Chuong 2 DTCS

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TS. L MINH PHNG [CHNG II CC LINH KIN BN DN C BN ]CHNG II. CC LINH KIN BN DN C BN 1. TNG QUAN Cc linh kin bn dn cng sut trong lnh vc in t cng sut c hai chc nng c bn: ng v ngt dng in i qua n. Trng thi linh kin dn in (ng) l trng thi linh kin c tc dng nh mt in tr rt nh (gn bng khng). Trng thi linh kin khng dn in (ngt) l trng thi linh kin c tc dng trong mch nh mt in tr ln v cng. - Linh kin bn dn hot ng vi hai ch lm vic ng v ngt dng in c xem l l tng nu trng thi dn in n c st p bng khng v trng thi khng dn in (ngt), dng in qua n bng khng. 1. Phn loi linh kin bn dn: a. Linh kin bn dn iu khin c: Cc linh kin bn dn c th chuyn i trng thi lm vic ca mnh t trng thi khng dn in (ngt) sang trng thi dn in (ng) v ngc li thng qua tc dng kch thch ca tn hiu ln cng iu khin ca linh kin, gi linh kin c tnh iu khin. Tn hiu iu khin c th tn ti di dng dng in hay in p. V d BJT, MOSFET, IGBT, GTO, IGCT,MCT,MT SCR, TRIAC. - Linh kin bn dn iu khin hon ton linh kin ng ngt cng bc (forced commutated device): l linh kin c th iu khin ng ngt hon ton bng tn hiu iu khin, v d BJT, MOSFET, IGBT, GTO, IGCT, MCT,MT. - Linh kin bn dn iu khin ng: : l linh kin ch c th iu khin ng bng tn hiu iu khin m khng iu khin ngt c: SCR, TRIAC

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b. Linh kin bn dn khng iu khin c: l nhng linh kin khng c cng iu khin v qu trnh chuyn trng thi lm vic ca linh kin xy ra di tc dng ca ngun cng sut. V d: diode, diac.

LINH KIN BN DN

DIODE

THYRISTOR

TRANSISTOR

SCR GTO TRIAC

BJT MOSFET IGBT

Hnh 2.1 Cc linh kin bn dn cng sut c bn

- Diode: Dng nh mc ca diode t 1A n 5000A. in p nh mc t 10V n 10kV. Thi gian ng ngt t 20 ns cho n 100 ms. Diode c ng dng trong b chnh lu v cc mch bin i DCDC: Zener, optoelectronic and Schottky diodes, and diacs - BJT (Bipolar Junction Transistor): dn dng Collector khi trn cc Base c dng in iu khin BJT dn. Dng nh mc ca BJT t 0.5A n 500 A; in p t 30V n 1200V. Thi gian ng ngt ca BJT 0.5ms n 100 ms. BJT c ng dng trong mch cc b bin i DC-DC; kt hp viBI GING IN T CNG SUT Page 1

TS. L MINH PHNG [CHNG II CC LINH KIN BN DN C BN ]diode s dng trong cc b bin tn. Tuy nhin trong cc b cng sut ln th ngi ta thay th BJT bng MOSFET v IGBT. - MOSFET (Metal Oxide Field Effect Transistor): dn dng Drain khi c in p va trn cc iu khin Gate. MOSFET c mc song song vi diode trong cu trc ca n. Dng in nh mc t 1n 100A, in p nh mc t 30 n 1000V. Thi gian ng ngt rt nh t 50 n 200ns. MOSFET ng dng cho b bin i DC-DC, v trong cc b bin tn. - IGBT (Insulated Gate Bipolar Transistor): y l dng c bit kt hp gia BJT v MOSFET. L linh kin rt d s dng, thi gian ng ngt nh hn thi gian ng ngt ca BJT. Dng nh mc t 10 n 600 A, in p nh mc t 600 n 1700V. IGBT ng dng nhiu trong cc b bin tn t1 dn100kW v c ng dng rng ri trong in t cng sut. - SCR (Silicon Controlled Rectifier): Thyristor cng ging nh diode khi c xung trn cc Gate. SCR ch ngt khi dng qua n bng 0. Dng nh mc thay i t 10 n 5000A. in p nh mc thay i t 200V n 6 kV. Thi gian ng ngt t 1 n 200ms. SCR c ng dng rng ri trong b chnh lu iu khin v l linh kin thuc h thyristor c ng dng rng ri nht. - GTO (Gate Turn-Off Thyristor) thuc h Thyristor v c kh nng iu khin ngt bng xung m trn cng Gate. GTO c th thay th BJT khi cn ng dng trong cc b cng sut ln, cn dng v in p ln. Dng v in p nh mc gn tng t nh SCR v n c ng dng trong cc b bin tn ln hn 100kW. - TRIAC (Triode for Alternating Current) L linh lin c cu trc cu to bi hai SCR mc i song. Dng in nh mc t 2 n 50A, in p nh mc t 200 n 800V. TRIAC c s dng trong iu chnh nh sang, nhng thit b in cm tay

