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#### cajunsparks

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Simple question; when sizing 3 phase generator, do you calculate the load and divide the amp draw by three????

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Nope.

#### cajunsparks

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Ok then what is the proper way to figure out the load for a 3 phase generator for an office that wants a standby gen that will run constant until main power resumes.

#### ponyboy

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cajunsparks said:
Ok then what is the proper way to figure out the load for a 3 phase generator for an office that wants a standby gen that will run constant until main power resumes.
There is no magic formula. This is an optional gen so it could be as big or as little as they want. Your customer needs to decide what they want on the gen backup and then you can figure it out. If it will be an automatic transfer then the gen needs to be large enough to handle the full connected load or it must have load shedding

#### That_Dude

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Simple question; when sizing 3 phase generator, do you calculate the load and divide the amp draw by three????
No. There's a reason they are sized by kW.

Watts/Volts will give you whatever amps.

IBTL.

#### cajunsparks

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ok I think That will help the decision. I still need to determine the 3 phase calculation.
Do I use a single phase calculation and divide it by 3. or is there another way.

#### ponyboy

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cajunsparks said:
ok I think That will help the decision. I still need to determine the 3 phase calculation. Do I use a single phase calculation and divide it by 3. or is there another way.
You divide by the square root of 3

#### cajunsparks

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Ok I think that will help. You may be to smart for L.A also. Thanks

#### triden

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Apparent Power = V*I*sqrt(3)

#### Roger

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Simple question; when sizing 3 phase generator, do you calculate the load and divide the amp draw by three????
You do realize that every motor, fuel type, altitude, etc.... comes into play don't you? Why not contact a generator manufacturer and let them help you?

Roger

#### hardworkingstiff

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I agree with Roger, get some assistance.

There are too many pitfalls for you based on the level of your question. I'm not insulting you, just letting you know that you should not try to do this by yourself.

Good luck.

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