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t nc Vit Nam trong cng cuc cng nghip ho - hin i ho, nn kinh t ang trn pht trin, vic s dng cc thit b in, kh c in vo trong xy 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 b in.

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 c in gm 4 phn vi nhng ni dung c bn sau:

- Phn 1: L thuyt c bn ca kh c in. - Phn 2: Tm hiu c tnh, kt cu, la chn s dng kh c in h p.

- Phn 3: Gii thiu c tnh, kt cu kh c in cao p.

- Phn 4: Mt s s cn bn v nguyn l iu khin, vn hnh. Gio trnh Kh c in 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


PHN I: L THUYT C BN CA KH C IN Chng I: PHT NNG KH C IN

I. KHI NIM V KH C IN 1. Khi nim

Kh c in 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 c in 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 c in 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 c bn ca kh c in

a) Phn loi Kh c in c phn ra cc loi sau:

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

- Kh c in dng m my: Cng tc t, Khi ng t, B khng ch ch huy

- Dng bo v ngn mch ca li in: Cu ch, Aptmat, Cc loi my ct, Rle nhit b) Cc yu cu c bn ca kh c in m bo an ton cho cc thit b in v m bo tin cy ca Kh c in th Kh c in m bo mt s yu cu:

- Kh c in m vo lm vic lu di vi cc thng s k thut trng thi lm vic nh mc: Um, Im.

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

- Kh c in lm vic chc chn, an ton khi lm vic.

II. TNH TON TN THT IN NNG TRONG KH C IN Tn tht in nng trong kh c in c tnh theo:


=t

0

2.R.tIQ

Trong : Q: in nng tn tht. i: dng in trong mch. R: in tr ca kh c. t: Thi gian c dng in chy qua. Tu theo kh c in 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 C IN Sau y l bng nhit cho php ca mt s vt liu:

Vt liu lm kh c in Nhit cho php (0C) Vt liu khng bc cch in hoc xa nht cch in.

110

Dy ni dng tip xc c nh. 75 Vt liu c tip xc dng hnh ngn 75 Tip xc trt ca ng v hp kim ng 110

Tip xc m bc. 120

Vt khng dn in v khng bc cch in. 110

Vt liu cch in Cp cch nhit Nhit 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


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

1. Ch lm vic lu di ca kh c in

Kh c in lm vic lu di, nhit trong kh c in 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 c in

Ch lm vic ngn hn ca kh c in l ch khi ng in nhit ca n khng t ti nhit n nh, sau khi pht nng ngn hn, kh c c 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 c in

Nhit ca kh c in 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 c in lm vic lp li. Sau khong thi gian, nhit tng ln ln nht gn bng nhit gim nh nht th kh c in t c ch dng.

n nh

Bt u t(s)

n nh

Bt u t(s)

Pht nng


CU HI CHNG 1 1. Nu khi nim, phn loi v cc yu cu ca kh c in. 2. Trnh by cc ch pht nng ca kh c in.

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 c bn ca tip xc in: - Ni tip xc in phi chc chn, m bo. - Mi ni tip xc phi c bn c kh 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 tr sut 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.


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 c nh Cc tip i c ni c nh 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 nh cc 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 c in.

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 t nh hng n in tr tip 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 tr tip xc cng ln. - Din tch tip xc. Thng thng dng hp kim lm tip im.

II. H QUANG IN 1. Khi nim

Trong 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


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 c bn 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 sinh ra in trng c cng rt ln (3.107V/cm) c th lm bt in t t Catt gi l pht x t ng in t (gi l pht x ngui in t). S in 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 k n hng chc nghn A/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 m xy ra thng xuyn.

b) Qu trnh dp tt h quang in


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 tr Shunt 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 cch

dng 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 tr Shunt tiu th nng lng h quang (dng in tr

mc 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 c bn ca phng in h quang

PHN II: TM HIU C TNH, KT CU, TNH TON LA CHN S DNG KH C IN H P.

Chng 3: KH C IN NG NGT - BO V MCH IN

A CB (CIRCUIT BREAKER) I. KHI NIM V YU CU.

