khi cu dien_2

8/8/2019 KHI CU DIEN_2

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LI NI U

t nc Vit Nam trong cng cuc cng nghip ho - hin i ho, nn

kinh tang trn pht trin, vic s dng cc thit bin, kh cin vo trongxy lp cc khu cng nghip, khu ch xut lin doanh, khu nh cao tng ngy

cng nhiu. V vy vic tm hiu c tnh, kt cu, tnh ton la chn s dng rt

cn thit cho sinh vin hc ngnh in. Ngoi ra cn phi cp nht thm nhng

cng ngh mi ang khng ngng ci tin v nng cao cc thit bin.

Vi mt vai tr quan trng nh vy v xut pht t yu cu, k hoch o

to, chng trnh mn hc ca Trng Cao ng Ngoi ng - Cng ngh Vit

Nht. Chng ti bin son cun gio trnh Kh cin gm4 phn vi nhngni dung cbn sau:

- Phn 1: L thuyt cbn ca kh cin.- Phn 2: Tm hiu c tnh, kt cu, la chn s dng kh cin h p.- Phn 3: Gii thiu c tnh, kt cu kh cin cao p.- Phn 4: Mt s s cn bn v nguyn l iu khin, vn hnh.Gio trnh Kh cin c bin son phc v cho cng tc ging dy ca

gio vin v l ti liu hc tp ca hc sinh.

Do chuyn mn v thi gian c hn nn khng trnh khi nhng thit st,

vy rt mong nhn c kin ng gp ca ng nghip v bn c cun sch

t cht lng cao hn.

TC GI


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PHN I: L THUYT CBN CA KH CIN

Chng I: PHT NNG KH CIN

I. KHI NIM V KH CIN

1. Khi nim

Kh cin l thit b dng ng ct, bo v, iu khin, iu chnh cc

li in, mch in, cc loi my in v cc my trong qu trnh sn xut.

Kh cin lm vic lu di trong cc mch dn in, nhit ca kh c

in tng ln gy tn tht in nng di dng nhit nng v t nng cc b phn

dn in v cch in ca kh c. V vy kh cin lm vic c trong mi ch khi nhit ca cc b phn phi khng qu nhng gi tr cho php lm vic an

ton lu di.

2. Phn loi, cc yu cu cbn ca kh cin

a) Phn loi

Kh cin c phn ra cc loi sau:

-

Kh c in dng ng ct cc mch in: Cu dao, My ct,Aptmat

- Kh cin dng mmy: Cng tc t, Khi ng t, B khng ch chhuy

- Dng bo v ngn mch ca li in: Cu ch, Aptmat, Cc loimy ct, Rle nhit

b) Cc yu cu cbn ca kh cin

m bo an ton cho cc thit bin v m bo tin cy ca Kh c

in th Kh cin m bo mt s yu cu:

- Kh cin m vo lm vic lu di vi cc thng s k thut trngthi lm vic nh mc: Um, Im.

- n nh nhit, in ng, c cng ckh cao khi qu ti, khi ngnmch, Vt liu cch in tt, khng b chc thng khi qu dng.

- Kh cin lm vic chc chn, an ton khi lm vic.II. TNH TON TN THT IN NNG TRONG KH CIN

Tn tht in nng trong kh cin c tnh theo:


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=t

0

2.R.tIQ

Trong : Q: in nng tn tht.

i: dng in trong mch.R: in trca kh c.

t: Thi gian c dng in chy qua.

Tu theo kh cin to nn t cc vt liu khch quan, kch thc khc

nhau, hnh dng khc nhau s pht sinh tn tht khc nhau.

III. CC CH PHT NNG CA KH CINSau y l bng nhit cho php ca mt s vt liu:

Vt liu lm kh cin Nhit cho php (0C)

Vt liu khng bc cch in hoc xa

nht cch in.

110

Dy ni dng tip xc cnh. 75

Vt liu c tip xc dng hnh ngn 75

Tip xc trt ca ng v hp kim ng 110

Tip xc m bc. 120Vt khng dn in v khng bc cch in. 110

Vt liu cch in Cp cch nhitNhit cho

php (0C)

Vi si, giy khng tm cch in. Y 90

Vi si, giy c tm cch in. A 105

Hp cht tng hp E 120

Mica, si thu tinh B 130

Mica, si thu tinh c tm cch in F 155

Cht tng hp Silic H 180

S cch in. C >180


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Tu theo ch lm vic khc nhau, mi kh cin s c s pht nng

khc nhau:

1. Ch lm vic lu di ca kh cin

Kh cin lm vic lu di, nhit trong kh cin bt u tng v n

nhit n nh th khng tng na, lc ny s to nhit ra mi trng xung

quanh.

2. Ch lm vic ngn hn ca kh cin

Ch lm vic ngn hn ca kh cin l ch khi ng in nhit

ca n khng t ti nhit n nh, sau khi pht nng ngn hn, kh cc

ngt nhit ca n st xung ti mc khng so snh c vi mi trng xung

quanh.

3. Ch lm vic ngn hn lp li ca kh cin

Nhit ca kh cin tng ln trong khong thi gian kh c lm vic,

nhit gim xung trong khong thi gian kh c ngh, nhit gim cha t

n gi tr ban u th kh cin lm vic lp li. Sau khong thi gian, nhit

tng ln ln nht gn bng nhit gim nh nht th kh cin t c ch

dng.

n nh

Bt u t(s)

n nh

Bt u t(s)

Pht nng


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CU HI CHNG 1

1. Nu khi nim, phn loi v cc yu cu ca kh cin.

2. Trnh by cc ch pht nng ca kh cin.

Chng 2: TIP XC IN - H QUANG

I. TIP XC IN

1. Khi nim

Tip xc in l ni m dng in i t vt dn ny sang vt dn khc. B

mt tip xc ca hai vt dn c gi l tip xc in.

Cc yu cu cbn ca tip xc in:

- Ni tip xc in phi chc chn, m bo.- Mi ni tip xc phi c bn ckh cao.- Mi ni khng c pht nng qu ga tr cho php.- n nh nhit v n nh ng khi c dng in cc i i qua.- Chu c tc ng ca mi trng (nhit , cht ho hc...)m bo cc yu cu trn, vt liu dng lm tip im c cc yu cu:

- in dn v nhit dn cao.- bn chng r trong khng kh v trong cc kh khc.- bn chng to lp mng c in trsut cao.- cng b gim lc nn.- cng cao gim hao mn cc b phn ng ngt.- bn chu h quang cao (nhit nng chy).- n gin gia cng, gi thnh h.


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Mt s vt liu dng lm tip im: ng, Bc, Nhm, Vonfram...

2. Phn loi tip xc in

Da vo kt cu tip im, c cc loi tip xc in sau:

a) Tip xc cnh

Cc tip ic ni cnh vi cc chi tit dn dng in nh l: thanh

ci, cp in, ch ni kh c vo mch. Trong qu trnh s dng, c hai tip im

c gn cht vo nhau nhcc bu lng, hn nng hay ngui.

b) Tip xc ng m

L tip xc ng ngt mch in. Trong trnghp ny ht sinh h

quang in, cn xc nh khong cch gia tip im tnh v ng da vo dng

in nh mc, in p nh mc v ch lm vic ca kh cin.

c) Tip xc trt

L tip xc c gp v vnh trt, tip xc ny cng d sinh ra h quang

in.

3. Cc yu tnh hng n in trtip xc

- Vt liu lm tip im: vt liu mm tip xc tt.- Kim loi lm tip im khng b xy ha.- Lc p tip im cng ln th s to nn nhiu tip im tip xc.- Nhit tip im cng cao th in trtip xc cng ln.- Din tch tip xc.Thng thng dng hp kim lm tip im.

II. H QUANG IN

1. Khi nimTrong cc kh c in dng ng ngt mch in (cu dao, contactor,

rle...) khi chuyn mch s pht sinh hin tng phng in. Nu dng in ngt

di 0,1A v in p ti cc tip im khong 250 300V th cc tip im s

phng in m . Trng hp dng in v in p cao hn tr s trong bng sau s

sinh ra h quang in.

Vt liu lm tip im U(V) I(A)

Platin 17 0,9


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Vng 15 0,38

Bc 12 0,4

Vonfram 17 0,9

ng 12,3 0,43

Than 18 22 0,03

2. Tnh cht cbn ca phng in h quang

- Phng in h quang ch xy ra khi cc dng in c tr s ln.- Nhit trung tm h quang rt ln v trong cc kh c c th n

600080000K.

- Mt dng in ti Catt ln (104 105)A/cm2.- St p Catt bng 10 20V v thc t khng ph thuc vo dng in.

