The Parameters of Generated Sound Level of Transformer Cores

摘要

Low level of the audible sound is a compulsory aspect for transformers today. Therefore it is important to determine the parameters of generated sound in transformer. The sources of sound in transformer are; Load sound in the windings, auxiliary equipment sound and mainly core sound (no load sound).The paper will focus on the core sound. Core sound generated by magnetostrictive vibration of core steel laminations and magneto-motive Maxwell forces. It is extremely sensitive to applied compressive stress. For better understanding of those effects it is necessary to investigate flux distribution in core. One of the main sources of sound in the core is magnetostriction in laminations. This study performed to reduce the generated sound at the source. In order to have correct result the tests made in a special sensitive noise lab according to rules mentioned in IEC 60076-10. In 3 cases, study illustrate the parameters of core sound levels. 1. Effects of stacking performance of magnetic steel (limbs, yokes, corners, T-joints) presented in a case study in detail. How big the difference is shown in the measurement results in table and curves. 2. Some quality difference of magnetic steel from different supplier shows the measurement curves. 3. The clamping arrangement influences strong the structural dynamic behavior of the core. The vibration behavior of core structure has a big effect to sound generation. For mitigation of core sound provide various actions. A case study shows the results. In the paper various test procedures with different core size are described and results with curves are presented. The Prediction of transformer core sound can be clarified with these tests. In order to mitigate the sound level in cores this test results can give some support. IEC 60076-10 Power transformers Part 10: Determination of sound levels has detail information for test environment and procedure.