Running tombstone welder on 5KW generator

[slowrev]

How about a PTO driven welder made from an automobile alternator ? Do a search in the build it yourself forum. Pretty interesting, I plan on trying it this winter.
Ben

 

[3RRL]

That is an interesting idea.
I have been looking for a trailerable generator/welder/air compressor. When I was a kid I worked for a company that installed gas and water lines. Each truck towed one of those things. We had to dig several ditches to feed the new pipes through underground and used a water drill to make room for the pipes. Then had to weld up everything as needed on site and test under pressure. I wish I had one of those units. That would be super handy for all us guys having to work out on the property. Anybody know where to get one?

 

[Highbeam]

Well there was this one time when I needed to weld and cut at my remote property and I had no oxy/acetylene torch but the neighbor had a plasma cutter. So... I loaded my coleman generator in the truck, then the lincoln welder, then the 5HP 30 gallon air compressor, then the plasma cutter. Worked like a champ since the plasma cutter used the same plug as our welders.

Unfortunately I only got to plasma cut for about a half hour before realizing that the sparks and slag were starting the fairly dry ground on fire.

I even painted my entire 20 foot long shipping container inside and out with oil based paint and my automotive style paint gun fed by the 5 HP air compressor run by the coleman generator.

You probably are referring to those big trailer mounted air compressors that can run jackhammers through a large hose.

 

[3RRL]

You probably are referring to those big trailer mounted air compressors that can run jackhammers through a large hose.

Exactly...I ran one of those every Summer working my way through school. Definitely hard labor.

 

[patrick_g]

Maybe my generator isn't as good as it should be and I know for a fact that I am not a GOOD welder but when I get into the top amp ranges (AC or DC) on my Lincoln Tombstone then my generator doesn't seem to be "STIFF" enough.

I don't think it is a sales ploy promoting other purchases when the MFG tells you to use a 50 amp circuit for the 240 volt welder. You can't get something for nothing. 240 volts at 50 amps is 12000 Watts. Of course you probably don't ordinarily pull 50 amps. But you would be pulling 6000 Watts if you had 240 volts and drew only 25 amps.

You can't get something for nothing. There are always some losses so you never get as many watts out to the welding as you pull from the source. If you give the tombstone enough input power it will deliver 235 amps at about 24 volts which is 5640 Watts you will be giving it more than 5640 Watts input as there are losses, significant losses. The losses are what causes the box to heat and require a powerful (at least noisy) fan.

I suspect that although folks may be satisfied with the results they get they aren't actually getting the rated power they may think they are getting. As long as the user is satisfied, the results are good, and the genny doen't become a crispy critter too early in life then happiness should ensue.

If someone actually NEEDED to get the FULL rated welding power from a tombstone They would find out they couldn't get there without a genny rated well above 6KW. Can't get something for nothing. A tombstone can draw around 10KW or so at max. Even a 7500Watt continuous genny won't do that.

Pat

 

[Highbeam]

"when I get into the top amp ranges (AC or DC) on my Lincoln Tombstone then my generator doesn't seem to be "STIFF" enough."

Seems to me that the generator would pop a breaker if it was being asked to deliver more than it is capable of. Why doesn't that happen?

"I don't think it is a sales ploy promoting other purchases when the MFG tells you to use a 50 amp circuit for the 240 volt welder."

That's a standard plug and Lincoln knows that if they sold that welder with anything but a standard 50 amp plug that people would just have to replace it. I don't think that the machine needs 50 amps. Whoa, this is easy, does someone have a clamp on ampmeter to measure amps being fed to their tombstone at full welding output? Have you seen the size of the wiring on the tombstone's power feed cord? It is very light.

"There are always some losses so you never get as many watts out to the welding as you pull from the source..... there are losses, significant losses. The losses are what causes the box to heat and require a powerful (at least noisy) fan."

I agree. The trouble is that we don't know how inefficient the welder is at transforming. But again, if the welder asks for 7000 watts from a generator with a 5000 watt breaker then I would expect that breaker to pop. Does anyone see any fault with that logic?

"I suspect that although folks may be satisfied with the results they get they aren't actually getting the rated power they may think they are getting. As long as the user is satisfied, the results are good, and the genny doen't become a crispy critter too early in life then happiness should ensue."

