Transformer for spot-welder buildup
trg-s338
transformer. I bought this long ago from eBay and have lost the
associated information for it. I intend to use this in a spot-welder
build. The plated has only the 1.2k (as best I can read it)VA and
60Hz indent stamped on it. The primary has 200, 0, 240 taps. Does
this mean single phase power lead to 240, neutral to 0, and ground to
the frame outputs the 1.2k VA? Is this suitable for the intended
build? Thanks.
Manny
[IMG]http://img.photobucket.com/albums/v429/trg-s338/eBay%20pix/
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Bob Engelhardt
> .... The primary has 200, 0, 240 taps. Does
> this mean single phase power lead to 240, neutral to 0, ...
No - one leg of 240 to "240", the other leg of 240 to "0"
> and ground to he frame ...
Yes
> Is this suitable for the intended build? Thanks.
Maybe. It depends mostly on the output voltage. A couple of volts is
good. Much more means that the 1.2kva won't be enough current, which is
the main parameter.
1.2kva is marginal, but that rating is almost certainly continuous use
and a spot welders duty cycle is so low that you can draw much more than
that. E.g., if the out is rated for 1000A at 1.2v, you could draw
2000, or 3000 amps for the second or so that a weld takes & then let it
cool while readying the next weld. The duty cycle might only be 10 -
20%. The unknown is whether your secondary winding can supply it. It
looks like it from the pictures. Do you know the guage or dimensions of
the secondary winding?
I made my spotwelder from MOT's and my output voltage is 2 volts (IIRC)
and it draws 17A at 240v, giving 4kva input and 2000A output (less core
loss). See it here:
http://www.metalworking.com/dropbox/MOTSpotwelderPrintable.pdf
Bob
RoyJ
spot welder use. But the secondary winding looks to be multiple wraps,
probably won't be low enough voltage to get the amperage you want.
Ignore the 200 terminal, hook the two hots of a 240 line to the 0 and
240 terminals, ground to the frame, no neutral, measure the voltage output.
Paul Hovnanian P.E.
See if you can post a picture of the nameplate. The little metal tag on top
in this photo:
http://img.photobucket.com/albums/v429/trg-s338/eBay pix/100_1319.jpg
Your guess about the connections appears to be correct. I usually take an
ohmmeter and check continuity (and rough resistance values) between each
pair of terminals and each terminal and the frame. Just to make sure
nothing will bite me when I hook it to 240V.
For smaller transformers, I'd put a resistance in series with the primary
for the initial power-up. The only thing that will be easily obtainable for
240V would be two 120V light bulbs in series. This will limit the energy if
there's a short in it.
--
Paul Hovnanian pa...@hovnanian.com
----------------------------------------------------------------------
Have gnu, will travel.
Denis G.
I wouldn't have thought of making a secondary winding out of aluminum
bar like that. Nice execution of the idea too!
IanM
The design can be considerably simplified. If you use a U shaped single
turn winding that fully fills the core, you will get the maximum
current output possible from that transformer. Just slide extra
transformers onto the open end of the U until the desired open circuit
voltage is reached. The secondaries are effectively in series so if the
voltage drops, reverse the primary connections on the transformer you
just added.
This removes the need for complicated machining and also reduces the
loss due to circulating currents caused by mis-matched OC voltages which
is almost inevitable if the secondaries are paralleled and the
transformers aren't *IDENTICAL*.
One arm of the U would extend to the lower arm and contact, the other
would need some sort of flexible connection to the upper arm. (This is
visible as the shiny black taped cable in the second to last picture
in the PDF which in my opinion should be a lot thicker. Pure aluminium
has approximately 1.5 times more resistivity than pure copper, therefore
to fully utilise the aluminium secondary, that connection should be
about 2/3 of the CSA of the secondary.)
I dont like the use of paint for insulation with the current capability
it has. I strongly recommend lacquered card or similar all round the
secondary where it passes through the cores and heatshrink, self
amalgamating tape or similar over the rest of it. For safety, its
probably a good idea to fully insulate *BOTH* arms from the base and
pressure mechanism so that you dont get unexpected current paths through
your workbench etc. if there is a little dirt under one tip.
I would also be inclined to split the ends of the aluminium arms and add
clamping bolts either side of each hole for the copper contacts.
Why not add an adjustable over centre toggle mechanism with a strong
return spring that trips a microswitch when it reaches its limit and is
operated by a bowden cable from a foot pedal? Think mole grips or
ratchet crimper for the sort of action required. That would give single
pedal operation for clamping and welding. You would adjust contact
pressure with the lockout switch OFF.
