Dry Type Transformer Sound Level
Dry Type Transformer Sound Level
(OP)
I have a 75kVA dry type transformer. 480v:120/208v, wye-delta configuration. The transformer is one of two installed as part of a recent project, and is appreciably louder than the other transformer on the project.
When I measure the sound pressure level of the room with the 'noisy' transformer I obtain a 70dBA reading. When I measure the sound level of the room with the other transformer, I obtain a reading of 70dBA also. Based on how I read NEMA ST-20 it appears that both transformer installations are compliant with this standard for overall sound pressure levels.
Yet, when I do a spectral analysis of the sound, at the 125Hz range the sound level is 68dB for the 'noisy' transformer and 42dB for the 'quiet' transformer.
Both transformers are feeding the same types of loads (A mix of coffee pots, computers, refrigerators, copiers, incandescent lights, video monitors, etc. for a med/surg area in a hospital.) Both transformers are 30% loaded.
My acoustical engineer indicates that I should expect to see the most noise in the 125Hz range. Why is that?
Any thoughts as to why one is 'louder' than the other?
Thanks!
When I measure the sound pressure level of the room with the 'noisy' transformer I obtain a 70dBA reading. When I measure the sound level of the room with the other transformer, I obtain a reading of 70dBA also. Based on how I read NEMA ST-20 it appears that both transformer installations are compliant with this standard for overall sound pressure levels.
Yet, when I do a spectral analysis of the sound, at the 125Hz range the sound level is 68dB for the 'noisy' transformer and 42dB for the 'quiet' transformer.
Both transformers are feeding the same types of loads (A mix of coffee pots, computers, refrigerators, copiers, incandescent lights, video monitors, etc. for a med/surg area in a hospital.) Both transformers are 30% loaded.
My acoustical engineer indicates that I should expect to see the most noise in the 125Hz range. Why is that?
Any thoughts as to why one is 'louder' than the other?
Thanks!






RE: Dry Type Transformer Sound Level
Eng-Tips: Help for your job, not for your homework Read FAQ731-376
RE: Dry Type Transformer Sound Level
RE: Dry Type Transformer Sound Level
Iron expands and contracts (slightly) in varying magnetic field.
If transformers are identical and one is louder than the other, the location and what it is sitting on may be big factor.
If it's an issue, there are various rubber gizmos available for isolating the transformer from what it's sitting on.
RE: Dry Type Transformer Sound Level
RE: Dry Type Transformer Sound Level
RE: Dry Type Transformer Sound Level
Especially in hospital applications, we specify as quiet an installation as we possibly can. This being a 'recent' project, I would look at the specifications and see if a sound level was specified, because it sounds as if the installation is not quite up to par. Is there installation details/specifications where isolation may have been covered?
It would be interesting to know what you discover. Good luck and keep us posted.
RE: Dry Type Transformer Sound Level
Loose/tight
Different chemical content & mechanical properties.
We have a different sound from three Toshiba Transformers (130MVA, 230/33kV), caused by the material for the core coming from different sources.
RE: Dry Type Transformer Sound Level
To date we have determined that the shipping anchors were released and the conductors were properly terminated within the transformer housings. Since these measures were verified and the transformer appears to be operating within NEMA standards, I am tending to conclude the difference in noise is due to differences in manufacturing.
Regards!