Tieu Luan EMC Ngoc Cao Hoc K21 Nop Thay

7/27/2019 Tieu Luan EMC Ngoc Cao Hoc K21 Nop Thay

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Tiu lun mn hc: Tm hiu tng thch in t trong h thng thit b sunroof t ng ca xe c

Chng 1:

GII THIU

1.1 KHI NIM V TNG THCH IN TNhiu giao thoa in t (EMI: Electromagnetic Interference) c nh ngha nh mt

tn hiu in khng mong mun, n em li nhng kt qu khng mong i trong h thng.

Chng hn, trong cc phng tin xe c hin i, EMI gy ra nhiu ting n popping c

nghe t radio, gy ra s trc trc cho b iu khin thm ch c th dn n nhng tai nn

nghim trng. Thut ng EMC (Electromagnetic Compatibility: nhiu in t) lin quan

n mt h thng in t c kh nng thc hin chc nng tng thch vi cc h thng

in t khc v khng to ra hoc khng nhy vi nhiu.Nu mt h thng l EMC th phi tha mn ba tiu chun sau:

Khng gy ra nhiu vi cc h thng khc.

Khng nhy vi s pht x t cc h thng khc.

Khng gy ra nhiu cho chnh n.

Hnh 1.1: Ba yu t trong tin trnh EMI

Tm li, cc vn ca EMC lin quan n s pht sinh, s truyn v s thu nhn nng

lng in t. Hnh 1.1 minh ha ba yu t ca mt vn EMC: ngun to ra s pht x,

v ng ghp ni mang nng lng pht x chuyn t ngun n b thu, v v vy nng

lng in t khng mong mun c chuyn i thnh mt s tc ng khng mong i.

Bng cch chia ng ghp ni thnh hai loi, c hai nhm nh cho vn EMC, l:bc x v dn.

T quan im ca b thu v b pht, cc vn EMC c th c chia thnh Pht x in

t (EME: Electromagnetic Emission) v nhy in t (EMS: Electromagnetic

Susceptibility). Tiu lun s tp trung vo vn lm th no gim pht x.

C ba cch c p dng lm gim nhiu bc x v nhiu dn.

Hc vin: Trn Th Phng Hoi Ngc Trang 1


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Trit s pht x ti ngun pht.

Lm v hiu ha ng ghp ni cng nhiu cng tt.

Lm cho b thu min dch vi ngun pht.

1.2 CC IU KIN C TNG THCH IN T

Trong ngnh cng nghip t ng, mt vi yu cu v EMC t ra cho sn phm in t

c ci t trong phng tin xe c. Cc yu cu ny c ra lnh bi cc c quan nh

nc. Nhng qui nh ny l nhng yu cu hp l mang tnh bt buc, c ngha l thit b

trong qui nh th khng th c bn khi khng tun theo nhng qui nh EMC ny.

Trong ngnh cng nghip t ng, hu ht EMC lin quan n cc qui lut v cc qui nh

c lit k trong Bng 1.1.

Bng 1.1: Cc tiu chun quc t v khu vc c s dng trong ngnh cng nghip t ng

Hi ng Chun Ni dungIEC CISPR-12 Cc phng tin xe c, thuyn my v cc thit b dn ng

d bt la Cc c tnh nhiu radio Gii hn v phng

php o.IEC CISPR-25 Cc c tnh nhiu radio bo v cc b thu c s dng

on board trong cc phng tin xe c, tu thuyn v cc

thit b khc Gii hn v phng php o.

SAE SAE-J551 Th tc v gii hn o tng thch in t i vi phngtin xe c v thit b.

SAE SAE-J1113 Th tc v gii hn o tng thch in t i vi cc

thnh phn phng tin xe c.ISO ISO 7637 Nhiu in bng cch dn v ghp.ISO ISO 10605 Cc phng tin xe c trn ng i Cc phng php

kim tra i vi nhiu in qua vic phng tnh in.EU 95/54/EC iu khin EMC t ngJASO JASO 7637 Yu cu v nhy in t t ng

ISO ISO 11451 Nhiu in bng cch bc x nng lng in t bng hp Cc phng php kim tra trn xe c

ISO ISO 11452 Nhiu in bng cch bc x nng lng in t bng hp

Cc phng php kim tra thnh phn



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Chng 2:

TNG THCH IN T TRONG H THNG THIT BSUNROOF T NG CA XE C



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2.1 H THNG THIT B SUNROOF TRONG XE C

2.1.1 Cu trc ca h thng thit b sunroof

H thng thit b sunroof trong xe c thng thng c ba phn chnh. l: cu trc

thit b sunroof, b SCU (Sunroof Control Unit: b iu khin Sunroof) v mt. Hu nh,chng c mua t cc nh cung cp khc nhau, v nh thit k b SCU chu trch nhim

thit k tc ng ca b SCU n vic m, ng panel knh v tp trung cc yu cu ca

nh cung cp h thng thit b sunroof. Cc h thng thit b roof c nhiu hnh dng khc

nhau trong cc xe t. Kiu ph bin nht l thit b sunroof thng gi trt nghing.

Panel knh c hai ch m, l ch nhc ln v ch trt. Ch nhc ln em

li s thng gi khi tri ma m khng b t, cn ch trt s cho php khong tip

xc vi khng kh ln nht.Mt h thng thit b sunroof in hnh nh trong hnh 2.1.

Hnh 2.1: H thng thit b sunroof in hnh

B SCU v mt c lp t c nh trong cu trc sunroof. Truyn ng bnh rng

trong trc ca mt dn hai si cp qua cc bnh rng chuyn i chuyn ng quay

thnh chuyn ng thng ca panel knh. V l do an ton, cu trc thit b sunroof c

gn c nh trong xe. B SCU, mt v thit b sunroof c gn vo trong thn xe. Cc

m ca ngun in c u vo thn xe, nhng kt ni in gia v mt v thn xe

khng c nh r. l yu t EMC quan trng v c thit k theo cch nh th

t c mc EMI thp nht.



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Mt b chuyn mch c lp t cho vic iu khin thun tin. Cp ca b chuyn

mch kt ni b chuyn mch vi SCU v cc dng ca ngun. Mt c kt ni vi

SCU qua cp mt. Hu ht cp mt s dng cp hai si khng bc. B SCU cng c

cp ngun bi cp hai dy khng bc, sau y n c gi l cp ngun-SCU. S u

ni in trong h thng thit b sunroof nh trong Hnh 2.2. Phm vi di cp cng ccho.

Hnh 2.2: u ni in ca mt h thng sunroof in hnh

2.1.2 Hot ng ca thit b sunroof

C hai ch vn hnh thit b sunroof. Ch th nht l bng cch chuyn mch.

C ba v tr trong b chuyn mch, hai v tr trt l trt m v trt ng, v tr n nt

ngha l dng. Cc in tr vi gi tr khc nhau c chuyn hng bng thit b chuyn

mch nh dng ba v tr. Ch th hai l qua B iu khin mng vng (CAN:

Controller Area Network). Dy bus ca b CAN c kt ni vi SCU chuyn i

thng tin t b iu khin trung tm. Khi ng c ngng, cho an ton, thit b roof sc ng mt cch t ng, y lnh ng c gi trc tip qua dy bus ca CAN.

Khi thit b chuyn mch trt n v tr m hoc v tr ng, b SCU pht hin c

trng thi ny v iu khin FET lm hot ng rle. Rle c kt ni iu khin

cc mt mt chiu nh mt mch cu H. u im ln ca mch cu H l mt c th

c truyn ng v pha trc hoc pha sau. Hu ht cc loi mt dn ng SCU theo



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cch ny. Khi rle hot ng hoc ngh, mt c kt ni hoc khng kt ni n ngun

ngay tc th. y gi ln tc ng ny l khi ng nhanh hoc ngng nhanh. Loi SCU

ny sau y c gi l SCU truyn thng.

Trong nhng nm gn y, sn phm thit b SCU mi s dng PWM (Pulse Width

Modulation: iu ch rng xung) iu khin ngun MOSFET m c t trong ccchui mch vng chnh ca mt, c c s iu khin vi tc thay i. Bng vic

thay i chu trnh hot ng mt cch tri chy t 0% n 100% v t 100% n 0%, mt

c th c bt u v ngng mt cch nh nhng. y gi th tc ny l khi ng

mm v ngng mm vi PWM. Hin ti ch c mt sn phm thuc cu trc kiu ny,

PWM s c s dng rng ri hn trong tng lai. Mt b SCU nh vy c gi l

PWM SCU.