I think a low voltage (chosen to suit the OC voltage) torch bulb wired
across the arms near the tips (its insulated wiring can run back along
the arms to any convenient location) would add a useful indicator as it
will light brightly if the unit is energised with the tips not in
contact and while actually welding its brightness will vary inversely
with the welding current.
--
Ian Malcolm. London, ENGLAND. (NEWSGROUP REPLY PREFERRED)
ianm[at]the[dash]malcolms[dot]freeserve[dot]co[dot]uk
[at]=@, [dash]=- & [dot]=. *Warning* HTML & >32K emails --> NUL:
cl...@snyder.on.ca
How say??
The bulb will virtually go out when the contacts make contact with
the work if you are actually making a weld.. The working voltage and
the Open Circuit voltage will be QUITE different.
IanM
Well that depends on how much voltage drop there is across the workpiece
and how much in the rest of the loop. The bulb will of course be rather
dim in normal operation, but a 6V bulb still glows very noticeably on
1.5V. It would be cheap and easy to try it out. An indicator lamp wired
across the primaries would still be needed as well.
This is only a minor idea I tacked on the end of suggesting redesigning
the spot welder to put single turn secondaries in series rather than
paralleling multi turn secondaries.
Denis G.
>
> - Show quoted text -
Malcom,
To complete a turn on the secondary I think that you need to complete
360 degrees. The U-shape really constitutes a 1/2 turn. Your idea
may still work, (I haven't tried it), but I'm not sure how effective
this transformer will be.
IanM
No, a half turn would go through ONE hole in the core. You agree that
solid ring round the centre leg is a single turn shorted winding?
Now stretch out one side of the ring without breaking it. The topology
hasn't changed so this is still a single turn winding. Add another core
(+ primary) with the centre leg inside the ring and the two outer legs
outside it. You now have two single turn windings in series, but still
shorted. Now break the ring on the far side of one of the cores and you
have exactly the arrangement I propose which is the series circuit
x--Sec2A--Sec1--Sec2B--x where Sec1 is the single turn secondary of the
transformer at the base of the U and Sec2A and Sec2B are the two half
turn secondaries of the other transformer.
Incidentally, the 360 degree loop you mentioned is completed by the
workpiece. Most soldering guns use a single turn U shaped secondary and
it works nicely in that application.
Denis G.
Ian,
Sorry, you're right. I was imagining a magnetic field torus made by a
loop of wire and not taking advantage of the entire field. The
ferrite core conducts most of the field around the two loops that you
describe.
Wild_Bill
magnetic field of the core laminations doesn't extend as far as the welding
tips at the ends of the arms.
The number of full turns within the core (around the center E-section) would
be what I'd consider to be the actual number of turns.
I don't believe a *U* represents a full turn (only a half-turn).
In order for a *U* to be considered a full turn, would be if the ends
overlapped and were separated at 180 degrees. More like this, at opposite
sides of the core --o-- (passing thru the same core opening twice) or
separated at 180 degrees on the same side of the core.
This way, a full turn is fully within the field of the core.
Another pass-thru would equal 1-1/2 (1.5) turns, IMO, if the leads remain
parallel to each other.
--
WB
.........
metalworking projects
www.kwagmire.com/metal_proj.html
"IanM" <look.in...@totally.invalid> wrote in message
news:hjboe1$2mm7$1...@energise.enta.net...
pent...@yahoo.com
<wb_wi...@XSPAMyahoo.com> wrote:
>I disagree with your explanation, Ian. The majority of the strength of the
>magnetic field of the core laminations doesn't extend as far as the welding
>tips at the ends of the arms.
>
>The number of full turns within the core (around the center E-section) would
>be what I'd consider to be the actual number of turns.
>I don't believe a *U* represents a full turn (only a half-turn).
>
>In order for a *U* to be considered a full turn, would be if the ends
>overlapped and were separated at 180 degrees. More like this, at opposite
>sides of the core --o-- (passing thru the same core opening twice) or
>separated at 180 degrees on the same side of the core.
>This way, a full turn is fully within the field of the core.
>
>Another pass-thru would equal 1-1/2 (1.5) turns, IMO, if the leads remain
>parallel to each other.
Ian's explanation is correct.
The important criterion is whether or not the conductor
passes through a hole surrounded by the ferromagnetic return
path. This is easily experimentallly verified.