3. Qu trnh pht sinh v dp h quang

a) Qu trnh pht sinh h quang in:

i vi tip im c dng in b, ban u khong cch gia chng nh

tng khi in p t c tr s nht nh, v vy trong khong khng gian ny s sinhra in trng c cng rt ln (3.107V/cm) c th lm bt in t t Catt gi

l pht x tng in t (gi l pht x ngui in t). Sin t cng nhiu,

chuyn ng di tc dng ca in trng lm ion ho khng kh gy h quang

in.

i vi tip im c dng in ln, qu trnh pht sinh h quang phc tp

hn. Lc u m tip im, lc p gia chng c tr s nh nn s tip im tip

xc dng in di qua t. Mt dng in tng ng kn hng chc nghnA/cm2, do ti cc tip im s pht nng s tng n mc lm cho nhau, git

kim loi c ko cng ra tr thnh cu cht lng v ni lin hai tip im ny,

nhit ca cu cht lng tip tc tng, lc cu cht lng bc hi v trong

khng gian gia hai tip im xut hin h quang in. V qu trnh pht nng ca

cu thc hin rt nhanh nn s bc hi mang tnh cht n. Khi cu cht lng ct

ko theo s mi mn tip im, iu ny rt quan trng khi ngt dng in qu ln

hay qu trnh ng mxy ra thng xuyn.b) Qu trnh dp tt h quang in


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iu kin dp tt h quang l qu trnh ngi li vi qu trnh pht sinh h

quang:

- H nhit h quang.-

Ko di h quang.- Chia h quang thnh nhiu on nh.- Dng nng lng bn ngoi hoc chnh n thi tt h quang.- Mc in trShunt tiu th nng lng h quang

Thit b dp tt h quang.

- H nhit h quang bng cch dng hi kh hoc du lm ngui,dng vch ngn h quang c xt.

- Chia h quang thnh nhiu ct nh v ko di h quang bng cchdng vch ngn chia thnh nhiu phn nh v thi kh dp tt.

- Dng nng lng bn ngoi hoc chnh n thi tt h quang,nng lng ca n to p sut thi tt h quang.

- Mc in trShunt tiu th nng lng h quang (dng in trmc song song vi hai tip im sinh h quang).

CU HI CHNG 2

1. Nu khi nim, phn loi tip xc in.2. Nu khi nim, tnh cht cbn ca phng in h quang

PHN II: TM HIU C TNH, KT CU, TNH TONLA CHN SDNG KH CIN H P.

Chng 3: KH CIN NG NGT - BO V

MCH INA CB (CIRCUIT BREAKER)

I. KHI NIM V YU CU.CB (CB c vit tt t danh t Circuit Breaker), CB l kh cin dng

ng ngt mch in (mt pha, ba pha); c cng dng bo v qu ti, ngn mch,

st p... mch in.

Chn CB phi tho mn ba yu cu sau:


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- Ch lm vic nh mc ca CB thi l ch lm vic di hn, nghal tr s dng in nh mc chy qua CB lu tu . Mt khc, mch dng in ca

CB phi chu c dng in ln (khi c ngn mch) lc cc tip im ca n

ng hay ang ng.- CB phi ngt c tr s dng in ngn mch ln, c th vi chc KA.Sau khi ngt dng in ngn mch, CB m bo vn lm vic tt tr s dng in

nh mc.

- nng cao tnh n nh nhit v in ng ca cc thit bin, hn chs ph hoi do dng in ngn mch gy ra, CB phi c thi gian ct b. Mun vy

thng phi kt hp lc thao tc chc vi thit b dp h quang bn trong CB.

II. CU TO V NGUYN L HOT NG

1. Cu to

a) Tip im

CB thng c ch to c hai cp tip im (tip im chnh v h quang),

hoc ba cp tip im (chnh, ph, h quang).

Khi ng mch, tip im h quang ng trc, tip theo l tip im ph,

sau cng l tip im chnh. Khi ct mch th ngc li, tip im chnh mtrc,sau n tip im ph, cui cng l tip im h quang. Nh vy h quang ch

chy trn tip im im h quang, do o bo vc tip im chnh dn in.

Dng thm tip im ph trnh h quang chy lan vo lm h hi tip im

chnh.

b) Hp dp h quang

CB dp c h quang trong tt c cc ch lm vic ca li in,

ngi ta thng dng hai kiu thit b dp h quang l: Kiu na kn v kiu h.

Kiu na kn c dt trong v kn ca CB v c l thot kh. Kiu ny c

dng in gii hn ct khng qu 50KA. Kiu hc dng khi gii hn dng

in ct ln hn 50KA hoc in p ln 1000V (cao p).

Trong bung dp h quang thng dng, ngi ta dng nhng tm thp xo

thnh li ngn, phn chia h quang thnh nhiu on ngn thun li cho vic

dp tt h quang.

c) Ccu truyn ng ct CB

Truyn ng ct thng c hai cch: Bng tay v bng cin (in t, ng

cin).


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iu kin bng tay c thc hin vi cc CB c dng in nh mc khng

ln hn 600A. iu khin bng in t (nam chm in) c ng dng cc CB

c dng in ln hn (n 1000A).

tng lc iu khin bng tay ngi ta dng mt tay di ph theo nguynl n by. Ngoi ra cn c cch iu khin bng ng cin hoc bng kh nn.

d) Mc bo v

CB tng ct nhcc phn t bo v - gi l mc bo v, s tc ng khi

mch in c s c qu dng in (qu ti hay ngn mch) v st p.

Mc bo v qu dng in (cn gi l bo v dng in cc i) bo v

thit bin khong b qu ti v ngn mch, ng thi gian dng in ca mc

bo v phi nm di ng c tnh ca i tng cn bo v. Ngi ta thng

dng h thng in t v rle nhit lm mc bo v, t bn trong CB.

Mc kiu in t c cun dy mc ni tip vi mch chnh, cun dy ny

c qun tit din ln chu dng ti v t vng. Khi dng in vt qu tr s cho

php th phn ng b ht v nc s dp vo khp ri t do, lm tip im ca CB

mra. iu chnh vt thay i lc khng l xo, ta c thiu chnh c tr s

dng in tc ng. gi thi gian trong bo v qu t kiu in t, ngi ta

thm mt ccu gi thi gian.

Mc kiu rle nhit n gin hn c, c kt cu tng t nh rle nhit c

phn t pht nng u ni tip vi mch in chnh, tm kim loi kp dn nlm

nh khp ri t do m tip im ca CB khi c qu ti. Kiu ny c nhc

im l qun tnh nhit ln nn khng ngt nhanh c dng in tng vt khi c

ngn mch, do ch bo vc dng in qu ti.

V vy ngi ta thng s dng tng hp c mc kiu in t v mc kiu

rle nhit trong mt CB. Loi ny c dung CB c dng in nh mc n

600A.

Mc bo v st p (cn gi l bo vin p thp) cng thng dung kiu

in t. Cun dy mc song song vi mnch in chnh, cun dy ny c qun t

vng vi dy tit din nh chu in p ngun.

2. Nguyn l hot ng

a) S nguyn l ca CB dng in cc i (hnh v 1.1)


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Hnh 1.1 S CB dng in cc i

trng thi bnh thng sau khi ng in, CB c gi trng thi ngtip im nhmc 2 khp vi mc 3 cng mt cm vi tip im ng.

Bt CB trng thi ON, vi dng in nh mc nam chm in 5 v phn

ng 4 khng ht .

Khi mch in qu ti hay ngn mch, lc ht in tnam chm in 5 ln

hn lc l xo 6 lm cho nam chm in 5 s ht phn ng 4 xung lm bt nh

mc 3, mc 5 c th t do, l xo 1 c th lng, kt qu cc tip im ca CB

c mra, mch in b ngt.b) S nguyn l CB in p thp (hnh 1.2)

Hnh 2.2: S CB in p thp

Bt CB trng thi ON, vi in p nh mc nam chm in 11 v phn

ng 10 ht li vi nhau.


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Khi st p qu mc, nam chm in 11 s nh phn ng 10, l xo 9 ko mc

8 bt ln, mc 7 th t do, th lng, l xo 1 c th lng, kt qu cc tip im

ca CB c mra, mch in b ngt.

3. Phn loi v cch la chn CB

Theo kt cu, ngi ta chia CB ra lm ba loi: mt cc, hai cc v ba cc.

Theo thi gian thao tc, ngi ta chia CB ra loi tc ng khng tc thi v

loi tc ng tc thi (nhanh).

Tu theo cng dng bo v, ngi ta chia CB ra cc loi: CB cc i theo

dng in, CB cc tiu theo in p. CB dng in ngc ...

Vic la chn CB ch yu da vo:

- Dng in tnh ton i trong mch.- Dng in qu ti.- CB thao tc phi c tnh chn lc.Ngoi ra la chn CB cn phi cn c vo c tnh lm vic ca ph ti l

CB khng c php ct khi c qu ti ngn hn thng xy ra trong iu kin lm

vic bnh thng nh dng in khi ng, dng in nh trong ph ti cng

ngh.

Yu cu chung l dng in nh mc ca mc bo v ICB khng c b

hn dng in tnh ton Itt ca mch.

Tu theo c tnh v iu kin lm vic c th ca ph ti, ngi ta hng

dn la chn dng in nh mc ca mc bo v bng 125%, 150% hay ln hn

na so vi dng in tnh ton.

CU HI CHNG 3 PHN A

1. Cho bit cng dng, cu to, cc loi CB?2. Hy nu nguyn l hot ng ca cc loi CB?3. Cch chn CB?

B - CU CH

I. KHI NIM V YU CUCu ch l mt loi kh cin dng bo v thit b v li in trnh s

c ngn mch, thng dng bo v cho ng dy dn, my bin p, ng cin, thit bin, mch in iu khin, mch in thp sng.


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Cu ch c c im l n gin, kch thc b, kh nng ct ln v gi

thnh h nn c ng dng rng ri.

Cc tnh cht v yu cu ca cu ch:

-

Cu ch c c tnh lm vic n nh, khng tc ng khi c dng inmmy v dng in nh mc lu di i qua.

- c tnh A s ca cu ch phi thp hn c tnh ca i tng bo v.- Khi c s c ngn mch, cu ch tc ng phi c tnh chn lc.- Vic thay th cu ch b chy phi d dng v tn t thi gian.


