GENERATOR QUESTIONS FOR YOU EXPERT ELECTRICIANS

[Industrial Toys]

TOTALLY incorrect. 110/220 is NOT split PHASE, it's single phase, centre tapped neutral on a transformer.



Transsformer I drove to Buffalo for, to make 110/220 on my project. Harder to find a 110/220 to 110/220 transformer than I expected, especially in this third world
country.



Messing about with installation of transformer. Generator sits atop frame.

 

[techman]

You are correct that 120/240 is from a single phase. This is commonly referred to as "split phase", as in splitting one phase. The only issue with a transformer is that you need one large enough to handle inrush if you are starting motors. The inrush current is multiplied 2:1 at the 120 side. Too small of a transformer will result in saturation and major voltage drop when the load is applied, and possibly toasting the transformer if left in that state long enough.

paul

 

[3Ts]

Welders typically do not need (or use) the center tap on a 240 v circuit. (2 hot wires and a ground) The neutral is what provides 120 v for things like electric dryers, etc that use both 240 v and 120 v circuits - hence the 4 wires on the newer units.

 

[Industrial Toys]

I never really thought what the term split phase meant, but now that makes sense, although confuses people. This particular transformer has dual windings on each side and on the side you wish to use 110 input, you paralell up the windings, so I assume that increases the current capability. I LOVE transformers! Thanks Tesla!

 

[RNeumann]

Welders typically do not need (or use) the center tap on a 240 v circuit. (2 hot wires and a ground) The neutral is what provides 120 v for things like electric dryers, etc that use both 240 v and 120 v circuits - hence the 4 wires on the newer units.

In addition, the typical transformer that someone would source would simply step the voltage from 120v to 240v. Meaning, if you were to look at it on an oscilloscope the one wire would be making 240v and the other wire would be a neutral making 0 volts. This, as you state is different than what we have here in the USA- one wire making 120v and the second wire making 120v but out of phase 180 degrees. In this scenario each of the 120v wires is acting as the other wire’s neutral. This can be verified by using a volt meter and going from 1 of the legs to ground- you get 120v. But if you go from one of the 120v legs to the other 120v legs you get 240v. But if you simply grab a transformer and step the power from 120v to 240v you would get 240v from one leg to ground and 0v from the other leg to ground.
While it’s the same voltage, it’s not achieved the same way. Because of this some appliances don’t like it. Some obviously need a neutral for 120v. But even a “simple” 2 wire 240v appliance may not want a 240v and a neutral. It may want 2 wires that are 120v each but out of phase 180 degrees.

 

[BrokenTrack]

I got a crazy generator.

It is a 4 cylinder gas/propane generator, liquid cooled, but only produces 3000 watts. However, this is the crazy part, it produces that power at either 1 or 3 phase depending on what you want. I know there are many 3 phase generators, but I have never seen one so small in Kw's that can have either.

 

[Industrial Toys]

I could be wrong, but I understand that running a three phase capable set on single phase always means derating. There simply isn't a way around it. Unless it's maybe two generators in one, a single phase and a three phase, but that would be very wasteful and much larger than it had to be.

 

[grsthegreat]

When I bought my old generator that I used to power my trailer and build my house (1995ish) it was a 4,000 watt 1800 rpm propane unit that was sold as scrap as it was burning up peoples tools on the jobsite where it was located. I purchased it as a project unit thinking I could rebuild it. Turned out it was wired for 3 phase. I rewired it for single phase and I had it running smoothly until I sold it 3-4 years ago. Got it for a song and sold it for way more than I paid for it. In all the years since, I have not seen a generator like it that was multiphase, 1800 rpm air cooled. If it would have produced more power I would have kept it.

 

[BrokenTrack]

I could be wrong, but I understand that running a three phase capable set on single phase always means derating. There simply isn't a way around it. Unless it's maybe two generators in one, a single phase and a three phase, but that would be very wasteful and much larger than it had to be.

I am not sure. I has this box that allows it to be switched over. It is a 1943 US Air Force generator...a monstrosity considering it is only 3000 watt...

