Single Phase vs three phase

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3nd4

New User
Location
HK
Hello,


I'm about to rent an industrial place and the real estate person tells me that a 100a three phase generator generators as many watts as 3 100a single phase generator. Is that correct?


I want to put computers there and need a lot of watts to power them if that helps.


Thanks a lot for your answers.
 
R

retirede

Senior Member
Location
Illinois
Generators are generally rated in watts, I’ve never seen one rated in amperes. Is this a hypothetical question, or does this machine exist?
 
I

Ingenieur

Senior Member
Location
Earth
no

assuming equal voltage

1 ph ~ 240 x 100 x 3 each = 72 kva
3 ph ~ sqrt3 x 240 x 100 x 1 each = 41.57 kva

this is hypothetical and the question is vague
3 gensets in parallel at this kva range is not good practice
 
junkhound

junkhound

Senior Member
Location
Renton, WA
Occupation
EE, power electronics specialty
Depends on the prime mover (engine) :D

All I can discern as a fact from the OP is that the real estate agent is either a liar or ignorant or both. :lol:

Or, maybe 120 X 100 X 3 = 36 ? vs 72 to make any kind of math comparison? assuming 3 separate loads .....

the OP snuck past the mods for all of 4 hours ?
 
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kwired

kwired

Electron manager
Location
NE Nebraska
3nd4 said:
Hello,


I'm about to rent an industrial place and the real estate person tells me that a 100a three phase generator generators as many watts as 3 100a single phase generator. Is that correct?


I want to put computers there and need a lot of watts to power them if that helps.


Thanks a lot for your answers.
Click to expand...
They might want to stick with real estate, the answer isn't that simple.

If the rated current of both generators is 100 amps then the three phase unit will be capable of 1.73 times more watts then the single phase. The prime mover on the three phase unit will have more capacity also because it is capable of delivering more power.

Three 100 amp single phase generators would produce more power then a single 100 amp three phase unit.

All this is assuming same voltage rating on any of the units in question.

As mentioned not advisable to parallel this small of units. Also a single unit with needed capacity would likely be more efficient then three individual units regardless of whether it is single or three phase.
 
Besoeker

Besoeker

Senior Member
Location
UK
kwired said:
Three 100 amp single phase generators would produce more power then a single 100 amp three phase unit.

All this is assuming same voltage rating on any of the units in question.
Click to expand...
That would seem to be an obvious take given that they are intended for the same facility.
The actual voltage doesn't matter. The kVA or VA will differ by the ratio √3.
 
kwired

kwired

Electron manager
Location
NE Nebraska
Besoeker said:
That would seem to be an obvious take given that they are intended for the same facility.
The actual voltage doesn't matter. The kVA or VA will differ by the ratio √3.
Click to expand...
I almost missed it myself but read OP carefully.

a 100a three phase generator generators as many watts as 3 100a single phase generator
Click to expand...

3 100 amp single phase generators will be capable of more power then a single 100 amp three phase, won't be too significantly much more, and will very likely consume more fuel then a single unit with the same combined rating.
 
drcampbell

drcampbell

Senior Member
Location
The Motor City, Michigan USA
Occupation
Registered Professional Engineer
Sounds like your real-estate person has little or no expertise in electricity.

Is this industrial place powered by on-site generators or by a distribution line from a utility? If it doesn't use generators, the capabilities of generators is irrelevant.

Large motors (more than about 10 kilowatt) usually require a three-phase power supply and industrial buildings are usually supplied with three-phase power. Computers generally require only single phase. If the building is supplied with three-phase power, you can still power single-phase loads by simply not hooking up the other two phases. The only relevant question then becomes whether the incoming powerline can supply as much power (watts or VA) as your computers will consume.

Does "Location: HK" mean Hong Kong?
 
S

sameguy

Senior Member
Location
New York
Occupation
Master Elec./JW retired
3nd4 said:
Hello,


I'm about to rent an industrial place and the real estate person tells me that a 100a three phase generator generators as many watts as 3 100a single phase generator. Is that correct?


I want to put computers there and need a lot of watts to power them if that helps.


Thanks a lot for your answers.
Click to expand...

If the site is industrial why do you need generators?
 
junkhound

junkhound

Senior Member
Location
Renton, WA
Occupation
EE, power electronics specialty
curious

curious here also

First thought on reading OP was that there was going to be some operation in the rented location where power draw needed to be hidden from the authorities, such as pot growing in a local where it is illegal or bitcoin mining where regulated or taxed.
 
Jraef

Jraef

Moderator, OTD
Staff member
Location
San Francisco Bay Area, CA, USA
Occupation
Electrical Engineer
junkhound said:
curious

curious here also

First thought on reading OP was that there was going to be some operation in the rented location where power draw needed to be hidden from the authorities, such as pot growing in a local where it is illegal or bitcoin mining where regulated or taxed.
Click to expand...
Yeah, Hong Kong, I'm going to bet on Bitcoin mining...
 
infinity

infinity

Moderator
Staff member
Location
New Jersey
Occupation
Journeyman Electrician
Ingenieur said:
no

assuming equal voltage

1 ph ~ 240 x 100 x 3 each = 72 kva
3 ph ~ sqrt3 x 240 x 100 x 1 each = 41.57 kva

this is hypothetical and the question is vague
3 gensets in parallel at this kva range is not good practice
Click to expand...

Since we're talking hypothetical what if the OP is referring to 3-100 amp 120 volt generators versus a 3Ø, 100 amp, 208Y/120 volt generator?
 
G

GerryB

Senior Member
Location
woodbridge, ct. USA
drcampbell said:
Sounds like your real-estate person has little or no expertise in electricity.

Is this industrial place powered by on-site generators or by a distribution line from a utility? If it doesn't use generators, the capabilities of generators is irrelevant.

Large motors (more than about 10 kilowatt) usually require a three-phase power supply and industrial buildings are usually supplied with three-phase power. Computers generally require only single phase. If the building is supplied with three-phase power, you can still power single-phase loads by simply not hooking up the other two phases. The only relevant question then becomes whether the incoming powerline can supply as much power (watts or VA) as your computers will consume.

Does "Location: HK" mean Hong Kong?
Click to expand...

great reply:lol:
 
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