nAy
dli
duqc
ky
hieu tren hlnh 4.4 . Nhln
vAo
m~ch
di¢n ta
thi'fy
quan
he
gil1a
dbng di¢n day va dbng
dieD
pha nhu sau:
I
= I, (4-1)
b)
Quan
hf
gifla
4ifn
tip
ddy yd
4i~n
tip
pha
Di¢D
ap
pha
Up

day pha),
vi
dl,l
di¢D
ap day U
AB
(giC'a
pha A va pha B).
U"sc
(gifta pha B va
pha
C)
•
U·
CA
(giila pha C va
ph.
A).
Theo
dinh nghia di¢n ap
dAy
la e6:
U
AB
= U
A
-
U
B
(4-2a)

.
J3
AB = 2 AH = 2 OA cos
30'
= 2 OA
-=
J3
OA
2
U,=
J3
U,
AB la di¢n ap day U,
OA
Iii
di¢n ap pha
U,
TU
dd thi veeta.
ta
thA'"y:
Khi
dien
ap
pha d6i xUng. thl dien
ap
day d6i xllng.
-
V~
trj

t~o
thAnh
hlnh sao d6i xUng. dong
di~n
trong
da.y
trung tinh
Mng
kh6ng.
10=
IA
+
IB+
Ie
=0
-
Trong truoog hgp
nAy
c6
the
kh6ng clin
dAy
trung tinh,
ta
c6
m~ch
ba
pha
ba
day_

tnmg
tinh c6 dbng
di~n
Io
bAng
1,=
IA
+ IB+
Ie
Vi
d\ll:
MQt
nguOn
di{!:n
ba
pha doi
xUrig
noi
hlnh sao,
di~
lip
phs.
ngu6n
Up.,
=220
V.
Ngu6n
cung
ca"p
di~n

til
vA
cua
ngu6n.
V!
d6
thj
vectCf.
LM.
gii.i :
Ngu6n
nOi
hlnh
sao,
lip
dl,lDg
cOng
thm::
(4-3)
di¢n
lip
day
Ill.:
U
d
=
-fj
Up
=
,fj

u;;
A
I,
I;;
Upol
~
R
r.
u;:
I~
.""
10
c
•
"
C
•
r,
10
u •
. )
b)
Hinlr 4.5
83
Ngu6n
n6i sao, tili n6i sao,
.lip
dl,lng
eOng
thl1'e

CACH
N61
HtNH
TAM
GIAC
(l\.)
l.
Cach
n61
Mu6'n o6i hloh tam
gi~c,
ta
llfy
d&u
pha nlly n6i
v6'i
cu6i pha kia.
Vi
d~
PI
n6i
v6'i
Z ; B n6i
v6'i
X;
C olfi v6i Y (hloh 4.6).
C8.eh
n6i tam
gi~e
kh6ng

Ip
ella ogu6n nguqe
ehi~u
quay
kim
d6ng h6,
ehi~u
duan~
dbng
di~n
pha eoa
tAi
dinS
ehi~u
quay kim d6ng h6 (hlnh 4.6).
84
A
~
I,
A
u
.~
r.
c
B
C
IE
B
1.
.

(4-4)
b)
Quan
h~
giiia
ddng
4i~"
day
vd
ddng
4i,n
pha
Ap
d1,lng
djnh
lu:).t
KieeshOp 1
t~i
cae
nut. ta
e6
:
T~iDlltA:
IA=
lAo-
lCA
T~inutB:
10=
lee-
ICA

DOng
di¢n lAB' lee,
leA
eh~y
trong
cac
phs
Iii.
dong di¢n phs, l¢ch
pha
. . .

voi di¢n
ap
U
AB.
U
ee.
U
CA
mQt
gee
<p
(hlnh 4.6 b).
D~
ve dong di¢n
dAy
lA'
lB.
Ie.

di¢n
day
lA.
lB'
Ie
ve tI'tn
hlnh 4.6b.
X_I
tam
giac
OEF
.fj
'"
OF
~
2 OE-~,,3
OE
I"
~
.fj
I,
OF
IA
dOngdi¢n
dAy
I"
OE
IA
dong di¢n
ph>

pha
tuang
dng
gee
30
11
(IA
eh:).m
pha
lAB
mQt
gee
30°;
10
ch~m
phs lee
mQt
gee
30
11
;
Ie
cMm
pha
leA
mQt
goc
30
(1
).

sa
d6 ghi
rei
cac
d~i
luqng
pha w
dAy.
b) Hay
dc
djnh
dbrig di¢n pha
vll
di¢n
ap
pha cua
t!i
I,
Upt.
LIJi
glal ,
a) So
d6
n6i
dAy
m~ch
di¢n
ve
a
hinh

