B GIO DC V O TO TRNG I HC BCH KHOA HA NI ***********
CNG HA X HI CH NGHA VIT NAM c lp T do Hnh phc **********
NHIM V THIT K MN HCI- Cc s liu ban u: - Cng sut ng c (Pc) - in p nh mc (Um) - H s cos - Hiu sut () II- Gii thiu chung: 1- Gii thiu chung v cng ngh ca ng c khng ng b ba pha. 2- Gii thiu v cc phng php khi ng ng c khng ng b. III- Ni dung thit k: 1- Gii thiu v thit k mch lc. 2- Gii thiu v tnh ton mch iu khin. - Nguyn tc iu khin. - Khi ng pha, dng b. - Khi to lut iu khin. - Khi so snh. - Khi to xung iu khin v tch xung. - Khi khuch i xung. - Khi ngun. 3- Bn v s nguyn l tng th. 4- Kt lun. : 0,68 : 0,79 - Tc nh mc (n) : 580 v/p. : 80 KW. : 380/220 V. => = 470.
AXC 3 pha khi ng C KB roto ngn mch
Mn: in t cng sut
MC LCLI M U...............................................................................................................................................3 CHNG I: GII THIU CHUNG V NG C KHNG NG B 3 PHA.............................................4 V CC PHNG PHP KHI NG MY.............................................................................................4 I- GII THIU CHUNG V NG C KHNG NG B:....................................................................4 II- CC PHNG PHP KHI NG NG C KHNG NG B:.................................................4 1- Cc yu cu khi ng ng c:.....................................................................................................4 2- Cc phng php m my:............................................................................................................5 a/ Phng php Khi ng cng:.................................................................................................5 b/ Phng php Khi ng mm:.................................................................................................5 3- La chn phng n:......................................................................................................................5 CHNG II: NI DUNG THIT K.............................................................................................................6 I- GII THIU V THIT K MCH LC:...............................................................................................6 1- Gii thiu mch lc:........................................................................................................................6 2- Hot ng ca mch:......................................................................................................................6 3- Tnh ton mch lc:.........................................................................................................................7 a/ Tnh thng s valve:....................................................................................................................7 b/ iu kin lm mt cho valve:.......................................................................................................8 c/ Mch bo v valve:......................................................................................................................8 II- GII THIU V THIT K MCH IU KHIN:.................................................................................9 1- Khu ng b:...............................................................................................................................10 a/ ng pha:..................................................................................................................................10 b/ ng b:....................................................................................................................................10 2- Khu to in p rng ca:...........................................................................................................11 3- Khu to lut iu khin:...............................................................................................................12 a/ Chc nng:................................................................................................................................12 b/ Tnh ton linh kin:....................................................................................................................12 4- Khu so snh:...............................................................................................................................13 5- Khu to xung kp:........................................................................................................................14 a/ To xung n:...........................................................................................................................14 b/ Tch xung:.................................................................................................................................15 6- Khu khuch i xung:..................................................................................................................16 a/ Phn khuch i xung:..............................................................................................................16 b/ Bin p xung:............................................................................................................................16 7- Khi ngun:..................................................................................................................................17 a/ Mch cp ngun DC (W2):........................................................................................................18 b/ Bin th ngun:.........................................................................................................................18 8- Tng hp linh kin v s chi tit mch iu khin:...................................................................21 a/ Bng tng hp linh kin:............................................................................................................21 b/ S chi tit mch iu khin:..................................................................................................22 III- M PHNG MCH LC:.................................................................................................................23 1- Dng in ti:................................................................................................................................23 2- in p ra ti:................................................................................................................................23 3- Xung pht m valve ca cc pha:..................................................................................................23 KT LUN.................................................................................................................................................24 XUT...................................................................................................................................................24 TI LIU THAM KHO ..............................................................................................................................24 PHN MM M PHNG...........................................................................................................................24
SVTH: Nguyn Phc on
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AXC 3 pha khi ng C KB roto ngn mch
Mn: in t cng sut
LI M U-
Ngy nay, cng vi vic pht trin mnh m cc ng dng ca khoa hc k thut trong cng nghip, c bit l trong cng nghip in t th cc thit b in t c cng sut ln cng c ch to ngy cng nhiu. c bit l cc ng dng ca n vo cc ngnh kinh t quc dn v i sng hng ngy v ang c pht trin ht sc mnh m.
-
Tuy nhin, p ng c nhu cu ngy cng nhiu v phc tp ca cng nghip th ngnh in t cng sut phi lun nghin cu tm ra gii php ti u nht. c bit vi ch trng cng nghip ha hin i ha t nc, cc nh my, x nghip cn phi thay i, nng cao cng ngh bng cch a cng ngh iu khin t ng vo trong sn xut. Do i hi phi c thit b v phng php iu khin an ton, chnh xc. l nhim v m nghnh in t cng sut cn phi gii quyt.
-
gii quyt c vn ny, nh nc ta cn c i ng thit k ng o v nng lc. Sinh vin ngnh T ng ha tng lai khng xa s ng trong i ng ny, do cn phi t trang b cho mnh mt trnh v tm hiu bit su rng. Chnh v vy, n mn hc in t cng sut l yu cu cp thit cho mi sinh vin t ng ha. l bi kim tra kho st kin thc tng hp ca mi sinh vin v cng l iu kin cho sinh vin t tm hiu, nghin cu kin thc v in t cng sut.
-
Mc d vy, do kinh nghim thc t cha nhiu nn vn cn n s gip v hng dn ca thy gio. Qua y, em xin c gi li cm n n thy Phm Quc Hi tn tnh ch dn em c th hon thnh n ny.
