Host: The Japan Society of Mechanical Engineers
Name : [in Japanese]
Date : September 20, 2022 - September 22, 2022
For the transformer which is general industrial apparatus, electromagnetic noise and earthquake resistance are also important functions. Especially electromagnetic noise serves as an environmental load, so noise control is called for. In a transformer, at the time of operation, electromagnetism vibration is added to the iron core which is the main part, and electromagnetic noise occurs. First of all, an iron core stacks a thin electromagnetic steel sheet, and is being fixed with bolts. Therefore, when a fastening position and forces are not suitable, mechanical stiffness falls and it causes increase of electromagnetic noise, and earthquake-proof degradation. Then, it is necessary to predict correctly the oscillation characteristic of an iron core, especially natural resonance frequency, and to avoid resonance with electromagnetic vibration. In this case, the dynamic finite element method is generally used.
The finite element method generally predicts the mechanical property of apparatus in a design phase, and is used for problem solving. However, it is difficult to determine the material constants of the iron cores because these cores are composed of several thin electromagnetic steel plates laminated by bolting. The slippage between the steel plates and the bolt fastening force and position have a great influence on macroscopic material constants.
Therefore, in order to predict the oscillation characteristic of an iron core correctly, a suitable material constant is needed. This research considers the process of asking for this material constant efficiently. The oscillation characteristic is the eigenvalue and corresponding vibration mode of the iron core can be obtained by experimental modal analysis. This research shows that change of the oscillation characteristic at the time of changing bolt fastening force and bolt positions can be predicted by setting up a suitable material constant using steel sheets which imitated the iron core.
