How does dry type distribution transformer noise come from?

The dry type distribution transformer will also generate noise in the process of working. The noise generated by the dry-type transformer makes the performance and efficiency of the dry-type transformer continue to decline. The noise of dry-type transformers should be solved in time, so how does the noise of dry-type transformers come from?

1. Noise caused by magnetostriction of silicon steel sheet

When the core is excited, the size of the silicon steel sheet changes along the direction of the magnetic field, while the size perpendicular to the direction of the magnetic field changes in the opposite direction. Magnetostriction causes the dry type distribution transformer core to vibrate periodically as the excitation frequency changes. Since the change period of magnetostriction is half the power period, the core noise due to magnetostriction is based on twice the power frequency. Due to the non-linearity of the magnetostriction of the iron core and the different lengths of the magnetic flux paths along the inner frame of the iron core, in addition to the fundamental frequency, the iron core noise also includes noise in the high-order harmonic spectrum.

2. Iron core noise caused by electromagnetic action

There is electromagnetic attraction between the silicon steel sheet joints and the laminations due to magnetic flux leakage, which causes the core to vibrate. Due to the continuous improvement of the core stacking method, the core vibration caused by the electromagnetic attraction between the seams and the laminations is much smaller than the core vibration caused by the magnetostriction, so this part of the noise can usually be ignored.

3. Winding vibration noise caused by magnetic leakage

The leakage flux generated by the winding load current will cause the winding to vibrate. When the rated working magnetic flux density of the dry type distribution transformer is in the range of 1.5~1.8T. This vibration is small compared to the core vibration caused by magnetostriction. However, the noise generated by the magnetic leakage of the load current is proportional to the square of the load current, so when the rated magnetic flux density of the transformer is reduced to below 1.4T; the vibration of the winding will be connected with the vibration of the iron core caused by the magnetostriction of the silicon steel sheet.