Noisy 2MVA Cast Resin Transformer

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aggybooya

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Sunderland, UK
Hi all

Working on a query at the moment and wondering if anyone has any theories on what could be causing this.

There are 2 x 2MVA 11,000V/417V (400V) Cast Resin Transformers feeding two separate 400V LV panels.

Both transformers are running at less than half their full load capacity and the panels ultimately feed residential apartments. The transformer with the least amount of load seems to be generating alot of noise where the other Tx is sitting nice & quiet.

Checked the temperatures and nothing seems out of the ordinary.

Does anyone have any ideas what could be causing this? Could it be vibration caused by something such as harmonics? If that was the case wouldn't it be running hotter?

Out of my comfort zone a little here so any ideas or thoughts would be much appreciated.

Thanks

AT
 
I would perform a power study on both transformers. The quite transformer test results could be used as a baseline to compare the test results that are produced on the noisy transformer. At the very least, you would be able to know if there is anything strange taking place in the noisy transformer.
 
One of the specific benefits of using a cast coil transformer compared to other less expensive versions is in the fact that they are supposed to be very low noise, as in suitable for hospitals and such. If a cast coil transformer is making a loud hum, that's never a good sign in my experience. I would have a specialist, ie the manufacturer, take a look at it immediately.
 
"Transformer noise is caused by a phenomenon which causes a piece of magnetic sheet steel to extend itself when magnetized. When the magnetization is taken away, it goes back to its original condition. This phenomenon is scientifically referred to as magnetostriction. A transformer is magnetically excited by an alternating voltage and current so that it becomes extended and contracted twice during a full cycle of magnetization.
The magnetization of any given point on the sheet varies, so the extension and contraction is not uniform. A transformer core is made from many sheets of special steel to reduce losses and moderate the ensuing heating effect. The extensions and contractions are taking place erratically all over a sheet and each sheet is behaving erratically with respect to its neighbor, so you can see what a moving, writhing construction it is when excited. These extensions are miniscule proportionally and therefore not normally visible to the naked eye. However, they are sufficient to cause a vibration, and consequently noise. Applying voltage to a transformer produces a magnetic flux, or magnetic lines of force in the core. The degree of flux determines the amount of magnetostriction and hence, the noise level."

Maybe this may help and explain your noise.
 
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