Converting 3ph generator to 1ph

funkey_monkey

Got a small generator driven off a petrol engine.

I want to convert it from 3 phase to single phase.

What is the best way to go about this properly?

I've attached some photos so you can see what I have.

3 phase bridge rectifier and wind turbine inverter would do it...in theory..

Bruthal

In theory, 3 site transformers can have their primary windings connected in star formation to the gen output, and secondary windings in series.

Output would probably be around 220v in that setup once the secondaries are at the right polarity relative to each other.

But its just a sort of experimental thought in the head, and the universe might implode.

What do you want to do this for?

Wow, that sounds expensive and inefficient...Hrmmm I never tested that can I run them backwards and make 460V theory...be right back...

Bruthal

Sir Liamalot wrote: »

Wow, that sounds expensive and inefficient...Hrmmm I never tested that can I run them backwards and make 460V theory...be right back...

I doubt it is practical, it was more for the laugh. One experiment I never tried, and there have been many.

If 3 site transformers were used to output 3 phase 110v, would that be inefficient?

I'm pretty confident the wind turbine inverter would do.

ROFL at dreams vs reatily post in other thread.

Bruthal

Sir Liamalot wrote: »

I'm pretty confident the wind turbine inverter would do.

Im sure it would. Im more curious what the application is.

ROFL at dreams vs reatily post in other thread.

More about myself than anyone else I think

funkey_monkey

Plugged a 2.2kW kettle into it last night to test it and it was not able to boil the water.
It is to be used to power a shed and also maybe a secondary one to provide some necessary power into house during an outage (that would be wired in by a spark - not me!).
It will be used primarily for single phase items so the working theory is that converting to a single phase will be better for our needs.

Bruthal

funkey_monkey wrote: »

Plugged a 2.2kW kettle into it last night to test it and it was not able to boil the water.
It is to be used to power a shed and also maybe a secondary one to provide some necessary power into house during an outage (that would be wired in by a spark - not me!).
It will be used primarily for single phase items so the working theory is that converting to a single phase will be better for our needs.

Maybe 3 of those kettles, 1 on each phase, would have worked better.

To convert to single phase, rectify and invert is the practical way. The same as a VSD does it for frequency varying, and sometimes single in, to 3 phase out.

air

About the only practical option is to replace the head with a single phase one.
However, given the likely cost & hassle involved you'd be better off selling it & putting the proceeds towards a single phase set.
If on the other hand you just want to be able to boil a kettle, get a 1500W caravan one & you should be set.

bob mcbob

funkey_monkey wrote: »

Plugged a 2.2kW kettle into it last night to test it and it was not able to boil the water.
It is to be used to power a shed and also maybe a secondary one to provide some necessary power into house during an outage (that would be wired in by a spark - not me!).
It will be used primarily for single phase items so the working theory is that converting to a single phase will be better for our needs.

Check the current you are getting out of it before anything. In the pictures you sent it says it is rated to 6KW so one phase should be enough for a kettle.

Bruthal

bob mcbob wrote: »

Check the current you are getting out of it before anything. In the pictures you sent it says it is rated to 6KW so one phase should be enough for a kettle.

It should. But generators dont run as smoothly with 1 phase fully loaded and the other 2 with nothing.

air

The AVR on these is generally only monitoring one phase also & the rotor excitation applies to all 3 meaning a heavy load on one phase can lead to high voltages on the other 2 if they're lightly loaded.

funkey_monkey

Bruthal wrote: »

Maybe 3 of those kettles, 1 on each phase, would have worked better.

To convert to single phase, rectify and invert is the practical way. The same as a VSD does it for frequency varying, and sometimes single in, to 3 phase out.

I have access to 2 x 2.2kW kettles and a probably a 2kw hairdryer. That would be 6.4kW but if I turn hairdryer on low it should be okay for the limit.
What would be different about that setup compare to just a single kettle on a single outlet - why would that boil when it won't on its own?

Is there a device which I wire in that can do this or is it a matter of fiddling about with the preexisting wiring?

funkey_monkey

air wrote: »

The AVR on these is generally only monitoring one phase also & the rotor excitation applies to all 3 meaning a heavy load on one phase can lead to high voltages on the other 2 if they're lightly loaded.

The voltmeter was reading just shy of 300V when trying to boil the kettle.

Actually on second thought a turbine inverter won't work unless it's sooper cheep and nasty you'll have great difficulty getting past the anti-islanding.

If the set was working as it ought linking the outputs in delta and then transforming down would be the way forwards.

300V smells like AVR, proprietrary part on a smally, usually cheaper buy a new dino gobbler.

air

funkey_monkey wrote: »

The voltmeter was reading just shy of 300V when trying to boil the kettle.

