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Where does the transformer noise come from?

Where does the transformer noise come from?
Complex transformer noise from the transformer body and cooling system in two aspects. The research results at home and abroad show that the source of noise in transformer body vibration lies in:
(1) the vibration of the core caused by magnetostriction of silicon steel sheet.
(2) there is a magnetic attraction caused by magnetic leakage between the joint of the silicon steel sheet and the laminations, which results in vibration of the core.
(3) when the load current in the winding passes, the leakage of the magnetic field caused by the load current causes the vibration of the coil and the oil tank wall. In recent years, due to the improvement of core laminations and core and yoke with epoxy glass fiber tape bandage, core vibration electromagnetic attraction between the silicon steel sheet and laminated seams caused by the core vibration caused by magnetostriction than silicon steel sheet is much smaller, can be ignored. The rated flux transformer. Usually 1.5~1.8T, domestic and foreign research and test show that, within the magnetic density range, vibration core coil, the wall of the box caused by load leakage current generated by the porcelain than those caused by the magnetostriction of silicon steel sheet is much smaller, but also can be ignored. That is to say, the vibration of the transformer body depends entirely on the vibration of the core, and the vibration of the core can be regarded as entirely caused by the magnetostriction of the silicon steel sheet.
Another major source of complex transformer noise is cooler. The fan produces noise at frequencies from 500Hz to 2000Hz, and the human ear is sensitive to this harmonic over the harmonic produced by the core at the basic frequency of the IOOHz. The dominant frequency depends on a number of factors, including fan speed, blade count, and blade shape. The sound power level depends on the number of fans and the speed of rotation.
Like the mechanism of the transformer body noise, the noise of the cooling device is also caused by their vibration, and the root of the vibration lies in the noise:
(1) vibration of cooling fan and oil pump during operation.
(2) the vibration of the transformer body is transmitted to the cooling device through the insulating oil, the pipe joint and the assembly parts, so that the vibration of the cooling device is increased, and the noise is increased. In addition, when the core is heated, the noise will increase with the increase of temperature due to the change of resonant frequency and mechanical stress. The operating environment (such as the surrounding walls, buildings and installation foundations) also has an impact on noise.
For many strong wind cooling transformers, cooler fans are a more visible source of noise than the transformer itself.

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