Humming sound in Dry type Transformer

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Laminations , wire, cable busbars all vibrate to produce a humming sound

I do as well but with me its because I've forgotten the words...

John.

Depending on age, it could be the windings, insulation failure,or something loose, mounting bolts inside the enclosure or even the rubber mounts could be deteriorated and not insulating the sound prperly its an older unit.

I had a new transformer installed about 6 months ago and it was loud new out of the box. I took a look into the manufacturers specifications and they listed the sound rating ranges for the different size transformers they manufacture.

We turned everything else off in the room, and measured the tranformer DB noise, it was over the specified limit. Square D provided a replacement transformer and we changed it out. Another new equal transformer in the same room was within normal limits and had no problem.

Another reason they hum is they don't know the words.

If it hums softly, it's happy. Transformers do that.

If it hums loudly, it's trying to tell you something.

If it crackles, it's too late.

Some humming noise is natural, due to the magnetostriction (according to the changes of the magnetic field the size of the iron core changes). In addition, the loosen parts of the transformer also can produce humming sound.

Magteostriction

If you can find one that doesn't then please let me know.

Dear Sir,

We have total 8 numbers of such type of transformers mouted on ship to shore cranes and air cooled, dry type transformers(make ABB). Ratiangs are 1200KVA and 250KVA.Only one of the 250KVA is giving humming sound, infact it just started giving such sound All others are almost quiet.

Regards,

Syed Ziauddin

My guess would be magnetic forces between windings and between core laminations.