. Based on electromagnetism, the information transmission path of magnetic field force field sound field is analyzed, and a sequential coupling model of multiple physical fields is constructed. Firstly, the electromagnetic mechanical acoustic model of transformer magnetic bias effect is established. Based on electromagnetic coupling, a dynamic information base for virtual simulation of multiple physical fields is established. According to the time point index, the vibration acceleration of transformer winding and iron core is calculated with electromagnetic information as excitation; The sound pressure and sound pressure level of the winding and iron core are calculated by taking the vibration acceleration as the excitation and substituting it into the sound field propagation domain. Establish dynamic multi field physical information base. The simulation model of three-phase transformer is established, and different measuring points are selected. Based on the sequential coupling of multiple physical fields, the changes of winding magnetic leakage, Lorentz force, acceleration, noise, core vibration and noise under different DC disturbance modes are simulated and analyzed. The simulation results show that: firstly, under the DC disturbance, the magnetic flux leakage, Lorentz force, vibration acceleration, sound pressure and current of the transformer winding have similar change laws, showing the asymmetric change characteristics of "half wave enhancement and half wave attenuation"; Secondly, the vibration and noise of transformer magnetic bias effect mainly come from the iron core. A three-phase transformer dynamic simulation test platform is built, and the test points consistent with the simulation are selected to measure the vibration and noise of the transformer under different modes. The experimental results show that the experimental noise has the same trend as the simulated noise. Aiming at the vibration and noise problems of transformer, the magnetic bias noise suppression measures are proposed from the aspects of physical information monitoring and capacitance isolation. Through the comparison between simulation and experiment, the following conclusions are drawn: (1) Under DC disturbance, the vibration and sound pressure of iron core and winding change obviously; The noise increases with the increase of DC interference. The abnormal noise of transformer magnetic bias effect mainly comes from the iron core. The consistency between simulation results and experimental data verifies the correctness of this method. (2) The physical process of transformer magnetic bias effect and abnormal feature information of vibration and noise are fused, and the morphological characteristics of vibration and noise of transformer magnetic bias effect are analyzed from the perspective of multi-dimensional, multi temporal and spatial scales and multi field information. The key electromagnetic parameters are identified through measurable electrical information to reflect other unmeasurable physical characteristics. © 2023 Chinese Machine Press. All rights reserved.