1. Cu to

Cu ch bao gm cc thnh phn sau:

+ Phn t ngt mch: y chnh l thnh phn chnh ca cu ch, phn tny phi c kh nng cm nhn c gi tr hiu dng c dng in qua n. Phn

t ny c gi trin trsut b (thng bng bc, ng hay cc vt liu dn c gi

trin trsut nh ln cn vi cc gi tr nu trn...). Hnh dng ca phn t c

thdng l mt dy (tit din trn), dng bng mng.

+

Thn ca cu ch: Thng bng thu tnh, ceramic (s gm) hay cc vtliu khc tng ng. Vt liu to thnh thn ca cu ch phi m bo c hai

tnh cht:

- C bn ckh.- C bn viu kin dn nhit v chu ng c cc s thay i

nhit t ngt m khng h hng.

+ Vt liu lp y (bao bc quanh phn t ngt mch trong thn cu ch):Thng bng vt liu Silicat dng ht, n phi c kh ngng hp thc nng

lng sinh ra do h quang v phi m bo tnh cch in khi xy ra hin tng

ngt mch.

+ Cc u ni: Cc thnh phn ny dng nh v cnh cu ch trn ccthit bng ngt mch; ng thi phi m bo tnh tip xc in tt.

2. Nguyn l hot ng

c tnh cbn ca cu ch l s ph thuc ca thi gian chy t vi dng

in chy qua (c tnh Ampe - giy). c tc dng bo v, ng Ampe giy

ca cu ch ti mi im phi thp hn c tnh ca i tng cn bo v.


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+ i vi dng in nh mc ca cu ch: Nng lng sinh ra do hiu ngJoule khi c dng in nh mc chy qua s to ra mi trng v khng gy nn

s nng chy, s cn bng nhit sc thit lp mt gi tr m khng gy s

gi ho hay ph hng bt c phn t no ca cu ch.+ i vi dng in ngn mch ca cu ch: S cn bng trn cu ch b

ph hu, nhit nng trn cu ch tng cao v dn n s ph hu cu ch:

Ngi ta phn thnh hai giai on khi xy ra s ph hu cu ch:

- Qu trnh tin h quang (tp).- Qu trnh sinh ra h quang (ta).

Trong : t0: Thi im bt u s c.

tp: Thi im chm dt giai on tin h quang.

tt: Thi im chm dt qu trnh pht sinh h quang.

* Qu trnh tin h quang: Gi s ti thi im t0 pht sinh s qu dng,

trong khong thi gian tp lm nng chy cu ch v pht sinh ra h quang in.

Khong thi gian ny ph thuc vo gi tr dng in to nn do s c v s cm

bin ca cu ch.

* Qu trnh pht sinh h quang: Ti thi im tp h quang sinh ra cho n

thi im t0 mi dp tt ton b h quang. Trong sut qu trnh ny, nng lng

tp ta t

Dng intin h quang

l

t

Dng in

phng on

Dng in trongQu trnh h quang

Thi gian tin h quang Thi gian sinh h quangThi gian ton b qu trnh

Gin thi gian ca qu trnh pht sinh h


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sinh ra do h quang lm nng chy cc cht lm y ti mi trng h quang sinh

ra; in p hai u cu ch hi phc li, mch in c ngt ra.

3. Phn loi, k hiu, cng dng

Cu ch dng trong li in h th c nhiu hnh dng khc nhau, trong s

nguyn l ta thng k hiu cho cu ch theo mt trong cc dng sau:

Cu ch c th chia thnh hai dng cbn, ty thuc vo nhim v:

+ Cu ch loi g: Cu ch dng ny ch c kh nng ngt mch, khi c sc hay qu ti hay ngn mch xy ra trn ph ti.

+ Cu ch loi a: Cu ch dng ny ch c kh nng bo v duy nht trngthi ngn mch trn ti.

Mun phn bit nhim v lm vic ca cu ch, ta cn cn c vo c tuyn

Ampe giy (l ng biu din m t mi quan h gia dng in qua cu ch v

thi gian ngt mch ca cu ch).

Gi ICC: Gi tr dng in ngn mch.

IS: Gi tr dng in qu ti.

Vi cu ch loi g: Khi c dng ICC qua mch n phi ngt mch tc th, v

khi c dng IS qua mch cu ch khng ngtm ch tc th m duy tr mt khong

thi gian mi ngt mch (thi gian ngt mch v gi tr dng IS t l nghch vi

nhau).

Do nu quan st hai c tnh Ampe giy ca hai loi cu ch a v g; ta

nhn thy c tnh Ampe giy ca cu ch loi a nm xa trc thi gian (trc tung)

v cao hn c tnh Ampe giy ca cu ch loi g.

c tnh Ampe giy ca cc loi cu ch


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4. Cc c tnh in p ca cu ch

- in p nh mc l gi trin p hiu dng xoay chiu xut hin haiu cu ch (khi cu ch ngt mch), tn s ca ngun in trong phm vi 48Hz

n 62Hz..- Dng in nh mc l gi tr hiu dng ca dng in xoay chiu m

cu ch c th ti lin tc thng xuyn m khng lm thay i c tnh ca n.

- Dng in ct cc tiu l gi tr nh nht ca dng in s c m dy chc kh nng ngt mch. Kh nng ct nh mc l gi tr cc i ca dodngfin

ngn mch m cu ch c th ct.

Sau y l cc v tr trn biu ca cc dng in khc nhau:

CU HI CHNG 3 PHN B

1. Nu cng dng ca cu ch?2. Cho bit cu to ca cu ch gm cc thnh phn no?3. Cu ch c my loi. Chc nng ca tng loi cu ch?

Cc c tnh cadng in

Cc c tnh ca

cu ch

Dng ins dng

Dng inngn mch

Dng innh mc

Dng inct cc tiu

Dng inct gii hn

Kh nngct nh mc


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C - THIT B CHNG DNG IN R

I. KHI NIMC th ngi rt nhy cm vi dng in, v d: dng in nh hn 10mA

th ngi c cm gic kim chm; ln hn 10mA th cc cbp co qup; dng inn 30mA a n tnh trng co tht, ngt thv cht ngi. Khi thit bin b

h hng r in, chm mt m ngi s dng tip xc vo s nhn dng in i

qua ngi xung t in p ngun. Trong trng hp ny, CB v cu ch khng

th tc ng ngt ngun in vi thit b, gy nguy him cho ngi s dng.

Nu trong mch in c s dng thit b chng dng in r th ngi s

dng s trnh c tai nn do thit b ny ngt ngun in ngay khi dng in r

xut hin.


1. Cu to

Thit b chng dng in r hot ng trn nguyn l bo v so lch, c

thc hin trn cscn bng gia tng dng in vo v tng dng in i ra tit

b tiu thin.

Khi thit b tiu thin b r in, mt phn ca dng in c r nhnhxung t, l dng in r. Khi c dng in v theo ng dy trung tnh rt

nh v rle so lch s d tm s mt cn bng ny v iu khin ct mch in nh

thit b bo v so lch.

Thit b bo v so lch gm hai phn t chnh:

- Mch in tdng hnh xuyn m trn c qun cc cun dy caphn cng sut (dy c tit din ln), chu dng cung cp cho thit b tiu thin.

- Rle mmch cung cp c iu khin bi cun dy o lng (dy ctit din b) cng c t trn hnh xuyn ny, n tc ng ngt cc cc.

a)i vi h thng in mt pha


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Ch thch:

- I1: Ddng in i vo thitb tiu thin.

- I2: Dng in i t thit btiu thin ra.

- Isc: Dng in s c.- In: Dng in i qua cth

ngi.

- 1: Thit bo lng s cnbng.

- 2: Ccu nh.- 3: Li t hnh vnh xuyn.Trng hp thit bin khng

c s c: 21 II =

Trng hp s c: sc21 III =

21 II do xut hin mt

s cn bng trong hh xuyn t,

dn n cm ng mt dng in

trong cun dy d tm, a n

tc ng rle v kt qu lm m

mch in.

b)i vi h thng in ba pha

Ch thch:

- I1: Dng in i quapha 1.

- I2: Dng in i quapha 2.

-

I3: Dng in i qua pha 3.- I0: Dng in i qua dy trung tnh.


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in ra khi h thng cung cp in. Nh vy m bo tnh chn lc, vic cung cp

in khng nh hng n phn cn li.

- Nu RCD lp t khng ng yu cu k thut th RCD s khng tcng ct mch khi xut hin dng in r phn ng dy hay ph ti tng ngvi chng, hoc tc ng khng ng yu cu ra.

a) Kh nng chn lc tng hp

Kh nng chn lc tng hp l nhm loi tr duy nht thit b c s c.

t c kh nng ny phi tho mn hai iu kin:

- Dng in so lch dnh mc ca RCD pha trn phi c gi tr lnhn dng in so lch dnh mc ca RCD pha di.

- Thi gian ti thiu khng lm vic ca RCD pha trn phi c gi trln hn thi gian ti thiu khng lm vic ca RCD pha di.

b) Kh nng chn lc tng phn

Tnh chn lc c gi l tng phn v n khng tip snhn i vi mt s

gi tr dng in s c. Tnh chn lc c tho mm khi cc h qu ca mt s s

c c th ko theo ngt in tng phn hay ngt in ton b h thng cung cp

in.