SVTH: Nguyn Phc on
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AXC 3 pha khi ng C KB roto ngn mch
Mn: in t cng sut
CHNG I:
GII THIU CHUNG V NG C KHNG NG B 3 PHA V CC PHNG PHP KHI NG MY
I- GII THIU CHUNG V NG C KHNG NG B: - Trong lch s my in, my in khng ng b (KB) ra i mun hn so vi cc loi my in khc, nhng n hin nay, n l loi my in c s dng rng ri nht trong cc ngnh kinh t quc dn vi cng sut t vi chc n hng trm kW. - Trong cng nghip thng dng my in khng ng b lm nguun ng lc cho cc my gia cng ch to sn phm. - Trong i sng hng ngy, my in khng ng b cng dn dn chm mt v tr quan trng nh: qut gi, ng c bm gia dng .. - S d my in khng ng b c s dng v pht trin nhanh chng nh vy bi nhng tnh nng ni bt v vt tri so vi my in mt chiu v my in ng b nh: C kt cu n gin, d ch to. Lm vic chc chn, vn hnh tin cy, hiu sut tng i cao. Chi ph vn hnh v bo tr sa cha thp. S dng trc tip vi li in xoay chiu do khng tn chi ph cho cc b bin i. Gi thnh thp, d chp nhn. - Tuy nhin, my in khng ng b ch yu c s dng ch ng c nn mt trong nhng nhc im ca n l dng khi ng thng cao (thng t khong 4 7 ln dng nh mc). iu ny khng nhng lm cho thn my b nng mau gim tui th ng c m cn lm cho in p li in gim st nhiu, nht l vi nhng li in cng sut nh. - Do vn t ra l ta phi gim c dng in m my ca ng c khng ng b v c bit l ng c khng ng b roto ngn mch. Vic tc ng vo ng c roto ngn mch thng kh khn hn so vi ng c roto dy qun, tuy nhin, hin nay vi vic p dng nhng ng dng ca in t cng sut th cng vic tr nn d dng hn. II- CC PHNG PHP KHI NG NG C KHNG NG B: - Khi bt u m my, roto ang ng yn, h s trt = 1 nn dng in m my c tnh theo mch in tng ng vi cng thc nh sau:
Ik =
U1' (r1 + C1r2' ) 2 + ( x1 + C1 x2 ) 2
- T cng thc trn, ta thy dng in khi ng ph thuc vo cu to ca ng c v ph thuc nhiu vo in p li. 1- Cc yu cu khi ng ng c: i vi mt ng c, cng vic m my cn t c cc yu cu sau: - Momentt m my cng ln cng tt hoc ln thch ng vi c tnh c ca ti. - Dng in m my cng nh cng tt. - Tn hao cng sut trong qu trnh m my cng nh cng tt. - Phng php m my v thit b cn dng nn n gin, r tin, chc chn.
SVTH: Nguyn Phc on
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AXC 3 pha khi ng C KB roto ngn mch
Mn: in t cng sut
2- Cc phng php m my: - Hin nay c kh nhiu phng php khi ng my, nhng c th phn chia thnh hai phng php chnh, l phng php khi ng cng v phng php khi ng mm. a/ Phng php Khi ng cng: - M my trc tip thng qua cc thit b ng ct nh: cu dao, khi ng t . - H in p m my bng bin p t ngu, phng php ny gim c dng m my nhng ng thi cng lm gim momentt m my. Vi cch ny, bn cao p c ni vi li in, bn h p ni vi ng c, sau thi gian m my, bin p c loi ra khi mch in. - Ni in khng trc tip vo mch in stator. Khi m my, mt in khng c t ni tip vo trong mch in stator, sau thi gian m my th in khng ny s b ni ngn mch. - i ni Y-. + u im: Thit b khi ng n gin, d lp t, gi thnh thp, d bo tr sa cha. + Nhc im: Ch s dng cho nhng ng c c cng sut nh, kh ng b ha vi vic iu khin cho ton h thng. Kh nng p ng chm, khng thc hin c vic dng mm khi c yu cu. b/ Phng php Khi ng mm: - S dng phng php Bin tn. - S dng phng php iu p xoay chiu. + u im: Thit b iu khin nh gn. Kh nng p ng nhanh. c tnh iu chnh trn. D ng b ha vi vic iu khin ton h thng. Ph hp vi nhu cu hin i ha trong cng nghip. C th thc hin vic dng mm khi c nhu cu. Vi gi thnh hin nay, chi ph lp h thng khi ng mm cng khng cao. S dng c cho nhng ng c cng sut ln. + Nhc im: Dng in p v dng in qua iu khin cp cho ti s khng cn l hnh sin trong di iu chnh. Do mch iu khin phc tp nn ngi vn hnh cn phi c mt trnh hiu bit nht nh. Vic kim tra bo tr phc tp hn. 3- La chn phng n: - So snh u v nhc im ca hai phng n khi ng ng c khng ng b trn, kt hp vi thi k cng nghip ha hin nay ca nc ta v do s liu ca ng c, n ny xin chn phng n khi ng mm khi ng cho ng c m c th l phng php iu p xoay chiu ba pha dng 6 thyristor u theo kiu song song ngc v y l phng php thng dng nht hin nay v c gi thnh thp trong khi yu cu ch cn khi ng mm cho ng c.
