power control

I'm lining up my winter shop projects already...
I plan to upgrade a horrible fright 220 volt spot welder with a weld
timer. The parts just came in from fleabay yesterday for the timer and I mocked it up.
Then I thought a power control would be nice too. is there a quick 'n easy device to control power here kinda like a dimmer on electric lights? I don't want to buy SCRs, 555timers, and a pot to design my own - too complex for me.
Karl
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Karl Townsend wrote:

Variac?
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

You can control the output power a LITTLE, if it's a transformer-based unit, but not a lot. Transformers don't do a very good job running at load with greatly-reduced voltages on their primaries.
If it's switcher-based, good luck! Ain't gonna happen.
Unless you're just blasting holes in thin sheet metal, timing should be enough. If you are, the best solution is a multi-tapped unit.
LLoyd
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Pete and you gave me an idea...
Its basically a 1.5 KVA step down transformer. I can do most of the control with a timer.
What if I got a 2:1 transformer to run for "LOW" mode and not use it in "HIGH". If I look, I might find one with several taps. there are lots of tansformers in the old semi trailer full of junk out back.
My application is spot weld AK47 rails to receiver flats. Many folks report trouble with the 220 volt spot welder burning a hole. I'm sure the timer will help, but its just too much power.
Karl
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Karl Townsend wrote:

Shouldn't that be better TIG plug welded?
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Karl Townsend wrote:

If you can find a transformer with a bunch of taps, like 50, 60 70 80 and 90% of input, that would likely be perfect. 2:1 may be too much reduction, it will reduce power to the weld by 4:1
Jon
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Jon Elson wrote:

I've got a few 2KW variacs kicking around, there were originally a ganged, motor driven three phase Lutron dimmer.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
wrote:

Pete, would you like to send one to a good home?
karl
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Karl Townsend wrote:

That would be one less to trip over. I'll check to see if it will fit in a small PMFRB.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
"Pete C." wrote:

What I've got:
http://wpnet.us/Luxtrol1.jpg
http://wpnet.us/Luxtrol2.jpg
120V input, might need two of them ganged back together.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
wrote:

I've got 220 here. I assume two will work?
Why don't you email me your price and shipping to MN karltownsend<AT>embarqmail.com
karl
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Karl Townsend wrote:

Two would work. They were originally configured as a motorized three phase bank for lighting control from the days when auditoriums were lit with a zillion 300W mogul base incandescents. You just need to re-gang them with some threaded rod to tie them together and something like a 5/8 shaft and knob.

2x USPS Medium PMFRB @ $11.35
As long as I have one left it should cover any odd low line voltage testing I might need to do and that's two less to trip over.
Based on the other replies I'm not sure the spot welder will benefit since weld time seems to be the controlling factor. Do any commercial spot welders have any sort of amperage control or just weld time control?
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

    [ ... ]

    With a couple of caveats for US power systems.
1)    Wire both Powerstats (these are that brand, not Variac, which     was General Radio's brand) with the CCW end of the winding     connected to neutral, and the CW ends of each to the two hot     lines
2)    Wire the load to the two wipers.
    With this wiring, your load will remain centered around ground, and both sides will increase together.
    Oh yes -- also be sure to turn both to fully CCW before you tighten the setscrews for the common shaft to the knob.
    Hmm ... another thing to watch out for. At least the General Radio Variacs used shafts covered by a black plastic (Bakelite, perhaps, given when they were designed) and there was no attempt to insulate the center of the rotor plate from the shaft, so you would have a short between the two output sides. I forget whether Superior Electric (the maker of the Powerstat) did the same or not. Check it out for insulation if you are going to use a bare metal shaft. Perhaps a Delrin shaft would be a better bet.
    With other wirings, you would likely burn out one of the variable autotransformers (Powerstats, Variacs) and/or have more hazardous voltages.
    Also, fuse both hots -- ideally with a shared circuit breaker.
    Good Luck,         DoN.
--
Remove oil spill source from e-mail
Email: < snipped-for-privacy@d-and-d.com> | Voice (all times): (703) 938-4564
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

sounds fair. email me how to pay and I'll email back my ship address. My email karltownsend<AT>embarqmail.com
Karl
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Karl Townsend wrote:

They're on the way, all 21.8# each.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
wrote:

Thanks Pete,very generous of you to give these to me. I'll put them to good use.
Karl
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
wrote:

My 90 KVA spot has both. Multiple taps on the transformer and a controller package mounted on the side to control time, pulse rates etc.
Want to buy it? Cheap enough. In fact..Id swap you something for it.
Gunner
--
You just opened the window for a glimpse at the liberal mindset. You
people think, for some unknown reason, that since you are infinitely
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
wrote:

Correction..its a 20 KVA.
Brand is "American"
Gunner, organizing the cargo container
--
You just opened the window for a glimpse at the liberal mindset. You
people think, for some unknown reason, that since you are infinitely
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
wrote:

I have just this in a large three phase unit. I've often wondered if you can use just one of the three coils and have a single phase transformer. Will this work?
karl
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Right. If you cut the voltage in half, the current will also drop in half so the power will be 1/4th. Easy to see the result. Just plug your 220 volt spot welder into 120 volts.
You could use a buck boost transformer. Even make one from a Microwave Oven Transformer.
Dan
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Polytechforum.com is a website by engineers for engineers. It is not affiliated with any of manufacturers or vendors discussed here. All logos and trade names are the property of their respective owners.