does this brilliant idea of mine violate any code sections or UL listing?

[weressl]

i posted a thread here a few days ago, about a VERY noisy
300 kva xfmr, actually several of them...... nema 1's,
in electrical rooms.

now, this sunday, i'm downing them for PM, megger,
torquing, vibration pad inspection, etc.

assuming there is nothing mechanically or electrically
wrong with these xfmr's, and the noise is just lamination's
fluttering, and that is not something that is solvable without
replacing the xfmr's.... here is my idea....

there is a product called mass loaded vinyl, that is a nonconductive
rubber sheet weighing about 1 lb per sq. ft. it comes with a 1/4"
foam backing, and you attach it to a surface by the foam, so the
vinyl is floating 1/4" above the surface, and not mechanically coupled
to it except by the foam.....

cover the exterior of the transformer case with this, leaving all air
vents, slots, and whatnot uncovered, so that the sheet metal case
and front and back covers are covered with this product, to dampen
sound.....

this stuff has a greater sound isolation than lead sheets of the same
thickness, and is nonconductive, and i'm wondering if, as it is outside
of the enclosure, it would compromise the UL listing of the xfmr?

you still will have airborne sound coming out the vents, but i'm guessing
a huge amount of it would be dampened....

whatchoo guys think?

the stuff is NOT cheap, but it sure does work.... i used it in a sound
studio, and it rocks. nothing much goes thru it.

Couple of thoughts:

• you are modifying the equipment and potentiall violating it's listing, so NEC may frown on that.
• the transformers are tested and the conductive case also acts as a heat-shink, so it contributes to the heat removal even though the majority of the heat removal by air-convection via the vent holes largely remains as designed.
• the insulating material that you intend to use as a sound buffer has temperature limitation and as it ages and deteriorates it COULD fall on the core and winding, causing it to overheat and could be a fire hazard.

 

[Fulthrotl]

Couple of thoughts:

• you are modifying the equipment and potentiall violating it's listing, so NEC may frown on that.
• the transformers are tested and the conductive case also acts as a heat-shink, so it contributes to the heat removal even though the majority of the heat removal by air-convection via the vent holes largely remains as designed.
• the insulating material that you intend to use as a sound buffer has temperature limitation and as it ages and deteriorates it COULD fall on the core and winding, causing it to overheat and could be a fire hazard.

that's why i wouldn't put anything INSIDE the case, just externally, to dampen panel resonance...

when all else fails, ask the people who built it... so i did....
factory is located in comerce, calif. and i gave them a call
and spoke with one of their engineers.... his thoughts:

check first input voltage, if it's high, the xfmr will get *really* loud.
the core is clamped. not bolted or riveted.
sustained high voltage for extended periods can loosen the clamps.
tightening the clamps unevenly can warp the stack, and cause it to sing louder.
dirty input power can make it sing on a second or third harmonic.
dynamat can keep panels from resonating, and will not violate the listing,
if used on the outside of the case, and not covering any vents.

they have had occasions where transformers were damaged to the
point of replacement by excessive voltage. not field reparable.

a 300kva weighs 1,600 lbs.

for the acoustically interested folk who have chimed in here,
there is a company called studio six digital, in boulder colorado,
that have a whole suite of iphone and ipad apps for sound engineers....
professional grade stuff..... decay rates, spectrum analysis, etc.

 

[Joethemechanic]

Is that in the listing or labeling?



Now have some fun, call me a code Nazi, but if you are planning on inspections you better know the code sections the inspector could come up with.

Would you fail a transformer that had a damaged piece of the enclosure replaced with a locally fabricated replacement part?

personally though I think if the laminations are moving enough to make noise, they are moving enough to wear the coating off of the faces. Once they develop enough shorts between the laminations, they are going to be full of eddy currents in the core anyway and if the trans is pushed to near capacity it could overheat.

There is a reason the lamination pack is made that way, if the iron core was a solid piece of plate, or a big casting, the transformer would overheat.

Personally I cringe when I see an electric motor get put together roughly and just the edges of the laminations get a little banged up.


Now if it was my transformer, I'd keep my eye on it, and watch the temp, especially on heavy usage days. But a customer is never going to do that.

I sure would sleep better with a couple of stiffeners fabbed up out of 2 x 2 by 1/8" angle, then I would with some kind of thermally insulating coating. (that is also flammable)

 

[Fulthrotl]

well, first and foremost is to make sure the things are safe with a meggar, and nothing is loose
mechanically.

i'll post what i find, and toss in some photos.... thanks again for the thoughts.

i'll get some photos up, but everything meggers good.

the one thing that i did find out of kilter was one of the 300 KVA units,
the core, which is clamped, and tight, is skewed, as in twisted.

it's a 24" x 30" core about 6" thick. the left hand side is pretty close to plumb,
if you measure the top of the lamination's, they lean forward about an inch
towards the front of the enclosure, going from bottom to top.

the right hand side is out of plumb going the other way, 2 1/2".

so if you were to lay the laminations flat on a surface, it's look like a
potato chip, the top is twisted out of a flat plane an inch on one side
and 2 1/2" on the other side.

back to the engineers who manufacture this tomorrow morning, for
a course of action.... straighten it, leave it alone, replace it?

i know how i can straighten it, if it needs it, but i need something from
the manufacturer in writing before i take my liability insurance out for a
test drive.

 

[jim dungar]

If it is twisted, the laminations no longer line up as they were designed to, if they do something there is a bend or bulge where you can't see it. Imagine 'twisting' a deck of cards while keeping all of the edges lined up.

