Thuc Hanh Quan MBA Hoan Chinh

7/29/2019 Thuc Hanh Quan MBA Hoan Chinh

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Trng C ng Du Nng Bi ging thc hnh My Bin p

BI THC HNH S 01TNH TON V QUN MY BIN P C LP MT PHA C NHThi 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 mtpha, nguyn l lm vic, cch tnh ton thit k mt my bin p c lp mt phacng 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 toCu 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, nbo, 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 t0,35 - 0,5 mm, nhm mc ch gim tn hao in nng do dng Fuc v hin tngt 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 dyqun trn ct t chnh. Nh th t tn nh i. Dng mch ny dng cho my bin pmt pha cng sut nh nh my bin p gia dng, my bin p cp in p cho ccmy thu thanh, tng m v.v- Mch t kiu tr (hoc kiu ct) c dng U, gm nhiu l st hinh ch I ghp livi nhau, dng cho my bin p cng sut trung bnh tr ln, loi my bin p 1 phahay 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 qunDy qun c nhim v tng p v h p, gm c cun s cp v th cp. Dyqun phi l dy ng in phn hoc nhm, c bc lp e-may hoc coton cchin.

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 rac 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,

GVTH: Trng Hnh Ly - 1 -


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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 2a ra ti vi in p l u2. T thng mc vng vi c hai dy qun s cp v thcp gi l t thng chnh. Ph ti cng tng dng i2 cng tng lm dng i1 tng theotng 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 lithp

+ o kch thc tiu chun ca l thp E,I* K hiu v tn gi cc kch thc c bnca li thp:

a. B rng tr gia ca li thpb. B dy ca li thep bin pc. B rng ca s li thp bin ph. B cao ca s li thp

Cc kch thc ny khi o tnh theo n vl [cm] hay [mm]

* Kch thc tng qut ca ton b l thp sau khi ghp st c xc nh theo hnh1.2

- My bin p c cng sut nh thng dng li thp kiu ch E,I (kiu "bc) vkiu 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 cpP (cm2) PCP = P2 = 22

2,1

S

+ Vi li U (kiu tr) : S = a x b = 0,7 cpP (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:

Dng in s cp I1 =1.U

PCP

(A)

Tra bng chn hiu sut ca my bin p v tnh ra dng in s cp:

P CP 3 10 25 50 100 1000(%) 60 70 80 85 90 >90

Dng in th cp I2 = 2U

PCP

(A)Trong :



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I1 : dng in s cpI2 : dng in th cpU1: in p s cpU2: in p th cpP1 cng sut s cp, P2 cng sut th cp

: l hiu sut ca my bin p (

: 0,85-0,9) =

1

2

P

P P1 =

2P

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

- Tit din dy qun s cp : S1 =J

I1 (mm2)

- Tit din dy qun th cp : S2 =J

I2 (mm2)

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/mm23. Tnh s vng dy s cp v th cp:

Chn mt tthng (hay tcm) B dng tnh ton cho li thp.p dng cng thc tnh sc in ng to ra trong dy qun bin p tnh s vngto ra 1 Vn sc in ng cm ng. (S vng/vn: Ngha l c bao nhiu vng dytrong cun dy th sinh ra c sc in ng bng 1 vn).

Cng thc kinh nghim: nv =SB

K

.=

SB.

45(vng/vn)

Trong : nV l s vng vn (Vng/vn)K l h sph thuc v mt tB

B mt twb/mm2S: tit din mch t(cm2).K c chn ph thuc vo mch thay t cm theo bng sau:

K 64 56 50 45 37,5 32,4 30B 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 U1S vng dy th cp: Khi tnh s vng dy cun th cp, cn phi d tr tng thmmt 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 >1500U2 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 chngi tr mt t thng B = 1T n B = 1,2T (hm lng Silic thp, t cm B chnthp). 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 thpthuc dng tle lnh v hm lng Silic khong 4%; gi tr mt t thng nmtrong phm vi B=1,4T n B=1,6T. y l dng l thp dn t nh hng, l thpny mch t c cu to theo hnh dng c bit : hnh xuyn . .v khng thucdng 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

Sd = 2

14,3

S= 1,13 S

Suy ra: d1 = 1,13 1S v d2 = 1,13 2S

5. Kim tra h s lp y: kl

Kl =

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.

