How to Join Generator plug outlets for higher capacity

[april]

I have a Generator which produces via the normal 3 phases wiring which then passes that to an inverter which outputs 240 volt on each of two outlets rated at 8 amps each.

The manual says don't combine them and I expect they mean directly

Is there a way I can join them and double the output for welding ? Would I have to slow a phase down on one outlet or something like that?

 

[Sceadwian]

You'd have to perfectly phase match them, or design an appropriate ballast network to keep one generator from powering the other one during out of phase moments, but oscillation would be a serious problem under during load dumps or sudden onset of loading (such as with a welder)

The ONLY proper and safe way to do what you want is to buy a generator that can provide the required load (with an overhead)

 

[dr pepper]

As allready mentioned it isnt practical to do that.
Theres probaby 2 switchers, one for each 240 o/p.
You could in theory use 2 dc welders then join up the outputs of both, but that isnt practical either.

 

[april]

Hm Im hoping for suggestions how it might be approached not don't do its.

This is a common problem with a lot of the Chinese made generators comming in now. You buy a 6KVA and really you get the practical use of two 3KVA's only .
You don't seem to be any better off than buying a cheap 3KVA and using it.

How might the two welder outputs be joined?
I dont see that the phase difference would still be an issue then ? - 240 A/c runs one . Transformer makes it DC 70 Volts or something the the second also produces 70 volts so join them there in parallel and I would think that the phase difference would be isolated in the transformers

So why not use this method ? sounds good to me.I've got 2 welders so should I try it?

 

[jpanhalt]

This is a common problem with a lot of the Chinese made generators comming in now. You buy a 6KVA and really you get the practical use of two 3KVA's only .
You don't seem to be any better off than buying a cheap 3KVA and using it.

I just checked the manuals for two, "6500 Watt" generators from Harbor Freight that are made in China. Neither one had the configuration that you describe. Each had a single, 240 VAC, twist-lock socket rated at the full capacity.

To get further on your question, please provide more information about your generator. The product manual would be most helpful. It also seems that you have or have derived the wiring diagram. Please post that too.

John

 

[dr pepper]

You can join 2 weld sets together, its done in industry however both sets must be dc, ac ones would probably fry.
Also both sets need to be transformer - bridge rectifier type, inverter type sets unless they are designed to wont like being paralled.

 

[april]

I just checked the manuals for two, "6500 Watt" generators from Harbor Freight that are made in China. Neither one had the configuration that you describe. Each had a single, 240 VAC, twist-lock socket rated at the full capacity.
To get further on your question, please provide more information about your generator. The product manual would be most helpful. It also seems that you have or have derived the wiring diagram. Please post that too.John

You might look deeper see here:-https://www.electro-tech-online.com/threads/6kva-diesel-chinese-generator-bought-from-ebay.130030/
Most of what I have seen have two 8 amp outlets that are in different phases

 

[april]

You can join 2 weld sets together, its done in industry however both sets must be dc, ac ones would probably fry.
Also both sets need to be transformer - bridge rectifier type, inverter type sets unless they are designed to wont like being paralled.

You are not being clear
Do you mean A/c mains transfomed to DC and rectified?
Then connect the two outlets in parrallel or do you mean something else ?

 

[jpanhalt]

You might look deeper see here:-https://www.electro-tech-online.com/threads/6kva-diesel-chinese-generator-bought-from-ebay.130030/
Most of what I have seen have two 8 amp outlets that are in different phases

So Hey its for sale now and working after 5 minutes each time it seems . Well thats today at least.

Please confirm whether you are still talking about that same cheap generator or you have bought another one.

I think your responses to people who have tried to help you in this thread can best be described as pretty cheeky. Do you really expect everyone here to remember every post you have made? Good questions get good answers. If you had the information, including the schematic posted in that thread, why didn't you post it here?

That schematic seems to show the AC outlets are wired in parallel; although, it is kind of fuzzy and hard to read. If they are in parallel, they cannot be added together.

John

 

[Sceadwian]

Dr Pepper wasn't talking about the generators at all april, he was talking about theoretically connecting two DC welders together, which has absolutely nothing to do with what you're trying to do.

DO NOT CONNECT THEM IN PARALLEL

As suggested provide more information about your generator and there may be options.

 

[KeepItSimpleStupid]

https://en.wikipedia.org/wiki/Alternator_synchronization

Here is a video for DC master/slave. https://www.youtube.com/watch?v=9aBARFGXHpo Note that that he mentions that one supply acts as a current source and one a voltage source, but the supplies are designed to be paralleled. On PDF page 96, there is a good circuit description as to what's required for a DC supply. https://www.electro-tech-online.com/custompdfs/2012/09/DC20Power20Supply20Handbook.pdf

Honda has an inverter based generator that can be paralleled. At a minimum they would have to synchonize the generators which is easy because only one clock would be used. next one would have to configured as a voltage source and the other a current source with a slightly higher compliance voltage.