Mt vng ring t tnh nh c gn c nh xung quanh trc ca mt, nh minh ha

trong Hnh 5.2. Khi mt quay, t trng c to ra khi vng ring thay i. Ln quay ca

trc mt c m bng con IC cm bin Hall trong b SCU. Sau khi kim nh trong

nh my, b SCU ghi nh v tr m hon ton v ng hon ton. Bng phng php ny,

SCU s ngng mt mt cch nh nhng khi panel knh c m hoc ng hon ton.

2.1.3 Cc vn tng thch in t chnh trong thit b sunroof

Theo p ng t nh cung cp h thng thit b roof v vn gp phi khi thit k v

th nghim, chng ta c nhng vn EMC chnh nh sau:

Khi y cng tc ln, nhiu ting n popping xut hin.

Khi mt ang chy, nhiu s xut hin v nhiu sinh ra khi mt o chiu.

Trong tc ng ngng nhanh ca PWM SCU, hoc trong tc ng khi ng

nhanh hoc ngng nhanh ca SCU truyn thng, sinh ra ting n popping c

nghe t sng AM ca radio. Khi mt ang vn hnh trong ch PWM, chu trnh hot ng thay i gia

0% v 100%, EMI vt tri trong mt s bng tn. N xy ra trong tc ng ca

khi ng mm hoc ngng mm.



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Trong tiu lun ny s phn tch cc vn trn thy cc yu t no hu nh lin

quan n nhng vn ny, v bng cch no chng c th c gii quyt mt cch hiu

qu.

2.2 CC M HNH CHUNG2.2.1 M hnh cp

Cp c s dng trong h thng thit b sunroof ni SCU vi mt v ni SCU vi

ngun cung cp. Chng c t gn nhau v song song vi nhau. Nu chng ta b qua

cc ch bc cao hn v gi s ch in t ngang (TEM: Transverse ElectroMagnetic)

l ch truyn theo ng thng, chng ta c th chia cp thnh t theo nhng phn nh

ca dy dn, v mi phn c th c thay th bng mt m hnh mch tham s tp trung

lin quan n cc tham s theo n v di.Hnh 3.1 trnh by mt on dy c chiu di z tng ng vi mt mch in nh

sau:

Hnh 3.1: Mch in tng ng ca mt on gm hai dy dn

Trong , 1R v 2R l in tr ca hai dy dn, 1L v 2L l in cm ca hai dy dn,

v 1C v 2C l in dung gia hai dy dn. B qua dn in ca mi trng in mi.

L do ti sao y tch cc tham s cho hai dy dn l v thng thng si cp bao gm

hai dy cn bng nhau v khng bao bc.

Mch tng ng ny c th c s dng d on tn hiu ch sai khc, m

phm vi ch yu l di 2 MHz.

Trong phm vi tn s cao, dng ch chung (CM: Common Mode) tr nn chim u th

v s nh hng ca tham chiu cn phi c xem xt. V hu ht trong cc trng hp,

cc dy u c gn c nh gn vi thn xe, nn n to ra tham s tp nhiu v tham s



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ny tr nn c hiu lc khi tn s cao. Mch tng ng c dng nh ch ra trong Hnh

3.2 sau:

Hnh 3.2: Mch cp mt

Trong , 3C v 4C c thm vo c trng cho in dung gia 1 dy dn v tham

chiu, v 5C v 6C l in dung gia dy dn cn li v tham chiu. y xem nh b

qua in cm tham chiu. in cm tng h gia hai dy dn cng khng xt n, bi vvn chnh l dng ch sai khc (DM: Differential Mode) gia hai dy dn gii thiu

dng CM trong tham chiu nh th no.

Nu di bc sng ca thnh phn tn s cao nht t ngun tn hiu di hn nhiu so

vi khong cch ln nht ca dy truyn dn, chng ta ni rng dy truyn dn ny l

ngn in. Trong tnh hung nh vy, s phn b dng in gn nh ng u trn dy

dn. Cp c th c thay th bng mt on mch in biu th y i vi cc tn s

ln n mt vi MHz.

2.2.2 Cc tham s trn di n v (PUL: Per-Unit-Length) ca cp

Trong h thng thit b sunroof, v yu t gi thnh nn cp ngun-SCU v cp mt l

i dy khng xon v khng bc.

