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BI THC HNH S 01 TNH TON V QUN MY BIN P C LP MT PHA C NH Thi gian: I. Mc ch, yu cu. 1. Mc ch: Trang b cho hc sinh nhng kin thc v cu to my bin p c lp mt pha, nguyn l lm vic, cch tnh ton thit k mt my bin p c lp mt pha cng sut nh. 2. Yu cu: - Nm vng nguyn l lm vic v cc tnh ton cho mt my bin p c lp mt pha cng sut nh. - Sn phm phi t yu cu k thut v tnh thm m. - Bit sa cha cc pan thng thng ca my bin p c lp mt pha cng sut nh. II. Tm tt l thuyt. A. Cu to Cu to c bn ca my bin p gm mch t v dy qun. Ngoi ra, ty theo vic s dng m my bin p cn c thm cc ph kin nh v bc, vn k, n bo, cng tc hiu chnh in p. 1. Mch t c ghp bi cc l st mng, c cha lng silic t 1% - 4% v c b dy t 0,35 - 0,5 mm, nhm mc ch gim tn hao in nng do dng Fuc v hin tng t tr lm pht nhit. i vi cc my bin p cng sut ln, cc l st cn c cch in vi nhau bng lp sn cch in hoc l lp giy mng. C hai dng mch t : - Mch t c dng EI, mch t c phn nhnh ra hai bn v bc ly cun dy qun trn ct t chnh. Nh th t tn nh i. Dng mch ny dng cho my bin p mt pha cng sut nh nh my bin p gia dng, my bin p cp in p cho cc my thu thanh, tng m v.v - Mch t kiu tr (hoc kiu ct) c dng U, gm nhiu l st hinh ch I ghp li vi nhau, dng cho my bin p cng sut trung bnh tr ln, loi my bin p 1 pha hay 3 pha nh my hn in - Mch t hnh ch X, t hiu sut cao hn nhng gia cng kh, gi thnh cao. 2. Cun dy qun Dy qun c nhim v tng p v h p, gm c cun s cp v th cp. Dy qun phi l dy ng in phn hoc nhm, c bc lp e-may hoc coton cch in. My bin p nh dng dy trn. i vi dy chu ng ln th dng dy dp. 3. Nguyn l lm vic Nguyn l lm vic ca my bin p da trn c s hin tng cm ng in t. Kho st mt my bin p n gin gm 2 cun dy c qun trn li st mch t. Cun w1 mc vi ngun in c gi l cun s cp, cn cun w2 ly in ra c gi l cun th cp. t in p xoay chiu u1 vo dy qun s, trong dy qun s s c dng i1. Trong li thp s c t thng mc vng vi c hai dy qun s cp v th cp,
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cm ng ra cc s e1 v e2. Khi MBA c ti, trong dy qun th s c dng in i 2 a ra ti vi in p l u2. T thng mc vng vi c hai dy qun s cp v th cp gi l t thng chnh. Ph ti cng tng dng i2 cng tng lm dng i1 tng theo tng ng gi n nh t thng khng i. l nguyn l lm vic ca my bin p.

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Bi 1: TNH TON CH TO MY BIN P C LP 1 PHA C NH Cc bc tin hnh: 1. Tnh ton cng sut theo tit din li thp + o kch thc tiu chun ca l thp E,I * K hiu v tn gi cc kch thc c bn ca li thp: a. B rng tr gia ca li thp b. B dy ca li thep bin p c. B rng ca s li thp bin p h. B cao ca s li thp Cc kch thc ny khi o tnh theo n v l [cm] hay [mm] * Kch thc tng qut ca ton b l thp sau khi ghp st c xc nh theo hnh 1.2

- My bin p c cng sut nh thng dng li thp kiu ch E,I (kiu "bc) v kiu U,I (kiu "tr"). Xc nh cng sut theo tit din mch t (li thp) Gi S l tit din mch t (cm2). P l cng sut ca my bin p (V.A) + Vi li E (kiu bc): S = a x b = 1,2 Pcp (cm2) PCP = P2 =
S2 1,2 2

+ Vi li U (kiu tr) : S = a x b = 0,7 Pcp (cm2) 2. Tnh dng in v tit din dy qun s cp v th cp: + Dng in s cp I1 v dng in th cp I2:
PCP (A) .U1 Tra bng chn hiu sut ca my bin p v tnh ra dng in s cp:

Dng in s cp I1 = 3 60 I2 = 10 70
PCP U2

P CP (%)

25 80 (A)

50 85

100 90

1000 >90

Dng in th cp Trong :
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I1 : dng in s cp I2 : dng in th cp U1: in p s cp U2: in p th cp P1 cng sut s cp, P2 cng sut th cp : l hiu sut ca my bin p ( : 0,85-0,9)
=
P2 P2 P1 = P1

Bit mt dng in J: (A/mm2) ta tnh c tit din dy s cp v th cp:

I1 (mm2) J I - Tit din dy qun th cp : S2 = 2 (mm2) J - Tit din dy qun s cp : S1 =

Trong : J l mt dng in A/mm2 Vi dy ng mt dng in Jcu = (3 5) A/mm2 Vi dy nhm mt dng in JAl = (3-5) A/mm2 3. Tnh s vng dy s cp v th cp: Chn mt t thng (hay t cm) B dng tnh ton cho li thp. p dng cng thc tnh sc in ng to ra trong dy qun bin p tnh s vng to ra 1 Vn sc in ng cm ng. (S vng/vn: Ngha l c bao nhiu vng dy trong cun dy th sinh ra c sc in ng bng 1 vn). Cng thc kinh nghim: nv =
K 45 = (vng/vn) B.S B.S Trong : nV l s vng vn (Vng/vn)

K l h s ph thuc v mt t B B mt t wb/mm2 S: tit din mch t (cm2). K c chn ph thuc vo mch t hay t cm theo bng sau: K 64 56 50 45 37,5 32,4 30 B 0,7 0,8 0,9 1 1,2 1,3 1,4 T tnh c s vng dy ca cc cun s cp v th cp. S vng dy s cp N1= nv x U1 S vng dy th cp: Khi tnh s vng dy cun th cp, cn phi d tr tng thm mt s vng dy b tr s st p do tr khng ca cun dy. N2 = nv x (U2+ U2) d tr in p U2 c chn theo bng sau: S(VA) 100 200 300 500 750 1000 1500 >1500 U2 4,5 4 3,9 3 2,5 2,5 2,5 2 Vi U1,U2 l in p s cp v th cp ca MBA. N1,N2: l s vng dy qun s cp v th cp * Lu : Vi l thp k thut in c b dy tiu chun 0,5mm n 0,35 mm; thng chn gi tr mt t thng B = 1T n B = 1,2T (hm lng Silic thp, t cm B chn thp). L thp k thut in thuc dng dn t ng hng.