S1e =2

1

2

ed =

4

.d 21e (mm2)

S1e =2

2

2

ed =

4

.d 22e (mm2)

Vi dy trng emay: ec = 0,03 0,08 mmdy bc cotton: ec = 0,15 0,40 mm

d1e = d1 + ecd2e = d2 + ec

Tra bng ch to dy ng, nhm ca nh sn xut ta c d1e, d2eNh vy ta c cng thc kim tra h s lp y nh sau: Kld

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 thcp Ut=12V, mt dng in j=4A/mm2. (kim tra h s lp y).


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

Tit din ca s

Kld

= ACS

.100

S1e

.N1

+ S2e

.N2


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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=12V1. Vi li E (kiu bc): A= a Xb = 1,2 CPP = 2,4 x 4,5 = 10,8 (cm2)

PCP = 22

2,1

S= 2

2

2,1

8,10= 81 (VA)

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

Dng in s cp I1 =1.U

PCP

=1109,0

81

x= 0,818 (A)

Dng in th cp I2 =2

2

U

P=

12

81= 6,75 (A)

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

Tit din dy qun s cp : S1 =J

I1 =4

818,0= 0,2 mm2

Tit din dy qun th cp : S2 =J

I2 =4

75,6= 1,68 mm2

3. Tnh s vng dy s cp v th cp:

Cng thc kinh nghim: nV =SB

K

.=

8,10

45= 4,17 (vng/vn)

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 1S = 1,13 x 2,0 = 0,5 (mm)

d2 = 1,13 2S = 1,13 x 68,1 = 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 vmch 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 ngncch.- Vi khun khng c vch ngn cch: Cun s v cun th lng vo nhau, thngthng 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 tthc hin:1- o kch thc ca mch t:* K hiu v tn gi cc kch thcc 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 ph: B cao ca s li thp.

Cc kch thc ny khi do tnh theon v l [cm] hay [mm].

Lu : Cc kch thc a, c v hc 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 mil 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 hnhti tn s f =50Hz, b dy tiu chun ca l thpthng thuc mt trong hai c sau:0,5 mm; hay0,35 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


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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 qundy cc gc khun khng b bp mo nh li, nu nh li s khng lp ghp cli thp.- Khc g lm li khun c cc kch thc hk x ak x bk gia khoan mt l bngtrc quay ca my m vng dy cho vo nng khun khi qun, dy khi bpnh khun khng lp li thp c.7- Lm tm g p khun:Sau khi lp khun vo my qun, hai u khun phi ctm 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 chtvn vo khun.8- Trn tai khun: Trn tai khun mt a nh v cc l lun cc u dy vo vra 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 khiqun dy.V kh nng chu nhit ca khun nha khng cao so vi cc loi vt liu cch inkhc: bakelite, carton cch in, giy presspahn. .. ng thi to d dng trongqu trnh ch to b dy ca khun nha thng bng hay ln hn 1mm; nh vy bcao hiu dng dng ri dy qun s nh hn b cao ca s li thp lm gim thp svng 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; lmtng dy ca li thp trong qu trnh lp ghp (cng ngh dp l thp cng chnhxc 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 ccl thp vo khun nha xc nh kh nng cha ca khun. Nu khun qu rngso vi b dy l thp, sinh ra hin tng rung v ting n tn s thp khi bin pvn hnh. Ngc li nu khun qu hp, chng ta khng th ghp ht ton b lthp 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 khunTrong hnh 1.3 chng ta trnh by hnh dng khun nha, cc v tr cnh cn lmsch 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 hnhqun 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 catrc 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 nhc kh nng lm t dy ti cc thi im bt u quay, hay ti cc thi im ngngquay t ngt.

Vi cc bin p c ng knh dy qun ln hn 0,5 mm, chng ta nn dng bnqun dy c t l 1/1. Tc quay cng thp cng d dng iu chnh nh hngtrong 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 trthp nht. Cc mp ca khun qun dy ti pha ra dy phi c nh v nm phatrn 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 dyc ng knh nh b tr bn trong, b dy c ng knh ln hn c b tr bnngoi.



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Thc hin theo phng php ny chng ta trnh gp hin tng lm cng mtngoi lp men cch in khi dy qun i qua cc giao tuyn ca cc mt phng xpdy; trnh c s c lm bong v lp men cch in ti cc v tr chuyn hngtrong 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 mtb 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 phangoi nhau, xem hnh 2.3, 2.4 .