I think you are correct based on my experience switching between utility feed power and genny power. It seems the same welding job requires a step or two more amps to get the job done. It works, but I feel that welding in a garage with shop power is more ideal.

"a tombstone can draw around 10KW or so at max"

Really? How do you know this? Are you assuming that an appliance with a 50 amp plug WILL use 50 amps of feed power?

 

[schmism]

based on lincons on products i can tell you you dont need 10K + to run 250amp ac/dc unit.

look at there Ranger 250. It list 9K generator for that same size welding unit, and if you ask me id say thats oversized by at least 30% because of its rated duty cycle.

Granted your gonna be running a 5K generator fairly hard but IMHO it would work fine under non-maxumum output settings.

 

[Zoombah]

I am a believer. Purchased a Hobart LX 235 235AC/160DC yesterday and built an adapter cord to run it off my 5KW generator. Was getting dark by the time I got everything hooked up but did quickly try out a 3/32 6013 on low amp DC. No problem at all striking an arc and maintaining it. Per my SWAG estimate I think I can probably get about 150 AC and somewhat less DC out of this combination....plenty for what I might occasionally need to do in the field.

I do not understand why the Lincoln expert thinks a 12KW generator is needed to run a tombstone. Just look at all the smaller generator/welder combos on the market. Miller must have worked some real magic to get 185A DC out of the Blue Star 185 which uses a 5.5KW generator. And even Lincoln's Weldenpower gets 125A out of a 4,250 watt generator. Also worthy of note is the input wire on my Hobart...the wire hooked to the big honkin 50A plug that you plug into the wall outlet. The wiring is 12 guage wire.

In the end analysis I think the combination I now have will serve my occasional remote needs plenty well.

 

[sandman2234]

12 guage wire with a 50 amp plug? Now that is a fire hazard just waiting on the right timing. Hopefully the circuit breaker is less than 50 amps (closer to 20 amps) so the fire harard isn't quite so bad.
David from jax

 

[SPYDERLK]

Maybe my generator isn't as good as it should be and I know for a fact that I am not a GOOD welder but when I get into the top amp ranges (AC or DC) on my Lincoln Tombstone then my generator doesn't seem to be "STIFF" enough.

I don't think it is a sales ploy promoting other purchases when the MFG tells you to use a 50 amp circuit for the 240 volt welder. You can't get something for nothing. 240 volts at 50 amps is 12000 Watts. Of course you probably don't ordinarily pull 50 amps. But you would be pulling 6000 Watts if you had 240 volts and drew only 25 amps.

You can't get something for nothing. There are always some losses so you never get as many watts out to the welding as you pull from the source. If you give the tombstone enough input power it will deliver 235 amps at about 24 volts which is 5640 Watts you will be giving it more than 5640 Watts input as there are losses, significant losses. The losses are what causes the box to heat and require a powerful (at least noisy) fan.

I suspect that although folks may be satisfied with the results they get they aren't actually getting the rated power they may think they are getting. As long as the user is satisfied, the results are good, and the genny doen't become a crispy critter too early in life then happiness should ensue.

If someone actually NEEDED to get the FULL rated welding power from a tombstone They would find out they couldn't get there without a genny rated well above 6KW. Can't get something for nothing. A tombstone can draw around 10KW or so at max. Even a 7500Watt continuous genny won't do that.

Pat

This is exactly right.

That being said, I have been able to weld unimpaired with my Coleman 4kW and old JC Penny 230A buzzbox using 3/32 rods. This rig will carry 6011 1/8 also, but softly. I would predict a 5kW would power 1/8 strongly.

As for why the genny breakers dont blow - - I think its because the gennys cant deliver enuff amps to blow them except in certain steady state maxxed out conditions. Like when theyre good and hot and are asked for just slightly above FULL rated power for an extended period.

I just did sometests on the buzzbox. Conditions; output looped (shorted), 240VAC mains power, 50A breaker. Results:
1) 235A setting - Measured input 70A, Output 290A
2) 200A set - Input 64A, Output 260A
This supports Lincolns claim of a 15K input requirement for fully hard welder output.
It is interesting to note that the 50A breaker never blew - even tho each test ran for 10 or 20 seconds TWICE while I ran around checking the meters. - - I find that most breakers take quite a while to go at their rating unless they are already hot. It takes several times their rating to make them go right now.
Larry