buzzing welder transformer?

Grant, I used to make those things back in the 60's. The stock solution is to add another wedge. Wedging was the normal way to tighten the laminations. Bolting can be used, but not knowing the type of steel or thickness of the lams, I'd also be afraid it might mess up the excitation current of the transformer, if you used a metal bolt. It's kind of like adding a magnetic shunt, and might or might not screw things up some. (probably not much, though).

So, since it's so big a hole and it doesn't take much pressure to stop the buzz, if you want to bolt it and not mess with the eddies, use a phenolic "bolt".

LLoyd

I wouldn't use a metal bolt. Can you track down a nylon bolt the right size? Or use a tie-wrap through the hole?

Bob

"Bob" wrote: I wouldn't use a metal bolt. (clip) ^^^^^^^^^^^^^^ If I understand, the reason for laminated cores is to cut down on eddy currents. If you run a metal bolt through the hole, even insulated, it could take away a little of the transformer power and turn it into heat. I wonder whether it would be enough to notice. Why not just try it? (I don't think insulating the bolt matters.)

Looks like nylon bolts long enough are pretty scarce. What about brass? I don't think there's an electrical issue here, only magnetic.

Grant

The magnetic field will still induce eddy currents in the brass bolt.

Am I missing something here????

Does anyone here own a lathe? Taps, dies, scrap nylon rod, scrap lexan rod, etc...

Even easier, and just as safe: Get yourself a "plain old" screw/bolt that fits, with nut to match, stuff it through, and crank it down tight, but not tight enough to deform the lams. Task complete.

The lams see magnetic fields, but no electricity, aside from maybe some insignificant eddy currents that would be conducted plate-to-plate through the lams anyway, so insulation or lack of it on the bolt is irrelevant. (or bolts, since I'd bet on a matching set of holes on the opposite corner, if not all three other corners, and being a "might as well do it while I'm already in here" kind of guy like I am... Do I need to continue? :) )

I've also seen them (performing flawlessly for years after the procedure) with an owner-added fine bead down each corner of the stack, just rounding the corners and locking the lams together wonderfully. Buzz? What's that? :)

How long a nylon bolt do you need? I have seen 3 foot nylon allthread and have 3 inch nylon bolts. Glenn

Cut yourself another thin wedge and tap it into place... it'll quiet right down. Ken.

The whole transformer has been dipped in varnish, essentially potting it. It would be difficult to crack the coil loose enough to get a wedge in there, otherwise I'd do this.

Miller tech support told me to go ahead and put a steel bolt through the hole, that's what they're there for. I have it all buttoned back up again but will look soon (maybe later tonight) to see how long a bolt should be in case I decide to try a nylon one.

Grant

Another old trick for noisy transformers - Pour some airplane dope in the core crack. Varnish will likely work as well.

Martin

Martin H. Eastburn @ home at Lions' Lair with our computer lionslair at consolidated dot net NRA LOH & Endowment Member NRA Second Amendment Task Force Charter Founder IHMSA and NRA Metallic Silhouette maker & member

Lloyd E. Sp>

^^^^^^^^^^^^^^^^^^^^ Bingo! ^^^^^^^^^^^^^^^^^^^^ (clip) in case I decide to try a nylon one. ^^^^^^^^^^^^^^^^^^^^ Still thinking nylon? Miller's word isn't good enough?

Don't use brass. You want a high resistance. Do use a mild steel bolt, preferably insulated say with some varnish to keep down eddy currents. But not a big deal. You are using 60 hertz, not 60 kilohertz. Adding the steel bolt will help in that it will add slightly to the core and more core is better than less. So in my opinion steel bolt is better than nylon.

Dan who designed transformers many decades ago

Grant Erw>

I've probably seen many hundreds of power transformers mounted with steel screws going thru the corner holes, but not as many actual welding transformers.

Mounting transformers with steel screws is a widely accepted method. Many times the screws hold 90 degree angle brackets (also steel) for mounting the transformer frame/core perpendicular to a metal mounting surface (aluminum, steel) with no apparent issues from current or heat.

I believe the synthetic washers that are sometimes used with mounting screws is more of a choice for compensating for thermal cycling of the steel part (screw, bolt) related to expansion and contraction properties of the mounting hardware. I've also seen many mounting nuts that use keps nuts (nuts with integrated multi-toothed washers) that intentionally pierce the varnish, so conduction is not considered to be an issue, IMO.

One way to find out would be to stick a piece of copper wire thru the hole and take some measurements, while proceeding cautiously to be careful of all electrically hot terminals.

WB ..............

Grant Erw> I have a main transformer in one of my welders that's just starting to buzz. I

The magnetic field "shakes" electrons. There are free electrons in all metals - else they wouldn't be conductive! So alternating magnetic fields will induce eddy current in any metal.

Richard S.

I was a bit non plussed about that myself.....

Gunner

"I think this is because of your belief in biological Marxism. As a genetic communist you feel that noticing behavioural patterns relating to race would cause a conflict with your belief in biological Marxism." Big Pete, famous Usenet Racist

Mechanical bracing is likely only a temporary fix. Remove the trans and take it to a industrial elec. motor repair shop and have them dip it in their varnish tank and bake it. If they can do vacuum-pressure impregnation, even better. This will fill all the open cracks and loose joints with solid insulating material and is a permanent fix.

Randy

And thus the reason to have laminated plates as a core of the transformer. Simply to keep eddy currents from flowing. The plates are insulated from each other by oxide, paper, and dope/varnish.

Martin Martin H. Eastburn @ home at Lions' Lair with our computer lionslair at consolidated dot net NRA LOH & Endowment Member NRA Second Amendment Task Force Charter Founder IHMSA and NRA Metallic Silhouette maker & member

Richard Smith wrote:

Wild Bill has the idea - put a wire thru and measure the voltage (first) then if nil try the ammeter on high current at first.

But considering the hole is not in the magnetic field section of the core - a Winding doesn't cross over it or is in line with it.

Transformers mount to chassis using corner holes every day. The only ones that don't are molded in plastic or are in MIL spec oil or wax filled cans. High rel cans. Then the can has studs.

Martin

Martin H. Eastburn @ home at Lions' Lair with our computer lionslair at consolidated dot net NRA LOH & Endowment Member NRA Second Amendment Task Force Charter Founder IHMSA and NRA Metallic Silhouette maker & member

Wild Bill wrote: