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Core noise - — The first big source of dry type transformer noise

by:Transmart     2021-01-12
Core noise - — The first great sources of dry type transformer noise - 2019 03 - 30 15:05:38 dry type transformer noise are mainly large amount of source, which is the largest source, transformer noise source ontology. And there are silicon steel sheet main transformer noise of ontology and magnetostriction iron core, silicon steel sheet vibration caused by the joint between magnetic flux leakage and laminated iron core vibration, winding, etc. 1, silicon steel sheet magnetostrictive noise caused by core excitation, under the effect of alternating magnetic field, the small changes will happen by the size of the silicon steel sheet, silicon steel sheet in the direction along the lines of magnetic force to increase the size, direction and perpendicular to the magnetic field lines silicon steel sheet size to close, the dimensional change is called the magnetostriction. Produce the magnetostriction, magnet core change with excitation frequency to vibration. Due to the change of the magnetostrictive cycle is a half cycle of mains frequency, magnetostrictive cause the vibration of the power transformer of ontology, is twice mains frequency as the base frequency, so the vibration of the silicon steel sheet is mainly caused by the magnetostrictive properties of ferromagnetic materials. For iron core of nonlinear and magnetostriction along the casing outside the core box and magnetic flux path length of different reasons, such as iron core in the noise in addition to the fundamental frequency also contains higher harmonic spectrum of the noise. Magnetostrictive rate are related to the material of silicon steel sheet. Magnetostrictive ratio increases, the greater the noise. Under the same magnetic field intensity, material is qualitative good silicon steel sheet magnetostriction is small, so the noise is small. 2 seams, electromagnetic noise caused by core silicon steel sheet and laminated between due to leakage of electromagnetic attraction, the resulting core vibration. Because the core pile method for continuous improvement, seams and laminated iron core vibration caused by electromagnetic attraction between much smaller, so this part of the noise is usually negligible. 3, the magnetic flux leakage caused by the vibration noise windings magnetic flux leakage resulting from the load current will be winding vibration. When the rating of the transformer magnetic flux density in 1. 5 ~ 1. 8 t, the core caused by vibration and magnetostrictive vibration than small. But the load current and the noise produced by magnetic flux leakage is proportional to the square of the load current, so when the rating of the transformer magnetic flux density decreased to 1. The vibration of the 5 t, winding and silicon steel sheet of magnetostrictive vibration phase close to the core. Seams by what time we can see that on the silicon steel sheet and laminated core vibration caused by electromagnetic attraction between than silicon steel sheet of magnetostrictive vibration has a much smaller core, can be ignored. The transformer rated flux density usually take 1. 5 ~ 1. 8 t, domestic and foreign research and experiment have proved that in the range of the flux density, load current generated by the coil in magnetic flux leakage cause, the vibration of the tank wall than silicon steel sheet of magnetostrictive vibration has a much smaller core, also can be ignored. This means that the vibration of the transformer ontology depends entirely on the vibration of core, and the vibration of the core can be viewed as completely is caused by the magnetostriction of silicon steel sheet.
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