CB (CB c vit tt t danh t Circuit Breaker), CB l kh c in 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:


- Ch lm vic nh mc ca CB thi l ch lm vic di hn, ngha l 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 b in, hn ch s 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 c hc 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 m trc, 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 v c 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 h c 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) C cu truyn ng ct CB

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


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 nguyn l n by. Ngoi ra cn c cch iu khin bng ng c in hoc bng kh nn. d) Mc bo v

CB t ng ct nh cc 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 b in 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 m ra. iu chnh vt thay i lc khng l xo, ta c th iu chnh c tr s dng in tc ng. gi thi gian trong bo v qu t kiu in t, ngi ta thm mt c cu 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 n lm 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 v c 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 v in 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)


Hnh 1.1 S CB dng in cc i trng thi bnh thng sau khi ng in, CB c gi trng thi ng

tip im nh mc 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 t nam 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 m ra, 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.


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 m ra, 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 CU

Cu ch l mt loi kh c in 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 c in, thit b in, mch in iu khin, mch in thp sng.


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 in

m my 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.


Cu ch bao gm cc thnh phn sau: + Phn t ngt mch: y chnh l thnh phn chnh ca cu ch, phn t

ny phi c kh nng cm nhn c gi tr hiu dng c dng in qua n. Phn t ny c gi tr in tr sut b (thng bng bc, ng hay cc vt liu dn c gi tr in tr sut nh ln cn vi cc gi tr nu trn...). Hnh dng ca phn t c th dng l mt dy (tit din trn), dng bng mng.

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

- C bn c kh. - C bn v iu 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 th c 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 c nh cu ch trn cc thit b ng ngt mch; ng thi phi m bo tnh tip xc in tt.

2. Nguyn l hot ng c tnh c bn 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.


+ i vi dng in nh mc ca cu ch: Nng lng sinh ra do hiu ng Joule khi c dng in nh mc chy qua s to ra mi trng v khng gy nn s nng chy, s cn bng nhit s c 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 in tin h quang

l

t

Dng in phng on

Dng in trong Qu trnh h quang

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

Gin thi gian ca qu trnh pht sinh h quang


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 c bn, ty thuc vo nhim v: + Cu ch loi g: Cu ch dng ny ch c kh nng ngt mch, khi c s

c 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 trng

thi 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


4. Cc c tnh in p ca cu ch

- in p nh mc l gi tr in p hiu dng xoay chiu xut hin hai u 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 ch c kh nng ngt mch. Kh nng ct nh mc l gi tr cc i ca dodngf in 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 ca dng in

Cc c tnh ca cu ch

Dng in s dng

Dng in ngn mch

Dng in nh mc

Dng in ct cc tiu

Dng in ct gii hn

Kh nng ct nh mc


C - THIT B CHNG DNG IN R I. KHI NIM

C 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 c bp co qup; dng in n 30mA a n tnh trng co tht, ngt th v cht ngi. Khi thit b in 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.


Thit b chng dng in r hot ng trn nguyn l bo v so lch, c thc hin trn c s cn bng gia tng dng in vo v tng dng in i ra tit b tiu th in.

Khi thit b tiu th in b r in, mt phn ca dng in c r nhnh xung 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 t dng hnh xuyn m trn c qun cc cun dy ca

phn cng sut (dy c tit din ln), chu dng cung cp cho thit b tiu th in. - Rle m mch cung cp c iu khin bi cun dy o lng (dy c

tit din b) cng c t trn hnh xuyn ny, n tc ng ngt cc cc. a) i vi h thng in mt pha


Ch thch: - I1: Ddng in i vo thit

b tiu th in. - I2: Dng in i t thit b

tiu th in ra. - Isc: Dng in s c. - In: Dng in i qua c th

ngi. - 1: Thit b o lng s cn

bng. - 2: C cu nh. - 3: Li t hnh vnh xuyn.

Trng hp thit b in khng c s c:

21II

=

Trng hp s c: sc21III

=

21II

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 qua

pha 1. - I2: Dng in i qua

pha 2. - I3: Dng in i qua pha 3. - I0: Dng in i qua dy trung tnh.


- 1: C cu nh. - 2: Li t hnh vnh xuyn.

Trng hp thit b in khng c s c: 0IIII0321

====

. T thng tng

trong mch t hnh xuyn bng 0, do s khng c dng in cm ng trong cun dy d tm.

