
34-6 Power Electronics and Motor Drives
34.2.1 Wye and Delta Connections
e currents in the system will be determined by the load impedances. If the currents (a, b, c) are to be
b
alanced (i.e., equal in magnitude; 120° phase displaced), the impedances must meet two conditions:
•
e three-phase connection must be symmetrical.
•
e three phase impedances must be equal.
e two connections that meet the rst criteria are shown in Figure 34.7.
Note
t
hat
i
n
t
he
w
ye
c
onnection,
t
he
n
eutral
c
an
b
e
“
brought
o
ut”
a
nd
c
onnected
i
nto
a
f
our-wire
s
ystem, whereas in the delta connection, the neutral always leads to an open circuit.
e currents in the wye cas ...