V d v chn lc tng phn:

H thng cung cp in cng nghip vi kh nng chn lc tng 3 mc

chm (tr) mc 1: chm 200ms; mc 2: chm 50ms; mc 3 khng c thi gian tr.

CU HI CHNG 3 PHN C

1. Trnh by cu to v nguyn l hot ng ca thit b chng r.2. Trnh by s tc ng ca thit b chng dng in r.


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Chng 4: KH CIN IU KHIN BNG TAY

I. CU DAO

1. Khi qut v cng dng

Cu dao l mt kh cin dng ng ct mch in bng tay, c s

dng trong cc mch in c ngun di 500V, dng in nh mc c th ln ti

vi KA.

Khi thao tc ng ngt mch in, cn m bo an ton cho thit b dng

in. Bn cnh, cn c bin php dp tt h quang in, tc di chuyn li dao

cng nhanh th h quang ko di nhanh, thi gian dp tt h quang cng ngn. V

vy khi ng ngt mch in, cu dao cn phi thc hin mt cch dt khot.

Thng thng, cu dao c b tri cng vi cu ch bo v ngn mch

cho mch in.

2. Cu to, nguyn l hot ng v phn loi

a) Cu to

Phn chnh ca cu dao l li dao vh thng kp li, c lm bng hp

kim ca ng, ngoi ra b phn ni dy cng lm bng hp kim ng.

b) Nguyn l hotng ca cu dao ct nhanh

Khi thao tc trn cu dao, nhvo li dao v h thng kp li, mch in

c ng ngt. Trong qu trnh ngt mch, cu dao thng xy ra h quang in

ti u li dao v im tip xc trn h thng kp li. Ngi s dng cn phi

ko li dao ra khi kp nhanh dp tt h quang.

Do tc ko bng tay khng th nhanh c nn ngi ta lm thm li

dao ph. Lc dn in th li dao ph cng li dao chnh c kp trong ngm.Khi ngt in, tay ko li dao chnh l trc cn li dao c ko cng ra v ti


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mt mc no s bt nhanh ko li dao ph ra khi ngm mt cch nhanh

chng. Do , h quang c ko di nhanh v h quang b dp tt trong thi gian

ngn.

c) Phn loiPhn loi cu dao da vo cc yu t sau:

- Theo kt cu: cu dao c chia lm loi mt cc, hai cc, ba cc hocbn cc.

- Cu dao c tay nm gia hoc tay bn. Ngoi ra cn c cu dao mtng, hai ngc dng o ngun cung cp cho mch v o chiu quay ng

c.

- Theo in p nh mc: 250V, 500V.- Theo dng in nh mc: dng in nh mc ca cu dao c cho

trc bi nh sn xut (thng l cc loi 10A, 15A, 20A, 25A, 30A, 60A, 75A,

100A, 150A, 200A, 350A, 600A, 1000A...).

- Theo vt liu cch in: c loi s, nha, .- Theo iu kin bo v: loi c np v khng c np (loi khng c np

c t trong hp hay tiu khin).

- Theo yu cu s dng: loi cu dao c cu ch bo v ngn mch hockhng c cu ch bo v.

K hiu cu dao khng c cu ch bo v:

Mt cc Hai cc Ba cc Bn cc


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K hiu cu dao c cu ch bo v:

d) Cc thng snh mc ca cu dao

Chn cu dao theo dng in nh mc v in p nh mc:

Gi Itt l dng in tnh ton ca mch in.

Ungun l in p ngun ca li in s dng.

Imcu dao = Itt

Um cu dao = Ungun

II. CNG TC

1. Khi qut v cng dng

Cng tc l kh cin dng ng ngt mch in c cng sut nmh v

c dng in nh mc nh hn 6A. Cng tc thng c hp bo v trnh sphng in khi ng m. in p ca cng tc nh hn hay bng 500V.

Cng tc hp lm vic chc chn hn cu dao, dp tt h quang nhanh hn v

thao tc ngt nhanh v dt khot hn cu dao.

Mt s cng tc thng gp:

Cng tc hnh trnh Cng tc ba pha Cng tc ba pha hai ng

2. Phn loi v cu to

a) Cu to

Cu to ca cng tc: phn chnh l tip im ng mc gn trn

nha v c l xo thao tc chnh xc.b) Phn loi

Mt cc Hai cc Ba cc Bn cc


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Phn loi theo cng dng lm vic, c cc loi cng tc sau:

- Cng tc ng ngt trc tip.- Cng tc chuyn mch (cng tc xoay, cng tc o, cng tc vn nng),

dng ng ngt chuyn i mch in, i ni sao tam gic cho ng c.- Cng tc hnh trnh v cui hnh trnh, loi cng tc ny c p dng

trong cc my ct gt kim loi iu khin tng ho hnh trnh lm vic ca

mch in.

3. Cc thng snh mc ca cng tc

Um: in p nh mc ca cng tc.

Im: Dng in nh mc ca cng tc.

Ngoi ra cn c cc thong s trong vic th cng t nh bn ckh,

cch in, phng in

4. Cc yu cu thca cng tc

Vic kim tra cht lng cng tc phi th cc bc sau:

- Th xuyn thng: t in p 1500V trong thi gian mt pht ccim cn cch in gia chng.

- Th cch in: o in trcch in < 2M.- Th pht nng.- Th cng sut ct.- Th bn ckh.- Th nhit i vi cc chi tit cch in: cc chi tit cch in phi

chu ng 1000C trong thi gian hai gim khng b bin dng hoc si nhm.

III. NT NHN1. Khi qut v cng dng

Nt nhn cn gi l nt iu khin l mt loi kh cin dung ng ngt

t xa cc thit bin t khc nhau: cc dng c bo hiu v cng chuyn i

mch in iu khin, tn hiu lin ng bo v mch in mt chiu in p

n 440V v mch in xoay chiu in p 500V, tn s 50Hz, 60Hz, nt nhn

thng dng khi ng, o chiu quay ng cin bng cch ng v ngt cc

cun dy ca Contactor ni cho ng c.


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Nt nhn thng c t trn bng iu khin, tin, trn hp nt nhn.

Nt nhn thng c nghin cu, ch to lm vic trong mi trng khng m

t, khng c hi ho cht v bi bn.

Nt nhn c th bn ti 1.000.000 ln ng khng ti v 200.000 ln ngngt c ti. Khi thao tc nhn nt cn phi dt khot mhoc ng mch in.

2. Phn loi v cu to

a) Cu to

Nt nhn gm h thng l xo, h thng cc tip im thng h - thng

ng v v bo v.

Khi tc ng vo nt nhn, cc tip im chuyn trng thi: khi khng cn

tc ng, cc tip im trv trng thi ban u.

b) Phn loi

Nt nhn c phn loi theo cc yu t sau:

- Phn loi theo chc nng trng thi hot ng ca nt nhn, c cc loi:+ Nt nhn n:

Mi nt nhn ch c mt trng thi (ON hoc OFF)

K hiu:

Tip im thng h Tip im thng ng

+ Nt nhn kp:

Mi nt nhn c hai trng thi (ON v OFF)

K hiu:

Tip im thng h

Lin kt

Tip im thng ng

Trong thc t, d dng s dng vo tho rp lp ln trong qu trnh sa

cha, thng ngi ta dng nt nhn kp, ta c th dng n nh l dng nt nhnON hay OFF.


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- Phn loi theo hnh dng bn ngoi, ngi ta chia nt nhn ra thnh 4loi:

+ Loi h

+ Loi bo v.+ Loi bo v chng nc v chng bi.

Nt nhn kiu bo v chng nc c t trong mt hp kn kht trnh

nc lt vo.

+ Loi bo v khi n.

Nt nhn kiu chng ni dng trong cc hm l, m thanh hoc ni c cc

kh n ln trong khng kh. Cu to ca n c bit kn kht khng lt c tia la

ra ngoi v c bit vng chc khng b ph vkhi n.

- Theo yu cu iu khin ngi ta chia nt n ra 3 loi: mt nt, hai nt,ba nt.

- Theo kt cu bn trong:+ Nt n loi c n bo.

+ Nt n loi khng c n bo.

3. Cc thng s k thut ca nt nhn

Um: in p nh mc ca nt nhn.

Im: dng in nh mc ca nt nhn.

Tr sin p nh mc ca nt nhn thng c gi tr 500V.

Tr s dng in nh mc ca nt nhn thng c gi tr 5A.

IV. PHCH CM V CM IN cm v phch cm c dng cp in, ni chuyn tip trong sinh hot

hng ngy.Thng thng, cm v phch cm c ch to in p 250V, dng in

nh mc 10A, nn dy ni in l:

- i vi phch cm: ti thiu 0,75mm2, ti a 1mmm2.- i vi cm: ti thiu 1mm2, ti a 2,5mm2.


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V. IN TR- BIN TR

1. Khi qut cng dng

in trdng thay i cc gi tr trong mch in cc gi tr ph

hp vi iu kin vn hnh hay ch lm vic ca cc ng cin.Bin trl in trnhng c th thay i c gi tr ca n nhcc cn gt

hoc nm vn. C cc loi in trthng dng: in trmmy v in triu

chnh, in trhm, in trphng in...

- in trmmy l in trc s dng khi mmy ng cnhmhn ch dng in khi ng cho cc ng c c cng sut trung bnh v ln

(phng php mmy gin tip) nhm trnh st p trn li in v bo vng

cpht nng qu nhit cho php khi c dng khi ng ln (P = 10KV).- in triu chnh: iu chnh dng in trong mch kch thch hay

mch phn ng ca ng cin mt chiu nhm thay i tc quay ca n.