 

[Fulthrotl]

If it is twisted, the laminations no longer line up as they were designed to, if they do something there is a bend or bulge where you can't see it. Imagine 'twisting' a deck of cards while keeping all of the edges lined up.

imagine more like clamping the bottom of the deck in a vise, and twisting the top of the deck counterclockwise,
viewed from the top, and doing it unevenly, so it only moves an inch on the left side, and 2.5" inches on the right
side..... the bottom seems to be in line with original placement. the top is kaddywompus.

 

[jim dungar]

imagine more like clamping the bottom of the deck in a vise, and twisting the top of the deck counterclockwise,
viewed from the top, and doing it unevenly, so it only moves an inch on the left side, and 2.5" inches on the right
side..... the bottom seems to be in line with original placement. the top is kaddywompus.

My point is, there is no way to twist a transfromer core without 'unaligning' the laminations which could be a mojor source of the increased noise. FWIW, can you get temperature measurements of the core which can be compared to factory design specs?

 

[Joethemechanic]

imagine more like clamping the bottom of the deck in a vise, and twisting the top of the deck counterclockwise,
viewed from the top, and doing it unevenly, so it only moves an inch on the left side, and 2.5" inches on the right
side..... the bottom seems to be in line with original placement. the top is kaddywompus.

Have these transformers spent any considerable amount of time out of service? And then returned to service?

 

[ritelec]

Fulthrotl.........Do you have stock or some other vested interest in this company?

Trying to do our best for the costumer and sometimes overextending ourselves to do so and maybe message our ego is one thing......But why are you trying to be a hero?

With all respect....just curious.

 

[ramsy]

......But why are you trying to be a hero?

Being an extraordinary-individual or talent is part of Western culture. All the latest Hollywood movies are spawning heroes, "Captain America", Green Lantern, Thor, etc.. How can you ask suck an obvious question. Don't you remember, "Roger ramjet, he's our hero".

You must admit, thinking outside the forum box, bringing in OEM support could find alternatives to equipment replacement. Its a brilliant way to save customer costs / bill cheep customers / promote your service excellence, and some of us are quite interested in how this story ends.

 

[Joethemechanic]

Fulthrotl.........Do you have stock or some other vested interest in this company?

Trying to do our best for the costumer and sometimes overextending ourselves to do so and maybe message our ego is one thing......But why are you trying to be a hero?

With all respect....just curious.

What's the difference?

Maybe he likes the guy and the guy is a little strapped for cash in this economy.

Maybe it's a friend in a start up company that has to watch his pennies.

Or maybe he's doing it just to prove it can be done to some idiot who said "you can't fix that"

One of my personal reasons for fixing stuff like that is it's educational. If you just replace it, what did you learn? Any idiot can replace a transformer another equivalent unit. At most what is there, 24 leads, maybe a couple tap choices for fine voltage adjustment? That ain't exactly rocket science. I can guarantee you this. He's a better transformer man now than he was a week ago.

 

[iwire]

One of my personal reasons for fixing stuff like that is it's educational. If you just replace it, what did you learn? Any idiot can replace a transformer another equivalent unit. At most what is there, 24 leads, maybe a couple tap choices for fine voltage adjustment? That ain't exactly rocket science. I can guarantee you this. He's a better transformer man now than he was a week ago.

DIYs can do anything.

 

[hurk27]

DIYs can do anything.

An't that the truth

"Where's the duct tape":lol:

 

[Fulthrotl]

Fulthrotl.........Do you have stock or some other vested interest in this company?

Trying to do our best for the costumer and sometimes overextending ourselves to do so and maybe message our ego is one thing......But why are you trying to be a hero?

With all respect....just curious.

why, shallow self serving ego needs are the driving force, of course... thanks for asking.

the main reason is simple. i was asked to take a look at it, and come see if what
the building manager was told by the FIRST electrician was true... that it was
going to blow up within a year, and they needed to replace it NOW, for a five digit number.

understand, the person making this proclamation had neither looked inside the can, or
powered it down for any kind of diagnostic testing at all.

so, i'll see what it'll take to make it right, and tell them the truth. i charged them a fair
wage for the work i did today, and i will give them a fair quote to do what seems the
best course of action, whatever that turns out to be.

i solve people's problems. that is what i earn my living doing.

what was the first electricians job? to make my customer grateful for being told the truth.
used to be his customer. that may have changed.

 

[iwire]

BTW, my DIY comment was not aimed at Fulthrotl, he is a professional electrical contractor.

 

[iwire]

i solve people's problems. that is what i earn my living doing.

And by reinventing the wheel to look like a hero it is possible you create more problems than you solve. (JMPO, you did ask on a public forum)


FWIW I have installed GE transformers that had regular sound insulation lining the inside of the enclosure but they also had cooling fans and overtemp alarms.

 

[Fulthrotl]

??????

??????

to whoever censored all the posts, if it's that big a problem,
just delete the thread.



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[roger]

to whoever censored all the posts, if it's that big a problem,
just delete the thread.

That would be me and I would rather just see if the conversation can continue in a civil manner.

Roger

 

[cowboyjwc]

That would be me and I would rather just see if the conversation can continue in a civil manner.

Roger

Roger, now you're just being silly.

I know, deleated, Off topic.:angel:

 

[roger]

Roger, now you're just being silly.

I know, deleated, Off topic.:angel:

Miracles do happen.

Roger