The conventional E + I construction has two such holes. In
the case of single turn, half of the voltage is induced in the
passage through the first hole and the second half as it passes
through the second hole.
The total length of the conductors to the load or to parts
of the turn does NOT affect the induced voltage but simply adds
series resistance and a small amount of leakage inductance.
The series resistance together with the reflected
primary resistance limits the short circuit current available.
Leakage inductance can also reduce the short circuit current but
at 60Hz the effect is pretty small -total circuit resistance is
dominant.
Jim
Wild_Bill
I was thinking in terms of a secondary placed over a primary winding.
The coupling of the two separate windings has no affect at all?
--
WB
.........
metalworking projects
www.kwagmire.com/metal_proj.html
<pent...@yahoo.com> wrote in message
news:8gpll5d9efj5mqe81...@4ax.com...
pent...@yahoo.com
<wb_wi...@XSPAMyahoo.com> wrote:
>Thanks for adding your explanation, Jim.
>
>I was thinking in terms of a secondary placed over a primary winding.
>
>The coupling of the two separate windings has no affect at all?
In the absence of iron small voltages would be induced
dependent on the physical positioning of the windings. However
when the iron circuit is installed the very high permeability
(typically more than 5000) provides such a low reluctance path
that it diverts all but a tiny fraction of the flux through the
iron circuit.
Jim
Gunner Asch
Ive got a big spot welder question....
I wound up with a big 25 KW (50KW?)spot welder. No idea if it works or
not..and when I called the company that made it one morning..I got the
owner..who was cleaning out his office..they had just shut the doors. So
no diagrams etc etc.
Its got the two arms that stick horizontally..but it doesnt have the 1"
copper bars that are the actual welding thingies.
Can $omething be$ides copper bar$ be used with $ome $ort of conductive
tip? I rather suspect..tho$e copper bar$ are expen$ive.
Ill have to bring it home next week..that shop Ive got Stuff stored in
looks to be DOA.
When I get it home..of course Ill have further questions...shrug.
And do I really need water cooling?
Gunner
Whenever a Liberal utters the term "Common Sense approach"....grab your
wallet, your ass, and your guns because the sombitch is about to do
something damned nasty to all three of them.
Mark Rand
>
>
>Can $omething be$ides copper bar$ be used with $ome $ort of conductive
>tip? I rather suspect..tho$e copper bar$ are expen$ive.
>
Yeah, either silver or molybdenum will do a pretty good job <G>
>
>When I get it home..of course Ill have further questions...shrug.
>
>And do I really need water cooling?
Maybe not for low duty cycle
Mark Rand
RTFM
dca...@krl.org
> Ive got a big spot welder question....
>
> I wound up with a big 25 KW (50KW?)spot welder. No idea if it works or
> not..and when I called the company that made it one morning..I got the
> owner..who was cleaning out his office..they had just shut the doors. So
> no diagrams etc etc.
>
> Its got the two arms that stick horizontally..but it doesnt have the 1"
> copper bars that are the actual welding thingies.
>
> Can $omething be$ides copper bar$ be used with $ome $ort of conductive
> tip? I rather suspect..tho$e copper bar$ are expen$ive.
>
> Gunner
>
You could use aluminum. It has 65% of the copper conductivity. So if
you use the same size bars you will only have about half the power.
Dan
Gunner Asch
Ok..that sounds duable.
cl...@snyder.on.ca
Can't use aluminum for the welding contacts though - has to be
copper.
Gunner Asch
True..Id need to put on copper tips. Which would be a hell of a lot
cheaper than 5 feet of 1 1/4" copper bar.
How about brass?
Gunner
IanM
> On Sat, 23 Jan 2010 23:05:12 -0500, cl...@snyder.on.ca wrote:
>
>> On Sat, 23 Jan 2010 18:19:10 -0800, Gunner Asch
>> <gun...@lightspeed.net> wrote:
>>
>>> On Sat, 23 Jan 2010 14:10:31 -0800 (PST), "dca...@krl.org"
>>> <dca...@krl.org> wrote:
>>>
>>>> On Jan 23, 8:52 pm, Gunner Asch <gun...@lightspeed.net> wrote:
>>>>> Ive got a big spot welder question....
>>>>>
>>>>> I wound up with a big 25 KW (50KW?)spot welder. No idea if it works or
>>>>> not..and when I called the company that made it one morning..I got the
>>>>> owner..who was cleaning out his office..they had just shut the doors. So
>>>>> no diagrams etc etc.