Trng hp thit b c s c: 0IIII0321

=

. T thng tng trong mch t

hnh xuyn khng bng 0, do s c dng in cm ng trong cun dy d tm, vy cun dy d tm s tc ng m cc cc in. c) Phn loi RCD theo cc ca h thng in.

RCD tc ng tc thi v RCD tc ng c thi gian tr.

III. S TC NG CA THIT B CHNG DNG IN R 1. S tc ng tin cy ca RCD

- RCD tc ng nhy v tin cy. - Dng in tc ng r thc t lun thp hn dng tc ng r danh nh

(ghi trn nhn hiu ca RCD) khong 20 40% khi dng in r xut hin tng dn hay t ngt.

- Thi gian tc ng thc t u nh hn thi gian tc ng c nh sn xut quy nh (ghi trn nhn hiu) khong 20 80%. Thng thng thi gian tc ng ct mch c ghi trn nhn hiu ca RCD l 0,1s v thi gian tc ng ct mch thc t nm trong khong 0,02 0,08s.

2. S tc ng c tnh chn lc ca RCD bo v h thng in s in.

- Khi xut hin dng in r ln on ng dy in hoc ph ti, RCD c lp t gn nht s tc ng ct mch, tch on dy hoc ph ti b r

RCD 4 RCD 3 RCD 2


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 tc ng ct mch khi xut hin dng in r phn ng dy hay ph ti tng ng vi 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 d nh mc ca RCD pha trn phi c gi tr ln hn dng in so lch d nh mc ca RCD pha di.

- Thi gian ti thiu khng lm vic ca RCD pha trn phi c gi tr ln 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.


Chng 4: KH C IN IU KHIN BNG TAY I. CU DAO

1. Khi qut v cng dng

Cu dao l mt kh c in 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 tr i 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 hot ng ca cu dao ct nhanh Khi thao tc trn cu dao, nh vo 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


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 loi Phn loi cu dao da vo cc yu t sau: - Theo kt cu: cu dao c chia lm loi mt cc, hai cc, ba cc hoc

bn cc. - Cu dao c tay nm gia hoc tay bn. Ngoi ra cn c cu dao mt

ng, hai ng c 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 t iu khin). - Theo yu cu s dng: loi cu dao c cu ch bo v ngn mch hoc

khng c cu ch bo v. K hiu cu dao khng c cu ch bo v:

Mt cc Hai cc Ba cc Bn cc


K hiu cu dao c cu ch bo v:

d) Cc thng s nh 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.

Im cu dao = Itt Um cu dao = Ungun

II. CNG TC 1. Khi qut v cng dng

Cng tc l kh c in 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 s phng 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 m c gn trn nha v c l xo thao tc chnh xc. b) Phn loi

Mt cc Hai cc Ba cc Bn cc


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 t ng ho hnh trnh lm vic ca mch in.

3. Cc thng s nh 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 c kh,

cch in, phng in

4. Cc yu cu th ca 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 cc

im cn cch in gia chng. - Th cch in: o in tr cch in < 2M. - Th pht nng. - Th cng sut ct. - Th bn c kh. - Th nhit i vi cc chi tit cch in: cc chi tit cch in phi

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

III. NT NHN 1. Khi qut v cng dng

Nt nhn cn gi l nt iu khin l mt loi kh c in dung ng ngt t xa cc thit b in 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 c in bng cch ng v ngt cc cun dy ca Contactor ni cho ng c.


Nt nhn thng c t trn bng iu khin, t in, 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 ng ngt c ti. Khi thao tc nhn nt cn phi dt khot m hoc 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 tr v 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 nhn ON hay OFF.


- Phn loi theo hnh dng bn ngoi, ngi ta chia nt nhn ra thnh 4 loi: + 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 v khi 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 s in 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.


V. IN TR - BIN TR

1. Khi qut cng dng

in tr dng 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 c in.

Bin tr l in tr nhng c th thay i c gi tr ca n nh cc cn gt hoc nm vn. C cc loi in tr thng dng: in tr m my v in tr iu chnh, in tr hm, in tr phng in...

- in tr m my l in tr c s dng khi m my ng c nhm hn ch dng in khi ng cho cc ng c c cng sut trung bnh v ln (phng php m my gin tip) nhm trnh st p trn li in v bo v ng c pht nng qu nhit cho php khi c dng khi ng ln (P = 10KV).