- in trhm nhm gim dng in khi hm ng c.- in trphng in gim in p khi c s bin thin t ngt nhm

gim s phng in xy ra trong qu trnh bin thin ny.

2. Cu toBin trc cu to bng cc dy Kim loi Al, Zn, hp kim ng, thng

c qun trn cc li t (hnh tr trn hnh xuyn).

Bin trcng c th l thanh kim loi c a ra cc u dy theo cc gi

trnh trc. Bin trn c th ghp thnh bin tri.

Cc gi tr ln nht v nh nht c ghi r trn bin tr.

CU HI CHNG 4

1. Cu dao: nu cng dng, cch phn loi, k hiu, nguyn tc hotng, cch la chn.

2. Cng tc: cng dng, phn loi, cch la chn.3. Nt nhn: nu cng dng, phn loi, k hiu, cch la chn.4. in tr, bin tr: cng dng, phn loi, cu to in tr, bin tr.


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CHNG 5: KH CIN IU KHIN MCH IN

A CONTACTOR

I. KHI NIMContactor l mt kh cin dng ng ngt cc tip im, to lin lc

trong mch in bng nt nhn. Nh vy khi s dng Contactor ta c thiu

khin mch in t xa c ph ti vi in p n 500V v dng l 600A (v triu

khin, trng thi hot ng ca Contactor rt xa v tr cc tip im ng ngt

mch in).

Phn loi Contactor tu theo cc c im sau:

- Theo nguyn l truyn ng: ta c Contactor kiu in t (truyn inbng lc ht in t), kiu hi p, kiu thu lc. Thng thng s dng Contactor

kiu in t.

- Theo dng dng in: Contactor mt chiu v Contactor xoay chiu(Contactor 1 pha v 3 pha).

II. CU TO V NGUYN L HOT NG.

1. Cu toContactor c cu to gm cc thnh phn: C cu in t (nam chm

in), h thng dp h quang, h thng tip im (tip im chnh v ph).

a)Nam chm in:Nam chm in gm c 4 thnh phn:

- Cun dy dng to ra lc ht nam chm.- Li st (hay mch t) ca nam chm gm hai phn: Phn c nh v

phn np di ng. Li thp nam chm c th c dng EE, EI hay dng CI.- L xo phn lc c tc dng y phn np di ng trv v tr ban y

khi ngng cung cp in vo cun dy.


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Trng thi nam chm cha ht Trng thi nam chm to lc ht

b)H thng dp h quang in:Khi Contactor chuyn mch, h quang in s xut hin lm cc tip im b

chy, mn dn. V vy cn c h thng dp h quang gm nhiu vch ngn lm

bng kim loi t cnh bn hai tip im tip xc nhau, nht l cc tip im

chnh ca Contactor.

c)H thng tip im ca ContactorH thng tip im lin h vi phn li t di ng qua b phn lin ng v

c. Tu theo kh nng ti dn qua cc tip im, ta c th chia cc tip im cuContactor thnh hai loi:

- Tip im chnh: C kh nng cho dng in ln i qua (t 10A n vinghn A, th d khong 1600A hay 2250A). Tip im chnh l tip i thng h

ng li khi cp ngun vo mch t ca Contactor lm mch t Contactor ht li.

- Tip im ph: C kh nng cho dng in i qua cc tip im nh hn5A. Tip im ph c hai trng thi: Thng ng v thng h.

Tip im thng ng l loi tip im trng thi ng (c lin lc vinhau gia hai tip im) khi cun dy nam chm trong Contactor trng thi ngh

(khng c cung cp in). Tip im ny hra khi Contactor trng thi hot

ng. Ngc li l tip im thng h.

Nh vy, h thng tip im chnh thng c lp trong mch in ng

lc, cn cc tip im ph s lp trong h thng mch iu khin (dng iu khin

vic cung cp in n cc cun dy nam chm ca cc Contactor theo quy trnh

nh trc).


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Theo mt s kt cu thng thng ca Contactor, cc tip e ph c th

c lin kt cnh v s lng trong mi b Contactor, tuy nhin cng c mt

vi nh sn xut ch b tr cnh s tip im chnh trn mi Contactor, cn cc

tip im phc ch to thnh nhng khi ri n l. Khi cn s dng ta chghp thm vo trn Contactor, s lng tip im ph trong trng hp ny c th

b tr tu .

2. Nguyn l hot ng ca Contactor

Khi cp ngun in bng gi trin p nh mc ca Contactor vo hai u

ca cun dy qun trn phn li t cnh th lc t to ra ht phn li t di ng

hnh thnh mch t kn (lc t ln hn phn lc ca l xo), Contactor trng thihot ng. Lc ny nh vo b phn lin ng v cgia li t di ng v h


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thng tip im lm cho tip im chnh ng li, tip im ph chuyn i trng

thi (thng ng s mra, thng hsng li) v duy tr trng thi ny. Khi

ngng cp ngun cho cun dy th Contactor trng thi ngh, cc tip im trv

trng thi ban u.Cc k hiu dng biu din cho cun dy (nam chm in) trong

Contactor v cc loi tip im.

C nhiu tiu chun ca cc quc gia khc nhau, dng biu din cho cun

dy v tip dim ca Contactor

Cun dy Tip im thng ng Tip im thng h

III. CC THNG S CBN CA CONTACTOR

1. in p nh mc

in p nh mc ca Contactor Um l in p ca mch in tng ng m

tip im chnh phi ng ngt, chnh l in p t vo hai u cun dy ca nam

chm in sao cho mch t ht li.Cun dy ht c th lm vic bnh thng in p trong gii hn (85

105)% in p nh mc ca cun dy. Thng s ny c ghi trn nhn t hai

u cun dy Contactor, c cc cp in p nh mc: 110V, 220V, 440V mt

chiu v 127V, 220V, 380V, 500V xoay chiu.

2. Dng in nh mc

Dng in nh mc ca Contactor Im l dng in nh mci qua tipim chnh trong ch lm vic lu di.

Dng in nh mc ca Contactor h p thng dng c cc cp l: 10A,

20A, 25A, 40A, 60A, 75A, 100A, 150A, 250A, 300A, 600A. Nu t trong tin

th dng in nh mc phi ly thp hn 10% v lm km mt, dng in cho

php qua Contactor cn phi ly thp hn na trong ch lm vic di hn.


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B RLE IU KHIN V BO V

I. KHI QUT V PHN LOIRle v kh cin dng tng ng ct mch iu khin, bo v v

iu khin s lm vic ca mch in.C nhiu cch phn loi rle:

* Phn loi theo nguyn l lm vic c:

- Rle in t.- Rle in ng.- Rle tin.- Rle cm ng.- Rle nhit.- Rle bn dn v vi mch.* Phn loi theo vai tr v i lng tc ng ca rle c:

- Rle trung gian.- Rle thi gian.- Rle nhit.- Rle tc .- Rle tc .- Rle dng in.- Rle in p.- Rle cng sut.- Rle tng tr.- Rle tn s...* Phn loi theo dng in c:

- Rle dng in mt chiu.- Rle dng in xoay chiu.* Phn loi theo gi tr v chiu ca i lng i vo Rle.

- Rle cc i.- Rle cc tiu.- Rle sai lch.- Rle hng...


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II. MT S LOI RLE THNG DNG

1. Rle trung gian

a) Khi nim v cu to

Rle trung gian l mt kh cin dng trong lnh vc iu khin tng,ccu kiu in t. Rle trung gian ng vai tr iu khin trung gian gi cc thit

biu khin (Contactor, Rle thi gian...).

Rle trung gian gm: Mch t ca nam chm in, h thng tip im chu

dng in nh (5A), v bo v v cc chn ra tip im.

b) Nguyn l hotng

Nguyn l hot ng ca Rle trung gian tng t nh nguyn l hot ng

ca Contactor. Khi cp in p bng gi trin p nh mc vo hai u cun dyca Rle trung gian (ghi trn nhn), lc in t ht mch t kn li, h thng tip

im chuyn i trng thi v duy tr trng thi ny (tip im thng ng hra,

tip im thng hng li). Khi ngng cp ngun, mch t h, h thng tip

im trv trng thi ban u.

im khc bit gia Contactor v Rle c th tm lc nh sau:

- Trong Rle ch c duy nht mt loi tip im c kh nng ti dng innh, s dng cho mch iu khin (tip im ph).

- Trong Rle cng c cc loi tip im thng ng v tip im thngh, tuy nhin cc tip im khng c bung dp h quang (khc vi h thng tip

im chnh trong Contactor hay CB).

Cc k hiu dng cho Rle trung gian:

Trong qu trnh lp rp cc mch iu khin dng Rle hay trong mt s

mch in t cng nghip, ta thng gp cc k hiu sau y:

- K hiu SPDT:K hiu ny c vit tt t thut ng SING POLE DOUBLE THROW,

Rle mang k hiu ny c mt cp tip im, gm tip im thng ng v

thng h, cp tip i ny c mt u chung.

SPDT SPST DPST


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- K hiu SPST:K hiu ny c vit tt t thut ng SING POLE SINGE THROW, Rle

mang k hiu ny gm c mt tip im thng h.- K hiu DPST c vit tt t thut ng DOUBLE POLE SINGE

THROW, Rle mang k hiu ny gm c hai tip im thng h.