>>>>>
>>>>> Its got the two arms that stick horizontally..but it doesnt have the 1"
>>>>> copper bars that are the actual welding thingies.
>>>>>
>>>>> Can $omething be$ides copper bar$ be used with $ome $ort of conductive
>>>>> tip? I rather suspect..tho$e copper bar$ are expen$ive.
>>>>>
>>>>> Gunner
>>>>>
>>>> You could use aluminum. It has 65% of the copper conductivity. So if
>>>> you use the same size bars you will only have about half the power.
>>>>
>>>> Dan
>>> Ok..that sounds duable.
>>>
>> Can't use aluminum for the welding contacts though - has to be
>> copper.
>
>
> True..Id need to put on copper tips. Which would be a hell of a lot
> cheaper than 5 feet of 1 1/4" copper bar.
>
> How about brass?
>
No brass, Too high a resistance even just for the tips and I doubt the
zinc in the alloy would do anything good in contact with molten steel!
It only needs the last inch to be copper so it doesn't stick to the weld
or burn up. Duty cycle may suffer some as the aluminium supporting the
copper tip will loose strength as it gets hot before copper would.
Can you over-size the bars by 50% (cross section area) to retain nearly
all the current capacity? It shouldn't be a problem to reduce them at
the very ends to fit the existing terminals. They need to be the softest
purest aluminium you can lay your hands on for them to be low enough
resistance.
dca...@krl.org
> >>Ok..that sounds duable.
>
>
> True..Id need to put on copper tips. Which would be a hell of a lot
> cheaper than 5 feet of 1 1/4" copper bar.
>
> How about brass?
>
> Gunner
The tips are not pure copper. W.W. Grainger sells replacement tips
for the smaller spot welders.
Dan
Mark Rand
>
>
>True..Id need to put on copper tips. Which would be a hell of a lot
>cheaper than 5 feet of 1 1/4" copper bar.
>
Ah, I'd assumed you were only looking for the tips and that the arms were
already there.
Make the arms out of ali, if you make them one third larger in height and
width, they'll be the same strength as the copper, and almost the same
resistance. 50% bigger would be even better and still only be 2/3 the weight
of copper bars.
Use copper tips and make good joints :-)
Mark Rand
RTFM
Jack
Usually the bars that fit in the arms are steel with replaceable copper tips i.e:
http://www.portablewelders.com/welding-electrodes.html
Gunner Asch
Let me get this cleared up..the two (one movable) arms that come out of
the front of the machine are called ______________________
The two bars that are attached to the above arms and are pushed together
when one steps on the peddle are called _________________________
The tips of those two bars are called ____________________________
Im a newbie when it comes to spot welders..so really need the actual
terms so I dont sound even more stupid than usual <G>
Mine..IRRC..looks very similar to this one.
http://home.flash.net/~dgjco/TK-NewPics/Spot-welder.jpg
But mine has a box of cards on the right side that perform some sort of
timing functions (I think)..it may be a retrofit. Im trying to remember
the unfortunately short conversation I had with the maker as he was
shutting the doors.
Im struggling to remember what the brand is..Universal or Standard or
something similar. Probably 50 kva
cl...@snyder.on.ca
<gun...@lightspeed.net> wrote:
Depends on the brass - but MOST brass doesn't work very well.
Gunner Asch
Thanks!!
I wound up swapping for this and a bunch of other Stuff...
Anyone need a Kodak optical comparitor with a 30"..nearly 3 FOOT screen?
Its 110vts, with hummm at least 4 magnifying powers. Its smaller than a
VW bug..maybe 2/3 or half. <G>
But its quite georgious and works like a champ.
Make offer..Fullerton California.
Im gonna need to start moving some of this stuff out really soon.
Gunner
>>
>>Gunner
>>
>> Whenever a Liberal utters the term "Common Sense approach"....grab your
>> wallet, your ass, and your guns because the sombitch is about to do
>> something damned nasty to all three of them.
Whenever a Liberal utters the term "Common Sense approach"....grab your
Martin H. Eastburn
Gunner Asch wrote:
> On Mon, 25 Jan 2010 09:33:12 +1300, Jack <jmacn...@zmail.com> wrote:
>
>> Gunner Asch wrote:
>>> Ive got a big spot welder question....
>>>
>>> I wound up with a big 25 KW (50KW?)spot welder. No idea if it works or
>>> not..and when I called the company that made it one morning..I got the
>>> owner..who was cleaning out his office..they had just shut the doors. So
>>> no diagrams etc etc.
