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Causes Of Transformer Noise
May 08, 2018

The audible noise emitted by the transformer is caused by the magnetostrictive deformation of the core and the electromagnetic forces in the windings, the fuel tank and the magnetic shield. In the past, it has been considered that noise generated by magnetic field-induced laminations in the longitudinal direction of the laminations is the main component of transformer noise. The amplitude of this vibration is related to the magnetic flux density in the core laminations and the magnetic properties of the core material, but not to the load current.


    Specifically, there are three sound sources for transformer noise. One is the core, the other is the winding, and the third is the cooler, which is the sum of the noise caused by the no-load, load, and cooling system. The reason why the core generates noise is that the silicon steel sheet constituting the core undergoes a slight change, ie, magnetostriction, under the action of an alternating magnetic field, and the magnetostrictive causes the core to periodically vibrate with the change of the excitation frequency. The reason that the windings vibrate is that the electric current generates electromagnetic force in the windings, and the leakage magnetic field can also cause the structural parts to vibrate. The electromagnetic force (and vibration amplitude) is proportional to the square of the current, and the emitted acoustic power is proportional to the square of the vibration amplitude. Therefore, the emitted sound power has a significant relationship with the load current.