Ngoi ra, cc Rle khi c lp ghp trong tiu khin thng c lp

trn cc chn ra. Tu theo s lng chn ra c cc ku khc nhau: 8 chn,

11 chn, 14 chn...

2. Rle thi gian

a) Khi nim

Rle thi gian l mt kh cin dng trong lnh vc iu khin tng, vi

vai tr iu khin trung gian gia cc thit biu khin theo thi gian nh trc.

Rle thi gian gm: Mch t ca nam chm in, bnh thi gian lm bng

linh kin in t, h thng tip im chu dng in nh ( 5A), v bo v cc

chn ra tip im.

Tu theo yu cu s dng khi lp rp h thng mch iu khin truyn ng,

ta c hai loi Rle thi gian: Rle thi gian ON DELAY, Rle thi gian OFF

DELAY.

b) Rle thi gian ON DELAY.

K hiu:

- Cun dy Rle thi gian: hocin p t vo hai u cun dy Rle thi gian c ghi trn nhn, thng

thng 110V, 220V...

- H thng tip im:Tip im tc ng khng tnh thi gain: Tip im ny hot ng tng t

cc tip im ca Rle trung gian.

Thng ng: hoc

Thng m: hoc

Tip im tc ng c tnh thi gian:Tip im thng m, ng chm, mnhanh: hoc

TR TR

TR TR

TR TR

TR

TR

TR

TR


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Tip im thng ng, mchm, ng nhanh: hoc

* Nguyn l hot ng:

Khi cp ngun vo cun dy ca Rle thi gian ON DELAY, cc tip i tcng khng tnh thi gian chuyn i trng thi tc thi (thng g hra, thng

hng li), cc tip i tc ng c tnh thi gian khng i. Sau khong thi

gain nh trc, cc tip im tc ng c tnh thi gian s chuyn trng thi v

duy tr trng thi ny.

Khi ngng cp ngun vo cun dy, tt c cc tip im tc thi trv trng

thi ban u.

Sau y l s chn ca Rle thi gian ON DELAY:

b) Rle thi gian OFF DELAY

K hiu:

- Cun dy Rle thi gian: hocin p t vo hai u cun dy Rle thi gian c ghi trn nhn, thng

thng 110V, 220V...

- H thng tip im:Tip im tc ng khng tnh thi gain: Tip im ny hot ng tng t

cc tip im ca Rle trung gian.

Thng ng: hoc

Thng m: hoc

Tip im tc ng c tnh thi gian:

Tip im thng m, ng chm, mnhanh: hoc

Ngun

TR TR

TR TR

TR TR

TR

TR

TR

TR


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Tip im thng ng, mchm, ng nhanh: hoc

* Nguyn l hot ng:

Khi cp ngun vo cun dy ca Rle thi gian OFF DELAY, cc tip imtc ng tc thi v duy tr trng thi ny.

Khi ngng cp ngun vo cun dy, tt c cc tip im tc ng khng tnh

thi gian trv trng thi ban u. Tip sau mt khong thi gian nh trc,

cc tip im tc ng c tnh thi gian s chuyn v trng thi ban u.

3. Rle nhit (Over Load OL)

a) Khi nim v cu to:

Rle nhit l mt loi kh c bo vng cv mch in khi c s c

qu ti. Rle nhit khng tc ng tc thi theo tr s dng in v n c qun tnh

nhit ln, phi c thi gian pht nng, do n lm vic c thi gain t vi giy


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n vi pht.


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Phn t pht nng 1 c u ni tip vi mch ng lc bi vt 2 v m

phin lng kim 3. Vt 6 trn gi nha cch in 5 dng iu chnh mc un

cong u t do ca phin 3. Gi 5 xoay quanh trc 4, tu theo tr s dng in chy

qua phn t pht nng m phin lng kim cong nhiu hay t, y vo vt 6 lmxoay gi 5 m ngm n by 9. Nh tc dng l xo 8, y n by 9 xoay

quanh trc 7 ngc chiu kim ng h lm m tip im ng 11 khi tip im

tnh 12. Nt nhn 10 Reset Rle nhit v v tr ban u sau khi phin lng kim

ngui trv v tr ban u.

b) Nguyn l hotng:

Nguyn l chung ca Rle nhit l da trn cstc dng nhit lm dn n

phin kim loi kp. Phin kim loi kp gm hai l kim loi c h s gin nkhc

nhau (h s gin nhn km nhau 20 ln) ghp cht vi nhau thnh mt phin

bng phng php cn nng hoc hn. Khi c dng in qu ti i qua, phin

lng kim c t nng, un cong v pha kim loi c h s gin nb, y cn

gt lm l xo co li v chuyn i h thng tip im ph.

Rle nhit lm vic tr li, phi i phin kim loi ngui v ko cn

Reset ca Rle nhit.

c) Phn loi Rle nhit:

Theo kt cu Rle nhit chia thnh hai loi: Kiu hv kiu kn.

Theo yu cu s dng: Loi mt cc v hai cc.

Theo phng thc t nng:

- t nng trc tip: Dng in i qua trc tip tm kim loi kp. Loiny c cu to n gin, nhng khi thay i dng in nh mc phi thay i tm

kim loi kp, loi ny khng tin dng.


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- t nng gin tip: Dng in i qua phn tt nng c lp, nhitlng to ra gin tip lm tm kim loi cong ln. Loi ny c u im l mun

thay i dng in nh mc ta ch cn thay i phn tt nng. Nhc dim ca

loi ny l khi c qu ti ln, phn tt nng c tht n nhit kh caonhng v khng kh truyn nhit km, nn tm kim loi cha kp tc c m phn

tt nng b chy t.

- t nng hn hp: Loi ny tng i tt v va t trc tip va tgin tip. N c tnh n nh nhit tng i cao v c th lm vic bi s qu ti

ln.

d) Chn la Rle nhit

c tnh cbn ca Rle nhit l quan h gia dng in ph ti chy qua

v thi gian tc ng ca n (gi l c tnh thi gian dng in, A - s). Mt

khc, m bo yu cu gic tui th lu di ca thit b theo ng s liu k

thut cho ca nh sn xut, cc i tng bo v cng cn c tnh thi gian

dng in.

La chn ng Rle l sao cho ng c tnh A s ca Rle gn st ng

c tnh A s ca i tng cn bo v. Nu chn thp qu s khng tn dng

c cng sut ca ng cin, chn cao qu s lm gim tui th ca thit b

cn bo v.

Trong thc t, cch la chn ph hp l chn dng in nh mc ca Rle

nhit bng dng in nh mc ca ng cin cn bo v, Rle s tc ng

gi tr (1,2 1,3)Im. Bn cnh, ch lm vic ca ph ti v nhit mi trng

xung quanh phi c xem xt.


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- Lm vic theo nguyn tc phn ng in tc dng trong cc mchhm ca ng c.

- Rle c mc ng trc vi ng c v mch iu khin. Khi cquay, nam chm vnh cu quay theo. T trng ca n qut ln cc thanh dn s

sinh ra sut in ng v dng in cm ng. Dng in ny nm trong t trng

s sinh ra sut in ng v dng in cm ng. Dng in ny nm trong t

trng s sinh ra lc in t lm cho phn ng quay, di chuyn cn tip im n

ng tip im ca n. Khi tc ng cgim nh gn bng khng, lc in t

yu i, trng lng cn tip im a n v v tr c v mtip im ca n.

- Rle vn tc thng dng trong cc mch iu khin hm ngc ngc.

CU HI CHNG 5 PHN B

1. Nu khi nim, cu to v nguyn l hot ng ca Rle trung gian.2. Nu khi nim, cu to v nguyn l hot ng ca Rle thi gian

(ON DELAY v OFF DELAY).

3. Nu khi nim, cu to v nguyn l hot ng ca Rle nhit.C KHI NG T

I. KHI QUT V CNG DNGKhi ng t l mt loi kh cin dng iu khin t xa vic ng -

ngt, o chiu v bo v qu ti (nu c lp thm rle nhit) cc ng ckhng

ng b ba pha rto lng sc.

Khi ng t c mt Contactor gi l khi ng tn thng ng -ngt ng cin. Khi ng t c hai Contactor l khi ng t kp dng thay

i chiu quay ca ng cgi l khi ng to chiu. Mun bo v ngn mch

phi lp thm cu ch.

II. CC YU CU K THUTng cin khng ng b ba pha c th lm vic lin tc c hay khn

gtu thuc vo mc tin cy ca khi ng t. Do khng t cn phi thomn cc yu cu k thut sau:


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- Tip im c bn chu mi mn cao.- Kh nng ng - ct cao.- Thao tc ng - ct dt khot.-

Tiu th cng sut t nht.- Bo vng ckhng b qu ti lu di (c Rle nhit).- Tho mn iu khi ng (dng in khi ng t 5 n 7 ln dng in

nh mc).

III. KT CU V NGUYN L LM VIC

1. Khi ng tthng c phn chia theo:

- in p nh mc ca cun hy ht: 36V, 127V, 220V, 380V, 500V.- Kt cu bo v chng cc tc ng bi mi trng xung quanh: h, bo

v, chng bi, nc n

- Kh nng lm bin i chiu quay ng cin: Khng o chiu quayv o chiu quay.