 

[567Chief]

I am not sure. I has this box that allows it to be switched over. It is a 1943 US Air Force generator...a monstrosity considering it is only 3000 watt...

Must be from the Army Air Corps considering the Air Force began in 1947.

 

[3930dave]

TBone - if your truck has a receiver, what about one of these rxer platforms with a loading ramp ?

Hitch Cargo Carriers and Cargo Baskets

If your 240 gen has wheels (or you can strap it onto a dolly), might be easy enough for one person.

Rgds, D.

 

[BrokenTrack]

Must be from the Army Air Corps considering the Air Force began in 1947.

Or maybe a 1947 instead of a 1943? I am pretty sure it says US Air Force, but it is pretty rusted up so I could be wrong on either point...

 

[aczlan]

I could be wrong, but I understand that running a three phase capable set on single phase always means derating. There simply isn't a way around it. Unless it's maybe two generators in one, a single phase and a three phase, but that would be very wasteful and much larger than it had to be.

It depends on the set, if it's a 12 lead genset and all 12 leads are brought out, it can be configured for either 3 phase or single phase with full power for either one.

Aaron Z

 

[Industrial Toys]

I don't think that's possible. Unless maybe a third of it isn't being loaded so really doesn't cost fuel, but it would run unbalanced. I don't profess to understand how you can get single phase from the remaining two phases. Wouldn't the timing be different from a generator that makes 60 cycles with a varying equal number of poles?

I did Google it and it seems that I maybe right that you only can get 60% of the generator capacity.

 

[aczlan]

See the specs for the MEP002 and MEP003, both put out the full output on single phase or 3 phase: Steel Soldiers::Military Vehicles Supersite - MEP WIKI

It has to do with how the leads inside the generator head are wired. If all 12 leads come out and are spliced outside the head, you can rewire them to either single or 3 phase. If they are spliced inside the generator head (like most are), you can't.

Aaron Z

 

[BrokenTrack]

See the specs for the MEP002 and MEP003, both put out the full output on single phase or 3 phase: Steel Soldiers::Military Vehicles Supersite - MEP WIKI

It has to do with how the leads inside the generator head are wired. If all 12 leads come out and are spliced outside the head, you can rewire them to either single or 3 phase. If they are spliced inside the generator head (like most are), you can't.

Aaron Z

This makes sense as there is a box that is bolted to the generator, and the leads are inside that box. The box then has switches inside it that switch it over from single to 3 phase.

 

[Industrial Toys]

Then explain the physics to me, because I don't think it's possible. If it's a three phase alternator, you can only get 60%. Unless it's actually wound as two alternators, single and three phase. I wouldn't doubt it for the military, but I think it's unlikely.

 

[CobyRupert]

Then explain the physics to me, because I don't think it's possible. If it's a three phase alternator, you can only get 60%. Unless it's actually wound as two alternators, single and three phase. I wouldn't doubt it for the military, but I think it's unlikely.

It's been awhile...but...
Let's say it's a 3 phase, 2 pole (3600 rpm) generator like I think I show below. (Phases are "A", "B" & "C". "2 Poles" of phase A are labeled "A1" & "A2"; 2 poles of phase B are labeled "B1" & "B2", etc... p.s.: Notice how A1, B1, C1, etc.. are all 120 degrees out of phase with each other because this is 3 phase)

A picture can better describe.

I think if you connected together all the windings on the bottom half in series to form 1 big pole, and all other windings on the top half in series to form (the other) pole, you'd have a single phase, 2-pole, genny with full capacity:

 

[Industrial Toys]

I could be wrong, just sayin. But that sounds like a great big short! Trying to get a hold of the guy that rewinds my generators for his input. Because I would really like to know.

 

[Industrial Toys]

I saw something on wiring a zig-zag configuration on a MEPS 12 terminal type genset. It was not well explained. I am interested and will try and find something to make me understand it. Always interested in understanding how things work as opposed to just believing what I am told.

So do MEPPS sets typically have more windings than a run of the mill 3 phase alternator? Not that I yet understand the phase implications.