120V to 120/240V. Transformer or other ideas?

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190914-1132 EDT

Some additional thoughts.

When a generator starts up, if it sees no existing terminal voltage, then it says I am the master and sets an internal memory saying so. Thereafter it is in a master mode that defines frequency, and no load voltage. Both the frequency and no load voltage can be invariant values, but their values are defined within this master generator.

Then the inverter of the master can synthesize an internal impedance that is relatively non-dissipative. This is done by changing the generated voltage as a function of load current. This would be some reasonable value. Possibly 5% from no load to full load. If an external power source parallels this master, then the voltage would rise because the external source is supplying some power, and the master would supply less power and current.

When a slave generator is added, then a self balancing occurs based on the synthesized internal impedances. This I have to think about a little more.

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190914-1212 EDT

fastline:

Since you have a Honda inverter generator you could run some of the experiments I described. This would possibly help us better understand if any of our ideas are correct.

It even might be possible to simulate slave operation by using power company supply as the master. One would do this by creating an internal impedance from the power company supply to a load, for example 1 or 2 ohms in series with a 1500 W heater. Then parallel the heater with the Honda. The choice of the resistor would be based on what the internal impedance of the Honda looks like, and what the experiment is to show.

1000 ft of #12 copper wire is about 1.5 ohms if memory is correct.

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190915-1527 EDT

Nobody has responded with any quantitive information on Honda internal impedance, or a description on how the inverter generators balance load. The patent reference did not adequately address this question.

Tried a new search string and found this result that is very useful and informative, but does not provide an answer. Google is a rather poor search engine these days. If I include internal impedance in my string, then don't bring up results that don't include that string as the first results.

The useful site found is http://www.screenlightandgrip.com/images/Protocol_Clean_Power_ Part2.pdf . A continuation of the site referenced in my previous post. This site does not answer my question, but has much useful general information, and has scope pictures, and FFT plots.

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The search string "parallel inverter load sharing" brings up quite a few papers on a Google search. The few papers I viewed were not directed at inverter generators specifically. But I think they are applicable to PWM inverters that typically have an H-bridge output stage and drive a passive load (by that I mean not a nearly voltage source type load such as the POCO in solar applications). Such inverters are used in UPS applications, inverter generators, and other places. So there may be useful information in these papers that's relevant to the present discussion.

A few papers are:

https://www.researchgate.net/profil...sing-effective-design-of-output-impedance.pdf​​​​​​

https://www.sciencedirect.com/science/article/pii/S1474667016440358
 
190915-1715 EDT

synchro:

Thanks. Good reference. Probably what Honda is doing.

I would like to see some experimental data on operation of Honda generators.

Assuming the droop method is used by Honda, then I believe my suggestion of an autotransformer driven by two generators, one on each half of the autotransformer, would be a bad idea. Transformer impedance would probably degrade balancing between the two generators. Therefore, both generators need to be directly paralleled, and drive 1/2 of the autotransformer. Thus, the larger autotransformer is required.

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fastline said:
Going to be employing a Honda EU3000 generator as a backup charge source for an off-grid DC inverter system. I must provide the inverter with 120/240V, 180* power to make it happy. There is little sense in running a bigger generator that has 120/240V and it cuts into efficiency.


the EU3000 is an inverter genny. I have a little transformer to step up to 240V when I need it but I have never seen a transformer like what I am looking for. Ideas? I was trying to think how I might consider a 120/240:240/480 transformer for the job, or possibly a pair of buck/boost and make the neutral?

trying to avoid using two transformers going 120 to 240, then 240 back to 120/240 with center tap.
Click to expand...
That is a huge amount of strength. To handle this, you'll need two thick wires. And if you have newer wiring with a 20 amp circuit and at least 12 ga cable, it can only support around 1800 watts of constant load, at most. Unfortunately, one circuit will never operate.

(edit) btw, 240v circuits are created by merging two 120v circuits, all of which takes place within the fuse box. They're known as double pole breakers.
 
Welcome to the forum.

Areba1 said:
That is a huge amount of strength. To handle this, you'll need two thick wires. And if you have newer wiring with a 20 amp circuit and at least 12 ga cable, it can only support around 1800 watts of constant load, at most. Unfortunately, one circuit will never operate.

(edit) btw, 240v circuits are created by merging two 120v circuits, all of which takes place within the fuse box. They're known as double pole breakers.
Click to expand...
We know all these things. BTW, this thread is 1.5 years old.
 
Two good transformers for this application are made by Victron.
Autotransformer
isolation-transformer

The autotransformer is what I use with two paralleled Honda 2200is 's to run my 400' deep 240v 16 amp well as well as my AC.
It is also used for load balancing on my Honda 6500is( allowing grater singe non split phase loads ).
 
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