Amperage output of generator

[I start fires]

I did say that the engine was a 100 hp diesel but to be honest, I don't know the exact hp.
Could be 75 for all I know.

 

[kwired]

I assume 45kw 3 phase because
(1) the plate says 45 kw
(2) the only voltages listed are 120/208

Seems reasonable that the plate is trying to tell me that it is a 45 kw machine if it is configured for 120/208 volts.
I suppose it is possible that it is a 75Kw generator but the undersized diesel generator effectively makes it 45kw.
Does the nameplate take in to account the hp of the engine?

I'm just skeptical of 125 or 130 amps flowing down the same size wire that your electric range is hooked to. If the leads were 2 gauge wire I would have no problem swallowing the 245 amp output.

I know that chassis wiring amperage is rated differently, and of course there is a fan cooling the windings but this seems a little too ridiculous.

Maybe the wire can handle the heat but I would at least expect the electrical tape to melt off where the leads are joined if they're pulling 120+ amps.

The conductor can handle well over 125 amps, how much can handle before insulation lets out smoke depends on insulation characteristics,forcing cooling air throug the unit lowers the temp. A lot of motors have small leads compared to the branch circuit conductors we run to them, but they usually have higher temp rating then what we are running for branch circuits, and some motors have cooling air passing through the motor which helps. Any tape they use in such applications is likely high temp instead regular vinyl tape.

 

[Ingenieur]

I assume 45kw 3 phase because
(1) the plate says 45 kw
(2) the only voltages listed are 120/208

Seems reasonable that the plate is trying to tell me that it is a 45 kw machine if it is configured for 120/208 volts.
I suppose it is possible that it is a 75Kw generator but the undersized diesel generator effectively makes it 45kw.
Does the nameplate take in to account the hp of the engine?

I'm just skeptical of 125 or 130 amps flowing down the same size wire that your electric range is hooked to. If the leads were 2 gauge wire I would have no problem swallowing the 245 amp output.

I know that chassis wiring amperage is rated differently, and of course there is a fan cooling the windings but this seems a little too ridiculous.

Maybe the wire can handle the heat but I would at least expect the electrical tape to melt off where the leads are joined if they're pulling 120+ amps.

it also says 1 phase
you can find the same model rated for 100 kw 3 ph

 

[I start fires]

The machine can supply 245 A 120/240 1 ph
the nameplate is correct
each winding handles ~1/2 of that ~125 A

the machine can produce 75 kw, 0.8 pf, 93.75 kva, 120/208, 260 A
or 130 per winding

Why assume 45 kw 3 ph (why over size the engine???)

do not confuse the windings with the lead ampacity

If its a 75 kw machine, why did an employee of Kurz & Root stamp 45 kw on the plate?
Why is there no mention of the 93.75kva?
Where did you come up with 75KW?
Are all of the values on the plate for single phase?
If so, why is there a kva of 56.25 but a kw of 45?
Why not mention it makes the 245 amps @240 volts?
A single phase generator would have a power factor of 1.0
only a 3 phase generator would have a power factor of .8
56,250 x .8 = 45,000
Plate clearly lists the pf @.8
45,000 watts @ 56,250 VA screams 3 phase!
If single phase, KW and KVA would be the same number.

Maybe I'm simple.

 

[I start fires]

it also says 1 phase
you can find the same model rated for 100 kw 3 ph

I don't have any other info on this at all unfortunately.

If that thing can make 100 kw @ 208 I'll eat my hat.

100kw = 125kva
125,000 / 120v = 1,041.6 amps

1,041.6 amps@120 volts / 6 (120 volt windings) = 173.6 amps per winding.

Stator leads if I'm being generous are maybe 6 gauge. That's gonna get warm.

 

[kwired]

If single phase, KW and KVA would be the same number.

Why do you think that?

KW is what is passed on to the prime mover. KVA results in extra current that does no work between the source winding and the load.

Any inductive load is going to have kVA that is different then kW, whether single or three phase. Any capacitive load is going to have kVA that is different then kW, but in the opposite direction of an inductive load.

 

[I start fires]

The conductor can handle well over 125 amps, how much can handle before insulation lets out smoke depends on insulation characteristics,forcing cooling air throug the unit lowers the temp. A lot of motors have small leads compared to the branch circuit conductors we run to them, but they usually have higher temp rating then what we are running for branch circuits, and some motors have cooling air passing through the motor which helps. Any tape they use in such applications is likely high temp instead regular vinyl tape.

