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Discussion Starter · #21 ·
for me i just stick to the honda eu series of gen sets,
off the shelf item and yea you can modify them to suit your needs.
How do you switch between 120v and 240v? I'm trying to get 240v for the welder, but having the ability to parallel the alternator poles to get 120v would let me get the rated wattage out at 120v on 1 circuit, not split. That will be a huge benefit and give me more redundancy in my power options.

The other thing is I suspect a rotary is going to keep up with the arc starts better than an inverter - unless it is a real big inverter.
 

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the smaller eu honda gens are 120 vac up to eu3000i
the eu6500 and eu7000is are 120/240 and have a mode switch on the front to lock the gen set in 120 vac mode.
we modify the gens with a 50 amp socket and breaker so we can get out the 46 amps plus of power out of the gen set when in the 120 vac mode.

stock they only have a 30 amp outlet and breaker for the 120 vac mode.
 

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What kind of welder are you using? If it's one of the modern inverter welders, they are remarkably easy to power and have no quarrels being run off gennys with 10% THD.
Great little units that are simply invaluable in the field.
My 5k rotary welds farm equipment as it's primary role. Never had a problem. The old 4k one was a bit small.
I certainly wouldn't worry about running it off your dad's generator..

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Discussion Starter · #24 ·
What kind of welder are you using? If it's one of the modern inverter welders, they are remarkably easy to power and have no quarrels being run off gennys with 10% THD.
Everlast PowerArc 210STL.

I am not going to take any chances. Dirty power has been known to fry a lot of these little machines - not just Everlast, but a lot of lesser-expensive imports be it welders, plasma cutters, and the like.

Some of the higher end big-name machines may handle dirtier power.

Everlast says less than 5% THD. They will find any hole in operator/operating conditions to void warranties for service work also. The mere fact of generator power for their warranties, period, is a can of worms should you run in to an issue and have to rely on their warranty. That is a discussion for another day and another forum, not here.
 

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Everlast PowerArc 210STL.

I am not going to take any chances. Dirty power has been known to fry a lot of these little machines - not just Everlast, but a lot of lesser-expensive imports be it welders, plasma cutters, and the like.

Some of the higher end big-name machines may handle dirtier power.

Everlast says less than 5% THD. They will find any hole in operator/operating conditions to void warranties for service work also. The mere fact of generator power for their warranties, period, is a can of worms should you run in to an issue and have to rely on their warranty. That is a discussion for another day and another forum, not here.
Interesting. The lil 140 version claims 10% and can run on a generator. Weird the 210s are different.
I strongly considered one of the everlasts, But my el cheapo one just works so well. Maybe when it dies.

I can't see it hurting anything, but if it's worth the extra $$$ to you hey, have at it!

All the Mecc alternators claim less than 5%. Stick one of them to a Kohler diesel and go?


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Discussion Starter · #26 ·
All the Mecc alternators claim less than 5%. Stick one of them to a Kohler diesel and go?
Looking just at wattage and THD - the following are in an acceptable range, though not directly able to be paralleled off-the-shelf (they are split phase only, can't parallel poles to get 120v only as they sit):

Mecc Alte S20W-95, 7200w, under 5% THD

The other Mecc Alte's in a similar wattage range show under 6% - too high.
Bold and underline added.

As to the Kohler diesel - not sure on the Kohler brand, but that is an idea. I have looked at some of the small diesels before. Back in the day (15-20 years ago) there was a company called Robin, I believe, that made some single cylinder diesels. You don't see them around any.

There are some small (8-15hp) inboard diesel engines that have been used in sailboats for decades that might work, actually - electric start and liquid cooled. I forget what some of the brands are but there are some that are very serviceable (and the opposite is true - there is at least one brand that, I believe, is French or from some other European country that is extremely hard to get parts for). Though, that size engine - even an 8hp diesel - might be too much engine for the size power output.
 

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Bold and underline added.

As to the Kohler diesel - not sure on the Kohler brand, but that is an idea. I have looked at some of the small diesels before. Back in the day (15-20 years ago) there was a company called Robin, I believe, that made some single cylinder diesels. You don't see them around any.

There are some small (8-15hp) inboard diesel engines that have been used in sailboats for decades that might work, actually - electric start and liquid cooled. I forget what some of the brands are but there are some that are very serviceable (and the opposite is true - there is at least one brand that, I believe, is French or from some other European country that is extremely hard to get parts for). Though, that size engine - even an 8hp diesel - might be too much engine for the size power output.
Oops. Missed that. I must have been looking at something else. I have to read up on them more.

What is the reason you need to split the poles? Can't you just wire it to pull 120V off each leg and wire those in? Or does that unbalance the alternator?

