Three phase line currents

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mwdkmpr

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On a 208V three phase wye system all loads are 208V single phase. If A-B load is 200A and B-C load is 200A and there is no C-A load. What will the phase current on phase B be?
 
Smart $

Smart $

Esteemed Member
Location
Ohio
mwdkmpr said:
On a 208V three phase wye system all loads are 208V single phase. If A-B load is 200A and B-C load is 200A and there is no C-A load. What will the phase current on phase B be?
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Depends on the loads' power factor, but for power factors of 1 or unity... 200A ? sqrt(3) = 346.4A.

PS: The C-A load is irrelevant.
 
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Phil Corso

Senior Member
Location
Boca Raton, Fl, USA
Smart $; Mwdkmpr?? Each of the 3-lines will carry current for the conditions cited in Smart $?s post. Following is a solution using what I call the GiFiES (pronounced Jiffy?s) method, where: Gi => Given; Fi => Find; E => Equation(s); S => Solution

Given:
VAB=208∡+120⁰
VBC=208∡0⁰
VCA=208∡-120⁰
And if PF = 1.0, or unity, then,
IAB=200∡+120⁰
IBC=200∡0⁰
ICA=0

Find:
Line-Currents, IA, IB, and IC

Equations:
IA = IAB ? ICA
IB = IBC ? IAB
IC = ICA ? IBC

Solutions
IA = 200∡120⁰
IB = 346∡- 30⁰
IC = 200∡180⁰

Regards, Phil Corso
 
Smart $

Smart $

Esteemed Member
Location
Ohio
Phil Corso said:
...

Equations:
IA = IAB ? ICA
IB = IBC ? IAB
IC = ICA ? IBC

Solutions
IA = 200∡120⁰
IB = 346∡- 30⁰
IC = 200∡180⁰

Regards, Phil Corso
Click to expand...
Looks good... but assumes the asker knows vector math. If they don't, the equations and solutions (i.e. results) look mighty confusing.
 
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Phil Corso

Senior Member
Location
Boca Raton, Fl, USA
Smart $... you, of course, are right, that is, Line-B current is Sqrt(3) x 200A, and to solve the problem one must know complex math! The point of my answer was to identify of all three line-currrents!

Regards, Phil
 
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