SVTH: Nguyn Phc on
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AXC 3 pha khi ng C KB roto ngn mch
Mn: in t cng sut
CHNG II: I- GII THIU V THIT K MCH LC: 1- Gii thiu mch lc:
NI DUNG THIT K
- Cc b iu p xoay chiu (AXC) dng ng ngt hay thay i in p xoay chiu ra ti t mt ngun xoay chiu c nh, trong tn s in p ra bng tn s in p ngun. - AXC dng valve bn dn c y u im ca nhng mch cng sut s dng k thut bn dn nh: d iu chnh v t ng ha, lm vic n nh, phn ng nhanh vi cc t bin iu khin, tin cy v tui th cao, kch thc gn v d thay th, thch hp v qu trnh hin i ha, tp trung ha cc qu trnh cng ngh. - Nhc im chung v c bn nht ca AXC l in p ra ti khng sin trong ton di iu chnh, iu chnh cng su cng gim in p ra th mo cng ln, tc l thnh phn sng hi bc cao cng cng ln. Nhng v phm vi ca n ny l khi ng ng c, thi gian khi ng ch trong khong 3 30s v ti l ng c bm nn ta c th chp nhn c phng n ny. - Do ti yu cu l dng in xoay chiu nn valve bn dn y c th dng l: TRIAC, y l valve bn dn duy nht cho php dng in chy theo c hai chiu. Tuy nhin loi valve ny thng c cng sut nh v gi thnh tng i cao. Ghp hai valve ch cho php dn mt chiu bng cch u song song ngc nhau, lc mi valve m nhn mt chiu ca dng ti. Bng cch ny c th ghp hai thyristor vi nhau hay mt thyristor vi mt diode. Trong n ny, ta chn theo phng php l ghp 6 thyristor theo kiu song song ngc v y cng l phng php thng dng nht hin nay. - Nguyn tc iu chnh ca AXC l iu chnh gc m ca valve bn dn. Cc valve lm vic vi in p xoay chiu nn c kha t nhin bng in p ngun v cng chu nh hng ca li in n valve, kiu iu khin valve l dch pha im pht xung so vi pha ngun xoay chiu, tc l s dng mch iu khin xung - pha. 2- Hot ng ca mch: - Mch hot ng theo quy lut chung: Trng hp 3 valve dn: Mi pha c 1 valve dn => Uti = Ungun. Trng hp 2 valve dn: C 2 pha c valve dn v 1 pha khng valve no dn => in p pha ti = in p dy ngun v c 1 pha khng c in p. Trng hp khng c valve dn: Ton b ti b ngt khi ngun (Uti = 0). - Cc trng hp dn ca valve ph thuc vo gc iu khin . Gm 3 vng iu khin: 0o > > 60o: - Trong vng ny c hai trng thi k tip nhau l 3 valve dn 2 valve dn. Giai on 3 valve dn di 60o , giai on 2 valve dn bng chnh . - Gc dn ca valve = (180o ), valve ngt khi in p pha ngun = 0.
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AXC 3 pha khi ng C KB roto ngn mch
Mn: in t cng sut
60o > > 90o: - Vng iu khin ny lun ch c 2 valve dn v khng ph thuc vo gc iu khin . - Valve trong cng nhm (chn hoc l) thay nhau dn, valve sau m th valve trc mi kha li. Lc gc dn ca valve = 120o. - in p ra ti khng cn on bng in p ngun m ch c th = in p dy.
90o > > 150o: - Trong vng iu khin ny c 2 trng thi thay th nhau l 2 valve dn v khng valve no dn. - Valve khng dn lin tc m dn thnh 2 giai on xen gia mt khon ngh. - Valve ngt dng mi khi in p dy ngun v 0V.
3- Tnh ton mch lc:
a/ Tnh thng s valve: => Ung max =
2 Ud =
2 . 380 = 537,4 (V)3
Ivalve max khi = 0 vi = 0,79It =
80 .10 P = 3 U cos 0,79 3.380 .0,68t d
= 226 ( A)
- Theo cch u ca mch lc ny (6 thyristor u song song ngc), tra theo bng Cc tham s tnh ton cho AXC ba pha (Trang 188 Ti liu hng dn thit k TCS) ta c: Itb valve = 0,45.It.klv = 0,45 . 226 . 1,6 = 362 (A) (Chn thng s klv = 1.6 l h s d tr dng)SVTH: Nguyn Phc on Trang 7 / 24
AXC 3 pha khi ng C KB roto ngn mch
Mn: in t cng sut
b/ iu kin lm mt cho valve: Qua thc nghim cho ta thy: - iu kin lm mt t nhin, valve lm vic tt vi 25% dng in nh mc. - iu kin lm mt cng bc, valve lm vic vi 30%-60% dng in nh mc. => Ta chn iu kin lm mt cng bc valve c th lm vic tt vi 40% dng in nh mc. I 226 I tbvanthuc = tbvan = = 565 ( A) => 40 % 0,4 - Chn h s d tr in p cho valve: Chn kuv = 1.6 Ung valve = kuv . Ung max = 1,6 . 537,4 = 860 (V) - Theo iu kin Itb valve thc = 565A v Ung valve = 860V, tra theo bng 2.2.2 (Trang 437 - Ti liu hng dn thit k TCS), ta c th chn valve T588N l loi ca Ty u c dy in p trong khong 1200V n 1800V v cc tham s khc l:I tb = 588 Adi = 200 ( A / s ) dt du =1000 (V / s ) dt
c/ Mch bo v valve:
Bo v qu dng: - V valve c mc trc tip vo li in m khng qua bin p do cn phi c cun cm bo v cho valve trong trng hp qu dng. Tc di/dt s ln nht khi dng qua valve l cao nht. Gi s in p li khng n nh m dao ng trong khong 5%, vy Uv max lc ny s tng ng: Uv max = 2 .1,05 . 220 = 326,7 (V) di - Xt qu trnh qu trong mch: U f = iR + L dt - Tc tng dng ln nht khiU di max = f dt L
=> Chn cun khng L c tr s sao cho =>L> U van max 326 ,7 = =1.6( H ) di 200 .10 6 dt
U di di di max < van f < van dt dt L dt
=>
Chn L = 3H.
- Cc cun cm ny thng c li l khng kh, vi gi tr cun cm l 3H, ta chn kch thc cun dy l: D = h = 0,15m. Tra theo th H s iu chnh k ca cun cm l li khng kh ta c: tng ng vi h/D = 1 th k = 0,68.
