3Phase Genset Application

You could do that, or

How can we convert a three-phase AC to a single-phase AC? - Quora

No in certain circumstances, but there are other ways if you want to step the voltage down, create a single phase neutral line when one isn't available or provide isolation between sources that may be cheaper and more reliable.

What's the application exactly?

Yes it's foolish.

Three phase power is just three single phase lines 120 degrees out of phase with each other so you already have single phase available anywhere you have a three phase source and if the voltages required don't match the feed source a simple transformer is all that needed.

Actually it depends on the equipment and which country you are in and what earthing system you are using.

Single phase equipment designed to work with a single phase and a neutral bonded to ground potential won't necessarily work with two phases (atleast not for very long before going bang).

<...designed to work with a single phase and a neutral bonded to ground potential...going bang...>

What sort of equipment is that?

Equipment with internal EMI filter components spring to mind, or where the neutral is expected to be at 0V potential normally for either correct operation or electrical safety.

I have had problems in the past with power supplies not being rated for two phase operation for example.

What is your overall objective for doing this, greasy? Is it to derive a single phase from three phases with the load distributed evenly across all three? Just a hunch.

yes. I realize load balancing at low powers is probably not critical but I would like to utilize all three phases while retaining 3ph capability at the genset

You can run 3 phase or single phase from a 3 phase panel by using the proper leads....

That could be the best solution. All I need to do is find a used 3ph panel cheap. Thanks for the great diagram solareagle.

If this is meant for use on a "grounded" system, then the link between the neutral and the ground bus is missing. The drawing shows an ungrounded system.

Er, um, actually, what is shown could be part of a TT system; any neutral-to-earth connection at the upstream distribution transformer is not shown on the drawing.

how many TT based systems are 120/208 volt 3 phase?

None of them can be seen from here.

TT is used extensively in rural areas, and if the location is built-up, it doesn't matter what the voltage is as TT will very unlikely be seen.

There is no indication from the original poster as to the prevailing earthing arrangements in the location in question.

No neutral and earth bonding at the distribution panel? Oh hell no!

S.E. are you trying to kill this guy?

<...No neutral and earth bonding at the distribution panel...>

Ahem - one would not find it on a correctly-installed TT system.

True.

But greasy wants to use up all the three-phase into one single-phase line power and be totally balanced. I say it ain't gonna happen without other gymnastics of electrons.

What is the source voltages and power capacity and what the single phase load peak power consumption?

If none of its adds up to be a substantial value the rotary concept is just a huge waste of money and materials plus energy loss. Especially so if the single phase load ends up being only a fraction of the working capacity of any one single phase.

Also as far as I know rotary converters don't reach ~97% efficiency ranges until into the multiple 100's of KW/KVA range and only while operating at near 100% working capacity at that.

Realistically if you want to spread a single phase load out over all three phase, if its power consumption even justifies it, with a fairly even balance a simple transformer with a 'Zig-Zag' secondary output will do that.

Rotary converters (mg sets) are quite efficient, maybe 97 percent:

http://www.northamericaphaseconverters.com/faq/

Most sets on the market are used to convert single phase to three phase, but there is no reason the opposite could not be done.

Probably a more common method these days is to rectify the 3 phase to DC, then drive a single phase inverter.

Much easier and more efficient just to balance your loads across the 3 phases....any 2 leads will make 230v,, and any single lead will make 120v....unless you have a wild leg setup...

Any 2 will give 208, no? Granted this may be fine. Its that 3rd leg that bothers me. Anyway, if the transformational loses aren't too bad, it would be real easy....I have big 3ph motors just gathering dust..

If you have the motor already then it probably would be cost effective to build a rotary converter.

I have info on building one ^{somewhere but one that can cope with considerable power is pretty challenging, I thought.I know they are very expensive to buy too}

Do you actually need one? How big a single phase motor are you talking about?

I don't know, Solarreagle's seems to be grounded all right. Neutral and ground are apparently not bonded however. I've never fully grasped that part of things.

Consult a qualified electrician.

