
AC Machine Windings 2-21
2.3.2 Rotating Magnetic FieldinSquirrel
Cage Windings
e squirrel cage can be considered as an atypical case of poly-
phase
w
indings,
a
nd
i
t
i
s
f
requently
u
sed
a
s
a r
otor
w
inding
i
n
i
nduction
m
achines.
I
n
f
act,
i
n
e
ach
c
onductor
(
or
b
ar)
o
f
t
he
c
age,
t
he
c
urrent
i
s
d
ierent
f
rom
t
he
c
urrents
i
n
t
he
o
ther
b
ars,
a
nd
a
s
a c
onsequence,
e
ach
b
ar
c
an
b
e
c
onsidered
a
s
a p
hase
w
inding.
From
t
his
p
oint
o
f
v
iew,
t
he
s
quirrel
c
age
i
s
a p
olyphase
winding with a phase number m equal to the number of bars,
N
R
, and each phase is constituted by a unique conductor (Z
f
= 1)
(
Figure
2
.18).
In
a
ddition,
t
he
c
age
w
inding
d
oes
n
ot
h
ave