Hnh 1.7 Phng php gi cc u ra, lc bt u qun cun3. Phng php lt giy

cch in lp gia cc lpdy qun.- Sau khi thc hin s vngdy qun mt lp, trc khiqun tip lp th nh, chng tacn lt giy cch in lp.Cng dng ca lp giy ltcch in lp c trnh bynh sau:

- To lp phng qunlp dy k tip, trnh cc hin tng a dy qun do lc cng ca lp th hai tcng ln cc vng dy qun ca lp u tin (xem hnh 1.8).


Hnh 1.8 Phng php lt lp cch in


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- Vi phng php lt cch in lp c gp m bin, vng dy u ca lp th nhc nh v c nh v chng hin tng a chy dy qun. Tuy nhin, nhcim 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 ccvng dy pha lp giy gp m4 . Phng php gt gi u ra dy khi hon tt cun dy qun.

Khi thc hin qun cn khongmi vng dy th ng gi tr yu cu,chng ta dng li v b tr bng vi(hay bng giy cch in) gi u rady. V tr b tr bng vi c th thchin 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 quncui ny c qun ln bng vi hay

bng giy gi u dy. Khi n vngdy cui cng, chng ta m dira 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 mmni cc u dy ra trc khi lp ghp cc l thp vo b dy. Trnh t hn cc dymm vo cc u ra dy (ca cc b dyqun) tin hnh theo cc cng an nhsau:- 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 uon 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 mquanh thn on u ni cn hn.- Hn ch mi ni, hi ngui x gen bcm quanh mi hn. on gen phi ph che

d hai u mi hn v che kn mi hn(xem hnh 1.10).


Hnh 1.9 Phng php dng bng vi(hay bng giy) rt gi u ra dy

Hnh 1.10 Gen cch in che ph mi hn


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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 cngon lp ghp cc l thp vo cundy va thi cng. Khi thc hin thaotc lp ghp cc l thp, chng ta cnch :

Ghp ht ton b cc l thp chE vo cun dy, ghp cc l thp chE ngc nhau; sau mi ghp ccl thp ch I sau. Mi ln ghp chnn cho vo tng l mt (nu b dy

mi l thp l 0,5mm); trong trnghp b dy mi l thp l 0,35mmchng ta c th nhp 2 l ch E ghpvo cun dy cng mt lc.Khi ghp l thp E chng ta nn chn hai on pha u (nm gn cc mtra dy) mt vi v tr : ti c 2 l Ec nhp chung ghp cng 1 lc.Cc v tr dng chn thm cc lthp 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, slng 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 ccl 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 thngqua lp g trung gian, khng nn tc ng lc trc tip ln li thp. Trong qu trnhtc 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 linlc 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 ingia cun dy vi li thp; cch in gia cc b dy vi nhau; kim tra tnh linlc 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. Nuchm 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


Hnh 1.11 Phng php ghp l thp vo cun dy qun


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p th cp theo yu cu. Thng thng in p ra ln hn khong 5% phngkhi MBA mang tiin p th cpS 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 thxut xng.Ghi Ch: Vic thc hin (8) ny chs dng khi hc sinh ra trng lm victheo yu cu s dng. Tuy nhin, khi lm kim tra l thuyt qun dy my binp hc sinh phi a (8) vo bi lm.- i vi iu kin hin nay ca nh trng, khi thc hnh qun dy MBA hcsinh s khng tm nha cch in, sy khi qun xong MBA m ch cn kimtra in p th cp t yu cu l .

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



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I. Mc ch, yu cu1. 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 cngsut 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 nguII. Tm tt l thuyt

Trng hp cn bin i in p cung cp t 220V xung 110V hay ngcli cho ph hp vi in p nh mc ca cc thit b in trong gia nh nh nicm in, bn i, my xay tri cyth c th dung my bin i 110/220 c thunli 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 lpnhng c mt s im khc nhau nh sau:

My bin p t ngu, c cc cun s cp v th cp dng qun chung mtcun, do chng c cng mt mch.

Ch rng cc on cun dy chu ti c 2 dng in I1,I2 trong my bin p

t ngu th ch chu ti dng in c cng bng hiu ca hai dng I 1 v I2. Ta c:I = 21 II

Cng sut biu kin P2 c xc nh.

P = P2 cao

thapcao

U

UU

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.



