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Trng i hc in lc - Khoa h thng in
1
Bi m u I- Cc khi nim c bn: Cc my dng bin i in nng thnh c nng hoc ngc li c gi l my in. Cc my dng bin i c nng thnh in nng c gi l my pht in. Cc my dng bin i in nng thnh c nng c gi l ng c in. Cc my in u thuc h in t. S bin i c & in trong my in da trn nguyn l cm ng in t. My
bin p v bn cht l mt b bin i in nng t gi tr in p, dng in ny sang gi tr in p, dng in khc.
Phn loi: My in tnh: My bin p. My in quay (c phn t chuyn ng): 0
ng c in hoc my pht in. My in xoay chiu, my in mt chiu.
My in xoay chiu chia lm 3 loi:
+ My in ng b. + My in khng ng b(d b) + My in xoay chiu c vng gp.
II- Cc nh lut c bn dng nghin cu my in:
1. nh lut v cm ng in t. nh lut Pharaday: nh lut vit di dng Maxwell: e = - e = Blv Sc in ng cm ng t l vi tc bin thin ca t thng theo thi gian , ni cch khc sc in ng cm ng bng o hm ca t thng theo thi gian.
2. nh lut ton dng in:
FIHdl F: Sc t ng. F = iw (w: s vng dy ca dy dn)
d dt
e
B
v
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Trng i hc in lc - Khoa h thng in
2
Tch phn vng ca cng t trng theo mt ng khp kn bt k xung quanh mt s mch in bng tng dng in trong mch. F ch gi tr ca sc t ng tng tc ng ln mch in. 3. nh lut v lc in t. :
dfM = idl x BM
Lc tc dng trn mt n v dng in idl t im M c t cm BM f = Bisindl
Lc tc dng trn mt on dy dn mang in nm trong mt t trng f = Bilsin Lc tc dng trn mt on dy dn thng mang in nm trong mt t trng u 4. Nng lng trng in t: H2 1 1
W = dV = dV = Li2 Nng lng tng trong th tch t trng c khng i mi trng t ng nht
H2 W = dV = + + M12i1i2
Nng lng tng trong th tch t trng c khng i mi trng t ng nht khi thit b in t c hai hoc nhiu mch in c h cm in t.
III- Vt liu ch to my in: 1. Vt liu tc dng:
Vt liu dn in l ng hoc nhm dng ch to dy dn. in tr sut ca ng (tp cht khng qu 1%)
= 0,0172mm2/m - 20oC in tr sut ca nhm
= 0,0282mm2/m - 20oC 2. Vt liu kt cu: L cc vt liu dng ch to cc b phn chi tit trong my in, n khng lin
quan n in hoc t v c lm bng gang, thp, hp kim mu, cht do 3. Vt liu cch in: C c tnh bn v in, c, chu m, chu c ha cht.
c tnh chu nhit gii hn theo 7 cp:
2 2 2
2 2
L1 i21 L1 i
21
2
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Trng i hc in lc - Khoa h thng in
3
Cp cch in Y A E B F H C Nhit lm vic cho php oC 90 105 120 130 155 180 >180
Do tc ng ca mi trng, theo thi gian vt liu s b suy gim c tnh bn. Vt liu b suy gim c tnh bn khi nhit lm vic vt qu mc ti hn. Nu
qu nhit gii hn t 8oC n 10oC th tui th cch in gim i mt na. Tui th trung bnh ca vt liu khong 15 n 20 nm.
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Trng i hc in lc - Khoa h thng in
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Chng 1 MY BIN P
1.1. Gii thiu chung:
My pht in Ph ti ng dy ti in My bin p tng p My bin p gim p Hnh 1-1 S mng truyn ti
Cc my pht in thng c ch to vi in p thp t 3kV n 21kV. Mun truyn ti in nng i xa v gim c tn hao in nng cn phi dng my bin p nng cao in p u ng dy.
Cc ph ti thng dng in p thp t 0,4kV n 6kV do cn phi dng my bin p h in p xung cho ph hp vi yu cu in p ca ph ti.
My bin p lm nhim v bin i in p truyn ti v phn phi in nng. Cc my bin p trong h thng in c gi l my bin p lc. My bin p l thit b in t dng bin i dng in cp in p ny sang dng in cp in p khc nhng vn gi nguyn tn s. MBA lm n.v truyn ti in nng.