Even if you could manage to get two portable generators to synchronize, if one ran out of gas, look for the MAGIC SMOKE.

I hope that by reading the references, you will discover that unless the supplies are designed to be paralleled, they should not be. AC power supplies are much trickier to do so because, phase amplitude and frequency must be matched.

[highlight]DON'T do it UNLESS the the generators are designed for paralleling or MASTER/SLAVE operation.[/highlight]

 

[april]

OK thats fine ,you have got out your tell people what not to do frustrations and other rants .
Now I am still looking at doing this . The consequences are my own to bear and none of your business.

Is there anybody there who might suggest how one would approach doing this , cautiosly but definately.?
Thanks KISS for your input DON'T do it does not rub well with me. Going to the moon is dangerous ,perhaps we should never have attempted it.

Honda has an inverter based generator that can be paralleled. At a minimum they would have to synchonize the generators which is easy because only one clock would be used. next one would have to configured as a voltage source and the other a current source with a slightly higher compliance voltage.

This design is in fact based on a copy of a honda machine -see other thread and link to ebay
https://www.electro-tech-online.com/threads/6kva-diesel-chinese-generator-bought-from-ebay.130030/


An interesting thing is why the inverter part puts out power to two outlets only out of phase and not 3. Logic would say you produce 3 phases in the generator then feed each phase through the inverter to a separate outlet. So what has happened to the third phase? The 12 Volt is separately wired again.See the diagram .

I'm still intrigued by this plug one transformer welder into one outlet and another into the second outlet of the same machine ( some people cant or wont read)
Then paralleling the outputs .
Can anyone suggest any reason that would not work?

EDIT
I have just noticed on the wiring diagram that the outlets seem to be paralleled . Is that how you see it ? The manual says dont parallel them but if they are in fact joined the the whole output should be available through just one outlet. Don't understand this , will have to pull it apart again and have a look.

 

[april]

I think your responses to people who have tried to help you in this thread can best be described as pretty cheeky. Do you really expect everyone here to remember every post you have made? Good questions get good answers. If you had the information, including the schematic posted in that thread, why didn't you post it here?
John

You need to read more before you post . Your opinion of me is unnecessary John . Keep it to yourself

 

[KeepItSimpleStupid]

April:

Austrailia, I believe does things different than the US and I don;t know where you are and the generator characteristics.

Your schematic wa sof a three-phase generator, which I don't THINK yours is. In any event, there is one winding that is dependent on the residua magnatism and can generate a control voltage to get thing started. Then there is a control winding, usually the rotor which is applied DC and varies the magnetic field and thus the output. Engine RPM adjusts the frequency. If the generator is capable of 12v, then that winding may be separate.

OK, that's out of the way.
In the US, our system is really called split-phase. Think of a tranformer primary being applied a high voltage such a 9 KV and the secondary being enter tapped. In a generator only supplied system the center tap gets connected to the earth and it also becomes the neutral. Neutral and Ground in a distribution system is connected together at one point. That point is the center tap of the transformer. I'm not going into detail about Grounding and bonding at this point.

The transformer would then be a 240 VAC Center tapped. What is fed to the residence is 120 V, 180 degress out of phase relative to the center TAP. The generator is likely Bifilar wound or two cables wound together and then separated for the proper phase.

So, you have a system that can deliver 240 V and 120 V. The plug would have terminals labeled L1, L2, Gnd, and Neutral.
L and N are at the same potential, Gnd should only carry fault currents.

So, there will be 120 V from G to L1 and G to L2. There will also be 240 V from L1 to L2. So, nothing is in parallel. The currents are such that Neutral carries the unbalanced current between L1 and H and L2 and G. So, if L1 carries 10 A and L2 carries 10 A, the neutral carries 0 amps.
If L1 carries 15A and L2 carries 10 A, then 5 A is carried by the neutral. The neutral current can be in either direction in the wire.

OK, here is where the fun starts. Some welders are designed to work on single or 3 phase and you might say What?

Internally, the welder looks like a transformer with 3 primaries wound on the same core. In this case, you could, in theory, supply 2 of the phases. and increase the output. You don't need three.

You can't exceed the design of the input currents though. And the cool part, phase doesn;t matter and so what, if one of the phases is disconnected.