- Vy ta c s vng dy l: n= 1 D hL10 7 1 = k 0,15 0,15 .5.10 6.10 7 = 7(vng ) 0,68Trang 8 / 24
SVTH: Nguyn Phc on
AXC 3 pha khi ng C KB roto ngn mch
Mn: in t cng sut
Bo v qu p: - Gm cc phn t l R v C to thnh mch RC mc song song vi valve. Thng s cc phn t ny c tnh nh sau:0 =200 .10 6 dt = = 1140 .10 3 ( Rad ) s 0,564 .U f max 0,564 . 2 .220 du
- Do loi valve ny c du/dt = 1000 V/s, nhng valve lm vic iu kin khng phi l l tng, v vy ta ch chn thng s du/dt cho valve = 200 v/s. Ta c:C= 1 1 = = 0,256 .10 6 ( F ) 2 L0 3.10 6.1140 2.10 6L = 1,928 C 3 = 11,72 () 0,256
=> C = 0,25 F => R = 12
R = 1,928
+ Xc nh cng sut R: - Tn tht trn R khi cc valve trng thi kha: PR kha = (Ufmax ..C)2.R = (311.314.0,25.10-6)2.12 = 0,007 (W). - Tn tht trn R khi valve m:W1R = WC =2 CU f max CU C max 0,25 .10 6.311 2 = = = 0,012 (Ws ) 2 2 2 2
- Tn tht khi valve kha li: CU 2 max f W2 R = = 0,012 (Ws ) 2 - Cng sut pht nhit vi khong dn cc valve l 10ms, do cng sut trn R do cc valve m - kha l : W + W2 R 0,012 + 0,012 PR = 1R = = 2,4(W ) t 10 .10 3 - Do cng sut pht nhit trn valve ln nht khng th vt qu tng 2 cng sut va tnh: PR < (PR kha + PR) = 0,007 + 2,4 = 2,407(W) => Chn in tr c cng sut t 3W n 5W. -Vy gi tr cc phn t mch bo v valve l: L = 3H C = 0,25F R = 12/3W II- GII THIU V THIT K MCH IU KHIN: Yu cu chung ca mch iu khin: - Pht xung iu khin n cc valve lc theo ng th t pha v theo ng gc iu khin cn thit. - m bo phm vi iu khin min max tng ng vi phm vi thay i in p ra ti ca mch lc. - Cho php b iu p lm vic bnh thng vi cc ch khc nhau do ti yu cu. - Gc iu khin mi valve khng c lch qu (1 3)o in. - m bo mch hot ng n nh v tin cy khi li in xoay chiu dao ng c v gi tr in p v tn s. - C kh nng chng nhiu cng nghip tt. - tc ng ca mch iu khin nhanh, di 1ms. - m bo xung iu khin pht ti cc valve ph hp m chc chn valve. S khi mch iu khin: - Nguyn tc iu khin dc:Ulc B Ub Uta Urc SS Uss DX Udx K X Ugk
Uk
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AXC 3 pha khi ng C KB roto ngn mch
Mn: in t cng sut
- Hot ng: Khu B thng to ra in p hnh sin c gc lch pha c nh so vi in p lc. Uta to ra in p ta c dng c nh (thng c dng rng ca, i khi c dng hnh sin) theo chu k do nhp ng b ca Ub. Khu so snh (SS) xc nh im cn bng ca hai in p Uta v Uk pht ng khu to xung DX. Nh vy trong nguyn tc ny thi im pht xung m valve hay gc iu khin thay i do s thay i tr s ca Uk. 1- Khu ng b: a/ ng pha:
- Ti phn ng pha ny, ta c th s dng theo cch n gin l s dng bin p ng pha. C th dng 3 bin p 1 pha cho mi pha. Tuy nhin, v trong mch iu khin cn c nhng khu khc cng cn dng n bin p nn thng ch dng chung mt bin p c nhiu cun dy th cp, mi cun thc hin nt chc nng ring trong c cun dnh cho vic ly tn hiu ng pha. - Khu to in p ng b cho b AXC 3 pha iu chnh 6 thyristor thng cn mt h in p 6 pha lm in p ng b. Gc c tnh t gc 0. H in p pha ny bao gm 6 in p ng b hnh sin lch nhau mt gc = /3. Do ta cn phi u cun s cp ca bin p ng pha vi in p pha ca ngun lc, im trung tnh c ni vi im 0 ca mch iu khin. Cc in p ly ra t th cp a, a, b, b, c, c sau khi qua chnh lu c dng lm in p ng pha ca cc pha A, B, C tng ng. b/ ng b:
- Do kiu s u ca valve, ta c gc iu khin: 0o 150o. - Chn: Up = 10V f = 50Hz E = 15V. - Nhm chnh lu D1, D2 c in p t vo l in p ng pha vi Uhd = 10V nn Ungmax t ln diode l:
U ng max = 2 2U p = 2 2 .10 = 28(V )=> Chn D1 v D2 k loi 1N4002 vi tham s Itb = 1A v Ungmax = 100V. - Mch so snh to xung ng b, chn OA l loi TL082 l loi cha hai v trong cng mt IC do 1 v cn li s dng cho mch to xung rng ca. IC c s chn nh sau:
- Chn R1 = 15K. - c phm vi iu chnh gc iu khin 150o => gc iu khin nh nht l: min = 0,5(180o 150o) = 15oSVTH: Nguyn Phc on Trang 10 / 24
AXC 3 pha khi ng C KB roto ngn mch
Mn: in t cng sut
=> in p ngng l:
U ng= 2U p sin min = 2 .10. sin 15o = 3,66(V )
Do c st p trn diode chnh lu nn Ung gim i khong 0,7V. => Ungng = Ung 0,7 = 3V. - Chn dng i qua phn p P1 + R4 l 1mA => tng tr ca c b phn p l:
R =
E 15 = = 15.10 3 = 15( K) i 1.10 3