Bng 2.1 K hiu cc linh kin bn dn cng sut c bn

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TS. L MINH PHNG [CHNG II CC LINH KIN BN DN C BN ]

Hnh 2.2 Cc linh kin bn dn cng sut trong cng nghip

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TS. L MINH PHNG [CHNG II CC LINH KIN BN DN C BN ]

Hnh 2.3 in p v dng in nh mc ca cc linh kin bn dn cng sut

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TS. L MINH PHNG [CHNG II CC LINH KIN BN DN C BN ]Bng 2.2 Thng s k thut c bn ca linh kin bn dn cng sut

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TS. L MINH PHNG [CHNG II CC LINH KIN BN DN C BN ]Bng 2.3 K hiu v c tnh ca linh kin bn dn trong cng nghip

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TS. L MINH PHNG [CHNG II CC LINH KIN BN DN C BN ]2. LP TIP XC CNG NGH P-N. Bng cc bin php cng ngh Epitaxi (Plana khuch tn) ngi ta to ra c vng chuyn tip tnh dn in t loi p sang loi n gi l tip xc p-n. y l dng tip xc phi tuyn c tnh dn in khng i xng theo hai chiu in p t vo. Cht bn dn c kh nng dn in ch yu bng in t gi l cht bn dn tp cht loi n. Cht bn dn c kh nng dn in ch yu bng l hng gi l cht bn dn tp cht loi p - Bnh thng khi cha c tc ng bn ngoi trong vng tip xc mt phn in t t loi n s dch chuyn sang loi p v ngc li mt phn phn t l hng t loi p s dch chuyn sang loi n. in t v phn t mang in l hng b ln nhau v to ra vng mang in thp qu trnh ny c gi l qu trnh t hp li v tn ti cho n khi in t t vng n b y bi i-n m vng p v phn t mang in l hng vng p b y bi i-n dng vng n.

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Hnh 2.4 Lp p-n - Cc i-n dng vng n v cc i-n m vng p to ln in trng cc b hng t vng n sang p. in th c gi tr cc i ti trung tm ca vng tip xc. Gia hai vng to ra hiu in th in th ny ph thuc vo cht liu bn dn: i vi German l 0.3V i vi Silicon l 0.7V.

Hnh 2.5 Gin in p trn lp p-n BI GING IN T CNG SUT Page 7

TS. L MINH PHNG [CHNG II CC LINH KIN BN DN C BN ]3. 1. DIODE CNG SUT

Cu to v nguyn l hot ng. - Diode- l linh kin bn dn khng iu khin c hai in cc Anode (A) - Cathode (K) v c cha mt lp tip xc p-n.

Hnh 2.6 K hiu diode

- Khi in cc dng ca ngun in c gn vo cc Anode v cc m- cc Cathode ta c tip xc phn cc thun. in t t cc m vo vng n, vng tip xc, mt phn kt hp vi phn t mang in l hng phn cn li qua vng p ti cc dng ca ngu n in: Diode dn.

Hnh 2.7 Cu trc diode

- Khi in cc dng ca ngun in c gn vo cc Cathode v cc m- cc Anode ta c tip xc phn cc ngc. Ch c mt s t in t t vng p dch chuyn qua vng tip xc, mt phn kt hp vi phn t mang in l hng phn cn li qua vng n ti cc dng ca ngun: Diode ngt.2. K hiu v s kt ni

Hnh 2.8 S kt ni diode

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TS. L MINH PHNG [CHNG II CC LINH KIN BN DN C BN ]3. c tnh Volt-Amper ca diode (VI): c tnh V-I ca diode c chia lm 3 vng

Hnh 2.9 c tnh V-A ca diode Vng phn cc thun: Khi 0IG0 VB02 0 ; I G > 0 : SCR dnPage 3

TS. L MINH PHNG [CHNG II CC LINH KIN BN DN C BN ] 7. Mch bo v - Nu dU/dt qu ln dn n SCR dn ngoi mun V th ngi ta gii han tc thay i in p kho trong khong 10 100V / s Nu dIf/dt ln qu s lm tit din SCR b qu ti ch ni vi cng lm hng SCR .V th ngi ta gii hn tng ca dng thun trong khong 10-100A/s -

Mch bo v du/dt

Mch bo v du/dt

Mch bo v di/dt

8.