It may depend on internal circuitry on what's allowed but the three phases can be phase angle fired together or independently, but only one is used for the reference. The unconnected phase will still see a voltage on it, but with no current.

I think some of these concepts is what's confusing everybody.

So, if the welder is single or three phase, then operating it on two separate unsynced single phase sources should be permissible.

Does any of this help? There are pieces missing and there are lots of things going on and some won't make sense to some. The reason why I know is that I worked on a three phase 208 VAC 15 KVDC 1 Amp power supply that effectively created DC. Three phase really wasn;t necessary, but it's a good clean way of the high power it needed. The box required 208 50 Amp 3 phase. Another similar unit required 70 A 3-phase 208. taps were available for the transformer.

So, by understanding the system, and in this specific case it's possible that 1 to 3 INDEPENDENT AC sources of the same amplitude and various phases would effectively increase the power output available from the welder. One phase can also be totally left out.
The AC sources add to the available current to the magnetics. This only works if the transformer used has multiple INDEPENDENT or "Y-connected" primaries and a single secondary.

Sorry April, I was thinking the TYPICAL combining of outputs. This isn't typical and would throw probably 98-99% of the people here off.

 

[april]

Well I appreciate the effort ,typing alone for us one finger typists is a big chore

In Australia we mostly use a 240V supply A/C -- we don't have 110V
The circuit diagram is accurate for my machine exactly
The Generator produces 3 phase I think and feeds to to an inverter which outputs 240V A/C
See my bottom note which says I noticed the outputs seem to be paralled .-I have yet to check that-The manual says don't combine outputs but I can't see why not
The welders I would use would be 240Volt copper wound transformer jobs and afaik the outputs are DC 70Volts for welding
Discussing other configurations just seems to confuse - it confuses me anyway

 

[KeepItSimpleStupid]

Same deal;3 phase AC is combined and rectified to get DC. No big deal. Car alternators do that every time.

Then PWM (or Pulse Width Modulation) takes over and the inverter takes this DC and converts it to single phase AC. No big deal. I understand that. That all makes lots of sense.

Now I know your in Australia, so I have another point of reference. Your 240 VAC is like our (US) 120 VAC.

And we are back to if you want higher current:
1. the inverters need a singe reference frequency
2. One acts like a voltage source
3. one acts as a current source.

You do need to talk about the welder. Particularly if it can run on single and 3 phase power.

 

[april]

The welders are single phase only. I'm in Florida often and they are now mostly 240V from what I have seen . Memphis was much the same

 

[KeepItSimpleStupid]

Just so you were thinking I was pulling your leg.

A 1 and 3 phase generator: **broken link removed**

Now, your kinda back to the same problem - combining the generators. The wikipedia article is the way to go with the light bulb or an oscilloscope.

Not sure how to make the phase change for one of them. Getting a schematic and/or reverse engineering it is sometimes possible. I suppose that speeding or slowing down a generator and bringing it back to 60 Hz is a way to move the phase. The light bulb is a way to verify phase, so is a scope. One could hope that a breaker would be enough to protect the generators and backfeeding could be detected by a bidirectional current sensor.

In any event, you would have to be able to disable speed regulation to be able to change the phase. It would then be trial and error. It doesn't have to be a light bulb - a voltmeter would do.

So, I think if you wanted to do it relaiablly you would either need to:

1. Work on the inverter side, so that both use the same clock. That's step one anyway.

-and/or-

2. Two Frequency meters each generator, two voltmeters each generator (phase to common), a voltmeter for phase to phase.

Then you need a special relay/switch (transfer switch) where the contacts are physically moved between the outputs.

 

[Sceadwian]

April, from the information you have provided there is no solution to your problem that doesn't require to you DRASTICALLY alter electrical and possibly mechanical nature of your generator.

As originally stated, buy an appropriate generator that can source the current you require from the single outlet. There is no other sane solution to your issue.

 

[kinarfi]

Here's my guess and 2 cents, you do have a wye wound generator, but I would guess the one of the legs is for power for the controls and the other 2 are for your single phased power out put. Both outlets appear to be in parallel and you have a separate winding for the DC out put. My guess is that the inverter allows the engine to run at about 1/2 speed when you don't need all the power available and take the low frequency output and converts for from (say) 150 volts @ 30 hz to 240volts @ 60 hz and works when you only need (say) 30% of the generator's capacity. When you start adding the need for more power, the generator speeds up and drops the inverter out of the loop. That way when you're not needing all the power available, your saving fuel and wear and tear by have the motor run slow.
Just my guess.
https://wiki.answers.com/Q/Difference_between_an_inverter_generator_and_a_generator