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Vi l thp k thut in c b dy tiu chun 0,5mm n 0,35 mm; l thp thuc dng tle lnh v hm lng Silic khong 4%; gi tr mt t thng nm trong phm vi B=1,4T n B=1,6T. y l dng l thp dn t nh hng, l thp ny mch t c cu to theo hnh dng c bit : hnh xuyn . .v khng thuc dng E, I. 4. Tnh ng knh dy s cp v th cp: Bit tit din dy p dng cng thc tnh ng knh dy (hoc tra bng) d=2
S

d=2

S = 1,13 S 3,14

Suy ra: d1 = 1,13 S1 v d2 = 1,13 S 2 5. Kim tra h s lp y: kl Kl =

Tng tit din dy qun s + th cp (k c lp may) Tit din ca s

Gi S1e, S2e l tit din dy qun s cp v th cp k c lp may. d1e,d2e l ng knh dy qun s cp v th cp k c lp may.
2 d S1e = 1e = .d 1e (mm2) 4 2 2 d 2 S1e = 2 e = .d 2e (mm2) 4 2
2

Vi dy trng emay: ec = 0,03 0,08 mm dy bc cotton: ec = 0,15 0,40 mm d1e = d1 + ec d2e = d2 + ec Tra bng ch to dy ng, nhm ca nh sn xut ta c d1e, d2e Nh vy ta c cng thc kim tra h s lp y nh sau: Kld
S1e.N1 + S2e.N2 Kld = ACS.100

tnh c Kld t 0,36 n 0,46 l ph hp.

Trong Acs = c.h l tit din ca s. V d: Cho mch t c cc kch thc a.b.h.c=2,4x4,5x3,6x1,2. Hy tnh chn dy, s vng dy ca mt my bin p h p. Bit in p s cp Us=110V, in p th cp Ut=12V, mt dng in j=4A/mm2. (kim tra h s lp y).

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Gii:

Xc nh cc s liu ban u: a=2,4 cm ; b=4,5 cm ; c=1,2 cm ; h=3,6 cm. U1=110v ; U2=12V 1. Vi li E (kiu bc): A= a X b = 1,2 PCP = 2,4 x 4,5 = 10,8 (cm2) PCP =
S2 10,8 2 = = 81 (VA) 1,2 2 1,2 2

2. Tnh dng in v tit din dy: (hiu sut 90%)

PCP 81 = = 0,818 (A) .U1 0,9 x110 P2 81 Dng in th cp I2 = = = 6,75 (A) U 2 12

Dng in s cp I1 =

Bit mt dng in J: (A/mm2) ta tnh c tit din dy s cp v th cp: J=4

I1 0,818 = = 0,2 mm2 J 4 I 2 6,75 Tit din dy qun th cp : S2 = = = 1,68 mm2 J 4

Tit din dy qun s cp : S1 =

3. Tnh s vng dy s cp v th cp: Cng thc kinh nghim: nV =

45 K = = 4,17 (vng/vn) 10,8 B.S

S vng dy s cp: N1 = nv . U1 = 4,17 x 110 = 458,3 (vng) S vng dy th cp: N2 = nv . (U2 + 4,5)= 4,17 x (12+4,5) = 68,08 (vng) 4. Tnh s ng knh dy s cp, th cp: d = 1,13 S d1 = 1,13 S1 = 1,13 x 0,2 = 0,5 (mm) d2 = 1,13
S 2 = 1,13 x 1,68 = 1,46 (mm)

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BI 2: LM KHUN QUN DY MY BIN P Cc bc tin hnh: 1. Khun cch in: Khun cch in nhm mc ch cch in gia cun dy v mch t, lm sn cng nh hnh cun dy. * C 2 loi khun: Khun khng c vch ngn cch v khun c vch ngn cch. - Vi khun c vch ngn cch: Gia cun s v cun th c vch khun ngn cch. - Vi khun khng c vch ngn cch: Cun s v cun th lng vo nhau, thng thng cun no c ng knh nh qun pha trong.

2. Phng php gia cng khun qun dy bng giy cch in: Khi dng giy cch in lm khun qun dy my bin p, ta chn giy c dy khong 1mm nu khun mt lp hoc 0,5mm vi khun hai lp. Ba lm khun: L ba cch in cng, mng v do cng tt, c bn c hc. * Tnh t thc hin: 1- o kch thc ca mch t: * K hiu v tn gi cc kch thc c bn ca li thp: a: B rng tr gia ca li thp. b. B dy ca li thp bin p c: B rng ca s li thp bin p h: B cao ca s li thp. Cc kch thc ny khi do tnh theo n v l [cm] hay [mm]. Lu : Cc kch thc a, c v h c o trc tip trn mt l thp E, I. Ring kch thc b c xc nh gin tip bng cch o xc nh b dy ca mi l thp E, I; sau m tng s l thp E v tng s l thp I. T tnh ra b dy li thp bin p bng cch p dng quan h sau: b = (b dy ca 1 l thp) x (tng s l thp)

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Vi l thp k thut in tiu chun thuc dng tle cn nng hay cn lnh vn hnh ti tn s f =50Hz, b dy tiu chun ca l thp thng thuc mt trong hai c sau:0,5 mm; hay 0,35 mm. 2- Xc nh kch thc khun: (da vo kch thc mch t) - ak: Chiu rng ca khun (ak>ali thp khong 1mm) - bk: chiu di ca khun. (bk>bli thp khong 1mm) - hk: Chiu cao khun (hk<bli thp khong 2mm) - ck: Chiu rng tai khun (ck<bli thp khong 1mm) * Ch : Khi lm khun cn ch cc kch thc cn i nh sau: - ak>ali thp khong 1 mm - b=bli thp - hk<hli thp khong 2 mm - ck<cli thp khong 1 mm - Gc tip gip gia ak v bk theo chiu cao hk ( =90o) phi vung thnh, sc cnh, khng un ln khi lp li thp E st vi mt trong ca ak v hk. 3- V khai trin giy cch in lm khun:

4-Ct gp np hnh khai trin v dn hnh thnh khun.

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5-Ghp th mch t: Khi ghp mch t ghp tng l thp mt, ghp ht ton b l thp ch E sau n ghp l thp ch I. 6- Lm li khun: Sau khi lm xong khun, khun phi c nng bng g, gia nng khoan l bng trc my qun dy khi quay my qun dy, cun dy phi ng tm vi trc my qun dy. Cc kch thc ali, bli, hli, phi bng kht vi cc kch thc ak,bk,hk, khi qun dy cc gc khun khng b bp mo nh li, nu nh li s khng lp ghp c li thp. - Khc g lm li khun c cc kch thc hk x ak x bk gia khoan mt l bng trc quay ca my m vng dy cho vo nng khun khi qun, dy khi bp nh khun khng lp li thp c. 7- Lm tm g p khun: Sau khi lp khun vo my qun, hai u khun phi c tm g p cht khun gi cho 2 tai khun khng b cong vnh khi qun dy. - Hai tm vn p 2 u khun, kch thc 15x15 cm, gia tm vn khoan mt l bng trc qun dy lun vo trc my, vn cht cu trn trc my qun dy p cht vn vo khun. 8- Trn tai khun: Trn tai khun mt a nh v cc l lun cc u dy vo v ra ca hai cun s cp v th cp. - u dy vo ra phi nm v mt tai khun khng lp li thp (mt a). - u dy vo ra cun s cp 1 bn, cun th cp pha tai i din

3. Phng php dng khun nha c sn. Chng ta c th dng khun nha c sn, khi kch thc khun tng thch vi kch thc li thp. Chn theo phng n ny, khng tn thi gian lm khun, nhng phi thc hin cng tc chun b lm sch cc cnh khun nha trc khi qun dy. V kh nng chu nhit ca khun nha khng cao so vi cc loi vt liu cch in khc: bakelite, carton cch in, giy presspahn. .. ng thi to d dng trong qu trnh ch to b dy ca khun nha thng bng hay ln hn 1mm; nh vy b cao hiu dng dng ri dy qun s nh hn b cao ca s li thp lm gim thp s vng dy qun b tr cho mi lp. iu cui cng cn quan tm khi chn la khun l ch n b dy b ca li thp. Gi tr b dy li thp, xc nh trong qu trnh tnh ton s vng dy, s nh hn b dy li thp bin p thc t. S kin ny xy ra do ba v cc cnh mi l thp; lm tng dy ca li thp trong qu trnh lp ghp (cng ngh dp l thp cng chnh xc v tinh vi lm gim thp lp ba v xut hin trn cc cnh ca l thp).
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Tm li trong qu trnh thi cng, trc khi thi cng: chng ta nn ghp ton b cc l thp vo khun nha xc nh kh nng cha ca khun. Nu khun qu rng so vi b dy l thp, sinh ra hin tng rung v ting n tn s thp khi bin p vn hnh. Ngc li nu khun qu hp, chng ta khng th ghp ht ton b l thp vo khun, nh vy s liu tnh ton s sai lch.

