Do’s and Don’ts to avoid loud transformer humming




We like humming bees but not humming transformers.

Ever wondered, why transformers do humming?

Wondered, but don’t know yet? Don’t worry, be with us as here we would be revealing this mystery to you.

Transformers do hum because of stray magnetic fields, which cases the enclosure and other accessories to vibrate. Another cause that leads to humming is the iron core changing its shape due to continuous exposure to magnetic fields, though minutely.

The magnetostriction is the phenomena wherein the pieces of magnetic sheet steel extend itself slightly when magnetized. The alternating current flowing in the transformer makes the core to expand and contract to make the transformers hum.

The stray magnetic fields, however, can be limited by good designing and using quality material, besides good workmanship, and so could be the iron core changing its shapes in the core can be limited by good designing and using quality material. Thus, both can be limited/restricted to reduce the transformer humming.

Good assembling during manufacturing, proper installation using good rubber pads and providing a good enclosure are few of the measures generally take to reduce the humming noise by the users and the installers.


What are the best practices of transformer installation?

The best transformer installations drastically reduce the noise and the humming. Therefore, it’s an area which needs to be supervised properly to enjoy good surroundings with restricted humming after installation. The following practices lead to a good installation.

  1. It’s a good practice to install the transformer in an isolated area away from the sitting area of people.
  2. The transformer should be installed in an enclosed non-people room to limit the hum and keep the noise away.
  3. The mounting ground should be properly made to prevent it from amplifying the humming sound level. The best practice is to mount the transformer on a concrete floor weighing a minimum of ten times the load of the transformer.
  4. As the side walls reflect back the humming noise, therefore it is advised to avoid installing transformers in the corner area of the room.
  5. The thin walls amplify the noise to a great extent; therefore, the curtain walls or the plywood walls should be avoided to install a transformer on them.
  6. The vibration suppression devices, as mentioned in the installation guidelines, should be followed properly to prevent noise during operation and the lifecycle of the transformer.
  7. Isolation pads do reduce the noise and should be used during installation to keep the noise under check.
  8. The noise is greatly suppressed by providing encapsulation and thus should be used wherever feasible


What are the guidelines to be looked into while procuring a transformer?

It’ advisable to go for transformers with sound levels operating below NEMA standards, with good manufacturing facilities, state-of-the-art plant set up and which are certified for quality standards while it comes to using quality material, assembling, inspecting and testing. A good reputed, the branded manufacturer, cares for all.

In case you are going for installing the transformer in some public area such as market, residential apartments, high rise towers, shopping malls or gardens etc., it’s always better to order transformer as per your requirements of correct noise level rather than procuring a wrong transformer with higher noise and then keep struggling with it during its entire life to keep the noise under control.

  1. Reducing the flux density of the transformer during manufacturing results in reduced noise, but that costs you more.
  2. Good joints, consistent thickness, rugged supports, limited bolts and a good enclosure results in better transformers with reduced noise levels throughout life.
  3. A good isolation provided between the isolating core and the coils helps a lot in keeping the humming low.
  4. Using proper screen and bushes contributes a lot in controlling the noise level to a good extent.
  5. A complete enclosure made up of brick, concrete and steel with a high mass/weight ration reduces the noise level significantly by 25-30dBA.
  6. Prefabricated concrete block is a preferable option to reduce the noise level in comparison to mason enclosures, as it provides the flexibility to demount it in case required at a later stage.
  7. Limp panel technique provides a 15-20dBA noise reduction in addition to providing the convenience of demounting it as and when required. It is one of the commonly used technique where a small noise reduction is desirable.
  8. It’s always advisable to keep the transformer enclosure isolated from the transformer base. There should not be any physical contact between the base and the enclosure to prevent the noise. In the case of finding it difficult to achieve, it’s better to redesign the enclosure rather than keep trying to manage the noise throughout the transformer life.
  9. Connections, Cables and other accessories should be flexible and not fixed while connecting the transformers either to the electrical panels or directly to the load.
  10. Bushings tend to vibrate and require special protection to keep noise at bay, making flexible acoustic protection a must between the enclosure and the bushings.
  11. Steel plates used in enclosures should be provided with gaskets and sleeves wherever required, or better with some fillers to dampen the emerging noise from the transformer.
  12. There should not be any loose joints or connections or fastening bolts in the assembly/enclosure. All these loose elements not only make noise but also add to vibrations.
  13. Select Damping material used for damping vibrations as per the frequency of the transformer. The wrong type of damping material will not provide the expected vibrations/noise dampening.
  14. Steel plates used in enclosures should be provided with gaskets and sleeves wherever required, or better with some fillers to dampen the emerging noise from the transformer.
  15. Unnecessary bolting or stiffening received along with the shipment should be removed in consultation with the manufacturer before installing the transformer. Any useless addon left on the transformers considerably add on vibration and noise.

Conclusion – Nowadays transformers are being installed in public areas, shopping malls, commercial places, residential apartments, parks, offices or in other populace places raising the need and demand of noiseless transformers. But, manufacturing noiseless transformers is impractical and just not feasible, but what better could be achieved is to significantly adopt good manufacturing standards, quality raw material and proper installation practices to dampen the noise to the best extent to reduce the nuisance it creates to the surrounding inhabitants.

We, Servostar is an established and renowned manufacturer based out of India and is catering to entire pan India in power equipment like Servo Stabilizers and all type of transformers including isolation transformers for domestic households and other industrial applications.

We have a proven track record of supplying quality transformers and voltage stabilizers to various industries, commercial setups, residences, and the utility. We do provide consultancies services and customized transformers too.