Kohler is good stuff. They have 3600 and 1800 options. Even some with high run time features like oil filled air cleaners and large sumps.
Kubota makes lots of tiny diesels of all flavors.


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All,

I've looked at my generator options and I don't have anything between 2600 and 15,000w. One option that would be really handy is a 4-5kw inverter (120v). However, I am thinking a rotary that was in this range would be real nice - possibly with the ability to go all 120v or split 120/240v.

Looking at generators, engines, and options I don't like the form factor of any of the conventional open frame generators. The 15kw I have is an engine and alternator bolted to a bare steel base with 1x 50 amp connector - thats kinda what I'm after - just a bare bones set up, just smaller.

As far as engines go I like the Honda engines. If I can get an appropriately sized engine with electric start around, maybe, 10-13hp that might do the trick.

The bigger question is on alternators.

Is there such an alternator in the 5-8kw range that has a true split alternator with "2x center taps" and not just "center tapped"? I am not sure if I am using the right terminology, but what I am after is being able to phase the 2x halves together to get 120v. You can not do that with a center tapped alternator with 3 leads (2x hots and center tapped neutral) - you need 4 leads and each half physically split because when paralleling one of the neutrals in split phase mode is going to be a hot in paralleled mode, and one of the hots in split phase mode is going to be neutral in paralleled mode.

My goal is to be able to adequately run my small welder on 240v without needing the 15kw. It would be a whole lot easier to move a smaller generator, and would be a good bit more fuel efficient. The power distribution doesn't matter - if I have a 240v plug like an L14-30r for 240 and a 50a 120v like a 5-50r that is all I need at the unit.

As far as 120v goes - it would make the generator a whole other level more versatile as it would start and run heavier 120v loads that much easier (table saw, air compressor, etc). Redundancy on capabilities in the fleet is a good thing.

If there isn't a suitable off-the-shelf alternator -
How hard would it be to open one up and split it? I know alternators and motors can be rebuilt so I assume it isn't out of the realm of possibilities to get in there and split it then add an extra "center tap"? Being center tapped already that would be a pretty good dead give away where the center of the coil was = where to split.

Here is an example of something similar -

That company (Central Maine Diesel) appears to be defunct, and is actually who put my 15kw together. So I suspect trying to get that unit as a starting point to tweak to my idea I don't think is possible. I wouldn't want to try to go down the road of trying to contact them/order/lose money (already have reached out to them numerous times for info on the 15kw with no response, no biggie - I got all the service info and specs I was after through other channels). As far as a form-factor, though - the only thing different about that one and my idea is the outlets/breakers are on the end cap of the alternator whereas on my idea I want a box like the 15kw. That will be easier to do the wiring and let me put big connectors on it and a large polarity switch.
I bought a NorthStar generator some years back that was touted as all American built, copper windings, bristles ...etc. Not arguing the fact but until recently didn't know that the alternator was built by Mecc AAlte...and from what i've seen..they build good quality gear. this specific generator has a Honda 690...again..good quality.

If your looking to put one together, i don't think you can go wring with Mecc Alta and im certain their technical support can answer your voltage center tap question
As for the engine..love the Honda 690...but if you're doing this from scratch - i don't think these come with a muffler when ordering a stand alone engine...you might want to check on that.
A friend of mine, (picky about quality) built a high power pressure washer a while back and used the Predator 22 HP engine from Harbor Freight. He has been really happy with the result and it does come with a muffler ..so makes a DIY setup a little easier.

Electrical
The Mecc Alte has a small wiring block built into the compartment on the top of the alternator ( at least the larger ones do) where its easy enough to pull the 220 and 110 lines up to a breaker)

Breakers are simple. If you contact Northern Tool..they sell replacement breakers for the generators they sell. I had to replace a 58 amp breaker a while ago ( ya weird size) and it was literally 15 bucks. and of course - simple enough to get outdoor rated electrical box and mount a 50 amp female connection.

sounds like a fun project.
Cheers
 

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Your going to have to dumb it down a bit more.
Why can't you just wire a 120v plug off one leg of the 240V output?

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That’s exactly what they do.
Your going to have to dumb it down a bit more.
Why can't you just wire a 120v plug off one leg of the 240V output?

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If I recall my engineering right. That’s exactly how the generator windings are arranged. They tie the opposite poles together ( the neutral) and the other end of each coil is the hot leg Hot to neutral 120. Hot to hot 240. Regardless. The alternator will have terminals marked for these to connect to. It won’t be something you have to configure.
 