Hnh 1.3 Khun nha dng qun dy v phng php ghp li thp th khun Trong hnh 1.3 chng ta trnh by hnh dng khun nha, cc v tr cnh cn lm sch trc khi thi cng.

Hnh 1.4 B rng hiu dng qun dy

BI 3: QUN DY MY BIN P C LP
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Cc bc tin hnh: Sau khi lm khun v tnh ton cc s liu th tin hnh qun dy: 1. Lp rp li g v khun qun dy vo bn qun. Vi cc bin p c cng sut nh, ng knh dy qun nh hn 0,5mm chng ta c th s dng cc bn qun (hay tay qun dy) c t s truyn ng 1/10 hay 1/5. T s truyn ng 1/10 tng ng vi mt vng quay tay bng 10 vng quay ca trc qun. T s bin tc ca trc quay tay so vi trc qun dy cng chnh lch xa, lc cng dy cng tng , dy qun cng st; tuy nhin vi ng knh dy qu nh c kh nng lm t dy ti cc thi im bt u quay, hay ti cc thi im ngng quay t ngt. Vi cc bin p c ng knh dy qun ln hn 0,5 mm, chng ta nn dng bn qun dy c t l 1/1. Tc quay cng thp cng d dng iu chnh nh hng trong qu trnh xp dy qun. Hnh dng ca mt b khun v li g sau khi c lp trn tay qun trnh by trong hnh 1.5

Hnh 1.5 Khun qun dy sau khi c lp ghp hon chnh trn trc ca tay qun dy, sn sang thi cng

V tr bt u qun dy c nh v sao cho: Cn ca tay quay bn qun nm v tr thp nht. Cc mp ca khun qun dy ti pha ra dy phi c nh v nm pha trn cng (xem hnh 1.6).

Hnh 1.6 V tr bt u qun dy sau khi lp khun qun dy ln bn khun

2 . Gi cc u dy ra trc khi bt u qun dy qun s cp . Thng thng thun li cho vic xp dy qun, chng ta thng chn b dy c ng knh nh b tr bn trong, b dy c ng knh ln hn c b tr bn ngoi.
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Thc hin theo phng php ny chng ta trnh gp hin tng lm cng mt ngoi lp men cch in khi dy qun i qua cc giao tuyn ca cc mt phng xp dy; trnh c s c lm bong v lp men cch in ti cc v tr chuyn hng trong qu trnh chuyn mt xp dy qun. Ngoi ra chng ta cn ch n v tr cc u ra dy ca mi b dy qun; to tnh m thut cho cun dy bin p sau qu trnh thi cng. Hai u ra ca cng mt b dy nn b tr ra mt mt v xp cng pha. Chng ta cn quan tm gi tr chn l ca s lp dy qun ca mi cun dy. Nu s lp c gi tr l, hai u dy ra thng c khuynh hng nm hai pha ngoi nhau, xem hnh 2.3, 2.4 .

Hnh 1.7 Phng php gi cc u ra, lc bt u qun cun

3. Phng php lt giy cch in lp gia cc lp dy qun. - Sau khi thc hin s vng dy qun mt lp, trc khi qun tip lp th nh, chng ta cn lt giy cch in lp. Cng dng ca lp giy lt cch in lp c trnh by nh sau:
Hnh 1.8 Phng php lt lp cch in - To lp phng qun lp dy k tip, trnh cc hin tng a dy qun do lc cng ca lp th hai tc ng ln cc vng dy qun ca lp u tin (xem hnh 1.8). GVTH: Trng Hnh Ly - 12 -

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- Vi phng php lt cch in lp c gp m bin, vng dy u ca lp th nh c nh v c nh v chng hin tng a chy dy qun. Tuy nhin, nhc im ca cng ngh ny lm tng b dy cun dy _ hai pha mp ba. Mun khc phc tnh trng ny, chng ta phi: - Dng dy ca giy cch in lp va . - dy gp m khng qu d. - ng thi trong qu trnh qun dy chng ta phi dng ba nha nh st cc vng dy pha lp giy gp m 4 . Phng php gt gi u ra dy khi hon tt cun dy qun. Khi thc hin qun cn khong mi vng dy th ng gi tr yu cu, chng ta dng li v b tr bng vi (hay bng giy cch in) gi u ra dy. V tr b tr bng vi c th thc hin hai mt: mt pha mt ra dy v mt phn din ca mt ra dy , xem hnh 2.7. Sau , chng ta tip tc qun tip s vng cn li, cc vng dy qun cui ny c qun ln bng vi hay bng giy gi u dy. Khi n vng Hnh dy cui cng, chng ta m di 1.9 Phng php dng bng vi(hay bng giy) rt gi u ra dy ra dy, dng km ct t on dy qun tch ri khi rouleau dy ra dy. Sau lun qua u cn d ca phn bng vi (hay bng giy); k tip rt st bng vi (hay bng giy) gi st v cht u ra dy, xem hnh v 1.9. 5 . Hon chnh cc u ra dy trc khi ghp li thp vo dy qun. Qui trnh thao tc qun cc b dy khc cn li, thc hin tng t theo tng trnh by nh trn. Sau khi qun xong cc b dy, chng ta cn hn cc dy mm ni cc u dy ra trc khi lp ghp cc l thp vo b dy. Trnh t hn cc dy Hnh 1.10 Gen cch in che ph mi hn mm vo cc u ra dy (ca cc b dy qun) tin hnh theo cc cng an nh sau: - Co sch lp men bc ti cc an dy u ra dy. - Xi ch cc u ra dy. - Lm sch lp oxid ng bm trn u on dy mm cn hn ni. - Nn dng m mu cho cc dy ni chng ta c th nh u : cc tnh ca cc b dy; in p nh mc. . . - Xon dy mm theo hnh xon c m quanh thn on u ni cn hn. - Hn ch mi ni, hi ngui x gen bc m quanh mi hn. on gen phi ph che d hai u mi hn v che kn mi hn (xem hnh 1.10).