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

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



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i vi MBA t ngu 1 ng vo v 1 ng ra th c hai ng ny c th hon i chonhau 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 dngin 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 tmy bin p ph thuc vo mch t, s linh gia Ptt vi tit din mch tl:

- Vi mch tkiu bc: A = 1,2 pttS

- Vi mch tkiu tr: A = 0,7 pttS trong A l tit din mch t.

+ Cng sut truyn ti ca my bin p tngu PTN

SPTN =CL

ptt

k

SVi kCL l h sc li : kCL =

cao

thapcao

U

UU

b. Tnh dng in, tit din dy:i vi my bin p t ngu cn lu , cng dng in trong on dy chu tichung cho c hai dng in s cp v th cp:b.1. Trng hp gim p:

- Dng in ti: Itai = I2 =dmtai

TN

U

P(Udmtai l in p nh mc

ti)

- Dng in s cp : Iso = I1 =so

TN

U

P

.85,0 (Udmso l in p s

cp)- Dng in trong cun dy chung: IC = 12 II

b.2.trng hp tng p:

- Dng in ti: Itai =dmtai

TN

U

P(Udmtai l in p nh mc ti)

- Dng in s cp : Iso =so

TN

U

P

85,0 (Udmso l in p s cp)

- Dng in trong cun dy chung: IC = 21 II

Trong hai trng hp my bin p t ngu tng p v gimp ch khc nhau vic tnh dng in qua on dy chung vc th tnh qua tr tuyt i IC = 12 II

c. Tnh tit din dy, ng knh dy:Tnh tit din dy v ng knh dy tng t nh my bin p thng.

- Khi tng p : Sab =J

I2 ; Sbc =J

IC

- Khi gim p : Sab =J

I1 ; Sbc =J

IC

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



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dbc = 1,13 bcS

d. Tnh s vng dy cho tng on cun

Tnh s vng vn: nV =AB.

45(vng/vn)

S vng dy cho tng on:

on ab: NVAB = nV.Uabon 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 =2U

SAB=

110

550= 5 (A) = Im

- Chn hiu sut= 90% tnh dng in s cp I1

I1 =1.U

SAB

=220.9,0

550= 2,8 (A) = 0,56Im

- 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 =2U

SAB=

220

550= 2,5 (A) = 0,5Im

- Chn hiu sut= 90% tnh dng in s cp I1

I1 =1.U

SAB

=220.9,0

550 = 5,6A = 1,1Im

- Tnh dng in trong on dy chung:IBC=IC=I1-I2=5,6-2,5=3,1 (A) =0,6 Idm- Kt quta c:

IBC (on 110220) IBA (on 0110)Ng ra l 110V 0,56Im 0,44ImNg ra l 220V 0,5Im 0,6Im

thun tin trong thi cng m vn m bo cng sut MBA c th chn mt loidy 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 cchin, 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.



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- 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 khunqun.+ 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 phini 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 incn 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 tho kim li cc cp in p ng ra.- Hn ni cc u dy vo ng s . Kim tra li s thay iin p ng ra khi iu chnh gallett G2 .

Ch : Khi lp rp phi m bo cch in tuyt i giacc 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 thct 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 thngv 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 scp 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 nggaine cch in. Vic ni dy gia chng cng phi a mi nira ngoi cun dy (Hnh 2.2c).- i vi loi khun khng c vch chn dy, gi cc lp dykhng b chi ra ngoi khun, dng bng vi hoc giy chn dyli 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



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

Hnh 2.1b: cch ni cc mini dy

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

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

h)

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

Hnh 2.2c: Cch c nh u dy cui cun dy Hnh 2.2d:Cch gi cc lp dy

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 idin nhau. Cc l st cui cng thng rt kh lp phi dng ba



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st lt mt ming g ng dn dn, nh nhng cho l st pcht vo li khun.

Sau khi lp cht cc l st ch E, v cc ch E tr unn gia 2 gng t ch E c mt khe h lp ch I. Cc lst ch I cng lp dn vo cc khe h c 2 pha ca

khunCh : Cc l st cng p cht, khi vn hnh MBA khi rung vkhng 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 dyvo ra ngi ta khoan hai l st nhau tai khun qun vi vngdy ca cc u ra phng dy qu nh rt d t.