=> Chn R4 = 10K v P1 = 10K, iu chnh P1 = 5K. - Ro l in tr ti ca mch chnh lu, chn Ro = 10K.T
300.00
U luc-300.00 50.00
Udf-10.00 20.00
Udb-20.00 0.00 10.00m 20.00m Time (s) 30.00m 40.00m
- Biu trn l kt qu m phng vi cc thng s linh kin tnh ton. 2- Khu to in p rng ca:
- Chn
Urcmax = 10V Up = 10V1 1
E = 15V f = 50Hz
iu chnh = 150o
- Chn OA2 l v dng chung IC vi OA1 ( gii thiu ti phn trc) l IC loi TL082. - Do T = f = 50 = 20(ms) trong khi , ti mi chu k ca in p lc ta phi to c 1 xung rng ca => trc = tp + tn =10ms - Thi gian t C1 phng in chnh l thi gian tng ng phm vi iu chnh gc iu khin , do , gc 150o c quy i thnh thi gian l:
tp =
150.10( ms) = 8,33(ms) => 180 o
t n = 10 8,33 = 1,67(ms)
- Chn diode n p Dz1 l loi: BZX79A10 c UDz = 10V. - Chn t C1 = 220 nF. - Vi tp = 8,33ms, ta c:
R3 =
E.t p U DZ .C1
=
15.8,33.10 3 = 56795,45() 10.0,22.10 6
=> Chn R3 = 56K v 1 bin tr ni tip l P2 = 100K (chnh P2 = 50K). Cm in tr R3 v P2 ny dng chnh thi gian phng ca t, do vy chnh P2 cng s chnh c thi gian phc hi cho t.SVTH: Nguyn Phc on Trang 11 / 24
AXC 3 pha khi ng C KB roto ngn mch
Mn: in t cng sut
- Vi tn = 1,67ms v in p bo ha ca OA2 l: Ubh = E 1,5 = 15 1,5 = 13,5 (v) =>
R2
U bh 0,7 13,5 0,7 = = 8093,73() C.U DZ E 0,22.10 6.10 15 + + tn R3 1,67.10 3 56795,45
=> Chn R2 = 3,9K (hoc c th chn nh hn). Thay i R2 s lm thay i gi tr bin ca xung rng ca, R2 cng ln th bin xung rng ca cng gim.T
20.00
Udf-20.00 20.00
Urc-10.00 0.00 10.00m 20.00m Time (s) 30.00m 40.00m
- Biu trn l kt qu m phng ca khu to xung rng ca vi cc thng s linh kin c tnh ton nh trn. 3- Khu to lut iu khin: a/ Chc nng: - Khu ny c chc nng ch yu l to ra quy lut iu khin khi ng v c th xy dng trn c s mch PI. S nguyn l v ng c tnh ra ca mch PI nh sau:
- Mch c tip im K ca rle iu khin khi ng, khi cha chy, tip im ny m lm cho T1 thng, ni ngn mch t C2 m bo iu kin u ca mch l: U c(0) = 0. Mt khc, in p Uv = 0, do in p ra cng bng 0. - Khi n nt khi ng my, rle ng tip im K li: mt mt a in p ngun m (-E) qua R5 vo BT1 kha bng ny li, cho php t C2 tin hnh np in, mt khc a ngun E vo cm phn p (R5 - P5) to in p vo ca OA3 vi Uv = const v mch bt u hot ng nh mch PI. - Diode n p Dz2 nhm hn ch in p iu khin ti a sao cho ph hp vi in p rng ca thit k. - P4 dng chnh Uo l in p khi ng ban u. - P3 dng iu chnh tc tng p v chnh l t thi gian khi ng. - P5 dng t in p Uv, thng in p t vi gi tr thp xp x 1V. b/ Tnh ton linh kin: - Chn: Bin in p rng ca l 10V (Urc max = 10V). E = 15V. Phm vi iu chnh: Uo = 20% 60%. Thi gian khi ng di nht l 25s.
- V Urc max = 10V => phm vi iu chnh mc ban u l Uo = (2 6)V.
SVTH: Nguyn Phc on
Trang 12 / 24
AXC 3 pha khi ng C KB roto ngn mch
Mn: in t cng sut
- Ta chn mc in p Uv = 1V, do vy in p tch phn tng t nht khi khi ng vi mc Uo max = 6V, do :
Uv
U v .t k 1 1.25 t k = U m U o max C 2 P3 = = = 6,25( s ) . C 2 .P3 U m U o max 10 6=> Chn P3 = 50K. (chnh P3 = 20K).
- Chn t C2 = 330F (l t ha). =>
P3 =
6,25 = 19 K 330.10 6
- Theo thnh phn Uo = a, ta c: U o =
U P4 U v P4 = o P3 P3 Uv
- T ta c phm vi iu chnh bin tr P4 l: U 2 P4 min = o min P3 = 20 .10 3 = 40 .10 3 = 40 ( K ) Uv 1
U o max 6 P3 = 20 .10 3 = 120 .10 3 = 120 ( K ) Uv 1 => Vy chn P4 gm in tr R = 27K v bin tr P4 = 100K. - Nhm in tr phn p R5 v P5 cn c tng tr Chn R10 = 4,7K v Dz3 l loi 1N2808 c Ungng = 10V. - T hng s thi gian ca mch = R.C, ta c:
C=T 20.00
=>
Chn C3 = 1nF.
- Dng sng ca Uk qua m phng vi cc thng s linh kin va tnh nh sau:
Uss
-20.00 5.00
Uk
2.00 13.00 13.50 14.00 Time (s) 14.50 15.00
SVTH: Nguyn Phc on
Trang 14 / 24
AXC 3 pha khi ng C KB roto ngn mch
Mn: in t cng sut
- Dng sng ca Uk theo Uk trong thi gian u (0 15)ms:T 5 .0 0 Ud k 0 .0 0 2 0 .0 0 Ur c - 1 0 .0 0 9 .0 0 Uk - 3 .0 0 2 0 .0 0 Us s - 2 0 .0 0 0 .0 0 2 0 0 .0 0 m 4 0 0 .0 0 m Time ( s ) 6 0 0 .0 0 m 8 0 0 .0 0 m
b/ Tch xung:
- u vo (+) ca OA = 1mA R11 = R13 = 10K. - Do OA c chn l loi TL082 (c hai v, dng cho OA5 v OA6 trn s ) c E = 15V Ura = 15V. Trong khi , IC logic ch lm vic mc +5V v dng = 1mA. =>
R12 =
15 = 15( K) 1.10 3
=>
Chn R12 = R14 = 15K.
