
14-26 Power Electronics and Motor Drives
would generate the 17th as the rst harmonic equivalent to 850 Hz. On the contrary, a 550 Hz carrier
P
WM
w
ould
h
ave
c
entral
h
armonics
a
t
5
50
H
z,
a
nd
si
gnicant
l
ow-order
si
debands
a
t
4
50
H
z,
a
lmost
t
wo
t
imes
l
ower
t
han
S
HE.
N
evertheless,
t
he
m
ain
d
rawback
o
f
S
HE
i
s
t
he
f
act
i
t
i
s
c
omputed
o
-line
a
nd
s
tored
i
n
l
ookup
t
ables,
w
hich
a
re
i
nherently
d
iscontinuous
i
n
n
ature.
I
n
a
ddition,
t
he
a
ngles
a
re
c
omputed
a
ssuming
p
ure
si
nusoidal
w
aveform
o
peration
i
n
s
teady
s
tate,
h
ence
i
n
d
ynamic
o
peration
f
or
v
ariable
f
requency
a
nd
a
mplitude
t
he
a
ngles
a
re
n
o
l
onger
o
ptimal
a
nd
l
ow-order
h
armonics
d
o
a
ppear.
ese ...