The OP did provide a diagram.
Amperage output of generator
- Thread starter I start fires
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kwired
Electron manager
- Location
- NE Nebraska
Yes, the double delta configured to get 120/240 single phase that was pictured in post 1.
not sure if that is correct for the machine or what he thinks it is and copied from the internet?
kwired
Electron manager
- Location
- NE Nebraska
At some point he said it was how it was already connected when he acquired the machine.
he 'thinks' that is how it is wired, he has no manual or drawings
I believe the nameplate is correct
45 kw
120/208
1 ph
but who knows without opening up and looking at it
kwired
Electron manager
- Location
- NE Nebraska
I thought he did open it up and has verified the connections. If each coil is 120 volts, then he has two connected in series - that will yield 240 with a 120 volt center tap. Other 4 coils are there to sell excess copper and steel I guess.:blink:
kwired
Electron manager
- Location
- NE Nebraska
Which I assume prompted OP to post questions in the first place.
My best guess as has been suggested is this generator can be configured in multiple ways, but the nameplate is sort of geared toward one possible connection, yet not everything on the plate seems to go together.
the nameplate is correct imo
I have seen others on the net from the same company stamped 120/240
what we don't know is how the 3 ph was derated: 33%, 40%, 50%???
and how they rounded that: was it 47.2 kw rounded to the nearest 5, ie, 45
he is calling it a 3 ph 45 kw machine with a 100 HP derated to 37 kw
the 3 ph to 1 ph derating factor is 33% or 50% depending on source, but nowhere is it <20%
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We can speculate til the cows come home. Perhaps we should ask him if he can respond to the question I asked in post #15.
kwired
Electron manager
- Location
- NE Nebraska
So if it is more then 45kW if one utilized all three phases, yet they intentionally de-rated the machine and gave it a single phase rating, why not put single phase amps that corresponds to the kw and power factor they marked it with? Maybe amps is correct and one of those other values is wrong?
If it is rated 45 kW but for just the one third of windings being utilized, seems like that would be pretty expensive compared to a unit designed or single phase only with similar capacity, but those that design things never go overboard on specifications and the OEM never complained about making that sale either:happyno:
If it is rated 45 kW but for just the one third of windings being utilized, seems like that would be pretty expensive compared to a unit designed or single phase only with similar capacity, but those that design things never go overboard on specifications and the OEM never complained about making that sale either:happyno:
If you take my suggestion that is based on 230V utilisation from a 240V generator (which is the exact same ratio as 460/480) then no rounding is required for the current, the kW or the kVA.
You get the exact data that's on the nameplate.
- Location
- San Francisco Bay Area, CA, USA
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- Electrical Engineer
The problem here as I see it is that the configuration he is seeing would provide 120/240V single phase, BUT the nameplate says 120/208V single phase, then when he looks inside, he sees 6 windings, indicating a 3 phase base design.
As I said earlier, above 25kW single phase, this is S.O.P. for generator mfrs, they use a standard 3 phase generator and allow it to be connected as that diagram shows to get single phase at 1/3 reduced capacity (2/3 of stated capacity). It saves the genset mfrs from having to make a lot more versions of single phase generators available.
All of that would be standard industry practice, EXCEPT that his NAMEPLATE says 120/208V. The only valid way of getting 120/208V single phase from that generator is if he connected it for 3 phase and only uses one. If that's the case, then what does the 45kW refer to PER THE NAMEPLATE? Is that saying 45kW AT single phase, which would mean it is a larger 3 phase generator and he is only using one phase that gives him 45kW capacity? Or is it saying it is a 45kW 3 phase generator but if using only 1 phase from it, the capacity he has at that one phase is less than that? Or is the nameplate voltage stamped wrong and the single phase output is 45kW at 120/240V split phase?
As I said earlier, above 25kW single phase, this is S.O.P. for generator mfrs, they use a standard 3 phase generator and allow it to be connected as that diagram shows to get single phase at 1/3 reduced capacity (2/3 of stated capacity). It saves the genset mfrs from having to make a lot more versions of single phase generators available.