I'm smart enough to know I don't know everything.
You may be 100% right, but If I let the smoke out of the stator by doing something I'm unsure about, I'm going to have a tough time getting the smoke back in.

 

[I start fires]

Why do you think that?

KW is what is passed on to the prime mover. KVA results in extra current that does no work between the source winding and the load.

Any inductive load is going to have kVA that is different then kW, whether single or three phase. Any capacitive load is going to have kVA that is different then kW, but in the opposite direction of an inductive load.

You're right, I shouldn't have said it that way. It's just that the single phase generators that I have encountered always say 1.0 power factor. every 3 phase one I have seen has said .8
That's what I meant.

 

[kwired]

I'm smart enough to know I don't know everything.
You may be 100% right, but If I let the smoke out of the stator by doing something I'm unsure about, I'm going to have a tough time getting the smoke back in.

Look at the size of conductors used for windings, they may be smaller then the "leads", but still carrying same current. They don't have the same kind of insulation on them, and may have difference in air flowing over them as well. Those "leads are so short, they likely do sink some heat into your field conductors and the winding conductors as well.

 

[Ingenieur]

If its a 75 kw machine, why did an employee of Kurz & Root stamp 45 kw on the plate?
Why is there no mention of the 93.75kva?
Where did you come up with 75KW?
Are all of the values on the plate for single phase?
If so, why is there a kva of 56.25 but a kw of 45?
Why not mention it makes the 245 amps @240 volts?
A single phase generator would have a power factor of 1.0
only a 3 phase generator would have a power factor of .8
56,250 x .8 = 45,000
Plate clearly lists the pf @.8
45,000 watts @ 56,250 VA screams 3 phase!
If single phase, KW and KVA would be the same number.

Maybe I'm simple.

derated 33% 1 ph
Are you saying a single ph source can't power a reactive load?
nameplate is stamped 1 phase

45 kw / 0.8 / 240 ~ 245 A

200C #8 hook-up wire is good for 124 A
250 even higher 150 range

 

[kwired]

45 kw / 0.8 / 240 ~ 245 A

Is much closer to 235 then 245, but is also closer then trying to apply any three phase figures to the amps stated on the nameplate.

I didn't know we were playing horseshoes or hand grenades here, which is where close is actually a good achievement.

 

[Besoeker]

If its a 75 kw machine, why did an employee of Kurz & Root stamp 45 kw on the plate?
Why is there no mention of the 93.75kva?
Where did you come up with 75KW?
Are all of the values on the plate for single phase?
If so, why is there a kva of 56.25 but a kw of 45?
Why not mention it makes the 245 amps @240 volts?
A single phase generator would have a power factor of 1.0
only a 3 phase generator would have a power factor of .8
56,250 x .8 = 45,000
Plate clearly lists the pf @.8
45,000 watts @ 56,250 VA screams 3 phase!
If single phase, KW and KVA would be the same number.

Maybe I'm simple.

I'm not sure how you conclude that a single phase generator would be unity power factor. Doesn't that depend on the nature of the load?

 

[Ingenieur]

Is much closer to 235 then 245, but is also closer then trying to apply any three phase figures to the amps stated on the nameplate.

I didn't know we were playing horseshoes or hand grenades here, which is where close is actually a good achievement.

really? Closer to 235 than 245??? How did you figure that out????


it's a 3 ph machine derated to 1 ph
who knows what derating method, rounding, etc. they did
perhaps they limited to conductor rating
it is obviously not 3 ph = 245 x 208 x sqrt3 = 88+ kva

no need for the snarky last comment
engineering is a series of estimates and approximations
if I size a required vessel at 9768 gal, is it 'wrong' to order a 10,000?

 

[GoldDigger]

I'm not sure how you conclude that a single phase generator would be unity power factor. Doesn't that depend on the nature of the load?

A more correct statement would perhaps be that a single phase generator specifications may rate it for a unity power factor load. Clearly the output of the generator will have to match whatever load is attached. Some voltage regulation schemes will not work well with a capacitive or low power factor inductive load.
As a general rule the kVA is limited by the winding configuration while the kW is limited by the prime mover power. Like all general rules it does not always apply.

 

[Besoeker]

A more correct statement would perhaps be that a single phase generator specifications may rate it for a unity power factor load. Clearly the output of the generator will have to match whatever load is attached. Some voltage regulation schemes will not work well with a capacitive or low power factor inductive load.
As a general rule the kVA is limited by the winding configuration while the kW is limited by the prime mover power. Like all general rules it does not always apply.

