Transformer noise is an inherent characteristic of the transformer when it is operated. The relevant national standards have strict sound level limits. However, as the user's environmental awareness increases, complaints reflecting the excessive noise on the transformer site are gradually increasing, and the noise level is reflected. It is often a lot larger than the factory test data. The electrician forum Ligong has some reasons for analysis based on some on-site processing experience for reference:
1, the voltage problem
Cause: The high voltage will over-excitation the transformer, and the sound will increase and sharpen, which will directly affect the noise of the transformer.
Judgment method: first look at the low-voltage output voltage, can not see the voltmeter on the low-voltage cabinet, the voltmeter only serves as an indicator, should be measured with a more accurate multimeter.
Solution: The current 10KV voltage in the city is generally high. According to the low-voltage side output voltage, the tap file should be placed in the appropriate gear position. Under the premise of ensuring the quality of the low-voltage power supply, try to adjust the high-voltage tapping upwards (low-voltage output voltage is reduced), thereby eliminating the over-excitation phenomenon of the transformer and reducing the noise of the transformer.
2. Resonance problems of fans, enclosures, and other components
Cause: The resonance of the fan, the outer casing, and other components will generate noise, which is generally mistaken for the noise of the transformer.
Judgment method: 1) Shell: Press the aluminum plate (or steel plate) of the casing by hand to see if the noise changes. If the change occurs, the casing is resonating.
2) Fan: Use a dry long wooden stick to top the outer casing of each fan to see if the noise changes. If there is a change, the fan is resonating.
3) Other parts: Use a dry long wooden stick to top each component of the transformer (such as: wheels, fan brackets, etc.) to see if the noise changes. If the change occurs, the parts are resonating.
Solution: 1) If the aluminum plate (or steel plate) of the outer casing is loose, it is possible to step on the deformation when installing. It is necessary to tighten the screw of the outer casing to fix the aluminum plate of the outer casing and correct the deformed part.
2) If the fan is loose, you need to tighten the fastening bolt of the fan and pad a small piece of rubber between the fan and the fan bracket to solve the fan vibration problem.
3) If the transformer components are loose, they need to be fixed.
3, the installation problem
Cause: Poor installation will increase the vibration of the transformer and amplify the noise of the transformer.
Judgment method: 1) The transformer base is not strong or uneven (one corner is suspended), or the bottom plate is too thin.
2) Using a channel steel to frame the transformer will increase noise.
Solution: 1) The original installation method is modified by the installation unit.
2) Add a shockproof rubber pad under the transformer trolley to solve some noise.
4, the impact of the installation environment
Cause: The operating environment affects the noise of the transformer, and the environment is unfavorable to increase the transformer noise by 3dB to 7dB.
Judgment method: 1) The transformer room is large and empty, there is no other equipment, and there is echo.
2) The transformer is too close to the wall, less than 1 meter. The transformer is placed at the corner, and the wall reflection noise is superimposed on the transformer noise to increase the noise.
3) The original use of oil changes, after changing to dry, will affect the noise of the transformer. The reason is that the crude oil chamber is relatively small, and there is an oil spill chamber and a leak hole. The transformer is placed on a speaker.
Solution: Some sound absorbing materials can be added to the room.
5, the problem of busbar bridge vibration
Cause: Due to the large current passing through the side-by-side busbar, the busbar is vibrated due to the leakage magnetic field. The vibration of the busbar bridge will seriously affect the noise of the transformer, and the noise of the transformer will increase by more than 15dB. It is difficult to judge. The general user and the installation unit will mistake the noise of the transformer.
Judgment method: 1) The noise changes with the load size.
2) Use the wooden stick to force the top busbar bridge. If the noise changes, it is considered that the busbar bridge is resonating.
3) The busbar vibrates in the bridge, and it is useless to use the top of the wooden stick. Need to open the busbar bridge cover and check if the busbar is fixed.