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Discussion Starter · #32 ·
What is the reason you need to split the poles? Can't you just wire it to pull 120V off each leg and wire those in? Or does that unbalance the alternator?
On a 240V alternator, the two 120V poles are 180 degrees out of phase. That's how you get 240V across them.
Your going to have to dumb it down a bit more.
Why can't you just wire a 120v plug off one leg of the 240V output?
If I recall my engineering right. That’s exactly how the generator windings are arranged. They tie the opposite poles together ( the neutral) and the other end of each coil is the hot leg Hot to neutral 120. Hot to hot 240. Regardless. The alternator will have terminals marked for these to connect to. It won’t be something you have to configure.
Sorry for the mumble jumble of quotes. However, see the thread below. I studied this earlier this year - there are scope traces and diagrams in the thread for reference on the explanation.

 

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Sorry for the mumble jumble of quotes. However, see the thread below. I studied this earlier this year - there are scope traces and diagrams in the thread for reference on the explanation.

Wow. Thats pretty far above my pay grade, so correct me if I'm wrong in my over simplified summary.

If your gen makes 10A @ 240V having it wired like in your schematic allows you to have a 20A @ 120V circuit instead of just pulling power off each leg which gives you a Max of 10A @ 120v.

So it just allows you more amps at a single 120V plug. Correct?

(Ps, all the pic links are dead)

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Discussion Starter · #34 ·
Wow. Thats pretty far above my pay grade, so correct me if I'm wrong in my over simplified summary.

If your gen makes 10A @ 240V having it wired like in your schematic allows you to have a 20A @ 120V circuit instead of just pulling power off each leg which gives you a Max of 10A @ 120v.

So it just allows you more amps at a single 120V plug. Correct?
Yep. You got it.

Think of wattage. Watts = Amps X Volts.

If you keep the same wattage, say at 240v (which is what the vast majority of rotary dual voltage generators are rated to) then drop to 120v the available amperage has to double with the halving of the voltage. That is, IF the wattage stays the same.

The catch, the LARGE catch, to this is that the alternator is only rated to a particular amperage. That is the metric that most people leave out of the equation - in the capacity that the metric is accurate. That is to say - the Amperage is one number through the whole alternator. If an alternator can push, say, 30 amps it can only push 30 amps. It doesn't matter what part of the alternator pushes the 30 amps - pole 1, pole 2, or both poles 1 and 2 in series. Therein lies where people leave out the amperage metric in its correct interpretation.

Generator manufacturers/suppliers may rate their generators to amperage at 120v. Central Maine Diesel does this with theirs. This is not 100% accurate. The reason is that is a combined amperage. You absolutely can not pull that amperage from 1 circuit. It MUST be split in two. Therein, again, lies where people leave out the amperage metric in its correct interpretation.

(Ps, all the pic links are dead)
Check your web browser. Clear cookies, stored internet files, history, etc then reload. They all work fine on my end. Maybe try a different web browser also.
 

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so what are the stator connections on the end of the gen set?
are they the same 4 stud and 4 wire?

kinda cool how this works out for the 120/240 to 120 only switchable avr gens.

wacker and a few others in the construction gens have this as well.

it is ok if you are on a job site with cords for each item.
they still do not have a single plug outlet large enough on most of these mid size gens to get a snake to an octa box for total out of the gen that it can produce...
unless they are modified...
most just have 30 amp outlets as the large outlet ..
and have gen ratings for a bit over that...

hey flyfisher
so are your plans for the super large Anderson style?
or will a 50 amp 125 outlet work?
i forgot where your system planned wattage at 120 vac is to be.
 

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Discussion Starter · #36 ·
hey flyfisher
so are your plans for the super large Anderson style?
or will a 50 amp 125 outlet work?
i forgot where your system planned wattage at 120 vac is to be.
50 amps at 120v is 6kw. That is plenty. You can use a NMEA 5-50 plug for that.

I'm not too concerned with the upper end of the amp range on 120v. I am not sure what the high end of it would be that I would use. My ruling figure is the wattage at 240v with low THD - in that it is able to provide adequate power to my little welder at the upper end of the range where I operate it (which is not the upper end of the capacity of the machine - 120-130 amps welding current might be the top end, most of what I weld is under 100a) - the machine will provide more welding power, but I don't really have any reasons to run it there and if I did I'd be better off using the old tombstone as it will do 300a. So if I am close to 200a the tombstone won't even break a sweat, whereas the little welder will be at or near max juice.

6kw at 240v is 25 amps. That is still over where I would be. I will have to load test the little welder and see really what it pulls at 240v where I run it. I would be surprised if it pulled more than 20a.