- in tr iu chnh: iu chnh dng in trong mch kch thch hay mch phn ng ca ng c in mt chiu nhm thay i tc quay ca n.

- in tr hm nhm gim dng in khi hm ng c. - in tr phng 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 to

Bin tr c 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 tr cng c th l thanh kim loi c a ra cc u dy theo cc gi tr nh trc. Bin tr n c th ghp thnh bin tr i.

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 hot ng, 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.


CHNG 5: KH C IN IU KHIN MCH IN A CONTACTOR

I. KHI NIM Contactor l mt kh c in dng ng ngt cc tip im, to lin lc

trong mch in bng nt nhn. Nh vy khi s dng Contactor ta c th iu khin mch in t xa c ph ti vi in p n 500V v dng l 600A (v tr iu 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 in

bng 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 to

Contactor 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 tr v v tr ban y

khi ngng cung cp in vo cun dy.


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 Contactor H 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 cu Contactor thnh hai loi:

- Tip im chnh: C kh nng cho dng in ln i qua (t 10A n vi nghn 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 hn 5A. 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 vi nhau gia hai tip im) khi cun dy nam chm trong Contactor trng thi ngh (khng c cung cp in). Tip im ny h ra 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).


Theo mt s kt cu thng thng ca Contactor, cc tip e ph c th c lin kt c nh v s lng trong mi b Contactor, tuy nhin cng c mt vi nh sn xut ch b tr c nh s tip im chnh trn mi Contactor, cn cc tip im ph c ch to thnh nhng khi ri n l. Khi cn s dng ta ch ghp 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 tr in p nh mc ca Contactor vo hai u ca cun dy qun trn phn li t c nh 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 thi hot ng. Lc ny nh vo b phn lin ng v c gia li t di ng v h


thng tip im lm cho tip im chnh ng li, tip im ph chuyn i trng thi (thng ng s m ra, thng h s ng li) v duy tr trng thi ny. Khi ngng cp ngun cho cun dy th Contactor trng thi ngh, cc tip im tr v 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 C BN 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 tip im 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 t in 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.


3. Kh nng ct v kh nng ng

Kh nng ct ca Contactor in xoay chiu t bi s n 10 ln dng in nh mc vi ph ti in cm. Kh nng ng: Contactor in xoay chiu dng khi ng ng c in cn phi c kh nng ng t 4 n 7 ln Im.

4. Tui th ca Contactor

Tui th ca Contactor c tnh bng s ln ng m , sau s ln ng m y th Contactor s b hng v khng dng c.

5. Tn s thao tc

L s ln ng ct Contactor trong mt gi: C cc cp: 30, 100, 120, 150, 300, 600, 1200, 1500 ln/gi.

6. Tnh n nh lc in ng

Tip im chnh ca Contactor cho php mt dng in ln i qua (khong 10 ln dng in nh mc) m lc in ng khng lm tc ri tip im th Contactor c tnh n nh lc in ng.

7. Tnh n nh nhit

Contactor c tnh n nh nhit ngha l khi c dng in ngn mch chy qua trong mt khong thi gian cho php, cac tip im khng b nng chy v hn dnh li.

CU HI CHNG 5 PHN A 1. Nu cu to v nguyn l hot ng ca Contactor. 2. Phn bit cc loi tip im c trong Contactor. 3. Cho bit ch lm vic ca Contactor xoay chiu. 4. Cho bit ch lm vic ca Contactor mt chiu.


B RLE IU KHIN V BO V I. KHI QUT V PHN LOI Rle v kh c in dng t ng 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 t in. - 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...


II. MT S LOI RLE THNG DNG 1. Rle trung gian

a) Khi nim v cu to Rle trung gian l mt kh c in dng trong lnh vc iu khin t ng,

c cu kiu in t. Rle trung gian ng vai tr iu khin trung gian gi cc thit b iu 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 hot ng Nguyn l hot ng ca Rle trung gian tng t nh nguyn l hot ng

ca Contactor. Khi cp in p bng gi tr in p nh mc vo hai u cun dy ca 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 h ra, tip im thng h ng li). Khi ngng cp ngun, mch t h, h thng tip im tr v 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 in

nh, s dng cho mch iu khin (tip im ph). - Trong Rle cng c cc loi tip im thng ng v tip im thng

h, 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


- 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 t iu 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 c in dng trong lnh vc iu khin t ng, vi

vai tr iu khin trung gian gia cc thit b iu khin theo thi gian nh trc. Rle thi gian gm: Mch t ca nam chm in, b nh 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: hoc in 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, m nhanh: hoc