>>>
>>> Its got the two arms that stick horizontally..but it doesnt have the 1"
>>> copper bars that are the actual welding thingies.
>>>
>>> Can $omething be$ides copper bar$ be used with $ome $ort of conductive
>>> tip? I rather suspect..tho$e copper bar$ are expen$ive.
>>>
>>> Ill have to bring it home next week..that shop Ive got Stuff stored in
>>> looks to be DOA.
>>>
>>> When I get it home..of course Ill have further questions...shrug.
>>>
>>> And do I really need water cooling?
>>>
>>> Gunner
>>>
>>> Whenever a Liberal utters the term "Common Sense approach"....grab your
>>> wallet, your ass, and your guns because the sombitch is about to do
>>> something damned nasty to all three of them.
>>>
>> Usually the bars that fit in the arms are steel with replaceable copper tips i.e:
>> http://www.portablewelders.com/welding-electrodes.html
>
>
> Let me get this cleared up..the two (one movable) arms that come out of
> the front of the machine are called ______________________ Rocker arm
>
> The two bars that are attached to the above arms and are pushed together
> when one steps on the peddle are called _________________________ electrodes
Many types of these as well. Special functions.
http://www.resweld.com/catalog.php sample ideas to learn from...
>
> The tips of those two bars are called ____________________________
lots of names
since there many shapes for functions. e.g. high pressure
Sounds like a coll tool to have!
Martin
Bob Engelhardt
>Bob Engelhardt wrote:
>> I made my spotwelder from MOT's ... See it here:
>> http://www.metalworking.com/dropbox/MOTSpotwelderPrintable.pdf
> The design can be considerably simplified. If you use a U shaped single
> turn winding that fully fills the core, you will get the maximum
> current output possible from that transformer. Just slide extra
> transformers onto the open end of the U until the desired open circuit
> voltage is reached. The secondaries are effectively in series ...
Good idea. In the highly unlikely event that I ever build another one,
I'll do it that way. In building mine, the 2nd MOT was added only after
the 1st was finished & proved inadequate alone, not that I would have
thought of using conjoined cores anyhow <G>.
> This removes the need for complicated machining and also reduces the
> loss due to circulating currents caused by mis-matched OC voltages which
> is almost inevitable if the secondaries are paralleled and the
> transformers aren't *IDENTICAL*.
I wouldn't say the machining was complicated, but it would have been
easier your way. I suspect that the effect of the core mis-match is
secondary & not a problem on my welder.
> ...
> the shiny black taped cable in the second to last picture
> in the PDF which in my opinion should be a lot thicker. ...
Actually a "liquid tape" coating, but I quibble. I'd have used a
thicker cable if I'd had one. A central theme of mine is using what I
have in my box.
> I dont like the use of paint for insulation with the current capability
> it has. I strongly recommend lacquered card or similar all round the
> secondary where it passes through the cores and heatshrink, self
> amalgamating tape or similar over the rest of it. For safety, its
> probably a good idea to fully insulate *BOTH* arms from the base and
> pressure mechanism so that you dont get unexpected current paths through
> your workbench etc. if there is a little dirt under one tip.
Overkill, in my opinion. There is not much of a safety issue here.
> I would also be inclined to split the ends of the aluminium arms and add
> clamping bolts either side of each hole for the copper contacts.
I don't think that a press fit is any more likely to loosen.
> Why not add an adjustable over centre toggle mechanism with a strong
> return spring that trips a microswitch when it reaches its limit and is
> operated by a bowden cable from a foot pedal? Think mole grips or
> ratchet crimper for the sort of action required. That would give single
> pedal operation for clamping and welding. You would adjust contact
> pressure with the lockout switch OFF.
Much too complicated. Also, I've found the need to adjust the position
after the contacts are closed (the pressure is such that the work can be
slid around).
> I think a low voltage (chosen to suit the OC voltage) torch bulb wired
> across the arms near the tips (its insulated wiring can run back along
> the arms to any convenient location) would add a useful indicator as it
> will light brightly if the unit is energised with the tips not in
> contact and while actually welding its brightness will vary inversely
> with the welding current.
I don't think it would add anything: the welder isn't energized until
the tips are in contact & there's nothing to adjust about the welding
current. I.e., what good is knowing its intensity?
--------
But the bottom line, as they say, is that mine works. I'll never need
to weld stock more than 1/8" thick, so more power is irrelevant. As is
efficiency, for the little use mine gets. It could have been simpler,
but it wasn't that complicated to start.
Bob