1.2. Nguyn l lm vic ca my bin p:
My bin p hot ng trn nguyn l cm ng in t. Thng thng mt my
bin p phi c hai cun dy W1, W2 c s vng khc nhau c qun trn cng mt li thp. W1 l cun s cp c u vo li in xoay chiu, cc ph ti c u vo cun dy th cp W2. Khi c dng in i1 ~ i qua cun dy W1 s sinh ra t
~
W1W2
Zt
i1
i2
U2U1~
f
Hnh 1-2 S nguyn l lm vic
ca my bin p
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Trng i hc in lc - Khoa h thng in
5
thng trong li thp, t thng chy trong li thp (mch t) s mc vng qua 2 cun dy W1, W2 v sinh ra sc in ng cm ng e1 v e2 trn 2 cun dy W1, W2.
= msint
)2
sin(2cos 1111
tEtWdt
dWe m
)2
sin(2cos 1222
tEtWdt
dWe m
Tr s hiu dng ca sc in ng:
W1m 2fW1m E1 = = = 4,44 fW1m 2 2
W2m 2fW2m E2 = = = 4,44 fW2m 2 2 Sc in ng cm ng chm pha vi t thng sinh ra n mt gc / 2 T s bin ca my bin p:
2
1
2
1
2
1
W
W
U
U
E
Ek (nu b qua in p ri trn cc dy qun)
k: H s bin p.
apngtaMayUUk
aphaMayUUk
:1
:1
21
21
1.3. Cc i lng nh mc ca my bin p:
1. Dung lng hay cng sut nh mc Sm: L cng sut ton phn hay cn gi l cng sut biu kin c a ra cun dy
th cp ca my bin p tnh bng (kVA) hay (VA). 2. in p dy s cp nh mc:U1m
L in p dy trn cun dy s cp my bin p tnh bng (kV) hay (V) 3. Dng in dy nh mc s cp I1m v th cp I2m:
L dng in dy ca dy qun s cp v th cp ng vi cng sut v in p nh mc tnh bng Am pe (A) hay ki l Am pe (kA).
Vi my bin p 1 pha:
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Trng i hc in lc - Khoa h thng in
6
dm
dm
dm
dm
dm
dmU
SI
U
SI
2
2
1
1
Vi my bin p 3 pha:
dm
dm
dm
dm
dm
dmU
SI
U
SI
2
2
1
133
4. Tn s nh mc fm: Tnh bng Hz (hc). Thng thng tn s ca li in l 50Hz.
5. Cc thng s khc: S pha m t u dy in p ngn mch un% ch lm vic di hn hay ngn hn ch lm lnh Trng lng ton b Trng lng du
1.4. Phn loi theo cng dng: My bin p lc dng truyn ti v phn phi in nng trong h thng
in. My bin p chuyn dng: MBA l, dng cho cc thit b chnh lu, MBA
hn. My bin p o lng: dng cho cc mch in o lng dng cp in p
thp, in p tiu chun. My bin p th nghim dng th nghim cc thit b in c in p cao
1.5. Cu to my bin p: Li thp, dy qun v v my bin p:
a. Li thp
Hnh 1-3 My bin p kiu li ( cun dy bc li thp )
Tr Gng Gng
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Trng i hc in lc - Khoa h thng in
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(a) (b) Hnh 1-5 My bin p kiu bc ( li thp bc cun dy ) (a) (b) Hnh 1-6 My bin p kiu tr - bc ( tr thp phn nhnh sang hai bn ) Hnh 1-7 Cc kiu ghp li thp
Kiu ghp ri li thp Kiu ghp xen k li thp
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Trng i hc in lc - Khoa h thng in
8
(a) (b) (c) Hnh 1-8 Tit din ca tr li Hnh 1-9 Cc dng tit din gng t Khi my bin p mang in p, li thp phi ni t m bo an ton Dy qun:
Dy qun ng tm: l nhng vng trn ng tm, cun HA qun trong, cun CA qun ngoi gm c 3 kiu qun ng tm chnh l kiu dy qun hnh tr, dy qun hnh xon,dy qun xon c lin tc.
Dy qun hnh tr:
(a) (b)
Hnh 1-10 Dy qun hnh tr
7
8
9
10
11
1212
11
10
9
8
76
5
4
3
2
1
Dy bt qun 2 lp Dy trn qun nhiu lp
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