2.2.2.1 in tr

i vi thanh ng cng, in tr c tnh nh sau:

][

=

S

lR

(3.1)

Trong , 7108.5 = m/S l in dn sut ca ng.

S l tit din ca thanh ng, c n v l m2

l l di ca thanh ng, c n v l m



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Do hin tng hiu ng b mt, dng s tp trung gn pha bin bn ngoi khi tn s

cao. su b mt c xc nh nh sau:

][1

0

mf

= (3.2)

Do , n v di in tr ca si dy s thay i theo tn s, theo cng thc sau:

i vi cp in hnh c s dng trong thit b SCU, vi c dy theo tiu chun M

AWG18 (AWG: American Wire Gauge), n l mt dy dn gm 19 si dy c bn knh

0.127mm, ta c th tnh in cm v in dung bn ngoi ca n xp x ca mt si dy cng knh 1.02 mm.

Hnh 3.3 cho thy in tr theo tn s ca mt mu cp mt.

Hnh 3.3: Mu in tr ca cp mt theo tn s

2.2.2.2 in cmin cm ca dy dn ng vai tr ch yu trong vic quyt nh c tnh ca mch

tn s cao. Hnh 3.4 ch ra hai dy trong mt dy mang dng nng lng v mt dy

mang nng lng tr li dng.


vi

vi(3.3)


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Hnh 3.4: in cm gia hai dy dn song song

Cng thc 3.4 cho thy t cm trong hai si cp c bn knh bng nhau:

)ln(104 7

r

dlL = [H] (3.4)

Cng vi cp AWG18, ta gi s rng khong cch ca hai si cp l 2 cm v di l 1

m th in cm ca n bng 1.47 H .

V cp c t trn b mt ca thn xe, ta s xt n nh hng ca mt tip t.

Trong Hnh 3.5, dy dn c t cch mt tip t mt khong h. Dy dn ny mang dng

nng lng v mt phng tip t mang nng lng tr v dng.

Hnh 3.5: in cm gia dy dn v b mt kim loi

Cng thc 3.5 a ra t cm ca dy dn qua mt tip t.

= r

hlL

2ln102

7 [H]

(3.5)



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2.2.2.3 in dung

in dung l mt tham s PUL quan trng khc. tn s cao, in dung k sinh c th

tr thnh mt ng dn cng hng dn n dao ng.

Cng thc 3.6 cho ta in dung trong hai si cp c bn knh bng nhau:

=

r

dlC

ln

10778.2 11

[F]

(3.6)

Hn na vi cp loi AWG18, ta gi s rng khong cch gia hai si cp l 2 cm v chiu

di cp l 1 m. in dung gia chng l 7.5pF.

Cng thc 3.7 cho ta in dung gia mt si dy v mt tip t l:

=

r

hlC

2ln

10556.5 11

[F]

(3.7)

Vi cp loi AWG18, ta gi s rng khong cch gia cp v mt tip t l 5 cm v di

l 1 m. in dung gia chng l khong 10.5pF.

2.2.3 Ph tn hiu

Ph ca mt s tn hiu tun hon chung m chng ta s gp trong tiu lun ny c lit

k ra di y:

Tn hiu PWM l mt dng sng hnh thang tun hon nh Hnh 3-8 ch ra:

Hnh 3.8: Mt on ca dng sng hnh thang tun hon



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y, r l thi gian ln, f l thi gian xung, T l chu k ca dng sng, l thi

gian m bin ln hn 1/2 bin cc i. Tham s quan trng khc l chu trnh hot

ng c nh ngha bng T/ .

Hai ng tim cn c th c s dng v cc gii hn i vi bin ph ca tn

hiu tun hon trn.

Hnh 3.9 cho thy hai ng tim cn ca ph tn hiu i vi dng sng hnh thang.

Hnh 3.9: Cc ng tim cn ca ph c dng sng hnh thang

Bng cch thay i mt s tham s thit k, chng ta bit tc ng ca cc tham s ny.

Bng vic gim thi gian ln v xung, tn s gc th hai s di chuyn n mt tn

s thp vi cng chu trnh lm vic. Tn s gc th nht s di chuyn n tn s thp bng cch gim tc lp li vi

cng chu trnh lm vic.