- S lng v loi tip im: Thng h, thng ng.2. Nguyn l lm vic ca khi ng t

a) Khi ng tv hai nt nhn:

Khi cung cp in p cho cun dy bng nhn nt khi ng M, cun hy

Contactor c in ht li thp di ng v mch t khp kn li: Lm ng cc tip

i chnh khi ng ng cv ng tip im ph thng h duy tr mch

iu khin khi bung tay khi nt nhn khi ng. Khi nhn nt dng D, khi

ng t b ngt in, di tc dng ca l xo nn lm phn li di ng trv v tr

ban u; cc tip im trv trng thi thng h. ng cdng hot ng. Khi

c s c qu ti ng c, Rle nhit s thao tc lm ngt mch in cun dy, do

cng ngt khi ng t v dng ng cin.

S:


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b) Khi ng to chiu v ba nt nhn

Khi nhn nt nhn MT cun dy Contactor T c in ht li thp di ng v

mch t khp kin li; lm ng cc tip im chnh T khi ng ng cquay

theo chiu thun v ng tip im ph thng hT duy tr mch iu khin

khi bung tay khi nt nhn khi ng MT.

o chiu quay ng c, ta nhn nt nhn MN cun dy Contactor T mtin, cun dy Contactor N c in ht li thp di ng v mch t khp kn li;

lm ng cc tip im chnh N, lc ny trn mch ng lc o hai dy trong ba

pha in lm cho ng co chiu quay ngc li v tip im ph thng hN

duy tr mch iu khin khi bung tay khi nt nhn khi ng MN.

Qu trnh o chiu quay c lp li nh trn.

Khi nhn nt dng D, khi ng t N (hoc T) b ngt in, ng cdng

hot ng.

Khi c s c qu ti ng c, Rle nhit s thao tc lm ngt mch in cun

dy, do cng ngt khi ngt v dng ng cin.

S:


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IV. LA CHN V LP DP KHI NG THin nay nc ta, ng ckhng ng b ba pha rto lng sc c cng

sut t 0,6 n 100KW c s dng rng ri. iu khin vn hnh chng, ta

thng dng khi ng t. V vy thun li cho vic la chn khi ng t, nh

sn xut thng khng nhng ch cho cng dng in sut nh mc m cn

cho c cng sut ca ng cin m khi ng t phc vng vi cc in p

khc nhau. khi ng t lm vic tin cy, khi lp t cn phi bt cht cng khi

ng t trn mt mt phng ng ( nghing cho php so vi trc thng ng 50),

khng cho php bi mvo cc tip im v cc b phn ng. Sauk hi lp t

khi ng t v trc khi vn hnh, phi kim tra:

- Cho cc b phn chuyn ng bng tay khng b kt, vng.- in p iu khin phi ph hp in p nh mc ca cun dy.- Cc tip im phi tip xc u v tt.- Cc dy u in phi theo ng siu khin.- Rle nhit phi t khi ng t cn t km theo cu ch bo v.


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CU HI CHNG 5 PHN C

1. Nu khi qut, cng dng v cc yu cu k thut ca khi ng t.2. Nu cch phn loi, nguyn l lm vic ca khi ng t .

Phn 3: GII THIU C TNH, KT CU KH CIN CAO P

Chng 6: KH CIN CAO P

I. KHI QUTTrong iu kin vn hnh, cc kh cin c th lm vic cc ch sau:

- Ch lm vic lu di: Trong ch ny cc kh cin s lm vic tincy nu chng c chn ng in p v dng in nh mc.

- Ch lm vic qu ti: Trong ch ny dng in qua kh cin sln hn dng in nh mc, chng ch lm vic tin cy khi thi gian dng in

tng cao chayu qua chng khng qu thi gian cho php ca tng thit b.

- Ch lm vic ngn mch: Kh c sm bo s lm vic tin cy nutrong qu trnh la chn ch cc iu kin n nh nhit v n nh ng.

II. MT S KH CIN CAO P (1000V)1. My ct

a) Khi nim

My ct in p cao l thit bin chuyn dng ng ngt mch in

xoay chiu tt c cc ch vn hnh c th c: ng ngt dng in nh mc,

dng in ngn mch, dng in khng ti My ct l loi thit bng ct lm

victin cy song ga thnh cao nn my ct chcdng nhng ni quan trng.

b) Phn loi my ct

Thng thng my ct c phn loi theo phng php dp tt h quang,

theo dng cch in ca phn dn in, theo kt cu ca bung dp h quang.

Da vo dng cch in ca cc phn dn in, my ct c phn thnh:

- My ct nhiu du: Gia cc thnh phn dn in c cch in bngdu my bin p v h quang sinh ra khi ct my ct cng c dp tt bng du

bin p.

- My ct t du: Gia cc thnh phn dn in c cch in bng cchin rn v h quang sinh ra khi ct my ct cng c dp tt bng du bin p.


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- My ct khng kh.- My ct in t.- My ct chn khng.

c) Cc thng scbn ca my ct- Dng in ct nh mc: L dng in ln nht m my ct c th ct

mt cch tin cy in p phc hi gia hai tip im ca my ct bng in p

nh mc ca mch in.

- Cng sut ct nh mc ca my ct ba pha: Sm = 3 UmIcm (VA)Trong : Um l in p nh mc ca h thng (V)

Icm l dng in ct nh mc (A)

Khi nim cng sut ny l tng i khi dng in qua my ct Icm th inp trn hai du ca n trn thc t bng in p h quang v ch bng vi % so vi

in p ca mch in. Sau khi h quang b dp tt, trn cc tip im ca my ct

bt u phc hi in p nhng trong thi gian ny dng in bng 0.

- Thi gian ct ca my ct: Thi gian ny c tnh t thi im a tnhiu ct my ct n thi im h quang c dp tt tt c cc cc. N bao gm

thi gian ct ring ca my ct v thi gian chy h quang.

- Dng in ng nh mc: y l gi tr xung kch ln nht ca dngin ngn mch m my ct c thng mt cch thnh cng m tip im ca n

khng b hnh dnh v khng b cc h hng khc trong trng hp ng lp li.

Dng in ny c xc nh bng gi tr hiu dng ca dng in xung kch khi

xy ra ngn mch.

- Thi gian ng my ct: L thi gian khi a tn hiu ng my ct choti khi hon tt ng tc ng my ct.

d) La chn v kim tra my ctin cao p (1000V)

My ct in c chn theo in p nh mc, loi my ct kim tra n

nh ng, n nh nhit v kh nng ct trong tnh trng ngn mch.

2. Dao cch ly

a) Khi nim

Dao cch ly l mt loi kh cin dng ch to mt khong h cch

in c trng thy gia b phn ang mang dng in v b phn ct in nhm

mc ch m bo an ton, khin cho nhn vin sa cha thit bin an tm khilm vic.


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Dao cch ly khng c b phn dp tt h quang nn khng th ct c

dng in ln.

b) Phn loi

Theo yu cu s dng, dao cch ly c hai loi:- Dao cch ly mt pha.- Dao cch ly ba pha.Theo v tr s dng. dao cch ly c hai loi:

- Dao cch ly t trong nh.- Dao cch ly t ngoi tri.

c) La chn v kim tra dao cch ly

Dao cch ly c chn theo iu kin nh mc, chng c kim tra theo

iu kin n nh lc in ng v n nh nhit.

3. Cu ch cao p

a) Khi nim

Cu ch l mt kh cin dng bo v mch in khi qu ti hay ngn

mch. Thi gian ct mch ca cu hc ph thuc nhiu vo vt liu lm dy chy.

Dy chy ca cu ch lm bng ch, hp kim vi thic c nhit nng chy tng

i thp, in trsut tng i ln. Do vy loi dy chy ny thng ch to c

tit din ln v thch hp vi in p nh hn 300V i vi in p cao hn

(1000V) khng th dng dy chy c tit din ln c v lc nng chy, lng

kim loi to ra ln. Kh khn cho vic dp tt h quang, do in p ny

thng dng dy chy bng ng, bc, c in trsut b, nhit nng chy cao.

b) Dy chy

Thnh phn chnh ca cu ch l dy chy. Dy chy c kch thc v vt

liu khc nhau, c xc nh bng c tuyn dng in - thi gian. Song song vidy chy l mt si dy cng ra trit tiu s ko cng ca dy chy. tng

cng kh nng dp h quang sinh ra khi dy chy bt v bo m an ton cho

ngi vn hnh cng nh cc thit b khc xung quanh trong cu ch thng

chn y cc thch anh. Cc thch anh c tc dng phn chia nh h quang. V

cu chi c th l bng cht Xenluyl. Nhit cao ca h quang s lm cho

Xenluyl bc hi gy p sut ln nhanh chng dp tt h quang.

c) Phn loi cu chTu theo chc nng ca mi loi cu ch m ta c th phn nh sau:


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- Cu ch t ri (Fuse Cut Out: FCO): Hot ng theo nguyn tc ri domt dy ch c ni lin kt hai u. Vic dp tt h quang ch yu da vo

ng ph bn ngoi dy ch. Ngoi nhim v bo v qu ti v ngn mch cu ch t

ri cn c nhim v cch ly ng dy b s c.- Cu ch chn khng: L loi cu ch m dy chy c t trong mi

trng chn khng. Cu ch chn khng c thc lp bn trn hoc di du.

- Cu ch hn dng: Chc nng chnh l hn ch tc ng ca dng ins c c th c i vi nhng thit bc n bo v.

d) La chn v kim tra cu ch

Cu ch c chn theo in p nh mc, dng in nh c v dng in

ct nh mc (hay cng sut ct nh mc). Ngoi ra, cn ch v trt cu ch

(trong nh hay ngoi tri).

