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Old 08-08-2018, 06:38 PM   #1
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Default 3 Phase question.

Alright, just running through practice exam stuff and got a neat question. Seems simple, but I think the answer they say it is... Is wrong. So if someone would be able to explain that would be great.

The calculated load on a 25 unit apartment building is 295,750 VA, the main service is 120/208 volt three phase, what is the service amperes.

A, 1422amp
B, 821amp
C, 953amp
D, 727amp

I picked A. But the answer says its B. All I was given was the VA divided by 360... What the heck is 360 volts?
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Old 08-08-2018, 06:50 PM   #2
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Quote:
Originally Posted by EtrnlFlux View Post
Alright, just running through practice exam stuff and got a neat question. Seems simple, but I think the answer they say it is... Is wrong. So if someone would be able to explain that would be great.

The calculated load on a 25 unit apartment building is 295,750 VA, the main service is 120/208 volt three phase, what is the service amperes.

A, 1422amp
B, 821amp
C, 953amp
D, 727amp

I picked A. But the answer says its B. All I was given was the VA divided by 360... What the heck is 360 volts?
208*1.73 for 3 phase
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Old 08-08-2018, 06:54 PM   #3
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Quick answer:

360 = 208 x 1.732
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Old 08-08-2018, 06:55 PM   #4
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I see where I went wrong. If i'd just simply done that, I would have seen. Durp on me.
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Old 08-08-2018, 10:11 PM   #5
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Welcome to Electrician Talk.
Please take a few minutes and fill out your profile.



Seriously it helps all of us. Thanks
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Old 08-09-2018, 05:47 AM   #6
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It's the ol' square root of three.

Gets 'em every time.
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Old 08-09-2018, 03:00 PM   #7
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3 phase power yo!


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Old 08-09-2018, 03:21 PM   #8
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Welcome aboard @EtrnlFlux!

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Old 08-09-2018, 10:34 PM   #9
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Welcome to Electrician Talk.
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Seriously it helps all of us. Thanks
Alrighty. Done.
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Old 08-09-2018, 10:53 PM   #10
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3 phase power yo!


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