Agreed. You put it better than I did.........

 

[kwired]

really? Closer to 235 than 245??? How did you figure that out????


it's a 3 ph machine derated to 1 ph
who knows what derating method, rounding, etc. they did
perhaps they limited to conductor rating
it is obviously not 3 ph = 245 x 208 x sqrt3 = 88+ kva

no need for the snarky last comment
engineering is a series of estimates and approximations
if I size a required vessel at 9768 gal, is it 'wrong' to order a 10,000?

derated 33% 1 ph
Are you saying a single ph source can't power a reactive load?
nameplate is stamped 1 phase

45 kw / 0.8 / 240 ~ 245 A

200C #8 hook-up wire is good for 124 A
250 even higher 150 range

Well to start with your formula of 45kw/0.8/240 is 234.375, how close is close enough on such information.

10,000 gallon tank when 9768 is no different then OP having a 43, 324 VA load and ordering a 45 kVA generator. I would expect a nameplate on such a machine not to have any significant rounding of such figures. Rounding of 234.375 to 235 or even 237 to 240 I could understand, but not rounding either figure to 245.

Maybe it wouldn't have seemed so snarky if I had included a ? I wasn't trying to be too snarky.

 

[Besoeker]

Well to start with your formula of 45kw/0.8/240 is 234.375, how close is close enough on such information.

The calculation is one step simpler if you use the nameplate kVA. Not a biggie.
A thought. You have 480V as a nominal voltage and 460V as a utilisation voltage over there*. The factor is 0.958.
If you apply the same factor to the generator in question you would get a utilisation voltage of 230V.
Now 245A * 230V/1e3 gives 56.3kVA.
Maybe, just maybe, that's how the nameplate current was arrived at?

* I mean on your side of the pond..... I'm not sure if my terms are what you would call them but the arithmetic works out and would remove the need for the dubiious 235A approximation for 245A stamped on the nameplate.

 

[kwired]

The calculation is one step simpler if you use the nameplate kVA. Not a biggie.
A thought. You have 480V as a nominal voltage and 460V as a utilisation voltage over there*. The factor is 0.958.
If you apply the same factor to the generator in question you would get a utilisation voltage of 230V.
Now 245A * 230V/1e3 gives 56.3kVA.
Maybe, just maybe, that's how the nameplate current was arrived at?

* I mean on your side of the pond..... I'm not sure if my terms are what you would call them but the arithmetic works out and would remove the need for the dubiious 235A approximation for 245A stamped on the nameplate.

Could be. I am not as familiar with generators. NEMA motors are always marked 115, 230, 460 volts and the amps, power factor, efficiency, etc. on the nameplate are always based on nameplate volts, frequency and rated load being applied, though most of the time actual volts applied is higher then nameplate and the load of course can vary and seldom is exactly what is on the nameplate.

 

[Besoeker]

Could be. I am not as familiar with generators. NEMA motors are always marked 115, 230, 460 volts and the amps, power factor, efficiency, etc. on the nameplate are always based on nameplate volts, frequency and rated load being applied, though most of the time actual volts applied is higher then nameplate and the load of course can vary and seldom is exactly what is on the nameplate.

Sorry I muddled up the quotes in my previous post - had one too many [q_u_o-t_e]......
I'm not too familiar with single phase generators either. It just struck me that if the two ratios of nominal to utilisatiion voltages were the same, it could explain the 245A rating given on the nameplate.

 

[Ingenieur]

Well to start with your formula of 45kw/0.8/240 is 234.375, how close is close enough on such information.

10,000 gallon tank when 9768 is no different then OP having a 43, 324 VA load and ordering a 45 kVA generator. I would expect a nameplate on such a machine not to have any significant rounding of such figures. Rounding of 234.375 to 235 or even 237 to 240 I could understand, but not rounding either figure to 245.

Maybe it wouldn't have seemed so snarky if I had included a ? I wasn't trying to be too snarky.

we do not know how the machine was derated and rated
for all we know the 120/208 is correct
wired coils in parallel wye and did not use one line/pair
only 2/3 capacity

we do know this
45 kw
1 phase
clearly marked

those machines have a field v adjustment
it could be set at 115/230 which is close to 45 kw at 0.8 pf

it would be good to know
engine rated kw/hp
how the windings are actually configured