- Ngoi ra, lp thm D4 v D5 bo v u vo ca OA khi qu in p v R11 c tc dng hn ch dng qua cc diode ny khi chng dn tng chu k in p ng pha. - Chn D4 = D5 = D6 = D7 = D8 = D9 l loi N4001. - IC logic AND chn loi HC4081B v IC logic OR chn loi CD4071B c s chn nh sau:
SVTH: Nguyn Phc on
Trang 15 / 24
AXC 3 pha khi ng C KB roto ngn mch
Mn: in t cng sut
6- Khu khuch i xung: - Khuch i xung c nhim v tng cng sut do khu to dng xung DX hnh thnh n mc mnh m valve lc. a s cc thyristor m chc chn khi xung iu khin c gi tr UGK = (5 10)V v IGK = (0,3 1)A trong thi gian khong 100s. - Thc cht, nhim v ca KX l khuch i dng in. Vi c dng in I G th cn phi dng transistor lm chc nng khuch i, v v transistor thng dng c dng 1A c h s < 100 nn KX thng gm 2 tng khuch i. Phng php ny thng dng nht hin nay v d dng cch ly phn iu khin v phn lc. Tuy nhin do tnh cht vi phn ca bin p nn khng cho php truyn cc xung rng vi mili giy. n gin mch, ng thi vn m bo h s khuch i dng cn thit, tng khuch i thng u theo kiu Dalinton.
- Cc thng s ban u: Valve lc l loi T588N. IG = 250mA. UG = 2,2V. a/ Phn khuch i xung: - Chn bin p xung (BAX) c t s k = 2, ta c tham s dng in s cp nh sau:
U1 = U k .k = 2,2.2 = 4,4(V ) I1 = I k 0,25 = = 0,125( A) k 2
- Ngun cng sut, ta ly chung ngun 15V s dng cp cho mch iu khin, do ta chn bng T2 l loi BD135 c cc thng s sau: UCE = 45V ICmax = 1,5A min = 40. - Tuy nhin, tiu tn nhanh dng in qua BAX khi bng T2 kha, ta lp thm R16 ni tip vi cun s cp khi T2 kha, dng in qua BAX s chy vng qua D10-R16 v lm cho nng lng tiu tn trn R16 ny. iu ny trnh c tnh trng im lm vic ca li bin p b y ln vng bo ha.
R16 >
ECS 15 = = 10() I C max 1,5
=>
I1max =
15 = 1,5( A) 10
- Do dng qua in tr ny thng xuyn l ln => chn R16 = 10/2W. - Bng T3 chn loi BC107 c cc thng s sau: UCE = 45V ICmax = 0,1A min = 110.R - Vy R15 l in tr u vo c tr s l:
R15
1. 2 .ECS 40.110.15 = = 36666,6() S .I1max 1,2.1,5
=>
Chn R15 = 15K.
b/ Bin p xung: - Nhim v ca BAX gm: Cch ly mch lc v mch iu khin. Phi hp tr khng gia tng KX v cc iu khin ca valve lc. - Do BAX phi lm vic vi tn s cao nn li thp bin p cho tn s li in 50Hz khng p ng c. Li dn t trng cho BAX thng dng nht hin nay l li ferit dng xuyn, hnh tr hay c tit din kiu ch E. Tuy nhin do tn tht trong bin p tng mnh theo tn s nn cng t cm cng gim ng k so vi tn s 50Hz. th c tnh t ha li ferit tn s cao n 30kHz cho thy khi bin p lm vic theo trng thi t ha mt phn th gi tr
SVTH: Nguyn Phc on
Trang 16 / 24
AXC 3 pha khi ng C KB roto ngn mch
Mn: in t cng sut
B khng c vt qu 0,25 Tesla, tng ng H phi di 40A/m. Trng hp bin p lm vic theo ng t ha ton phn th s tng c gp i cc tr s trn.B0,4 100 0,2oC
20oC
0
H80 160 240
c tnh t ha li ferit tn s cao n 30kHz - Do ti khu to dng xung l xung n sau tch xung bng cng logic, iu ny ng vi mi chu k in p lc s c hai xung n (do phn tch xung xc nh khi pha lc n v tr 0) nn ta c chu k ca xung n l Tx = /3 v so vi chu k ca ngun li l:
1 20 Tx = Tng = (ms ) v c tx = 100s = 100.10-6s ( chn ti mc s 5). 6 6- Do ch lm vic ca BAX l lm vic mt phn nn theo th c tnh t ha li ferit, ta chn B = 0,2(T) v tng ng l H = 30(A/m). Thng chn st p cho php Ux = 0,1. Vy:
kba .U 2 .I 2t x .U x 2.2,2.7,5.10 3.100.10 6.0,1 V= = = 5,5.10 8 (m 3 ) = 0,55mm 3 B.H 0,2.30- Tra theo bng, ta chn loi li ch E c m hiu l 814E250 c din tch li t l 0,202 cm2 v din tch ca s l 0,171cm2. - S vng dy cun s cp v th cp l:
U1 .t x 4,4.100.10 6 = = 108,9(vng ) B.S ba 0,2.0,202.10 4 w 110 = 55(vng ) w2 = 1 = k 2 w1 = 7- Khi ngun:
=> =>
Chn w1 = 110 vng Chn w2 = 55 vng
- Gm mch ngun v bin th ngun. Mch ngun c chc nng cung cp ngun in mt chiu cho mch iu khin v khu khuch i xung hot ng. Bin th ngun l bin th ba pha m bn th cp c nhiu cun dy vi mi chc nng khc nhau. - Cu to ca bin th ngun nh sau:
SVTH: Nguyn Phc on
Trang 17 / 24
AXC 3 pha khi ng C KB roto ngn mch
Mn: in t cng sut
