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If the gen is rated to 4000w running load - that comes out to 33.333 amps, or 66% over the breaker rating, or 166% of the breaker rating.

By that math - it would counter your theory that a breaker should break at 145% - the gen's running wattage would be 21% beyond that 145% number.

So if that is the case - again, the breaker should be the weak point. Instead, the inverter faulted.
If they rate a gen at 4000W continuous, that is usually the 240V rating that they are giving (unless it has a switchable 120V only mode).

But your gen is rated at 5500W (on gasoline) so that gives 5500 / 2 = 2750W (22.9A) available at the 120V receptacles. However, they put 20A breakers on those receptacles. In terms of percentage, 22.9A is only 114% of the breaker rating of 20A.

However, I don't think the breaker is your issue as it is not tripping. The inverter is able to control the output current much faster than the breaker can react to your welder. The surge demand of the welder at the 110A output is pushing the inverter faster to overload quicker than the breaker reacts. Apparently, that particular load puts the gen just right at the point of either the breaker or the inverter tripping out. In this case, it is the inverter that is beating the breaker.

On some gens they don't even use a breaker on the highest capacity receptacle on the panel. They just let the inverter do the work of limiting the output at the receptacle. My gen is like that.
 

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Discussion Starter · #22 ·
I just found this: How to Easily Connect an Inverter Welder to a Portable Generator

View attachment 12670

If I key in 110A into the formula above, along with the welding inverter 85% efficiency and 25% margin, the power required comes out as 4,044W. I'm sure you have enough surplus capacity (5500W peak) and that the formula is a little conservative.

I have another theory however. I'm thinking that the current demand of the welder is too transient/instantaneous or spiky. The engine may not be fast enough to jump up to full throttle to supply the generator inverter's power demands. And so, the bulk capacitors runs out of reserve and the inverter just stalls and gives out an overload condition.

You can validate the generator's true capability by using a more traditional resistive load like a bunch of space heaters to find its upper limit. If it still falls short of the 4000W continuous or 5500W peak, then you'll have something to complain about.
Interesting post. I haven't totally digested all of it yet, but this appears to be good information.

One major question I have is on the inverter circuitry. That is all hidden in a "black box" labeled as "control unit" on the parts diagrams/schematics. If I could get a schematic of the "control unit" that would be pretty helpful.

I would venture a guess the capacitors you mention are on the DC side - post 3-phase AC alternator. If the capacitance was increased with more/larger capacitors I would be curious what would happen.

However, the "control unit" is a 5 sided box and is filled with potting compound - so it would be very difficult to work with any of the circuitry.
 

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Interesting post. I haven't totally digested all of it yet, but this appears to be good information.

One major question I have is on the inverter circuitry. That is all hidden in a "black box" labeled as "control unit" on the parts diagrams/schematics. If I could get a schematic of the "control unit" that would be pretty helpful.

I would venture a guess the capacitors you mention are on the DC side - post 3-phase AC alternator. If the capacitance was increased with more/larger capacitors I would be curious what would happen.

However, the "control unit" is a 5 sided box and is filled with potting compound - so it would be very difficult to work with any of the circuitry.
Yes, the capacitors would be on the DC side of things. Anyway, that was just speculation. That's coming from the nature of welders' demand for high current transients in general. At a certain point, the inverter may be unable to recover in time.

This is a particularly good candidate for fast-acting ammeters.... or an oscilloscope, to capture said transients and see if they actually do exist.
 

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Discussion Starter · #24 ·
On another parallel thought -

I'd be curious if there is a way to over-ride the throttle control and get the engine to run wide open. There is a steppir drive on the throttle on this gen, directly on the carb - no linkages. I imagine the drive to the steppir is fairly standard. I don't know off the top of my head how many wires there are, but it is conceivable to switch those out to an external control.

The overall theory here is to drive the alternator to where it is when it outputs full power before the inverter can tell it to throttle back - that way there is no "recovery time" as it is "already there" when the current hits.
 
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