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- Sp xp cc u ra dy song song, dng bng keo dn gi cht c nh cc u ra (xem hnh 2.10). - Sau cng dng giy cch in bc quanh pha ngoi cun dy qun. 6 . Lp ghp cc l thp vo cun dy qun. Sau khi hon tt cng on nu trong cc 1 n 5; chng ta thc hin cng on lp ghp cc l thp vo cun dy va thi cng. Khi thc hin thao tc lp ghp cc l thp, chng ta cn ch : Ghp ht ton b cc l thp ch E vo cun dy, ghp cc l thp ch E ngc nhau; sau mi ghp cc l thp ch I sau. Mi ln ghp ch nn cho vo tng l mt (nu b dy mi l thp l 0,5mm); trong trng hp b dy mi l thp l 0,35mm chng ta c th nhp 2 l ch E ghp vo cun dy cng mt lc. Khi ghp l thp E chng ta nn chn hai on pha u (nm gn cc mt ra dy) mt vi v tr : ti c 2 l E c nhp chung ghp cng 1 lc. Hnh 1.11 Phng php ghp l thp vo cun dy qun Cc v tr dng chn thm cc l thp E sau cng, khi chng ta khng cn kh nng p st li thp a cc l thp E sau cng vo cun dy. Sau khi ghp l thp ch E xong chng ta chn vo cc v trong cc l thp I, s lng l thp ch I chn vo mi v tr phi bng s thp E ang c ti v tr . Sau khi, ghp cc l thp E v I vo cun dy, chng ta dng ba ng st cc l thp E v I gn li vi nhau, lm gim thp khe h khng kh. Khi tc ng lc dn st cc l thp E, I, chng ta nn t ton b bin p ln mt tm g phng, sau dng ba tc ng lc ln mt trn li thp. Nn tc ng lc ln li thp thng qua lp g trung gian, khng nn tc ng lc trc tip ln li thp. Trong qu trnh tc ng lc dn st cc l thp, ta nn thay i mt (tr mt) c tc dng lc. Sau khi ghp hon chnh li thp vo cun dy, dng Ohm k kim tra li cch in gia cun dy vi li thp; cch in gia cc b dy vi nhau; kim tra tnh lin lc gia cc vng dy trong tng b dy qun. Cp ngun in vo dy qun s cp, do dng in khng ti v kim tra in p ra trn th cp; kim tra li t s bin p. 7 . Kim tra v cp ngun vn hnh khng ti. Sau khi ghp hon chnh li thp vo cun dy, dng Ohm k kim tra li cch in gia cun dy vi li thp; cch in gia cc b dy vi nhau; kim tra tnh lin lc gia cc vng dy trong tng b dy qun. Cp ngun in vo dy qun s cp, do dng in khng ti v kim tra in p ra trn th cp; kim tra li t s bin p. - Dng ng h mgm mt kim tra cc cun dy c chm li thp khng. Nu chm li thp phi tho dy ra qun li. Kim tra cun dy s cp, th cp c chm nhau khng. - u in vo cun dy s cp, kim tra in p th cp xem c ng vi yu cu chn khng. nu khng phi tho ra cho php tng, gim s vng dy t in
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Bi ging thc hnh My Bin p

p th cp theo yu cu. Thng thng in p ra ln hn khong 5% phng khi MBA mang tiin p th cp S gim xung (Udo=Uchn+5%). 8 . Sy tm nha cch in, sy li-xut xng: Sau khi kim tra khng c g tr ngi th sy kh hi m trong st, trong dy, trong ba cch in ri tm nha cch in, sy li kh nha cch in v c th xut xng. Ghi Ch: Vic thc hin (8) ny ch s dng khi hc sinh ra trng lm vic theo yu cu s dng. Tuy nhin, khi lm kim tra l thuyt qun dy my bin p hc sinh phi a (8) vo bi lm. - i vi iu kin hin nay ca nh trng, khi thc hnh qun dy MBA hc sinh s khng tm nha cch in, sy khi qun xong MBA m ch cn kim tra in p th cp t yu cu l .

BI THC HNH S 02 TNH TON CH TO MY BIN P T NGU

GVTH: Trng Hnh Ly - 15 -

Trng C ng Du Nng

Bi ging thc hnh My Bin p

I. Mc ch, yu cu 1. Mc ch: Trang b cho hc sinh kin thc v cu to my bin p t ngu, nguyn l lm vic, cch tnh ton thit k v qun mt my bin p t ngu cng sut nh. 2. Yu cu: - Nm vng nguyn l lm vic v cc tnh ton cho mt my bin p t ngu cng sut nh. - Sn phm phi t yu cu k thut v tnh thm m - Bit sa cha cc pan thng thng ca my bin p t ngu II. Tm tt l thuyt Trng hp cn bin i in p cung cp t 220V xung 110V hay ngc li cho ph hp vi in p nh mc ca cc thit b in trong gia nh nh ni cm in, bn i, my xay tri cyth c th dung my bin i 110/220 c thun li hn v gn nh, d s dng. Cu to dy qun ca my bin p l loi my bin p t ngu, ch c 2 dy mc vo ngun in v hai dy ly in ra cung cp cho thit b in tiu dng.

Cu to my bin p t ngu gm 3 phn tng t my bin p c lp nhng c mt s im khc nhau nh sau: My bin p t ngu, c cc cun s cp v th cp dng qun chung mt cun, do chng c cng mt mch. Ch rng cc on cun dy chu ti c 2 dng in I 1,I2 trong my bin p t ngu th ch chu ti dng in c cng bng hiu ca hai dng I1 v I2. Ta c:
I = I1 I 2

Cng sut biu kin P2 c xc nh.

U cao U thap

P = P2 U cao u, khuyt im ca my bin p t ngu so vi my bin p thng: * u im: - Khi lng dy ng v mch t gim rt nhiu. - cc on chu ti chung 2 dng I1 v I2 ch cn c tit din chu ti hiu hai dng in I1 v I2. - Hiu sut cao hn so vi my bin p thng. - Khng lu lp cch in gia cun dy s cp v th cp.
GVTH: Trng Hnh Ly - 16 -

Trng C ng Du Nng

Bi ging thc hnh My Bin p

* Khuyt im - Khng an ton in khi lm my bin p gim p. V d gy ra s ng nhn cho ngi s dng b git in. Ch dng my bin p t ngu khi ch s ku : 0,5 2 m thi.

BI 1: TNH TON CH TO MY BIN P T NGU

GVTH: Trng Hnh Ly

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Trng C ng Du Nng

Bi ging thc hnh My Bin p

i vi MBA t ngu 1 ng vo v 1 ng ra th c hai ng ny c th hon i cho nhau khi s dng, do khi tnh ton phi m bo 2 trng hp. Gi SAB l dung lng (cng sut) ca bin p c 2 trng hp. Cn c vo U1, U2, c suy ra I1, I2. Sau cn c vo s s tnh c dng in chy trong on dy chung IC. Tng t p dng tnh ton nh trng hp MBA c 2 cun dy nh trn. a. Tnh ton cng sut: + Tnh tit din mch t : A = axb (cm2) + Cng sut tnh ton Ptt l cng sut t my bin p ph thuc vo mch t, s lin h gia Ptt vi tit din mch t l: - Vi mch t kiu bc: A = 1,2 S ptt Vi mch t kiu tr: A = 0,7 S ptt trong A l tit din mch t. + Cng sut truyn ti ca my bin p t ngu PTN
-

SPTN =

S ptt k CL

Vi kCL l h s c li : kCL =

U cao U thap U cao

b. Tnh dng in, tit din dy: i vi my bin p t ngu cn lu , cng dng in trong on dy chu ti chung cho c hai dng in s cp v th cp: b.1. Trng hp gim p: - Dng in ti: Itai = I2 = ti) - Dng in s cp : Iso = I1 =
PTN (Udmso l in p s 0,85.U so PTN (Udmtai l in p nh mc U dmtai

cp) - Dng in trong cun dy chung: IC = I 2 I1 b.2.trng hp tng p:

PTN (Udmtai l in p nh mc ti) U dmtai PTN - Dng in s cp : Iso = (Udmso l in p s cp) 0,85U so

- Dng in ti: Itai =

- Dng in trong cun dy chung: IC = I1 I 2 Trong hai trng hp my bin p t ngu tng p v gim p ch khc nhau vic tnh dng in qua on dy chung v c th tnh qua tr tuyt i IC = I 2 I1 c. Tnh tit din dy, ng knh dy: Tnh tit din dy v ng knh dy tng t nh my bin p thng.
I2 ; Sbc = J I Khi gim p : Sab = 1 ; Sbc = J

Khi tng p : Sab =

IC J IC J

+ ng knh dy cc on: dab = 1,13 S ab

GVTH: Trng Hnh Ly

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Trng C ng Du Nng

Bi ging thc hnh My Bin p

dbc = 1,13 S bc d. Tnh s vng dy cho tng on cun Tnh s vng vn: nV =
45 (vng/vn) B. A

S vng dy cho tng on: on ab: NVAB = nV.Uab on bc: NVBO = nV.Ubc V d: Xc nh cc thng s ca MBA t ngu 220V/110V, S=550VA. S nh hnh v Gii: Gi Idm l dng in ng vi in p thp ca my bin p: * Khi ng ra l 110Vn - Dng in th cp I2 l: I2 = - Chn hiu sut = 90% tnh dng in s cp I1 I1 =
S AB 550 = = 2,8 (A) = 0,56Im .U 1 0,9.220 S AB 550 = = 5 (A) = Im U2 110

- Tnh dng in trong on dy chung: IBC=IC=I2-I1=5-2,8=2,2 (A) =0,44 Idm * Khi ng ra l 220Vn - Dng in th cp I2 l: I2 = - Chn hiu sut = 90% tnh dng in s cp I1 I1 =
S AB 550 = = 5,6A = 1,1Im .U 1 0,9.220 S AB 550 = = 2,5 (A) = 0,5Im U2 220

- Tnh dng in trong on dy chung: IBC=IC=I1-I2=5,6-2,5=3,1 (A) =0,6 Idm - Kt qu ta c: IBC (on 110220) IBA (on 0110) Ng ra l 110V 0,56Im 0,44Im Ng ra l 220V 0,5Im 0,6Im thun tin trong thi cng m vn m bo cng sut MBA c th chn mt loi dy theo dng in 0,6Idm=3(A). Vi dng in 3(A) tng t nh tnh ton my bin p ta tnh cc thng s. BI 2: QUN DY MY BIN P T NGU Cc tin hnh: 1. Qun dy: Bc 1: Chun b cc vt t, thit b cn thit (bn qun dy, dy in t, ghen cch in, ko, dy dai) Bc 2: G khun, m p ln bn qun v xit cht c nh v khun. Bc 3: Quay th v chnh b m v 0. Bc 4: Tin hnh qun dy. - Chn mt mt a trn khun qun t u dy ra u tin. - Kho cht vng dy u tin.
GVTH: Trng Hnh Ly - 19 -

Trng C ng Du Nng

Bi ging thc hnh My Bin p

- X ng ghen 1mm vo u dy ra. - Tin hnh qun ri dy theo tng lp. - Lt cch in lp (sau khi qun xong mi lp, mi cp in p) - Kho vng dy cui, x ng gen vo u dy cui. - Tho khun ra khi bn qun, gi c nh cun dy. - Tho cun dy ra khi khun qun, bc thm mt lp cch in bn ngoi. * Mt s im cn lu : + Cc u dy ra phi c cch in bng gen v phi b tr mt a ca khun qun. + Phi hn ch ti a cc mi dy cc khi vut sa dy. + Ch khng mt vng dy no nm ngoi giy cch in. + Cc mi ni, nu c th cng phi a ra x l hn ni bn ngoi. + Cc u dy ra phi di a t v tr li thp n cc cu u m khng phi ni dy. Nn sp xp ng th t thun tin trong vic lp rp. _ Lp rp - Tho khun qun ra khi cun dy. X l cc mi ni, cch in cn thn; sau kim tra li cc lp bc cch in. - Lng xen k cc l thp vo lng cun dy. - Co sch cc u dy ra, a vo ngun cho my vn hnh th o kim li cc cp in p ng ra. - Hn ni cc u dy vo ng s . Kim tra li s thay i in p ng ra khi iu chnh gallett G2 . Ch : Khi lp rp phi m bo cch in tuyt i gia cc phn mch in v v hp. a. K thut qun dy: - Trc khi qun dy phi v s b tr cc dy ra v tr thc t sau ny khi ni mch khng b vng v d phn bit (Hnh 2.1a). - Trc khi qun dy c nh u dy khi u nh hnh v (Hnh 2.2a). Trong lc qun dy c gng qun dy cho thng v song hng vi nhau. C ht mi lp dy phi lt giy cch in. i vi dy qu b (d < 0,15) c th qun sut lun khng cn lt giy cch in gia cc lp. Ch lt cch in k gia cun s cp v th cp m thi. - Khi qun na chng mun a dy ra ngoi thc hin nh hnh (Hnh 2.2b). Dy a ra ngoi ny phi c cch in bng ng gaine cch in. Vic ni dy gia chng cng phi a mi ni ra ngoi cun dy (Hnh 2.2c). - i vi loi khun khng c vch chn dy, gi cc lp dy khng b chi ra ngoi khun, dng bng vi hoc giy chn dy li c 2 pha u cun dy (Hnh 2.2d). - Khi sp hon tt vic qun s vng dy, phi t ai vi hoc giy (H3-3c) sau y qun dy chng ln bng vi, giy

GVTH: Trng Hnh Ly

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Trng C ng Du Nng

Bi ging thc hnh My Bin p

, cui cng ln dy qua v rt cht bng vi gia cho chc.

Hnh 2.1b: cch ni cc mi ni dy Hnh 2.1a: cch b tr cc dy ra v tr thc t

Hnh 2.1c: Cch un cc dy ra thc t dy ra thc t (dng khoen kn) h)

Hnh 2.1d: Cch un cc (dng khoen

Hnh 2.2a: Cch c nh u dy khi u u dy gia cun dy

Hnh 2.2b: Cch ra

Hnh 2.2c: Cch c nh u dy cui cun dy

Cch gi cc lp dy

Hnh 2.2d:

b.Cch rp li l st ca mch t: - Tu theo dng l st ghp thnh mch t l dng EI hoc cc thanh ch I m ghp theo trt t c tnh trc. Lp tng l st E sut dc chiu (b) ca khun, tr u i din nhau. Cc l st cui cng thng rt kh lp phi dng ba
GVTH: Trng Hnh Ly - 21 -

Trng C ng Du Nng

Bi ging thc hnh My Bin p

st lt mt ming g ng dn dn, nh nhng cho l st p cht vo li khun. Sau khi lp cht cc l st ch E, v cc ch E tr u nn gia 2 gng t ch E c mt khe h lp ch I. Cc l st ch I cng lp dn vo cc khe h c 2 pha ca khun Ch : Cc l st cng p cht, khi vn hnh MBA khi rung v khng pht ting . Nu cc l st lng ngoi ting ku v rung, MBA cn b nng ln do t tr ln.