a/ Mch cp ngun DC (W2): - a s mch iu khin i hi ngun cung cp l in p mt chiu, tr s in p v n nh ty thuc tng khu trong mch. Nng lc cp cho ngun ny thng thng vn ly t li in nh bin p iu khin. Cu trc thng thng ca b ngun cho mch iu khin nh sau:Up~ U1~ UdoLC IN DUNG
ECS
ECC Ech
BIN P IU KHIN
U2~
CHNH LU DIODE
N P 1
N P 2
- Trong cc phn tnh ton trc, ta chn ngun cung cp cho cc khu vi mc in p l 15VDC, do ti mch cp ngun mt chiu ny, ta chn ngun cung cp l 15V c n p bi hai vi mch l LM7815 n p ngun +15V v LM7915 n p ngun -15V. - S mch cp ngun mt chiu nh sau:
- Chn thng s cc linh kin: C01 = C02 = 1000F l t c nhim v san bng in p chnh lu. C03 = C04 = 100F l t c nhim v lc phng. C05 = C06 = 0,1F l t lc nhiu. D01=D02=D03=D04=D05=D06 l loi 1N4002 c thng s: Itb = 1mA v Ung max = 100V. b/ Bin th ngun: - W1 l cun s cp c ni vi ngun xoay chiu 3 pha 220/380V. - W2 l cun th cp thc hin chc nng cung cp U2 cho mch cp ngun mt chiu. - W3 l cun th cp thc hin chc nng l ly tn hiu ng pha cp cho khu ng b. W2: - Cp ngun cho mch iu khin v cho khu KX. + Ngun cho mch iu khin: - hai IC LM7815 v LM7915 c ng ra l 15V, ta cn c u vo ca hai IC ny > 15V. => chn Vin = 20V => Ud = 40V. - Do phn ngun ny ch dng cp cho cc khuch i thut ton l ch yu nn dng tiu th khng ln. => Chn Id = 500mA = 0,5A. Ta c:
Ud 40 = = 17,1(V ) 2,34 2,34 Pd = U d .I d = 40.0,5 = 20(W ) U d = 2,34U 2 U 2 = S ba = k s .Pd = 1,05.40.0,5 = 21(VA)
SVTH: Nguyn Phc on
Trang 18 / 24
AXC 3 pha khi ng C KB roto ngn mch
Mn: in t cng sut
+ Ngun cp cho khu khuch i xung: - cp ngun cho khu ny, ta ly ngun trc n p => Ud = 20V. - Theo phn tnh ton ca khu KX, ta c: TCmax = 1,5A = Id, vy: Pd = Ud.Id = 20.1,5 = 30(W). => Sba = ks.Pd = 1,05.20.1,5 = 31,5(VA). SbaW2 = 21 + 31,5 = 52,5 (VA). + Tn tht cng sut trong cc valve chnh lu: - Vi cun cm W2, ta c:
I tbvalve =
I d 0,5 + 1,5 2 = = = 0,67 ( A) 3 3 3
- in p ri trn diode chnh lu l 0,7V => tn hao cng sut trn diode l: Pt hao = 0,7 . 0,67 = 0,469 (W). - V ta dng chnh lu l cu 3 pha 6 diode, do : Pthc = 0,469 . 6 = 2,814 (W). W3: - Chn U2 = Up = 10V (theo thit k ti khu ng pha). - S chnh lu l hnh tia 1 pha. => Ud = 0,9.U2 = 0,9 . 10 = 9(V). - Chn Id = 100mA = 0,1A, ta c: Sba = 1,48 . Ud . Id = 1,48 . 9 . 0,1 = 1,33 (VA). Itb valve = Id = 0,1/2 = 0,05 (A) = 500mA. - Vi Uvalve = 0,7V => => Pth valve = 0,7 . 0,05 . 2(valve) = 0,07(W). Vi 3 cun dy trong W3, ta c:
Sba = 3 . 1,33 = 3,99(VA) 4 VA. Pth valve = 3 . 0,07 = 0,21(W). => Sba th cp = Sba W2 + Sba + Pth W2 + Pth W3 = 52,5 + 4 + 2,814 + 0,21 = 59,424(VA). - Theo bng tra Cc tham s tnh ton cho bin p cng sut nh (Trang 159 - Ti liu hng dn thit k in t cng sut), ta chn s b: = - Vy:
S2 = 0,85 . S1
59,424 = 69,9(VA) 70VA . 0,85 S ba .10 2 - T cng thc: S th .S cs = v bng tra Cc tham s tnh ton cho bin 2,22. f .Bmax . .k th .k cs S baW 1 =p cng sut nh ta c:
S th .S cs =
59,424.10 2 = 79,38 79,4 2,22.50.1,31.2,2.0,9.0,26
- Theo bng tra Li thp k thut in (Trang 473 - Ti liu hng dn thit k in t cng sut), ta chn c li thp k thut in l loi li 20x40 c cc thng s tng ng: a = 20 H = 70 Gt = 990(g) h = 50 Qt = 7,28 c = 20 Ltb = 17,4 S(50Hz) = 70VA b = 40 Qt.Qc = 80 C = 80. Vt = 125 S(400Hz) = 400VA.
SVTH: Nguyn Phc on
Trang 19 / 24
AXC 3 pha khi ng C KB roto ngn mch
Mn: in t cng sut
b
b = (1 - 1,5 )a c = (0,6 : 0,8)ac h H a/2 a a/2
h = (2 : 3)a
C
+ Xc nh tn hao li thp: - T cng thc Pth = pth . Gth.
P (w/kg)7 6 5 4 3 2 1 0 0,4 0,8 1,2 20 B(T) 0,9 1,6 9,1 100 80 60 40
q (VAR /kg)
B(T) 0,4 0,8 1,2 1,6
Hnh a th tn tht ring trong li thp
Hnh b
- Theo th tn tht ring trong li thp hnh a, ta c: Gth = 990 tng ng vi pth = 0,9. => Pth = pth . Gth = 0,9 . 0,99 = 0,891 (W). + Xc nh thnh phn dng t ha:
I xa =
Pth 0,891 = = 0,015( A) S ba 59,424 + 0,891
- Theo th tn tht ring trong li thp hnh b, ta c: qth = 9,1 tng ng vi pth = 0,9. Do :
I xp =
Qth qth .Gth 9,1.0,99 = = = 0,15( A) S ba S ba 59,424 + 0,891t yu cu.