As far as 120v amperage goes - if I can get over 30 amps that would be ideal. But I don't want to pull all that from 1 pole. If I did that would mean I would have to have a 7200w capable generator just to get 30a at 120v. If you go after the same wattage with paralleled poles then the "required wattage" drops in half to 3600w. So if I get back to the 5kw range running wattage, the lower end of the range I am targeting, that would be about 6kw peak/surge/starting which would be 25a @240v and [email protected] That would be plenty.

Also, for reference, here is a spec'd 8500w generator that does have a voltage selection to allow 120v-only (though, notice there is no 3 pin 120v-only twist-lock connection, only 4x 5-20's):

That is a couple thousand watts higher than what I'm after, and there is no mention of THD. However, one idea would be to see if I could acquire the head as a "replacement part". I am not sure what the overall quality is of Duromax heads and engines. I know there are a lot of them out there and there are probably several people on the forum here that have them and/or have experience with them. If the THD is low on the head then that might just be an "off the shelf" alternator that would work. I just don't need the engine, frame, wheels, outlet/control panel, etc - just the bare alternator (and what voltage regulation circuitry there is - I assume part of the alternator, but could be wrong). Another wildcard is what engine shaft configuration it requires. If they made some proprietary shaft connection that Honda doesn't make then that would be an issue - to pair the two would require an external jack shaft conversion that would be both a bit of a pain to make and would also rob HP.
 

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I browsed the previous threads and think I have an understanding in general. But what I don't see is any overall system description. You are pondering single and split phase options for a generator, the split phase to power the welder.

You are off grid? You want to power all normal loads while welding? You don't mention what the welder is, I'm guessing MIG but maybe arc too and hopefully not TIG?

If I had one generator, whatever it is, I just wouldn't be risky. When welding disconnect everything else regardless of the type of welding being done. Anyway, that's IMHO. And I wouldn't TIG weld with a HF start that was connected to the rest of the system even if all 3 or 4 lines could be disconnected. HF is HF. Ever keyed a TIG with the ground clamp disconnected and get tickled?
 

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Discussion Starter · #38 ·
But what I don't see is any overall system description. You are pondering single and split phase options for a generator, the split phase to power the welder.

You are off grid? You want to power all normal loads while welding? You don't mention what the welder is, I'm guessing MIG but maybe arc too and hopefully not TIG?
Lots of what you are asking is in the thread discussion here.

The idea of selectable voltage is to make the generator cover a lot more ground - with high amperage at 120v, done by paralleling the alternator poles, I could have a back up to heavier amperage 120v applications. I am wanting to fill that "gap" with around a 4.5kw inverter generator that does 120v-only.

What a 120v-only generator does not do, however, is provide 240v

The welder I am trying to run is an Everlast 210STL. I want to run it on 240v. It does run on 120v, but that isn't how I want to run it. All my welding the past couple years has been on 240v and that is where I know my settings. When you switch to 120v - even though the machine will run on it - the welding power does not correlate. That is to say that if I set the machine to run 100 amps (1/8" 6011 rod, lets say) on 240v it might take a setting of 110-115 amps with the welder on 120v to get the "same welding power", regardless of what the dial shows.

The 210STL is a tig machine, also, but does NOT have HF start.

I have multiple generators. My goal was to have 1 that I could set up as a "throw in the truck" rig that would cover a lot of ground and be pretty easy on fuel. My 15kw will provide all the power I could ask for in either 120v or 240v, but its too big and heavy of a generator to pair with the welder as a portable work solution. I use an EU2200i as my portable generator now and it works fantastic for 120v service.

For the record, I did try running the welder off of the EU2200i trying to see what I COULD weld with the power it puts out and the welder load running stick, even at the lowest wattage, is too much for the EU2200i. So I need a good bump up in power - and that is where the sizing and voltage options discussed in this thread are rooted. 120v-only (higher amperage there, from paralleling poles) significantly increases what the generator can run. Like I said - going to an inverter 4.5kw, if that unit quit I could use the unit discussed in this thread to fill in running 120v-only mode.
 

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Ever keyed a TIG with the ground clamp disconnected and get tickled?
Back story: I had a Miller 250 set up for Arc and TIG. I did a lot of TIG welding - I love to TIG weld. But I had to do it late at night. There were three (four) other houses on that pole transformer. If a TV or stereo was on in my house the TV would freak out and if the stereo the power amp would blow its breaker. Other things would malfunction or fail. As for the neighbors I would get immediate nasties as they knew the culprit. The momentary HF start was bad. If aluminum and continuous HF it would wipe out everybody's stuff.

This was on one utility pole out to 3 or 4 drops. Outside of that the system seemed to absorb the HF. It can go a way even from the pole. So on a small system this is critical. I don't care how much grounding you have, welding in general can be a problem.
 
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