Hnh 2.3: Cch ghp mch t vi l st EI

Cch ghp mch t vi l st ch I:

Hnh 2.4: Cch ghp mch t vi l st ch I

c. Hn 2 u dy vo-ra: Cc u dy vo ra ca hai cun dy phi nm cng mt pha ca tai khun. Vi nhng MBA dng c dy ng knh rt nh, cc u dy vo ra ngi ta khoan hai l st nhau tai khun qun vi vng dy ca cc u ra phng dy qu nh rt d t. Nhiu khi cc u ra ca cc loi dy qu nh, ngi ta gn mt ming tn st hoc tn ng ri hn cc u dy ra ca cun dy v cc u dy ngun v ti. Dy ngun v ti s dng loi dy si n, mm. Ty theo cng sut MBA m chn dy ngun, ti c tit din ph hp. d.Th nghim:
GVTH: Trng Hnh Ly - 22 -

Trng C ng Du Nng

Bi ging thc hnh My Bin p

S dng m k kim tra cch in gia 2 cun dy, gia cun dy vi li st. Nu 2 cun dy chm nhau hoc chm li st phi tho ton b ri qun dy li. u in ngun kim tra in p U2 c ng thit k khng. e. Sy s b: Thng trong iu kin mi trng m thp, lp may v ba cch in rt d ht m nn phi sy s b cho kh hi m. f. Tm sn cch in: Thng cc MBA lm vic trong iu kin mi trng m thp phi tm sn cch in. Sau khi sy s b phi tm sn cch in bng cch: - Nhng ton b MBA vo sn cch in n lc khng thy bt kh ni ln na mi ly MBA ra. - sn cch in t t vo cc cun dy. g.Sy li v xut xng: Sau khi tm sn phi sy li cho kh sn, kim tra cch in, U2 mt ln na ri cho xut xng. 2 . Cc pan thng thng trong my bin p: Pan chm masse: Trng hp ny gy hin tng in git, nu km s n cu ch, bc khi nh th do s chm masse lm chp mch cun dy. - C th do b chm gia cc cc ni vi v st hoc c s c ni tt gia cc cc ni cc do din. Dng n th hoc m k kim tra cc im cn lu xc nh ni b chm, chp mch... sau sa cha li cho ht b chm masse. - Nu my bin p vn vn hnh bnh thng, th ni b chm ch c 1 ch, c th ng dy ra cc ni b trc lp cch in chm vo v bc my bin p hoc cc ni b lng lo chm b bc hoc chm masse lp dy tip cn vi mch t. Trng hp sau cng ny, nu quan st khng thy c ch chm masse. - Nu my bin p vn vn hnh bnh thng m gy s git nh. Trng hp ny my bin p khng b chm masse m do my bin p b m, in tr cch in b suy gim (nu dng bt th in thy cch in bng M-gm k sao cho trn 1 M l tt. Nu khng t, lp cch in b lo ho cn phi qun li ton b. My bin p ang vn hnh b n cu ch: - Nu my bin p b pht nhit thi qu, c th l do mch tiu th qu ln. Thay li dy ch ng c v cho my bin p vn hnh khng ti, nu vn bnh thng chng t lc trc my bin p lm vic qu ti. - Nu my bin p vn hnh khng ti m cu ch vn n th chc chn my bin p chp vng trong cun dy, phi qun dy li. - i vi my bin p c cng sut nh th s chp vng kh lm cu ch n ngay nhng c s pht nhit rt nhanh.

GVTH: Trng Hnh Ly

- 23 -

Trng C ng Du Nng

Bi ging thc hnh My Bin p

- i vi my bin p np c quy, chnh lu ton k, lu diode b hng ni tt. Hoc mc nhm 2 cc (+) v cc (-) vo bnh c quy (Hnh 2.5) - Nu my bin p b pht nhit thi qu, c th l do mch tiu th

Hnh 2.5 Cc s c i vi my np c quy

My bin p vn hnh b rung ln, - Do dng in tiu th qu ln, qu cng sut ca my nn nn my bin p rung ln pht ting r, lu pht nhit nhanh, chng chy my bin p. khc phc cn gim bt ti. - Do mc khng ng vi in p ngun, nhm vo ngun c in p cao. - Do mch t ghp khng cht. Phi sit cht li cc bulong p gia cc l st ca mch t v tm verni vo cun dy v vo cc khe h chn cng cc l st li, dnh cht hn. - Do bn cht l st ca mch t km phm cht, qu r st hoc qun thiu vng dy. My bin p khng vn hnh: - Nu n bo khng sng hoc khng cm thy my bin p rung nh nh do c dng in vo, th lu ng dy vo b h mch, cc ni dy vo khng tip in, hoc tip xc xu o in. - Nu n bo sng, vn k hot ng m in p ly ra khng c, phi xem li cc ni dy ra b tip in xu, t dy ra.

GVTH: Trng Hnh Ly

- 24 -

Trng C ng Du Nng

Bi ging thc hnh My Bin p

Dng vn k hoc bt th in d tm xc nh ch pan khc phc. - Nu b h mch bn trong cun dy, c th do mi ni dy cu th, khng hn ch nn tip in xu sau mt thi gian s dng, hoc dy qun b gy t... Trng hp ny phi tho ra qun li. - i vi np c quy, c th diode chnh lu b hng t mch. Trng hp ny d pht hin khi dng vn k o c in p xoay chiu U2, nhng khng c in p ra UDC ch cn thay mi diode m thi. - n bo khng sng hoc khng cm thy my bin p rung nh nh do c dng in vo, th lu ng dy vo b h mch, cc ni dy vo khng tip in, hoc tip xc xu o in. - Nu n bo sng, vn k hot ng m in p ly ra khng c, phi xem li cc ni dy ra b tip in xu, t dy ra. Dng vn k hoc bt th in d tm xc nh ch pan khc phc. - Nu b h mch bn trong cun dy, c th do mi ni dy cu th, khng hn ch nn tip in xu sau mt thi gian s dng, hoc dy qun b gy t... Trng hp ny phi tho ra qun li. - i vi np c quy, c th diode chnh lu b hng t mch. Trng hp ny d pht hin khi dng vn k o c in p xoay chiu U2, nhng khng c in p ra UDC ch cn thay mi diode m thi. My bin p lc vn hnh, lc khng: - Nhn chung do ngun in cung cp vo my bin p lc c, lc khng hoc in p ra b t qung, chnh l do tip xc xu. Nn kim tra li t ngun in cung cp n my bin p v t my bin p n mch tiu th. Lu ni cu dao chnh, xit li cc c vt xit dy ch cho cht, co sch ni tip in ht ten ng ti cu dao chnh, cc cc ni my bin p... Mt s pan trong my bin p gia dng: Ngoi s pan nu trn i vi my bin p gia dng c c mt s pan nh sau: - Chung bo sm nhng in p ra vn khng cao do tc te iu khin chung b hng, nn thay ci mi. - Chung khng bo, mc d in p ra qu in p nh mc. Do tc te b hng lm h mch chung, cun dy chung b chy. - n bo khng sng nhng my bin p vn hot ng bnh thng. Do b t bng, mch n b h mch. - Vn k ch sai tr s in p. Hiu chnh li v i chiu vi vn k chun hoc thay vn k mi. - Khng tng c in p ra n in p nh mc. Do in p ngun xung qu thp ngoi khong cho php ca my bin p
GVTH: Trng Hnh Ly - 25 -