Nhiu khi cc u ra ca cc loi dy qu nh, ngi ta gnmt ming tn st hoc tn ng ri hn cc u dy ra cacun 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 chndy ngun, ti c tit din ph hp.d.Th nghim:



23/35


S dng m k kim tra cch in gia 2 cun dy, giacun dy vi li st. Nu 2 cun dy chm nhau hoc chm list 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 cchin 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 thpphi tm sn cch in. Sau khi sy s b phi tm sn cchin bng cch:- Nhng ton b MBA vo sn cch in n lc khng thy btkh 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, U2mt 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 nitt gia cc cc ni cc do din. Dng n th hoc m kkim tra cc im cn lu xc nh ni b chm, chpmch... sau sa cha li cho ht b chm masse.

- Nu my bin p vn vn hnh bnh thng, th ni b chmch c 1 ch, c th ng dy ra cc ni b trc lp cch inchm vo v bc my bin p hoc cc ni b lng lo chm b bchoc chm masse lp dy tip cn vi mch t. Trng hp saucng ny, nu quan st khng thy c ch chm masse.- Nu my bin p vn vn hnh bnh thng m gy s gitnh. Trng hp ny my bin p khng b chm masse m do mybin p b m, in tr cch in b suy gim (nu dng bt thin 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 tiuth qu ln. Thay li dych ng c v cho my bin p vn hnh khng ti, nu vnbnh 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 thchc chn my bin p chp vng trong cun dy, phi qundy li.- i vi my bin p c cng sut nh th s chp vng kh lmcu ch n ngay nh

ng c s pht nhit rt nhanh.



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

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 rungln 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 cckhe h chn cng cc l st li, dnh cht hn.- Do bn cht l st ca mch t km phm cht, qu r st hocqun thiu vng dy. My bin p khng vn hnh:- Nu n bo khng sng hoc khng cm thy my bin p rungnh nh do c dng in vo, th lu ng dy vo b hmch, cc ni dy vo khng tip in, hoc tip xc xu oin.- 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.



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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 dycu th, khng hn ch nn tip in xu sau mt thi gian sdng, 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 xoaychiu U2, nhng khng c in p ra UDC ch cn thay mi diodem thi.- n bo khng sng hoc khng cm thy my bin p rung nhnh do c dng in vo, th lu ng dy vo b h mch,cc ni dy vo khng tip in, hoc tip xc xu oin.- 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 dycu th, khng hn ch nn tip in xu sau mt thi gian sdng, hoc dy qun b gy t... Trng hp ny phi tho raqun 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 xoaychiu 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, lckhng 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 tmy bin p n mch tiu th. Lu ni cu dao chnh, xit licc c vt xit dy ch cho cht, co sch ni tip in ht tenng 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 span nh sau:- Chung bo sm nhng in p ra vn khng cao do tc te iukhin 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 bchy.- n bo khng sng nhng my bin p vn hot ng bnhthng. Do b t bng, mch n b h mch.- Vn k ch sai tr s in p. Hiu chnh li v i chiu vivn k chun hoc thay vn k mi.- Khng tng c in p ra n in p nh mc. Do inp ngun xung qu thp ngoi khong cho php ca my bin p



26/35


hoc do qu ti (my bin p rung rn ln). Trng hp ny do sthit k my bin p, cun s cp qun d vng nn c tr khngln gy s st p ln bn trong cun dy. V th khng th nngin 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 quyc cc trng hp sau:- My bin p pht nhit thi qu, n cu ch hoc cng tc bov qu ti (OVERLOAD) ca my xc ct mch. Cn phi xem libnh c quy c b chm ni tt khng. Hoc diode chnh luton 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 (-) vobnh 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 inp 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 03MY BIN P GIA DNG MT PHA (SURVOLTEUR)

I. Mc ch, yu cu1. 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


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Hnh 3S hnh 3 trnh by my bin p tng gim p c s dng thng thng ni gianh 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 ccpha bn phi. Trong s mch my bin p ny, vn k l loi in t, o in pra 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 chungbo 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 lmchung reo.