TR TR

TR TR

TR TR

TR

TR

TR

TR


Tip im thng ng, m chm, ng nhanh: hoc * Nguyn l hot ng: Khi cp ngun vo cun dy ca Rle thi gian ON DELAY, cc tip i tc

ng khng tnh thi gian chuyn i trng thi tc thi (thng g h ra, thng h ng 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 tr v 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: hoc in 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, m nhanh: hoc

Ngun

TR TR

TR TR

TR TR

TR

TR

TR

TR


Tip im thng ng, m chm, ng nhanh: hoc * Nguyn l hot ng: Khi cp ngun vo cun dy ca Rle thi gian OFF DELAY, cc tip im

tc 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 tr v 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 v ng c v 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


n vi pht.


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 lm xoay 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 tr v v tr ban u.

b) Nguyn l hot ng: Nguyn l chung ca Rle nhit l da trn c s tc dng nhit lm dn n

phin kim loi kp. Phin kim loi kp gm hai l kim loi c h s gin n khc nhau (h s gin n hn 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 n b, 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 h v 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. Loi

ny 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.


- t nng gin tip: Dng in i qua phn t t nng c lp, nhit lng 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 t t nng. Nhc dim ca loi ny l khi c qu ti ln, phn t t nng c th t n nhit kh cao nhng v khng kh truyn nhit km, nn tm kim loi cha kp tc c m phn t t nng b chy t.

- t nng hn hp: Loi ny tng i tt v va t trc tip va t gin 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 c bn 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 gi c 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 c in, 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 c in 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.


4. Rle dng in:

- Dng bo v qu ti v ngn mch. - Cun dy ht c t vng v qun bg dy to mc ni tip vi mch in

vn bo v, thit b thng ng ngt trn mch iu khin. - Khi dng in ng c tng ln n tr s tc ng ca Rle, lc ht

nam chm thng lc cn l xo lm m tip im ca n, ngt mch in iu khin qua cng tc t K, m cc tip im ca n tch ng c ra khi li.

5. Rle in p

- Dng bo v st p mch in. - Cun dy ht qun bng dy nh nhiu vng mc song song vi mch

in cn bo v. Khi in p bnh thng, Rle tc ng s lm nng tip im ca n. Khi in p st thp di mc quy nh, lc l xo thng lc ht ca nam chm v m tip im.

6. Rle vn tc


- Lm vic theo nguyn tc phn ng in t c dng trong cc mch hm ca ng c.

- Rle c mc ng trc vi ng c v mch iu khin. Khi c quay, 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 c gim nh gn bng khng, lc in t yu i, trng lng cn tip im a n v v tr c v m tip im ca n.

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

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 DNG

Khi ng t l mt loi kh c in dng iu khin t xa vic ng - ngt, o chiu v bo v qu ti (nu c lp thm rle nhit) cc ng c khng ng b ba pha rto lng sc.

Khi ng t c mt Contactor gi l khi ng t n thng ng - ngt ng c in. Khi ng t c hai Contactor l khi ng t kp dng thay i chiu quay ca ng c gi l khi ng t o chiu. Mun bo v ngn mch phi lp thm cu ch.

II. CC YU CU K THUT ng c in 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 kh ng t cn phi tho mn cc yu cu k thut sau:


- 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 v ng c khng 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 t thng 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 c in: Khng o chiu quay

v 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 t v 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 c v 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 tr v v tr ban u; cc tip im tr v trng thi thng h. ng c dng 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 c in.

S :


b) Khi ng t o 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 c quay theo chiu thun v ng tip im ph thng h T 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 mt in, 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 c o chiu quay ngc li v tip im ph thng h N 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 c dng

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 c in. S :


IV. LA CHN V LP DP KHI NG T Hin nay nc ta, ng c khng 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 c in m khi ng t phc v ng 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 m vo 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 s iu khin. - Rle nhit phi t khi ng t cn t km theo cu ch bo v.


