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Power transformer noise and how to reduce it

Even though the noise generated by a power transformer cannot be eliminated, it can be reduced through proper design and assembly, and/or masked through appropriate consideration of the installation.

The basic cause of transformer noise is Magnetostriction, which is the expansion and contraction of the iron core (laminations) due to the magnetic effect of alternation current flowing through the transformer coils.

The fundamental sound frequency is twice the power line operating frequency of the transformer (i.e., a 50 Hz transformer produces sound at 100 Hz and a 60 Hz transformer produces sound at 120 Hz). In addition to the fundamental frequency, harmonics are also produced.

The average office environment is about 50 decibels making the location of a 300 KVA transformer in such an area very likely to produce complaints. The 5 decibels (50db vs. 55db) difference between the normal office ambient sound level and the maximum sound level of the transformer may seem minor; but it should be kept in mind that a 3 decibel increase in sound level measurement represents a doubling of the actual sound level, so the 5 decibel increase becomes significantly bigger.

It is evident that even a well-designed transformer can present a problem if it is located without consideration of its surroundings. Transformer noise can be brought under control through proper installation.

The following guidelines will help assure you of an acceptable installation.

  1. The maximum sound level of the transformer should be compared with the projected ambient of its location. The unit should be relocated if it is higher than it's estimated ambient.
  2. When installing transformers in areas such as office buildings or motels, plan to have at least one "non-people" room between the transformer and "people areas".
  3. The mounting surface for a transformer should not increase the sound level. The mounting base (such as a concrete floor) should weigh at least 10 times as much as the transformer.
  4. A corner location should be avoided since the sound will be reflected out into the room.
  5. The unit should not be mounted on thin walls, such as plywood or curtain walls as they intensify the sound.
  6. The manufacturer's installation instructions should be followed so that any vibration suppression devices incorporated in the transformer design are used.

All Acme transformers operate at sounds levels below NEMA standards and each unit 30 kVA and larger, is shipped from the factory with vibration isolation pads to help ensure the quietest installation possible. Encapsulation greatly suppresses noise in units under 30 kVA, and vibration isolation pads are not required.

Reference:

ACME Electric FAQ

About Sonobex

Sonobex design and produce next generation noise reduction solutions with our patented technology for applications in Acoustic Barriers, Enclosures and bespoke engineering designs.

Our sectors include:

  • Power & Distribution Transformers
  • Compressors and Pumps
  • Gas Turbines
  • Extraction Units
  • Industrial Engineering Applications