Cch s dng- Khi in p ngun gim, tng nm iu chnh 2 tng bc ln n khi in p ra U2t 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 ngtng ln gn 100v, lm stac-te hot ng, ng mch h chung bo, dn dng inqua chung bo reo vang bo hiu cho ngi phi iu chnh li nm (2) v n bcm 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:1

2

1

2

N

N

U

U=

Vy U2 = N2 x 11

N

U

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 SurvolteurTnh ton cc s liu k thut qun 1 Survolteur c s nh trn vi cc yu

cu:U1 = 80v, 120v, 160v, 220vU2 = 110v-220vf = 50Hz


c

d

e

f


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iu kin tng gim 11 bc 5v/bcKch 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 ton1. Xc nh tit din ca li st:

S = a x b = 47 x 44 = 2068 (mm

2

) = 20,68 cm

2

Pt =2

2,1

S=

2

2,1

68,20

= 240 VA

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:

Phdtng = =2

11UU

Pt

=110801

240

857 VA

+ mc 220v:

Phd tng ==

2

11U

UPt

=

220

801

240375 VA

* Khi:U1 = 110v in p ra U2 l: - 110v bng nhau (khng tnh)

- 220v tng p

Vy mc U1 = 110v th

Phd tng ==

220

1101

240

5,0

240= 480 VA

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

- 220v tng p

Phd gim ==

160

1101

240

32,0

240= 750 VA

Phd tng ==

220

1601

240

28,0

240= 857 VA

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

220v bng nhau (khng tnh)

Phd gim ==

220

1101

240

5,0

240= 480 VA

Trong 4 cng sut trn ta chn cng sut ln nht: 857 VA2. Tnh s vng dy mi vn:



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Vi s = 1wb/m2 , chn K = 45 ta c:

N =S

K=

68,20

45= 2,17 (vng/vn)

3. Tnh s vng dy cho tng on cun:Nab = 2,17 . (220-160) = 130 vng

Nbc = 2,17 . (160-110) = 108,5 vngNcd = 2,17 . (110-80) = 65,1 vngNde = 2,17 . (80-5.10 bc) = 65,1 vngS 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 theoin p. Ta c cng dng in trong tng on nh sau

Vi j = 5 A/mm2 , %= 90% , ta c:

Iti a = Ifd = fdhd

U

P

= 90

857

= 9,52 A

Iti thiu = Ifa =fa

hd

U

P=

220

857= 3,89 A

ITB =110

hdP =110

857= 7,79 A

Sai bit gia cc dng in tnh:9,52 7,79 = 1,73 A7,79 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 tngu.T y ta tnh tit din ca dy:

s =j

I=

4

9,3 d

Hoc c th cho I2 = 2A

s =j

I2 =4

2= 0,5 mm2

d = 1,13 5,0 = 0,71 mm



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BI THC HNH S 04MY 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 phaII. Tm tt l thuyt

1. Cu toTi 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 mybin p 1 pha u chung li.



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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 cccun dy s cp v th cp. cc cun dy ny c qun ng tm, c lp cch indy gia cun s cp v th cp. Sc t ng sinh ra do 3 cun s cp to ra cc tthng 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 cacun 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 cundy 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 sUP2: in p nh mc ca cun th

- Khi u hnh sao: Ud = 3 UP- Khi u tam gic: Ud = UPUd: 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


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

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

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


Th cp: Ud2 = UP2Th cp: Ud2 = UP2

S cp: Ud1 = 3 UP1

Th cp: UP2 = UP2

A B C

X Y Z

S cp: Ud1

= UP1

Th cp: Ud2

= UP2

A B C

S cp: Ud1 = UP1


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3. Cng sut 3 phaCng 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 = 3dU

Id l dng chy trong ng dy phaId = IP

Ta c cng sut 3 pha:P3P = 3UP.IP = 3.

3dU . Id

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

Ud = UP , Id = 3 IP IP = 3dU

Cng sut 3 pha:

P3P = 3 UP.IPP3P = 3 Ud.IdTa 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 (I d = IP). Nu u ta c in p thp dng ra ngoi ln (Id = 3 IP).

Bng tham kho gia P3P v hCng sut (V.A) Hiu sut % P h

50 92 501 700 95,5

51 100 93 701 1000 96101 150 93,5 1001 1400 96,5


X Y Z

Th cp: Ud2 = UP2


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IP1 =1

1

3

)3(

dU

PP=

1

1

3

)3(

PU

PP

+ Nu u

IP1 =dU

PP

3

)3(1

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

IP2 =2

2

3

)3(

dU

PP

+ Nu u :

IP2 =2

2

3

)3(

dU

PP

- Tit din ca cun s cp:

s1 =j

IP1 mm2 d1 = 1,13 1s

- Tit din ca cun th cp:

s2 = jIP2 mm2 d2 = 1,13 2s

Thuc Hanh Quan MBA Hoan Chinh

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