3,464
kV
A
A
I.
e
Vl tai
nOi
hlnh tam giac,
nen
di¢n ap
pha
cua
taj
Up,
hang di¢n lip dlly
U
pt
==
U
d
=
3,464
kV
Ollng
di~n
pha cua tai
oM
hem
dong di¢n

v!
S(1
d6
Doi
day
m,ch
ba pha. Tren
so
d6
chi
rii
dlf,i
hlQIJ.g
pha
vA
day.
b)
HAy
de
dinh
dlmg
d.i¢n
pha
vA
d~n
lip
pha
cua
ngu6n
Ipn.

d
=I",=50A
I.
u"
I
u~
= fj
Up,
= fj. 220 = 380V
Bi'!t dong di¢n day
vA
di¢n lip day. ta co tbe' tfnh
dUQ'e
dong di¢n pha va di¢n
lip
pha ciJa ngu6n.
VI
ngu6n
d6'i
xling n6i hlnh tam giae, nen
ta
e6 di¢n ap pha
Up"
ella
ngu6n ia :
Up"
= U
d
= 380V
Dong di¢n pha eua ngu6n la

P
A
•
PB.
Pc luang
-ung
10.
ctmg su.!t
~e
dl}.ng
ella
pha
A.
B.
C
ta
co:
P = P
A
+ P
a
+ P
e
= U A
IA
eosQl
A +
UsIB
cost:p
+ U

=
COS<PB
=
eost:pe
=
COs<p
ta
co
ho~c
P =
3UrJPC;OSQl
P =
3R,I~
Trong
d6
Rp
Ii'!.
dien
tra
pha clla tai.
Thay
d{li
luqng
pha
bAng
d{li
luqng
day:
d6i
vai

vic!t
thea
d~i
luqng
day.
Ap.
dl,mg
cho
ca
truang
hqp
hlnh
sao
va.
hlnh
tam
giae
d6i
xUng.
p =
J3
U.I"cos~
(4·9)
87
trong d6
IP
- g6c
I~h
pha gina
di~n

=
UAIA.
simpA
+
UBIBsinIPB
+ UclcsinlPc
Khi
m~ch
d6i
xllng
ta
c6 :
ho~c
Q =
3U,r,sin~
Q = 3XpI'p
trong d6 :
x"
.
11
di¢n kbling
pb.
cUa
lai.
N!!u
tinh thea cac
d~i
luqng
dAy
Q =

c6
cOng sulit d!nh
mUe
P
llm
=
14kW,
hi¢u sulft
d¥ili
mUe
TJdm
=
0,89,
h¢ 56 cOng sulft d¥ili
ml1'c
cos<Pdm
= 0,88.
DAy
qulfn dQng
CO'
di¢n
n6i
hlnh
sao,
d.i¢n
I1p
day
m{Ulg
di¢n U
d

trtn
hlnh
4.9.
VI
day
qulfn dQng
CO'
n6i
hlnh
sao,
nen
di¢n!p
pha
d~t
vAo
m6i
day
qulfn
pha
IA
Ud
380
22
V
U'="Jj=J3=
0
b)
D6i
vm
dQng

d¢og
co
III
14.
10'
fjudeOSql<lmTJdm
J3.380.0,8~.O.89
Vi
dAy
quail
o6i
hlnh sao
nen
Ip==~==27,16A,
c

~~.,
/
" ,

_
.~ ~
Hinh
4.9
27.16
A.
VI
d~
5 :
M¢t

P
2
==
8kW;
Q2
==
2kVAr,
.a)
TInh
dbog
di¢n
dAy
eua
mOi
tM
b)
TCnh
dbng
di¢n
dAy
l.J
eua
ngueSn
cung
elp
eho
2
till
lIen.
Lbi

S:z==
Jpi+Q,2==
J
r
,2O;-+-2'2==8.246kVA.
Theo
cong
thllt
(4 - 14).
dbng
di¢n
dAy
cua
[ii
ItA
1=
S,
=~=IO.956A
I
JjU
d
J).380
89
dong
di~n
dAy
cUa
tii
2 I
A

: 'J" •
~80
.
I,
T'11
P
1
,Ql
Hinh
4.10
COng
suit
phan khang nguOn cung c/fp eho 2 [ai
Q = Qr + Q
2
= 4 + 2 =
6kVAr
COng
su/ft bieu ki6n ngudn
s=
~p2
+<1'
=
J14'
+6'
= 15.231kVA<
~
T.612
1\
,Qa

tei
s(
hi¢u
dl:mg
bAng
nhau,
vA
l~ch
pba nhau
mQt
g6c. Vi
v~y
khi
m~ch
d6i xllng,
t1
tach ra
mQt
pha
de
tfnh, khi bi.!t duqc
d~ng
di¢n cua
mQt
pha, ta
c6
the suy
r;
d~ng
di¢n

- BuOc 2 : Xac djnh di¢n
ap
pha
Up
cua
tM
N~u
tiii n6i hlnh sao
u,
U, = fj