Load Calculations

[kethlaney]

I am a little confused about loading 1 phase loads on a 3 phase circuit:

I have multiple 208V loads 1 phase loads (2-wire) that I am protecting with a 208V (3-wire) 3 phase breaker. I am connecting the loads phase to phase (A-B, B-C, C-A). The individual loads are 2.0A at 208V. If I have (3) of these individual loads per circuit (3-A/B, 3-B/C, 3-C/A) would I see 12A on each leg of the 3 phase system if I were to clamp a ammeter on each individual line? Does the 1.73 factor come into play at any point?

 

[Dennis Alwon]

If you are asking what the load on each phase is then you just add the respective loads for the phase.

If you clamped a meter you would get 12 amps on each phase.

 

[bob]

I am a little confused about loading 1 phase loads on a 3 phase circuit:

I have multiple 208V loads 1 phase loads (2-wire) that I am protecting with a 208V (3-wire) 3 phase breaker. I am connecting the loads phase to phase (A-B, B-C, C-A). The individual loads are 2.0A at 208V. If I have (3) of these individual loads per circuit (3-A/B, 3-B/C, 3-C/A) would I see 12A on each leg of the 3 phase system if I were to clamp a ammeter on each individual line? Does the 1.73 factor come into play at any point?

The wattage connected between each phase is 2 amp x 3 x 208 = 1248 watts
Total wattage = 3 x 1248 = 3744 watts.
A,B and C amperage = 3744 watts/(208 v x 1.73) = 10.4 amps on each conductor. Since the amperage is not in phase you would use vectors to add them together.

 

[Smart $]

.... If I have (3) of these individual loads per circuit (3-A/B, 3-B/C, 3-C/A) would I see 12A on each leg of the 3 phase system if I were to clamp a ammeter on each individual line? Does the 1.73 factor come into play at any point?

No and yes in that order.

9 ? 2.0A ? 208V = 3744VA... ? (120V ? 3) or (208V ? 1.73) = 10.4A