CU HI CHNG 6

1. Hy cho bit khi nim, phn loi v cch la chn my ct?2. Hy cho bit khi nim, phn loi v cch la chn dao cch ly?3. Hy cho bit khi nim, phn loi v cch la chn cu ch?

Phn 4: MT S S CBN V NGUYN L IUKHIN, VN HNH

Chng 7: MT S S CN BN V NGUYN LIU KHIN, VN HNH NG C.

I. MCH IN KHI NG - DNG MT NG CKB 3 PHA

a) Nguyn l:Dng mch khi ng mt ng cKB 3 pha, c tip im duy tr

ng clm vic, sau dng ng c.

b) S mch (hnh 1)

c) Thtthc hin:

- Nhn nt S2, Contactor K1 c in, cc tip im chnh ng li, ng chot ng, cc tip im ph thay i trng thi, tip im ph thng ng hra

lm cho n H1 tt, tip i ph thng hng li duy tr ngun cho Contactor K1v n H2.


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Hnh 1: S mch in khi ng - dng mt ng cKB 3 pha

II. MCH IN KHI NG THTHAI NG CKB 3 PHA

a) Nguyn lDng mch khi ng th t hai ng cKB 3 pha. ng c1 (iu

khin bi Contactor K1) chy trc, sau ng c2 (iu khin bi Contactor

K2) chy theo. Nu c s tc ng nhm lm, mch in khng hot ng. Cui

cng dng c hai ng c.

b) S mch: (hnh 2)

c) Thtthc hin:

-

Nhn S3, ng cM1 hot ng, n H1 sng.- Nhn S4, ng cM2 hot ng, n H2 sng.- Nhn S2, dng ng cM2, n H2 tt.- Nhn S1, dng ng cM1, dng ton b mch iu khin, n H1 tt.


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Hnh 2: S mch khi ng th t hai ng cKB ba pha

III. MCH IN O CHIU NG CKB BA PHAa) Nguyn l:


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o chiu quay ng cKB ba pha bng cch o hai trong ba dy ngun

trc khi a ngun vo ng c. Mch in ny dng iu khin ng cKB

ba pha lm vic hai chiu quay, sau dng ng c.

b) S mch: (hnh 3)c) Thtthc hin:

- Nhn S2, ng chot ng theo chiu thun, n H1 sng.- Nhn S3, ng chot ng theo chiu nghch, n H1 tt, n H2 sng.- Nhn S1, dng ton b mch iu khin, ng cngng hot ng.

Hnh 3: S mch o chiu ng cKB ba pha

IV. MCH IN KHI NG MT NG CKB 3 PHA - TNGDNGa) Nguyn l:

Dng mch khi ng mt ng cKB 3 pha, c tip im duy tr

ng c lm vic, sau thi gian lm vic nh trn Timer, tip im thng

ng mchm ca Timer hra, ng cdng.

b) S mch: ( hnh 4)

c) Thtthc hin:- Nhn S2, ng chot ng, n H1 tt, n H2 sng.


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- Rle thi gian KTON c in v bt u tnh thi gian ng clm vic.Khi ht khong thi gain nh, tip im thng ng KTON h ra lm ngng

cp in cho Contactor K1, ng cngng hot ng n H1 sng, n H2 tt.

-

Nhn S1 dng ng ckhn cp.

Hinh 4: S mch in khi ng - dng mt ng cKB 3 pha


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V. MCH IN TNG KHI NG THEO THTCA HAING CKB 3 PHAa) Nguyn l

Mch in s dng TON.

Dng mch khi ng th t hai ng cKB 3 pha. ng c1 (iu

khin bi Contactor K1) khi ng trc, sau thi gian khi ng ca ng cth

tip im thng hng chm li ca Rle thi gian TON ng li ng c(iu

khin bi Contactor 2) khi ng. Cui cng dng c hai ng c, ta nhn S1.

b) S mch: (hnh 5)

c) Thtthc hin:

- Nhn S1ng cM1 hot ng n H1 sng.- Rle thi gian KTON chuyn trng thi, ng cM2 hot ng, n H2

sng.

- Nhn S1 dng c hai ng c.


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Hnh 5: S mch khi ng th t hai ng cKB ba pha

CU HI CHNG 7

1. V mch lun phin hai ng c(ch c mt trong hai ng clm vic).2. V mch lun phin ba ng c(ch c mt trong ba ng clm vic).3. V mch khi ng ng cKB ba pha bng phng php i ni sao

tam gic (ng cmmy ch sao, l vic ch tam gic).

4. V mch iu khin o chiu ng cKB ba pha kt hp i ni sao tam gic.

5. V mch iu khin o chiu ng cKB ba pha, mi chiu quay lmvic hai cp tc .


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MC LCTrang

Li ni u 3

PHN I: L THUYT CBN CA KH CIN

CHNG I: PHT NNG KH CIN

I. KHI NIM V KH CIN 61. Khi nim 6

2. Phn loi, cc yu cu cbn ca kh cin 6

II. TNH TON TN THT IN NNG TRONG KH CIN 6

III. CC CH PHT NNG CA KH CIN 71. Ch lm vic lu di ca kh cin 8

2. Ch lm vic ngn hn ca kh cin 8

3. Ch lm vic ngn hn lp li ca kh cin 8

CU HI CH NG 1

CHNG 2: TIP XC IN - H QUANG

I. TIP XC IN 91. Khi nim 9

2. Phn loi tip xc in 10

3. Cc yu tnh hng n in trti p xc

II. H QUANG IN 101. Khi nim 10

2. Tnh cht cbn ca phng in h quang 11

3. Qu trnh pht sinh v dp h quang 11CU HI CH NG 2

PHN II: TM HIU C TNH, KT CU, TNH TON LA CHN SDNG KH CIN H P

CHNG 3: KH CIN NG NGT - BO VMCH IN

A CB (CIRCUIT BREAKER)

I. KHI NIM V YU CU. 12


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II. CU TO V NGUYN L HOT NG 131. Cu to 13

2. Nguyn l hotng 14

3. Phn loi v cch la chn CB 16

CU HI CHNG 3 PH N A

B - CU CH

I. KHI NIM V YU CU 16

II. CU TO V NGUYN L HOT NG 171. Cu to 17

2. Nguyn l hotng 17

3. Phn loi, k hiu, cng dng 19

4. Cc c tnh in p ca cu ch 20

CU HI CHNG 3 PH N B

C - THIT B CHNG DNG IN R

I. KHI NIM 21

II. CU TO V NGUYN L HOT NG 21

1. Cu to 21

III. STC NG CA THIT B CHNG DNG IN R 231. Stc ng tin cy ca RCD 23

2. Stc ng c tnh chn lc ca RCD bo v h thng in sin. 23

CU HI CHNG 3 PH N C

CHNG 4: KH CIN IU KHIN BNG TAY

I. CU DAO 251. Khi qut v cng dng 25

2. Cu to, nguyn l hotng v phn loi 25

II. CNG TC 271. Khi qut v cng dng 27

2. Phn loi v cu to 27

3. Cc thng snh mc ca cng tc 28

4. Cc yu cu thca cng tc 28

III. NT NHN 28


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1. Khi qut v cng dng 28

2. Phn loi v cu to 29

3. Cc thng skthut ca nt nhn 30

IV. PHCH CM V CM IN 30

V. IN TR - BIN TR 311. Khi qut cng dng 31

2. Cu to 31

CU HI CH NG 4

CHNG 5: KH CIN IU KHIN MCH IN

A CONTACTOR

I. KHI NIM 32

II. CU TO V NGUYN L HOT NG. 321. Cu to 32

2. Nguyn l hotng ca Contactor 34

III. CC THNG S C BN CA CONTACTOR 351.in p nh mc 35

2. Dng in nh mc 35

3. Kh nng ct v kh nng ng 36

4. Tui th ca Contactor 36

5. Tn sthao tc 36

6. Tnh n nh lc in ng 36

7. Tnh n nh nhit 36

CU HI CHNG 5 PH N A

B RLE IU KHIN V BO V

I. KHI QUT V PHN LOI 37

II. MT S LOI RLE THNG DNG 381. Rle trung gian 38

2. Rle thi gian 39

3. Rle nhit (Over Load OL) 41

4. Rle dng in: 45

5. Rle in p 45


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6. Rle vn tc 45

CU HI CHNG 5 PH N B

C KHI NG T

I. KHI QUT V CNG DNG 46

II. CC YU CU K THUT 46

III. KT CU V NGUYN L LM VIC 471. Khi ng tthng c phn chia theo: 47

2. Nguyn l lm vic ca khi ng t 47

IV. LA CHN V LP DP KHI NG T 49

CU HI CHNG 5 PH N C

PHN 3: GII THIU C TNH, KT CU KH CIN CAO P

CHNG 6: KH CIN CAO P

I. KHI QUT 50

II. MT S KH CIN CAO P (1000V) 501. My ct 50

2. Dao cch ly 51

3. Cu ch cao p 52

CU HI CHNG 6 53

PHN 4: MT S S CBN V NGUYN L IU KHIN, VN HNH

CHNG 7: MT S S CN BN V NGUYN L IU KHIN, VNHNH NG C.

I. MCH IN KHI NG - DNG MT NG C KB 3 PHA 53

II. MCH IN KHI NG THTHAI NG C KB 3 PHA 54

III. MCH IN O CHIU NG C KB BA PHA 55

IV MCH IN KHI NG MT NG C KB 3 PHA - T NG DNG 56

khi cu dien_2

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