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 C IN CAO P

Chng 6: KH C IN CAO P I. KHI QUT Trong iu kin vn hnh, cc kh c in c th lm vic cc ch sau:

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

- Ch lm vic qu ti: Trong ch ny dng in qua kh c in s ln 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 s m bo s lm vic tin cy nu trong qu trnh la chn ch cc iu kin n nh nhit v n nh ng.

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

a) Khi nim My ct in p cao l thit b in 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 b ng ct lm victin cy song ga thnh cao nn my ct ch cdng 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 bng du 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 cch in rn v h quang sinh ra khi ct my ct cng c dp tt bng du bin p.


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

c) Cc thng s c bn 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 in p 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 tn hiu 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 dng in ngn mch m my ct c th ng 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 cho ti khi hon tt ng tc ng my ct. d) La chn v kim tra my ct in 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 c in 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 b in an tm khi lm vic.


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 c in 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 tr sut 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 tr sut 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 vi dy 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 b t 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 ch Tu theo chc nng ca mi loi cu ch m ta c th phn nh sau:


- Cu ch t ri (Fuse Cut Out: FCO): Hot ng theo nguyn tc ri do mt 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 th c lp bn trn hoc di du.

- Cu ch hn dng: Chc nng chnh l hn ch tc ng ca dng in s c c th c i vi nhng thit b c 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 tr t 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 C BN V NGUYN L IU KHIN, VN HNH

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

I. MCH IN KHI NG - DNG MT NG C KB 3 PHA a) Nguyn l: Dng mch khi ng mt ng c KB 3 pha, c tip im duy tr ng c lm vic, sau dng ng c. b) S mch (hnh 1) c) Th t thc hin:

- Nhn nt S2, Contactor K1 c in, cc tip im chnh ng li, ng c hot ng, cc tip im ph thay i trng thi, tip im ph thng ng h ra lm cho n H1 tt, tip i ph thng h ng li duy tr ngun cho Contactor K1 v n H2.


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

II. MCH IN KHI NG TH T HAI NG C KB 3 PHA a) Nguyn l Dng mch khi ng th t hai ng c KB 3 pha. ng c 1 (iu khin bi Contactor K1) chy trc, sau ng c 2 (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) Th t thc hin:

- Nhn S3, ng c M1 hot ng, n H1 sng. - Nhn S4, ng c M2 hot ng, n H2 sng. - Nhn S2, dng ng c M2, n H2 tt. - Nhn S1, dng ng c M1, dng ton b mch iu khin, n H1 tt.


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

III. MCH IN O CHIU NG C KB BA PHA a) Nguyn l:


o chiu quay ng c KB ba pha bng cch o hai trong ba dy ngun trc khi a ngun vo ng c. Mch in ny dng iu khin ng c KB ba pha lm vic hai chiu quay, sau dng ng c. b) S mch: (hnh 3) c) Th t thc hin:

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

Hnh 3: S mch o chiu ng c KB ba pha

IV. MCH IN KHI NG MT NG C KB 3 PHA - T NG DNG a) Nguyn l: Dng mch khi ng mt ng c KB 3 pha, c tip im duy tr ng c lm vic, sau thi gian lm vic nh trn Timer, tip im thng ng m chm ca Timer h ra, ng c dng. b) S mch: ( hnh 4) c) Th t thc hin:

- Nhn S2, ng c hot ng, n H1 tt, n H2 sng.


- Rle thi gian KTON c in v bt u tnh thi gian ng c lm vic. Khi ht khong thi gain nh, tip im thng ng KTON h ra lm ngng cp in cho Contactor K1, ng c ngng hot ng n H1 sng, n H2 tt.

- Nhn S1 dng ng c khn cp.

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


V. MCH IN T NG KHI NG THEO TH T CA HAI NG C KB 3 PHA a) Nguyn l Mch in s dng TON. Dng mch khi ng th t hai ng c KB 3 pha. ng c 1 (iu khin bi Contactor K1) khi ng trc, sau thi gian khi ng ca ng c th tip im thng h ng 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) Th t thc hin:

- Nhn S1 ng c M1 hot ng n H1 sng. - Rle thi gian KTON chuyn trng thi, ng c M2 hot ng, n H2

sng. - Nhn S1 dng c hai ng c.