Trng C ng Du Nng

Bi ging thc hnh My Bin p

hoc do qu ti (my bin p rung rn ln). Trng hp ny do s thit k my bin p, cun s cp qun d vng nn c tr khng ln gy s st p ln bn trong cun dy. V th khng th nng in p ln c, khi in p ngun b suy gim thi qu. Mt s pan trong my bin p np c quy: Ngoi s pan ni chung, cn ring i vi my bin p xc c quy c cc trng hp sau: - My bin p pht nhit thi qu, n cu ch hoc cng tc bo v qu ti (OVERLOAD) ca my xc ct mch. Cn phi xem li bnh c quy c b chm ni tt khng. Hoc diode chnh lu ton k b ni ngn mch. - My bin p mi vn hnh pht ting rung r v pht nhit. Cn ct mch ngay, v do ni nhm cc cc (+) v cc (-) vo bnh c quy, gy ra dng in np ln trong my bin p. Nu lu c th lm hng diode, chy my bin p (trng hp khng c cng tc bo v qu ti). - My bin p np bnh yu. Do in p xc bnh thp hn in p ca c quy. Lu 1 diode b hng t (chnh lu cu 4 diode), khng xc bnh c (chnh lu bn k).

BI THC HNH S 03 MY BIN P GIA DNG MT PHA (SURVOLTEUR) I. Mc ch, yu cu 1. Mc ch: Trang b cho hc sinh kin thc v cu to, nguyn l lm vic, cch tnh ton thit k v qun Survolteur. 2. Yu cu: - Nm vng nguyn l lm vic v cc tnh ton cho mt Survolteur. - Sn phm phi t yu cu k thut v tnh thm m - Bit sa cha cc pan thng thng ca Survolteur II. Tm tt l thuyt

a b

GVTH: Trng Hnh Ly

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Trng C ng Du Nng

Bi ging thc hnh My Bin p

c d e

Hnh 3 S hnh 3 trnh by my bin p tng gim p c s dng thng thng ni gia nh c ngun in khng n nh. Ta thy pha trn, bn tri, c 2 cc mc vi ngun in. o din (1) dng chn in p cho ph hp vi in p ngun U 1. Cn o din (2) dng hiu chnh in p ra U2 t nh mc 110v hoc 220v c a ra mch tiu th 3 cc pha bn phi. Trong s mch my bin p ny, vn k l loi in t, o in p ra U2 theo t s bin p, c cung cp bng cun dy bit lp vi dy qun my bin p v c in p 5-6v. n bo cng c mc vo cun dy ny. H chung bo qu in p c mc vi in p khong 80v, ng vi in p U2 t nh mc (110v hoc 220v). V di in p ny khng sc lm stacte hot ng lm chung reo. Cch s dng - Khi in p ngun gim, tng nm iu chnh 2 tng bc ln n khi in p ra U 2 t nh mc. Khi ngun in mnh tr li in p bnh thng, th lc in p ra U2 li tng ln qu in p nh mc. D nhin in p 2 u stac-te cng tng ng tng ln gn 100v, lm stac-te hot ng, ng mch h chung bo, dn dng in qua chung bo reo vang bo hiu cho ngi phi iu chnh li nm (2) v n bc m in p ra U2 ng nh mc, th chung bo khng reo na. - khu vc c ngun in tng in p bt thng, th phi thit k my bin p 1 phn cun dy hiu chnh in p ra U2 cho ng nh mc. Cch iu chnh in p ni trn c th gii thch thng qua biu thc sau: Ta c: Vy
U2 N2 = U 1 N1 U1 U2 = N 2 x N1

Vi U2 khng i, N2 khng i, vy khi: - U1 gim th iu chnh N1 gim - U2 tng th iu chnh N2 tng III. Tnh ton s liu Survolteur Tnh ton cc s liu k thut qun 1 Survolteur c s nh trn vi cc yu cu: U1 = 80v, 120v, 160v, 220v U2 = 110v-220v f = 50Hz
GVTH: Trng Hnh Ly - 27 -

Trng C ng Du Nng

Bi ging thc hnh My Bin p

iu kin tng gim 11 bc 5v/bc Kch thc mch t: a = 47mm, b = 44mm, b dy l st efe = 0,35mm, B = 1wb/m2, mt dng j = 4A/mm2 Cc bc tnh ton 1. Xc nh tit din ca li st: S = a x b = 47 x 44 = 2068 (mm2) = 20,68 cm2
S 20,68 = 240 VA Pt = = 1,2 1,2
2 2

Trong trng hp ny c nhiu mc in p do cch tnh phc tp hn. * Khi: U1 = 80v in p ra U2 l: - 110v tng p - 220v tng p Dng cng thc: + mc 110v:
Pt = 240 = U1 80 Phdtng = 1 857 VA 1 U2 110

+ mc 220v:
Pt = 240 = U1 80 Phd tng = 1 375 VA 1 U2 220

* Khi: U1 = 110v in p ra U2 l: - 110v bng nhau (khng tnh) - 220v tng p Vy mc U1 = 110v th
240 = 240 110 Phd tng = = 480 VA 1 0,5 220

* Khi: U1 = 160v U2 l : - 110v gim p - 220v tng p

240 = 240 110 Phd gim = = 750 VA 1 0,32 160 240 = 240 160 Phd tng = = 857 VA 1 0,28 220

* Khi: U1 = 220v U2 l : 110v gim p 220v bng nhau (khng tnh)

240 = 240 110 Phd gim = = 480 VA 1 0,5 220

Trong 4 cng sut trn ta chn cng sut ln nht: 857 VA 2. Tnh s vng dy mi vn:
GVTH: Trng Hnh Ly - 28 -

Trng C ng Du Nng

Bi ging thc hnh My Bin p

Vi s = 1wb/m2 , chn K = 45 ta c: N=
45 K = = 2,17 (vng/vn) 20,68 S

3. Tnh s vng dy cho tng on cun: Nab = 2,17 . (220-160) = 130 vng Nbc = 2,17 . (160-110) = 108,5 vng Ncd = 2,17 . (110-80) = 65,1 vng Nde = 2,17 . (80-5.10 bc) = 65,1 vng S vng/bc = 2,17 . 5 = 10,85 vng 4. Tnh dng in, tit din dy, ng knh dy. Trc ht phi tnh cng dng in i trong tng on dy. Trong trng hp ny c phc tp hn v c nhiu mc in p nn cng dng s thay i theo in p. Ta c cng dng in trong tng on nh sau Vi j = 5 A/mm2 , %= 90% , ta c:
Phd 857 = = 9,52 A U fd 90 Phd 857 Iti thiu = Ifa = U = = 3,89 A 220 fa P 857 ITB = hd = = 7,79 A 110 110

Iti a = Ifd =

Sai bit gia cc dng in tnh: 9,52 7,79 = 1,73 A 7,79 3,89 = 3,9 A Ta chn cng sai bit ln nht l 3A, chnh l dng in chy trong on fd, v ti c dng ngc pha gia in vo v in ra, do hiu ng ca bin p t ngu. T y ta tnh tit din ca dy: s=
I 3,9 = d j 4

Hoc c th cho I2 = 2A
I2 2 = = 0,5 mm2 j 4 d = 1,13 0,5 = 0,71 mm

s=

GVTH: Trng Hnh Ly

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Trng C ng Du Nng

Bi ging thc hnh My Bin p

BI THC HNH S 04 MY BIN P BA PHA THNG THNG I. Mc ch, yu cu 1. Mc ch: Trang b cho hc sinh kin thc v cu to my bin p 3 pha, nguyn l lm vic, cch s dng v sa cha cc hng hc thng thng ca my bin p 3 pha. 2. Yu cu: - Nm vng nguyn l lm vic v cc tnh ton cho mt my bin p 3 pha . - Sn phm phi t yu cu k thut v tnh thm m - Bit sa cha cc pan thng thng ca my bin p 3 pha II. Tm tt l thuyt 1. Cu to Ti cc trm bin p t cao p t 15kv xung h p 220/380v-3PH phn phi in nng cho cc h tiu dng cn phi cn n my bin p 3 pha hoc 3 my bin p 1 pha u chung li.

