The noise of power transformer is mainly caused by magnetostriction of its core silicon steel. According to the actual structure of 50 MVA/110 kV transformer core

an equivalent four-angle core model is constructed to investigate the vibration of different areas and directions of the transformer core as well as the magnetostriction mechanism of the core’s silicon steel sheet. The results show that the vibration of the central region of the silicon steel sheet is significantly less than the joint region

and the vibration in parallel direction is less than that in vertical direction. In the central region of silicon steel sheet

the peak frequency of vibration in vertical direction mainly appears in the frequency bands 100

200

300

and 400 Hz

while in parallel direction it appears in the bands 100

200

and 600 Hz.In the joint area of silicon steel sheet

the peak frequency of vibration in vertical direction mainly appears in the frequency bands 100

200

300

and 500 Hz

while in parallel direction

it appears in100

200

300

600 and 700 Hz.The magnetostriction in plane center area and joint area of the silicon steel sheet with magnetic field applied is caused by grain boundary movement

grain deformation and rotation.