2 2 I x % = I xa + I xp .100% = 0,015 2 + 0,15 2 .100% = 15% =>
+ Tnh s vng cc cun dy: - Ta c cc gi tr: E1 = U1(1 0,01. U1%) = 380(1 0,01 . 5) = 361(V). E2W2 = U2(1 + 0,01. U2%) = 17,1(1 + 0,01 . 9,5) = 18,7245(V). E2W3 = U2(1 + 0,01. U2%) = 10(1 + 0,01 . 9,5) = 10,95(V). - T ta c s vng dy ca bin p l:SVTH: Nguyn Phc on Trang 20 / 24
AXC 3 pha khi ng C KB roto ngn mch
Mn: in t cng sut
W1 = W2=
E1 .10 4 361.10 4 = = 1551,6(vng ) 4,44. f .Bmax .S th 4,44.50.1,31.8 E 2W 2 .10 4 18,7245 .10 4 = = 80,5(vng ) 4,44. f .Bmax .S th 4,44.50.1,31.8
=> Chn W1 c 1560 vng.
=> Chn W2 c 85 vng.
E 2W 3 .10 4 10,95.10 4 = = 47,065(vng ) W3 = 4,44. f .Bmax .S th 4,44.50.1,31.8
=> Chn W3 c 50 vng.
- W3 gm 3 cun dy bng nhau v mi cun c s vng dy qun l 50 vng. 8- Tng hp linh kin v s chi tit mch iu khin: a/ Bng tng hp linh kin:LINH KIN 1- Mch lc - Valve lc - Cc phn t bo v T588N L = 3H/7vng C = 0,25F R = 12/3W THNG S LINH KIN 2- Khu ng b - D1, D2 - OA - R0 - R1 - R4 - P1 3- Khu to in p rng ca - Dz1 - D3 - C1 - R2 - R3 - P2 5- Khu So snh - R8, R9 10K BZX79A10 1N4002 220nF 3,9K 56K 100K/chnh = 50K - T1 - Dz2 - C2 -R - R5 - R6 - R7 - P3 - P4 - P5 6- Khu To dng xung - C3 - R10 - Dz3 1nF 4,7K 1N2808 7- Khu Tch xung - IC Logic AND - IC Logic OR - D4, D5, D6 - R11 8- Khu Khuch i xung - T2 - T3 - R15 - R16 - Bin p xung BD135 BC107 15K 10/2W Li E = 814E250 W1 = 110 vng W2 = 55 vng - R12 9- Mch cp ngun DC - IC n p +15V - IC n p -15V - C01, C02 - C03, C04 - C05, C06 - D01 D06 LM7815 LM7915 1000F 100F 0,1F 1N4002 HC4081B CD4071B N4001 10K 15K 1N4002 TL082 10K 15K 10K 10K/chnh = 5K C828 1N2816 330F (t ha) 10K 4,7K 20K 4,7K 50K/chnh = 20K 10K/chnh = 5K 1K/chnh = 500 THNG S
4- Khu To lut iu khin
SVTH: Nguyn Phc on
Trang 21 / 24
b/ S chi tit mch iu khin:
III- M PHNG MCH LC: 1- Dng in ti:ng c tuyn iu khin vi ax = 150o v min = 0o
- Theo biu trn, ta c th nhn thy trong phm vi gc m valve max = 150o th dng in ti c gi tr nh, iu ny ng vi thi im khi ng ng c. Khi gc nh dn th dng in ti cng tng dn n gi tr nh mc. 2- in p ra ti:
- Theo biu in p ra ti ta cng c th nhn thy ti thi im max = 150o th in p ra ti c gi tr nh tng ng vi thi gian khi ng ng c. Khi gc bt u gim dn v 0 th in p ra ti cng bt u tng dn cho n gi tr nh mc. 3- Xung pht m valve ca cc pha:
KT LUNSau qu trnh hc tp v nghin cu, cng vi s hng dn ca thy Phm Quc Hi, em hon thnh c n mn hc in t cng sut vi ti l Thit k h thng khi ng mm ng c bm nc s dng ng c khng ng b ba pha kiu roto ngn mch. Trong ni dung nghin cu v thit k n ny, em thc hin c cc nhim v sau: Tm hiu cng ngh v yu cu i vi vic khi ng ng c. p dng c kin thc c ging dy thit s nguyn l mch ng lc v mch iu khin h thng. p dng bi hc vo vic tnh ton v chn linh kin cho vic thit k.
Hin nay, tuy n ny hon thnh, nhng do kinh nghim bn thn cha c nhiu nn chc chn s c nhiu thiu st trong thit k. Em mong rng s nhn c s gp ca thy v cc bn n c th hon thin hn v bn thn em cng c thm kinh nghim trong thit k.
XUT- Tha thy, v y l ln u thc hin n nn bn thn em cng cn thit st mt s vn , em nhn thy rng theo nh thit k hin ti ca em th mch s hot ng sut trong qu trnh ng c hot ng, do vy s lm gim nhanh tui th ca nhng linh kin. - Do vy, theo em, ta c th lp thm mt mch chuyn i khi ng c hon tt thi gian khi ng v t c gi tr nh mc v dng in v in p th mch s c nhim v ngt mch lc v mch iu khin ra khi ngun lc v lc ny th ng c c cp ngun thng qua mch khi ng t dng contactor v aptomat bo v. Nh vy th cc linh kin ca h thng khi ng mm s t c tui th cao hn.
TI LIU THAM KHO1- Sch Hng dn thit k in t cng sut
Tc gi: Phm Quc Hi. Tc gi: V Minh Chnh (Ch bin) Phm Quc Hi Trn Trng Minh Tc gi: Phm Quc Hi Dng Vn Nghi Tc gi: L Phi Yn Lu Ph Nguyn Nh Anh
2- Gio trnh in t cng sut
3- Sch Phn tch v gii mch TCS 4- Sch K thut in t
5- Internet (Databook, Datasheet, .......)
PHN MM M PHNG1- Phn mm m phng mch in Tina 2- Phn mm m phng mch in Psim
M phng phn iu khin. M phng mch lc.