Does it read out from the phase you were trying to boil the kettle from though?
My point on voltage regulation was more to point out the risk of possibly damaging equipment than in regard to your kettle experiments.

You really need a volt (& ideally current) meter on the outlet you're testing on to see what's going on.

It should boil on any of them but it might be worth trying the other outlets.
The hair dryer on low would be better to start with since it's power is tbetter matched to the generator.

Bruthal

Bruthal wrote: »

Maybe 3 of those kettles, 1 on each phase, would have worked better.

Has nobody else invented the three phase kettle?

funkey_monkey

air wrote: »

Does it read out from the phase you were trying to boil the kettle from though?
My point on voltage regulation was more to point out the risk of possibly damaging equipment than in regard to your kettle experiments.

You really need a volt (& ideally current) meter on the outlet you're testing on to see what's going on.

It should boil on any of them but it might be worth trying the other outlets.
The hair dryer on low would be better to start with since it's power is tbetter matched to the generator.

I don'think think so. Will check later, but from recollection is sits around 400V unloaded and then when load is switched on it dips slightly.

Bruthal

Sir Liamalot wrote: »

Has nobody else invented the three phase kettle?

Three phase heating loads are not three phase in the same way a 3 phase motor is. They dont need the phase displacement to work.

But the point was that a fully loaded phase on a generator with the other 2 unloaded, wont run smoothly. Generators wouldnt last long run like that, especially as they get larger.

Stage lighting tech Bruthal...I know what a grumpy set looks like. (Dances in resonance to the imbalanced sub woofer loading)

I have a three phase burco, one of a kind

Howyda melt a neutral? mathematically or with vector drawing.

Funkey Monkey the set is done....put a fork in her, she's a go-cart engine now.

funkey_monkey

It has never been used!

Bruthal

Sir Liamalot wrote: »

Stage lighting tech Bruthal

Thats what everyone says. Then they wire it wrong. Technical means nothing. 2 or 3 questions and no one knows the answer.

Howyda melt a neutral? mathematically or with vector drawing

With heat.

How d'ya wire a filament lamp wrong?

funkey_monkey

funkey_monkey wrote: »

It has never been used!

I'd try looking for a replacement avr (usually cost prohibitive) or claim warranty.
Smally gensets are not known for reliability.

Bruthal

Sir Liamalot wrote: »

How d'ya wire a filament lamp wrong?

I would say that is easier to wire than stage lighting anyway.

Bruthal

Bruthal wrote: »

Too much current, a welding torch, nuclear fusion

Can you do it with phase imbalance because loadsa technicians say you can but can never draw or calculate it?


I just balance the set and then go feel the cables.

We don't wire things (officially) we only plug them in.

Bruthal

Sir Liamalot wrote: »

Can you do it with phase imbalance because loadsa technicians say you can but can never draw or calculate it?

Did they ever do stage lighting?

funkey_monkey

Can you tell from this if it is star or delta?
It looks like star to me.

Bruthal

For a 3 phase and N socket, it would be star output.

funkey_monkey

I've been told there is something that can be done by modifying one of the phases to tap one off with an earth.
Not quite sure what it means yet so still trying to figure it out.

air

funkey_monkey wrote: »

I've been told there is something that can be done by modifying one of the phases to tap one off with an earth.
Not quite sure what it means yet so still trying to figure it out.

There isn't, that's what you have already as Bruthal has pointed out.
Each of the 3 single phase sockets is likely connected to a point on the star.
The star centre point forms your neutral (and earth) connection if you install an earth rod when running it.

Without modification or additional equipment your only option is to use single phase loads under the power rating of each phase, I'd suggest no more than 1.5kW.

air

Bruthal wrote: »

It should. But generators dont run as smoothly with 1 phase fully loaded and the other 2 with nothing.

I think it may depend to some extent on the number of poles on the generator head and how they are distributed.
It can be possible to have a pretty balanced (mechanical) load with only a single phase so long as there is nothing at all on the other two in some cases.

I've certainly seen it done and one quite large set I know of has ran like that for many years without issue.

On a small set like this I wouldn't be too optimistic of smooth running!

funkey_monkey

air wrote: »

Without modification or additional equipment your only option is to use single phase loads under the power rating of each phase, I'd suggest no more than 1.5kW.

This is what I was initially asking. What do I need in order to do this fully and correctly.

