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hhsting

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In balanced three phase panelboard with phases A, B, C. The phase A has current 300A. What would the connected load in kVA be for the panelboard?
 
If you have all 120 volt loads it still comes out the same, dependent on rounding of SQRT of 3.

300 x 120 = 36000 and you have that three times so 108,000.

or 300 x 208 x 1.732 = 108076.8
 
To complicate things a little, if you got to 300A by saying "there are 3 L-L loads balanced A-B, B-C, and C-A, each 150A," then the math is different. The phase current isn't 300A, it's 150*sqrt(3).

Cheers, Wayne
 
wwhitney said:
To complicate things a little, if you got to 300A by saying "there are 3 L-L loads balanced A-B, B-C, and C-A, each 150A," then the math is different. The phase current isn't 300A, it's 150*sqrt(3).

Cheers, Wayne
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Its in panel schedule total at the end phase A column 300A, phase B column 300A, phase C column 300A. What do you think? Your opinion.
 
hhsting said:
Its in panel schedule total at the end phase A column 300A, phase B column 300A, phase C column 300A. What do you think? Your opinion.
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That means whoever did the calculating figured whatever combination of loads is connected, you would be able to clamp a meter around each supply conductor and read 300 amps on each one if the calculated load (maybe with extra allowance built in for whatever reasons) were actually present.
 
kwired said:
That means whoever did the calculating figured whatever combination of loads is connected, you would be able to clamp a meter around each supply conductor and read 300 amps on each one if the calculated load (maybe with extra allowance built in for whatever reasons) were actually present.
Click to expand...

Ok but does that mean 300A is L-L or L-N or L-G?
 
Yes :)
There should be no current on "G". That should only occur on faults.
The other loads could be any combination of L-L, L-L-L, or L-N on a 208Y/120 panel,.
If you are reviewing plans, the design engineer should have given you the KW load and panel OCP so the load detail isn't very relevant.
 
hhsting said:
Ok but does that mean 300A is L-L or L-N or L-G?
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See calculations I showed you in post 9, it doesn't matter when current on each supply line is the same, it gets a little more complicated when not the same though.

When the current on all three lines is the same the vector sum on the neutral is zero and to the supply feeder it don't know if it is a three phase load multiple single phase loads or combination of both.
 
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