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

CU HI CHNG 7 1. V mch lun phin hai ng c (ch c mt trong hai ng c lm vic). 2. V mch lun phin ba ng c (ch c mt trong ba ng c lm vic). 3. V mch khi ng ng c KB ba pha bng phng php i ni sao

tam gic (ng c m my ch sao, l vic ch tam gic). 4. V mch iu khin o chiu ng c KB ba pha kt hp i ni sao

tam gic. 5. V mch iu khin o chiu ng c KB ba pha, mi chiu quay lm

vic hai cp tc .


MC LC Trang

Li ni u 3

PHN I: L THUYT C BN CA KH C IN

CHNG I: PHT NNG KH C IN I. KHI NIM V KH C IN 6

1. Khi nim 6 2. Phn loi, cc yu cu c bn ca kh c in 6

II. TNH TON TN THT IN NNG TRONG KH C IN 6 III. CC CH PHT NNG CA KH C IN 7

1. Ch lm vic lu di ca kh c in 8 2. Ch lm vic ngn hn ca kh c in 8 3. Ch lm vic ngn hn lp li ca kh c in 8 CU HI CHNG 1 9

CHNG 2: TIP XC IN - H QUANG I. TIP XC IN 9

1. Khi nim 9 2. Phn loi tip xc in 10 3. Cc yu t nh hng n in tr tip xc 10

II. H QUANG IN 10 1. Khi nim 10 2. Tnh cht c bn ca phng in h quang 11 3. Qu trnh pht sinh v dp h quang 11 CU HI CHNG 2 12

PHN II: TM HIU C TNH, KT CU, TNH TON LA CHN S DNG KH C IN H P

CHNG 3: KH C IN NG NGT - BO V MCH IN

A CB (CIRCUIT BREAKER) I. KHI NIM V YU CU. 12


II. CU TO V NGUYN L HOT NG 13 1. Cu to 13

2. Nguyn l hot ng 14 3. Phn loi v cch la chn CB 16 CU HI CHNG 3 PHN A 16

B - CU CH I. KHI NIM V YU CU 16 II. CU TO V NGUYN L HOT NG 17

1. Cu to 17

2. Nguyn l hot ng 17 3. Phn loi, k hiu, cng dng 19 4. Cc c tnh in p ca cu ch 20 CU HI CHNG 3 PHN B 20

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. S TC NG CA THIT B CHNG DNG IN R 23 1. S tc ng tin cy ca RCD 23

2. S tc ng c tnh chn lc ca RCD bo v h thng in s in. 23 CU HI CHNG 3 PHN C 24

CHNG 4: KH C IN IU KHIN BNG TAY I. CU DAO 25

1. Khi qut v cng dng 25 2. Cu to, nguyn l hot ng v phn loi 25

II. CNG TC 27 1. Khi qut v cng dng 27 2. Phn loi v cu to 27 3. Cc thng s nh mc ca cng tc 28 4. Cc yu cu th ca cng tc 28

III. NT NHN 28


1. Khi qut v cng dng 28 2. Phn loi v cu to 29 3. Cc thng s k thut ca nt nhn 30

IV. PHCH CM V CM IN 30 V. IN TR - BIN TR 31

1. Khi qut cng dng 31 2. Cu to 31

CU HI CHNG 4 31

CHNG 5: KH C IN IU KHIN MCH IN

A CONTACTOR

I. KHI NIM 32 II. CU TO V NGUYN L HOT NG. 32

1. Cu to 32

2. Nguyn l hot ng ca Contactor 34

III. CC THNG S C BN CA CONTACTOR 35 1. 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 s thao tc 36 6. Tnh n nh lc in ng 36 7. Tnh n nh nhit 36 CU HI CHNG 5 PHN A 36

B RLE IU KHIN V BO V I. KHI QUT V PHN LOI 37 II. MT S LOI RLE THNG DNG 38

1. 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


6. Rle vn tc 45 CU HI CHNG 5 PHN B 46

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 47

1. Khi ng t thng 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 PHN C 50

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

CHNG 6: KH C IN CAO P I. KHI QUT 50 II. MT S KH C IN CAO P (1000V) 50

1. My ct 50 2. Dao cch ly 51 3. Cu ch cao p 52 CU HI CHNG 6 53

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

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

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

II. MCH IN KHI NG TH T HAI 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

V. MCH IN T NG KHI NG THEO TH T CA HAI NG C KB 3 PHA 58

CU HI CHNG 7 59

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