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Fixing a Noisy Transformer

04/17/2009 8:59 AM

If the laminations in one or two identical transformers of many are vibrating enough to be annoying, would it be reasonable to apply some form of lacquer or epoxy in the exposed edge of the laminations? What kind, if any, would be best for the job? Or would it just be better to buy a replacement transformer?

The application is for heavy duty battery chargers for fork lift trucks.

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#1

Re: Fixing a Noisy Transformer

04/17/2009 2:07 PM

I once fixed a transformer in an audio amp by unwinding it, fixing the problem and rewinding it by hand.

I did coat it very heavily with a spray that was made specifically for coating transformers which I can't locate online now. I don't recall where I got the stuff (before the internet) but it had a red tint to it and came in a spray can like spray paint. I found this stuff which claims to be for many things, transformers are in the list, but doesn't look anything like what I used. I also found a link to some other stuff.

The stuff I used worked well but took about a week to dry enough for the buzzing to stop. Sorry I can't find a link to the stuff I used, but its out there, or at least it used to be.

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#2

Re: Fixing a Noisy Transformer

04/17/2009 4:58 PM

If you have laminations that are stuffed, I would recommend heating the transformer (or use vacuum insertion techniques) and then apply a slow dry "epoxy". Vibration of a tranny needs to be taken care of as it may lead to wear and shorting of the affected coils. Cooling of the transformer (or equilibration to atmospheric air pressure) will then "suck" the "epoxy" into the laminations and also the copper windings as an added bonus. This is a specialized process, with attention to temperature etc and "epoxy" type etc.

No amount of spraying the outside of a transformer without some type of forced injection into lamination layers will solve vibration problems in the long term.

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#3

Re: Fixing a Noisy Transformer

04/17/2009 11:48 PM

If you have access to the transformer and can remove it and dip it into a transformer varnish vacuum impregnation tank and bake it = best.

How to do this? Take the transformer and make sure you have marked the wires with metal tags to a small motor repair shop.

They have small vacuum tanks and can, heat, dip and bake it for a fee.

Vaccuum impregnation can be done by yourself if you have a tank that will withstand vacuum. Preheat the transformer to 50C, place the tranformer in the tank, cover with transformer varnish and draw the vacuum. Leave vacuum on for an hour, then vent and lift out the transformer to drain for a few hours. Then bake it at 60C for 8 hours in a vented oven with exhaust. The motor rewinder will have all this in his shop = easier then making it yourself. Use of the Kitchen stove for all these steps = imminent bachelorhood, the judge wll grant decree nisi in a heartbeat...

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#4

Re: Fixing a Noisy Transformer

04/20/2009 12:58 PM

For larger transformers that are not encapsulated you can try the following with power down.

1) Tighten up all core bolts - as the transformer ages the core bolts work there way loose and audible noise increases.

2) Replace the damapening pads - these pads wear away over time and replacing them can reduce audible noise. The transformer get vary heavy at large kva capaties and a jack maybe required to get the transformer off the pads.

3) Make sure the shipping braces were removed when first set up - sometimes they are not removed and this will add to noise.

4) Ask the manufacture for dampening tape for the inside of the enclosure.

Keep in mind transformers are naturally loud devices because of the design, you may want to measure the audible noise to verify the transformer is loud. General Nema guidelines for transformer noise are as follows:

up to 9kva max 40db

10-50kva max 45db

51 - 150kva max 50db

151-300kva max 55db

301-500kva max 60 db

If you measure less than the stated value for your size (kva) transformer then your transformer is not loud but suggestions 1-4 still could possible help.

Transformer noise is a common complaint the transformer manufactures get when there is nothing wrong with the transformer.

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