The neutral is grounded at some point....Either at the source or at the panel or both....Depending on what type and configuration your transformer is will determine the voltage on each leg, which should be tested first to see what you have to work with....You should test each leg to ground and the voltage combined on the different lines in....

You said you had 3Ø motors lying around gathering dust....So do you have 3Ø power available, or are you planning on having it installed?

..."There are two basic three-phase configurations: wye (Y) and delta (Δ). As shown in the diagram, a delta configuration requires only 3 wires for transmission but a wye (star) configuration may utilise a fourth wire. The fourth wire, if present, is provided as a neutral and is normally grounded. The "3-wire" and "4-wire" designations do not count the ground wire used above many transmission lines, which is solely for fault protection and does not carry current under non-fault conditions.

A four-wire system with symmetrical voltages between phase and neutral is obtained when the neutral is connected to the "common star point" of all supply windings. In such a system, all three phases will have the same magnitude of voltage relative to the neutral. Other non-symmetrical systems have been used.

In North America, a high-leg delta supply is sometimes used where one winding of a delta-connected transformer feeding the load is center-tapped and that center tap is grounded and connected as a neutral as shown in the second diagram. This setup produces three different voltages. If the voltage between the center tap (neutral) and each of the two adjacent phases is 120 V (100%), the voltage across any two phases is 240 V (200%), and the neutral to "high leg" voltage is ≈ 208 V (173%).^[8]"...

^{https://en.wikipedia.org/wiki/Three-phase_electric_power}

<...Neutral and ground are apparently not bonded however...>

They wouldn't be on a correctly-installed TT system.

Wait a minute! There is a bonding line present, isn't there?

Put simply for you, in the drawing in post #12 the distribution board is a main distribution board and hence in systems that require the neutral and earth to be linked for system safety the link must be in here. If it were a sub distribution board to the main distribution board then the link wouldn't be present in the sub board.

There may be variations depending on local codes and regulations, so the above is more of a basic explanation on safety concerns mentioned by others. Others more knowledgeable on US Canadian wiring regs may have other ideas or corrections to my broad comments.

Please follow the link in #23⇑.

If in doubt, consult a qualified local Electrician.

That's enough guys. Lets not beat a dead horse. We're well off topic anyway. Thanks to all.

How is wanting the basic specifications of your source and load going off topic?

Dead horses, and skunks, are regularly flogged into unrecognizable masses of rotting flesh here.

It just goes with the territory when you get this many personalities together, all with out-sized egos, or egos, depending on who's being the editor on any given day.

tcmtech is excluded because (to hear him tell it) he's perfect in every way.

The rest of us are guilty.

Yes, it's a dismal day when one's ability to stick to the facts and rational aspects of the topic at hand (marginally better than a squirrel with ADD) places one on a pillar of perfection compared to all others.

Easy now, sport, you don't want a swell head!

I know you are a swell guy, but don't be like a horned toad and get all puffed up, LOL!

As you can see, my tongue is hiding in my cheek, to avoid biting it.

Don't stop him.

I like to watch him get all huffy and blustery and make proclamations of superiority to the forum.

I just don't ever take myself that seriously and then I can't get all riled up and defensive.

I wonder if he has a Twitter account, like the yellow cheeto?

Maybe I'm just feeling a little trollish today.

Thanks Lyn, I was thinking just this morning "this is weird, I cannot find one mention of Trump in this thread?".

If this keeps up I will have to propose we amend Godwin's law to include both Hitler AND Trump.

Since there is nothing we can realistically do about Trump can we perhaps wait until he actually gets into office and does something we disapprove of before complaining about it, and then try and keep it in the break room?

I think we have all complained enough on his getting in to office to hold us over for a while, and it is not like the regulars to the site are not intimately aware of each others personal views on the matter by now.

You're right. We'll have plenty of ground to plow soon enough.

Stop it with the Cheeto, I like Cheetos.

PEOTUS is no Cheeto, Cheetah, or Cheater. If you call him Cheeto just one more time, it's off to the moon for you. Besides Cheetah is leaving office in 10 days.

Yes, it is.