All of that would be standard industry practice, EXCEPT that his NAMEPLATE says 120/208V. The only valid way of getting 120/208V single phase from that generator is if he connected it for 3 phase and only uses one. If that's the case, then what does the 45kW refer to PER THE NAMEPLATE? Is that saying 45kW AT single phase, which would mean it is a larger 3 phase generator and he is only using one phase that gives him 45kW capacity? Or is it saying it is a 45kW 3 phase generator but if using only 1 phase from it, the capacity he has at that one phase is less than that? Or is the nameplate voltage stamped wrong and the single phase output is 45kW at 120/240V split phase?
If all 12 ends are brought out he can connect it any way he likes. The double delta configuratiiion shown in post #1 would hive 120-0-120 single phase.
Tony S
Senior Member
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- Resting under the Major Oak UK
This may jog a few memories http://forums.mikeholt.com/showthread.php?t=172825
I knew I’d seen the double delta layout before.
I knew I’d seen the double delta layout before.
Damn, you gave the solution with that post above! Here are my calcs:
Ouput - 45 kW
Voltage = 115 VAC
3-phase amps = 282.5 amps
But when connected in 1-phase (zigzag configuration), both phases loaded with 22.5 kW each (1/2 of the nameplate rating), the resulting line currents:
L1-N = 244.57 amps @ 0.8 PF;
L2-N = 244.57 amps @ 0.8PF
the voltage is 120/240 or 120/208
all that mfgs machines are marked that way, not 115
imo they derated the machine from ~70 rounded to ~ 45 (-33% actually 47 range but rounded down)
the firm that bought the rights from the mfg will know
this would jive with the HP
I start fires
Member
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- Litchfield, Connecticut, USA
Well, It looks like you're right. Thank you by the way,
At closer inspection the leads are more like #4's.
I thought they were smaller because I took it apart years age to tighten up the lead connections. I guess they looked smaller to me then.
It has to be a 70.6 kw machine if it were rewired in doubled-up star if it can pull 245 amps in the double delta.
245 amps from two windings =122.5 from a single one.
6 windings pulling 122.5 amps = 735 amps @120v.
735 divided by 3 phases = 245 amps per phase.
Wired in star = 208v @ 245 amps x 1.732 = 88.262KVA
88.262KVA X .8 pf = 70.6KW
The plate reflects the output of the machine with the double delta lead configuration.
I expected the plate to reflect the max potential output of the generator which would be 3 phase.
A dumb assumption, I guess.
I was further confused by the plate stating single phase but listing the voltage as 120/208.
120/208 implies a 3 phase internal connection.
Currently, the machine is single phase but it is incapable of making 208 volts while wired for single phase.
Seems to me the plate should say Amps: 490/245 Volts: 120/240 Phase:1
I think that 208 was a typo.
I did dig myself in a hole saying a single phase machine should only have a PF of 1, that was a dumb thing to say.
Yes, a single phase generator can power an inductive load, sorry.
It's my understanding that most industrial setting generators (especially 3 phase) are rated at .8 pf because they are expected to run mainly inductive loads which on average, are at a .8 pf.
Single phase generators are generally rated at 1.0 pf because they are generally used in household settings where the largest loads are expected to be resistive. Hot water, electric stove, dryer, etc.
This generator is certainly of the industrial class so the .8 pf does make sense. Sorry for sounding like a dimwit.
Actually, I don't understand why generators are rated in a specific power factor at all. The load makes the power factor, not the generator. If I use this 45 KW generator to run nothing but electric heat and light bulbs, wouldn't I have a 56.25KW generator?
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you are correct on the 1 ph pf rating issue, it is a bit confusing
although 1 ph can supply reactive power, most machines I looked at rate 1 ph at a pf = 1, go figure
but an older machine like this , who knows
the reason they give a pf is to give you an idea of how much reactive power the machine can supply and remain stable
0.8 should cover most motor loads under steady state conditions
the 120/208 is puzzling, I'd be curious as to what the mfg would have to say
#4 lead wire is good for ~ 200 A
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