Basic AC Power
THREE-PHASE CIRCUITS
2.
Current flow in lines B and C becomes the resultant of the loads in B and C
connected in series.
IB
VL
RB
RC
IC
IB
240
40
40
IB
3 amps
IC
3 amps
IN
IB
IC
3
3
IN
6 amps
3.
IB
VL
RB
IC
IB
240
40
IB
6 amps
IC
6 amps
The current in Phase A is equal to the neutral line current, IA = IN. Therefore, IN
is the phasor sum of IB and IC.
IN
3 IB
(1.73)(6)
IN
10.4 amps
In a fault condition, the neutral connection in a wye-connected load will carry more current than
the phase under a balanced load. Unbalanced three-phase circuits are indicated by abnormally
high currents in one or more of the phases. This may cause damage to equipment if the
imbalance is allowed to continue.
Rev. 0
Page 25
ES-09
