
4-16 Power Electronics and Motor Drives
speed regulation technique was used frequently in the past, but due to its low eciency is totally given
u
p
n
ow.
A
nyway,
t
his
s
peed
r
egulation
nds
a
pplication
i
n
l
arge
i
nduction
m
otors,
w
here
t
hank
t
he
s
olid
s
tate
p
ower
c
onverter,
t
he
d
ierence
b
etween
t
he
t
ransmitted
p
ower
a
nd
t
he
c
onverted
m
echanical
p
ower
c
an
b
e
r
ecycled
i
n
t
he
m
ain
s
upply.
e
p
ower
c
onverter
i
s
p
ositioned
b
etween
t
he
r
otor
o
utput
a
nd
t
he
m
ain
a
nd
a
llows
i
nterfacing
o
f
t
he
r
otor
c
ircuit
a
t
t
he
r
otor
f
requency
w
ith
t
he
m
ain
g
rid
a
t
t
he
s
tator
f
requency
a
s
s
hown
i
n
F
igure
4
.15.
A
s
p
reviously
m
entioned,
t
his
s
peed
r
egulation
c
an
s
ti