GVTH: Trng Hnh Ly

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Trng C ng Du Nng

Bi ging thc hnh My Bin p

My bin p 3 pha: (1) Bnh du ph (2) ng thot hi bo v bnh b n (3) Cnh tn nhit C cu gm: + Mt mch t c 3 ct c ghp bng cc l st t tnh. Trn 3 ct c b tr cc cun dy s cp v th cp. cc cun dy ny c qun ng tm, c lp cch in dy gia cun s cp v th cp. Sc t ng sinh ra do 3 cun s cp to ra cc t thng A, B, C. Tu thng A sinh ra bi cun AX i xuyn qua cc ct B,C. Cn t thng B to bi cc cun BY i xuyn qua cc ct A,C, t thng C ca cun CZ li i xuyn qua cc ct A,B. V th trn tng ct cc cun th cp sinh ra cc sc in ng tng ng cng pha vi cun s cp trn cng ct mch t. Cc cun dy pha s cp hoc th cp c th u Y hoc (K hiu cc cun dy s cp l AX, BY, CZ. Cn cc pha th cp c k hiu tng ng ax, by, cz. 2. S u dy c h thng in 3 pha, dy qun s cp hoc dy qun th cp c th u hnh (Y) hoc hnh ( ) * u hnh sao: 3 u u hoc 3 u cui ca mi cun dy u chm li cho ra 3 cun dy trung ha, 3 u kia l 3 dy pha. * u hnh tam gic: u u ca cun dy ny u vi u cui ca cun dy kia v u gip vng. Ti 3 ch ni cho ra 3 dy pha (khng c dy trung ha). Gi in p nh mc ti mi pha l UP ta c: UP1: in p nh mc ca cun s UP2: in p nh mc ca cun th - Khi u hnh sao: Ud = 3 UP - Khi u tam gic: Ud = UP Ud: in p o c gia 2 dy pha gi l in p dy. Ta c 4 dng u dy sau: a. S cp u sao Y, th cp u tam gic (Y/ )

S cp: Ud1 = 3 UP1

GVTH: Trng Hnh Ly

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Trng C ng Du Nng

Bi ging thc hnh My Bin p

Th cp: Ud2 = UP2

b. S cp u sao Y, th cp u sao Y (Y/Y)

S cp: Ud1 = 3 UP1

Th cp: UP2 = UP2

c. S cp u tam gic , th cp u sao Y ( /Y)

S cp: Ud1 = UP1

X Y Z

Th cp: Ud2 = UP2

d. S cp u tam gic , th cp u tam gic ( / )

A B C

S cp: Ud1 = UP1

GVTH: Trng Hnh Ly - 32 -

Trng C ng Du Nng

Bi ging thc hnh My Bin p

Th cp: Ud2 = UP2

3. Cng sut 3 pha Cng sut ca ton my 3 pha bng tng cng sut ca mi pha (mi phn t) Cng sut s cp: P1(3P) = P1(PA) + P1(PB) + P1(PC) P1(3P) = U1(PA).I1(PA) + U1(PB).I1(PB) + U1(PC).I1(PC) V 3 pha lun bng nhau nn: P1(3P) = 3(U1P.I1P) Tng t cng sut 3 pha th cp: P2(3P) = 3(U2P.I2P) Quan h gia s cp v th cp: P2(3P) = P1 . h (h: hiu sut ca MBA) h thay i trong khong 92% - 98% ty theo cng sut my * Nu s cp u sao hay th cp u sao ta c: Ud = 3 UP UP =
Ud 3

Id l dng chy trong ng dy pha Id = IP Ta c cng sut 3 pha: P3P = 3UP.IP = 3.

Ud . Id 3

P3P = 3 UP.IP * Nu s cp u tam gic hay th cp u tam gic, ta c: Ud = UP , Id = 3 IP IP =

Ud 3

Cng sut 3 pha: P3P = 3 UP.IP P3P = 3 Ud.Id Ta thy 2 trng hp u c kt qu nh nhau nn khi xc nh cng sut 3 pha ngi ta cn c vo Ud v Id ( l cc thng s o c trn ng dy pha). So snh 2 trng hp u Y v u , ta thy phn th cp ca 1 MBA 3 pha nu u hnh Y ta c in p cao, dng in cung cp ra ngoi nh (Id = IP). Nu u ta c in p thp dng ra ngoi ln (Id = 3 IP). Bng tham kho gia P3P v h Cng sut (V.A) Hiu sut % P h 92 95,5 50 501 700 93 96 51 100 701 1000 93,5 96,5 101 150 1001 1400
GVTH: Trng Hnh Ly - 33 -

Trng C ng Du Nng

Bi ging thc hnh My Bin p

151 200 201 300 301 500

94 94,5 95

1401 1900 1901 2500 > 2500

97 97,5 98

III. Tnh ton MBA 3 pha thng thng 1. Cng sut ca MBA - o tit din ca tr

b2

b3

- Tit din ca mi tr: S1 = b1. c (cm2) S2 = b2. c S3 = b3. c - Cng sut s cp mi pha t c: P1(P) =
S2 1,2 2

V.A

- Cng sut s cp 3 pha: P1(3P) = 3. P1 V.A - Cng sut th cp 3 pha: P2(3P) = P1(3P) . h (h: hiu sut MBA) 2. Tnh s vng dy qun - S vng vn s cp: NV1 = NV2 =
K 45 = B.S S NV 1 h

- S vng vn th cp: Ty theo s s u ta xc nh in p pha (UP) + Nu u (Y)

U d1 ; 3 + Nu u ( )

UP1 =

UP1 = Ud1 S vng ca mi cun s cp: N1 = NV1 . UP1 S vng ca mi cun th cp: N2 = NV2 . UP2 3. Tnh tit din ca mi cun - Dng in qua cun s cp: + Nu u Y:
GVTH: Trng Hnh Ly - 34 -

Trng C ng Du Nng

Bi ging thc hnh My Bin p

P1 (3P ) P1 (3P ) = 3U P1 3U d 1 + Nu u P1 (3P ) IP1 = 3U d

IP1 =

- Dng in qua mi cun th cp: + Nu u Y:

P2 (3P ) 3U d 2 + Nu u : P2 (3P ) IP2 = 3U d 2

IP2 =

- Tit din ca cun s cp: s1 =

I P1 mm2 d1 = 1,13 s1 j I P2 mm2 d2 = 1,13 s2 j

- Tit din ca cun th cp: s2 =

GVTH: Trng Hnh Ly

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