Mch kch SCR.

Th d s mch kch thyristor

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TS. L MINH PHNG [CHNG II CC LINH KIN BN DN C BN ]

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TS. L MINH PHNG [CHNG II CC LINH KIN BN DN C BN] 5. GTO - GATE TURN OFF THYRISTOR 1. Cu to v nguyn l hot ng - Cu trc ca GTO gm 4 lp tip xc n-p-n-p. Vi ba cc Anode (A), Cathode (K), v Gate (G), trong cc Anode v Cathode c cu to bi nhiu phn t cng ngh nh nhng thyristor mc song song, nh to kh nng ngt t cc iu khin.

2.

K hiu v s kt ni

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TS. L MINH PHNG [CHNG II CC LINH KIN BN DN C BN]

3. c tnh Volt-Amper GTO: c tnh V-A ca GTO tng t c tnh ca SCR. trng thi ng GTO c c trng bi cc thng s - in p ngng U - in tr thun. 4. c tnh ng ca GTO: a. Qu trnh ng bao gm thi gian tr ng v thi gian tng dng, m trong thi gian in p trn GTO gim n gi tr 10% so vi gi tr ban u. Tng hai khong thi gian trn gi l thi gian ng. gim thi gian ng v gim tn hao khi ng th dng iu khin (trn cc iu khin) thi im u cn phi c tc thay i ln di/dt>5A/mks. b. Qu trnh ngt GTO xy ra kh chm v bao gm hai gii on. Giai on 1 dng qua GTO gim n 10-20% gi tr dng ban u. Giai on hai dng in gim kh chm, thi gian ko di qu trnh ny ln hn kh nhiu so vi thi gian ca giai on 1. Dng trn cc iu khin phi c gi tr m v phi c bin kh ln v gia tc phi t gi tr di/dt>20A/mks. i vi GTO hin ti bin dng ngt c gi tr bng 30% bin dng anode. gim tn hao khi ng ngt v bo v GTO ngi ta cng thng s dng mch snubber. 5. Cc thng s v tnh cht c bn - GTO c kh nng iu khin ngt bng dng cng Gate gi tr m. V vy, GTO thch hp cho mt s ng dng khi yu cu iu khin c hai qu trnh ng v ngt kho bn dn. - nh mc GTO : dng vi kA , p vi kA : - Dng cho mch cng sut rt ln. 6. Cc trng thi ng ngt GTO c 3 trng thi: - Trng thi ngt khi in p trn cc anode m so vi cc cathode. - Trng thi ngt khi in p trn cc anode dng so vi cc cathode. - Trng thi dn.

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TS. L MINH PHNG [CHNG II CC LINH KIN BN DN C BN] 6. TRIAC - TRIOD ALTERNATIVE CURRENT 1. Cu to v nguyn l hot ng: - TRIAC c cu to bi hai Thyristor mc i song. Do linh kin dn in c hai na chu k.

2.

K hiu v s kt ni

3. -

c tnh Volt-Amper TRIAC c tnh Volt-Amper ca TRIAC v theo chiu quy c ca cc T1. c tnh Volt-Amper ca TRIAC c tnh i xng

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TS. L MINH PHNG [CHNG II CC LINH KIN BN DN C BN] 4. Cc thng s v tnh cht c bn TRIAC - Khi nim Anode v Cathode khng c ngha i vi TRIAC, ta nh s T1 l cc gn cc iu khin G. - TRIAC ch b kho khi I G = 0 v in p t nh hn p ngng. - u im c bn ca TRIAC l mch iu khin n gin. Nhng cng sut gii hn khng cao v nh hn Thyristor. - TRIAC t bo v chng li qu in p theo c hai chiu.

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TS. L MINH PHNG [CHNG II CC LINH KIN BN DN C BN] TRANSISTORS CNG SUT - POWER TRANSISTORS - Transistor cng sut l linh kin bn dn c iu khin ng v iu khin ngt. - Transistor cng sut hot ng vng bo ha v vy c in p khi ng nh, ging nh kha ng ngt. - Tn s ng ngt ca Transistor cng sut ln hn gp nhiu ln so vi thyristors, tuy nhin in p v dng in nh mc ca mt s transistor cng sut nh hn so vi Thyristors, v vy c ng dng trong