Page 437 - Basic Electrical Engineering

Line voltage V = V RY = V YB = V BR
L
Line current I = I = I = I B
Y
L
R
Phase voltage V = V RY = V YB = V BR
Ph
Phase current I = I RY = I YB = I BR
Ph

∴ V = V for delta-connected load. (4.6)
L
Ph
In Fig. 4.9 (a) is shown a three-phase delta-connected supply system

connected to a three-phase delta-connected load. The line currents are I , I ,
Y
R
and I , respectively. The phase currents are I RY , I YB , and I . The phasor
B
BR
diagram in Fig. 4.9 (b) has been developed by first showing the three-phase
voltages V YB , V , and V RY of equal magnitude but displaced by 120° from
BR
each other. Then the phase currents I YB , I , and I RY have been shown
BR
lagging respective phase voltages by power factor angle ϕ. The line currents
are drawn by applying KCL at the nodes R, Y, and B and adding the phasors,

as has been shown.

Figure 4.9 Delta-connected system: (a) a three-phase delta-connected load supplied from a delta-
connected supply source; (b) phasor diagram of voltages and currents