The method I was told about was phase-netural which you state above, but only having 1.5kW may not be sufficient for a kettle or some tools under load.

funkey_monkey

Can I sue something like this (maybe a better quality one, but similar nonetheless:

https://www.ebay.co.uk/itm/GENERATOR-SINGLE-PHASE-4-7-KW-AVR-VOLTAGE-REGULATOR/313038574076?hash=item48e28d91fc:g:oIgAAOSwLSZcFQy7

funkey_monkey

Just checked the AVR on the generator and the it is rated as 2.5kW.
So, as I told the owner initially I didn't think it was a 6kW generator. Or do the phases come into play here?

Would this be more than likely a 2kW generator and should it be expected to boil a kettle rated at 2.2kW?

air

It's just the rating per phase.
As I alluded to earlier, the AVR can only control the rotor current based on the voltage on a single phase (or the lowest voltage across all 3 hopefully).
Changing to a single phase avr won't help you at all. I'd imagine the only difference is that it only has a single voltage input.

The issue you have is that the generator head has 3 sets of windings instead of a single one (in simple terms).
The output of each of your 3 windings is unfortunately (for your purposes) 120 degrees out of phase so you can't simply parallel their outputs (this would short them out effectively).

Like I said, the best practical options in order of preference are:

1. Sell and buy a single phase unit
2. Make do with 1.5kW output
3. Find a single phase generator head and avr for it and swap that out.
4 . Rectify and invert the output as has been suggested

Option 1 really is the winner in my opinion.
A 3 phase set with that kind of power rating is going to have quite a limited market unfortunately as it's of limited use as you have discovered.

2011

I worked with a company (sadly no more) where we had exactly this issue. A 3 phase supply but we needed single phase. We also needed to balance the loading across the 3 phases as evenly as possible. One solution we explored was a “Scott-T” transformer. They are quite unusual but will do the trick.

As transformers are passive units there is very little to go wrong with them.

funkey_monkey

2011 wrote: »

I worked with a company (sadly no more) where we had exactly this issue. A 3 phase supply but we needed single phase. We also needed to balance the loading across the 3 phases as evenly as possible. One solution we explored was a “Scott-T” transformer. They are quite unusual but will do the trick.

As transformers are passive units there is very little to go wrong with them.

Rectify and invert the output as has been suggested

Any ideas if/where I could source a product (or even a price) for the transformer or a rectifier/inverter?
TBH - I'm not sure what I'd been looking for and the owner is asking me if I've found out what to do yet.

funkey_monkey

Penny might have dropped here. On front there are three 220v outlets and a 380v outlet of larger diameter.
Is the large outlet 3 phase and the 3 smaller ones an output for each phase?

2011

funkey_monkey wrote: »

Any ideas if/where I could source a product (or even a price) for the transformer or a rectifier/inverter?
TBH - I'm not sure what I'd been looking for and the owner is asking me if I've found out what to do yet.

That is the beauty of the Scott T transformer solution, simplicity. You don't need a rectifier, all you need is a transformer. I think you may have to get it specially made. From memory our 3 kVA unit cost around €400 and we got it made in Ireland.

Tuco88

I would be in the same camp as selling at at this stage.How often will it be needed?


You could install a VIP meter on the unit, anything that will tell you the amps/voltage per phase. So at least you can balance the loads over the 3 single phase outlets as best as you can.

funkey_monkey

So two of the single phases cannot be linked to provide increased current and there fore power?

funkey_monkey

Tuco88 wrote: »

I would be in the same camp as selling at at this stage.How often will it be needed?


You could install a VIP meter on the unit, anything that will tell you the amps/voltage per phase. So at least you can balance the loads over the 3 single phase outlets as best as you can.

It will be used regularly as in daily in the shed especially over winter, maybe less so in the summer months.

air

funkey_monkey wrote: »

Penny might have dropped here. On front there are three 220v outlets and a 380v outlet of larger diameter.
Is the large outlet 3 phase and the 3 smaller ones an output for each phase?

Yes, almost certainly.

funkey_monkey

Can one of these inverters be used on the Generators 12V DC/8.3A output?

It has a continuous power rating of 2kW and 4kW peak.

Yinleader 2000W (4000W Peak) POWER INVERTER DC TO AC 12V TO 230V 240V WITH SOFT START

air

funkey_monkey wrote: »

It has a continuous power rating of 2kW and 4kW peak.

It does, but to provide 2kW it needs a 12V supply source capable of providing about 200A - a bit more than the 8.3A the 12V winding on your head can provide!

That 12V output is designed for keeping starter batteries topped up and no more.

Bruthal

Yea the 12v output is about 0.1kw.

funkey_monkey

Owner now wants to know what would happen if he put a 3 plug on the end of the 3 phase outlet?
Would that be any different to his single phase outlets?
My understanding is that 3 phase has 3 hot wires - one for each phase and a neutral. There is also an earth. So he can't get anything better than what the single phase outlets provide him.
Correct?