Solution: 1) Mainly to destroy the condition of the busbar bridge resonance, tight or loose hanger screw.
2) Open the busbar bridge cover and fix the busbar.
3) The low voltage outlet uses a soft connection.
4) Please ask the manufacturer of the busbar bridge to solve it.
6, the transformer core itself resonance
Cause: There is an electromagnetic attraction between the seam of the silicon steel sheet and the lamination due to magnetic flux leakage.
Judgment method: 1) The transformer noise is too large, and other noise is mixed in the normal noise.
2) The transformer noise is wavy.
Solution: 1) Tightening the screws on the transformer, including the two screws of the clamp, the threading screw, and the spacer screw.
2) Add a shockproof rubber pad under the transformer trolley to solve some noise.
7, the transformer coil itself resonance
Cause: When a load current flows through the winding, the leakage current generated by the load current causes the vibration of the winding.
Judgment method: 1) The transformer noise is too large and the noise is relatively low.
2) When the load of the transformer reaches a certain level, noise starts to appear, sometimes there is no phenomenon when it occurs.
Solution: 1) Tightly press the spacer screw to increase the axial pressing force of the coil.
2) Loosen all the screws of the pad and loosen the bolts on the copper bar and the copper bar of the neutral wire. Shake the low voltage coil, translate the high voltage coil by 3 to 5 mm, and tighten all the bolts.
8, the nature of the load
Cause: The transformer's voltage waveform is distorted (such as resonance) and noise is generated.
Judgment method: 1) In addition to the noise of the transformer itself, the noise is also mixed with "giggle, clucking" noise.
2) During the operation, the transformer noise will suddenly increase and become normal again.
3) Check if there is a rectifier device and a frequency conversion device in the load.
Solution: Users can consider adding a device that reduces harmonics.
9, the problem of transformer phase loss
Cause: The transformer cannot be properly excited and produces noise.
Solution: 1) The transformer is powered off, check if the power supply lacks one phase;
2) Check if the transformer high voltage fuse blows a phase;
10. Problems with poor contact
Reason: First, it is caused by poor contact in the high voltage cabinet. Second, the knife gate is not in place.
Judgment method: The transformer sends out intermittent abnormal noise.
Solution: 1) Check the contacts and fuses of the high voltage cabinet and the entire high voltage circuit.
2) Please check with the person of the high voltage cabinet manufacturer.
11, the problem of floating potential
Reason: The components of the transformer, such as the channel steel, the nail bolt, the pull plate, etc., are sprayed with blue paint. The contact of each component is not very good. Under the action of the leakage magnetic field, a floating potential discharge is generated between the components. .
Judgment method: The suspension potential discharge emits a very slight "beep, bang" sound, which can be heard carefully. The user often mistakes the transformer for high voltage or low voltage discharge.
Solution: 1) This discharge will not affect the normal operation of the transformer.
2) It is possible to scrape off the paint in a bad place during power failure maintenance and make the parts of the transformer contact well.
12, the low-voltage line is grounded or short-circuited
When the low-voltage line is grounded or a short-circuit accident occurs, the transformer will make a loud sound; the closer the short-circuit point is to the transformer, the more obvious the sound; if the short-circuit point is close to the transformer, the transformer will make a roar like a tiger.
13, the transformers are compared with each other
It is generally believed that transformers of different manufacturers, different types of transformers, and different environments of use will make the noise of the transformers different.
14. The problem of understanding dry change
Reason: Some users have used oil change before, and they have a deeper understanding of oil change. For the first time, they contact dry-type transformers. They think that the noise of dry change and the noise of oil change should be the same.
Solution: In fact, the noise of the oil is also very large, but the inside is filled with oil, and a sealed iron shell is added outside, and the sound cannot be transmitted. The dry core is exposed, and a little sound will come out. Noise is an inherent characteristic of a transformer, and the amount of noise does not affect the quality of the transformer.
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