Transformer Noise

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I Have A 75 Kva Transformer That The Humming Is Getting Louder. Doesn't Have Any Real Loads.
It Is Loud Enough In A Production Area, That It Is Anoying People.
What Causes This?
 

SEO

Senior Member
Location
Michigan
Some transformers come with shipping restraints inside the transformer, read the installation instructions with the transformer.
 

acrwc10

Master Code Professional
Location
CA
Occupation
Building inspector
some transformers are just loud. we relocated one last year that had -0- load on it and was humming very load. it was also a 75kva.
 

beanland

Senior Member
Location
Vancouver, WA
Transformer Noise

The core of a transformer changes size with the magnetic flux inside it. The normal noise is 120Hz, 240Hz, 360Hz, etc. The sound level is proportional to the voltage. As the voltage increases, the flux in the core increases, the core vibration increases, and the sound output increases.

Change the primary tap on the transformer to a higher voltage to reduce the flux in the core and the sound will reduce.

Parasitic vibrations occur when the enclosure, mounting parts, etc. vibrate with the core. These need tightening or sound damping material applied.

The sound level DOES NOT vary with transformer loading, except to the extent that supply voltage varies with loading.
 

tyha

Senior Member
Location
central nc
there are two bolts in thefront and rear of the transformer that bolt the core to the frame. loosen these bolts and it should dampen the noise
 
beanland said:
Don't go messing around with core clamping and securing hardware. That violates the UL label and the warranty.

Tightening such hardware is a manitenance function, changing them would be the violation. So go right ahead, thighten them suckers.......:D

The noise WILL increase with time and also could increase with varying load since the transformer components will experience thermal expansion with increased currents.
 

Ragin Cajun

Senior Member
Location
Upstate S.C.
Timely thread. Just came today from a school where two 225 KVA transformers were on the noisy side, especially one. I've heard much worse. Didn't think these two were worth replacing or worrying about. Will have to check if there are shipping restraints, etc.

Thanks,

RC
 

eric9822

Senior Member
Location
Camarillo, CA
Occupation
Electrical and Instrumentation Tech
I had a similar problem a few months ago with a 45KVA transformer, the noise level doubled over the course of about two months. I de-energized it and opened it up to have a look and found that the bolts securing the core support to the frame had loosened and the core had shifted to one side. The frame supporting the core had come in contact with the sheet metal cover which caused the normal vibration to be amplified. I shifted the core over and retightened the fasteners. I suggest you open it up and take a look.
 

brian john

Senior Member
Location
Leesburg, VA
The bolts in question are shipping bolts to hold the core secure and are to be lessened per the manufacture.

Some transformer are loud due to.

Shipping bolts as noted.
Housing covers to tight to loose.
Not sitting flat on the floor or pad.
Core issues, delaminating.
Harmonic loads non 60 cycle hum as mentioned.

Manufactures do make defective products.

What I would do.

use a disturbance analyzer.
TTR
megger
load bank with resistive load.

Of course all this depends on the cost of the transformer.

AND YOU ARE WRONG
I'm surprised that nobody has already pointed this out ---
Because it doesn't know the words

It likes to hum just has the wrong beat.
 

TwinCitySparky

Senior Member
Location
Minnesota
peter said:
I'm surprised that nobody has already pointed this out ---
Because it doesn't know the words

~Peter


Oh man. I thought we were all going to resist temptation...



Just this one time...??!!




Guess not. :roll: :grin:
 
peter said:
I'm surprised that nobody has already pointed this out ---
Because it doesn't know the words

~Peter

Actually they did, even though not in such elaborate detail. What, I think, was not pointed out that dependent on the transformer mounting the noise could be amplified. Elastic mounting dampens the noise.
 
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