V. NOISE VARIATIONS DUE TO ARRANGEMENTS OF THE CORE VERTICALLY OR HORIZONTALLYThe LPA values for different core arrangements, horizontal type or vertical type, were shown in Fig.9. The result indicates that, in addition to magnetostriction, domain structure plays an important role in transformer noise generation. A-weighted sound power level taken with the core arranged vertically is approximately 5dB higher than that with the core arranged horizontally. The author considers that the pressure caused by dead weight of cores results in noise increase when cores are arranged vertically. In this sense, amorphous alloy cores which are arranged horizontally provide better flexibility in reducing transformer noise. For example, a shell form amorphous transformer whose cores are arranged horizontally is better than the core type transformer whose cores are arranged vertically.The background noise is 27dB during the test.VI. CONCLUSIONSExperimental Study of Testing Models for Low Noise Amorphous Alloy Core Power Transformers has been discussed. An increase of 0.1T of induction level can result in an increase of 3-10dB of transformer noise. Effect of clamping pressure on transformer noise has been evaluated for amorphous alloy based cores. The LPA values of amorphous alloy based cores appeared linear growth at various clamping force changed from 0MPa to 0.14MPa which is different from silicon steel cores whose noise are lower in a suitable range(0.08-0.12MPa), according to the relative report. Loading pressure on step-lap joint is not suggested in transformer design as clamping force result in both core and noise increase. An axial clamping force to fix cores is better than a clamping force
applied in radical direction. The amorphous alloy cores have a better performance and a lower noise when they are arranged horizontally compared with those arranged vertically. All above testing results are very helpful for improving manufacture technologies for the amorphous alloy core power transformers.
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