Three Phase Current Values in a 3-Phase System
1. The arrow symbols shown alongside three phase current (IR, IY and IB) in fig 1 and 2 does not indicate the currents directions in a particular moment but shows the current directions when we assume them positive. It may be noted that there is no moment in which the direction of all three phase currents are same, i.e., there is not a possible moment where all the three phase currents are going or leaving to the common point at once.
The arrow symbols show that the first current is leaving from R Phase, then after 120° phase time, this current leaving Y phase and for next 120°, it’s leaving B phase.
2. In any one or two conductors, the leaving current is same to the entering current in that conductor (or conductors). In other words, each conductor provides a return path to the currents of the other conductors. This way, current division is continuously changing in three lines. Hence, the algebraic sum of three currents is Zero (0) at any instant.
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- At point “b” = IR =+6A, IY = +2A, IB =-8A …. Now B provides returning path for Y and R currents
- At Point “C” = IY =+6A, IB = +2A, IR =-8A …. Now R provides returning path for Y and B currents
- At point “d” = IR =0A, IB = +6.9A, IY =-6.9A …. I.e. B current is outgoing and Y returning from the Y path