Vic gim chu trnh lm vic lm gim ni dung ph tn s thp ca dng sng,

nhng n khng c bt k nh hng no n tn s cao.



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Mt dng sng c bit khc tho lun y l dng sng hnh tam gic, m rt ph

bin trong gn sng dng in chuyn mch. Dng sng tam gic in hnh c ch ra

trong Hnh 3.10.

Hnh 3.10: Mt on dng sng tam gic tun hon

Dng sng tam gic c th c cp n nh mt trng hp c bit ca dng sng

hnh thang, trong chu trnh hot ng l 50%. Theo cc tc ng ca cc tham s chng

ta tho lun trc , chu trnh hot ng khng c tc ng quan trng no ti tn s

cao, v tham s quyt nh vn l thi gian ln v thi gian xung, quyt nh tn s gc

th hai.

Dng sng c bit sau cng hu nh xut hin trong dng in ca it qun tnh. Thi

gian ln ca bin trc rt ngn, thng thng l 100ns. Bin xung theo mt ng cong

hm m.

Hnh 3.11: Mt on ca dng sng tun hon



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i vi cc chui Fourier, chng ta c h s gin n nh sau:

Khi Tr


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2=R (3.10)

Bn trong bn knhR, n l trng gn, trong khi ngoi bn knh n thuc trng xa.

Hnh 3.12: ng gp chim u th ca thnh phn trng gn v trng xa

Hnh 3.12 ch ra gii hn gia min trng gn v min trng xa thch ng vi tn s.

y, ng-ten c t cch b phn ang th (DUT: Device Under Test) 1m trong php

o bc x pht ra. y v cc khi ch ra cc phm vi tn s quan tm trong Hnh 3.7.

R rng Hnh 3.12 cho thy tt c cc nhiu bng hp v phn chnh ca nhiu bng rng

t DUT l ch bc x trng gn.

2.2.4.3 M hnh cc bc x pht ra

t c m hnh ng-ten thc t, hai m hnh n gin nht, tc l dy dn ngn v

mch vng nh c xem xt u tin.

i vi mt lng cc in c bn, vect cng trng nh sau:



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y, /20 = , l gc im cc n bn knh r, v di ca dy dn ngn


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Trong : L l di ca dy dn, n v m.

nf l tn s tn hiu ph, n v Hz.

nI l dng tn hiu ph, n v A.r l khong cch t nn nhn n ngun, n v m.

2.3 B CHUYN MCH

2.3.1 Cc b chuyn mch l tng

M hnh ca mt chuyn mch l tng c c bng cch gi nh:

Thi gian chuyn tip i vi vic m hoc ng chuyn mch cng ngn cng tt.

Cc qu trnh chuyn tip ca vic m hoc ng th chc chn v khng c hin

tng ny ln.

Khi chuyn mch ng, in tr bng khng.

in cm k sinh trong cu ch ca b chuyn mch c th b qua.

Hnh 4.1 trnh by mch tng ng c n gin ha ca b SCU. Trong cc b

chuyn mch c s dng m phng tin trnh ca s kin ng v m ca rle, v

mt c c trng bng 1R v 1L .

Hnh 4.1: M hnh chuyn mch l tng

p dng nh lut ip p Kirchhoff (KVL) v nh lut dng in Kirchhoff cho Hnh 4.1,

ta c c cng thc sau:



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Trong 1V l in p gia hai u ni ca chuyn mch v i l dng in chy dc

theo vng dy. Khi chuyn mch 1U ang ng, dng s tng theo hm m n 1/RVs

vi hng s thi gian ca 11 / RL . Trong qu trnh chuyn tip khc, khi chuyn mch c

m vi gi s thi gian chuyn tip bng khng, dng trn mch vng i t ngt thay i

v 0. Ti thi im , in p qua in cm )/(1 dtdiL ln v cng, v in p qua

chuyn mch cng ln v cng lm cho Cng thc 4.1 cn bng. Khng mt thit b

no trong thc t chu c in p v cng, v vy phi c mt trng hp khc i vi

mch thc t.

2.3.2 M hnh ha chuyn mch thc t

Trong mch thc t, in dung k sinh gia hai u cui ca ti cn phi c xem xt.

Hnh 4.2 trnh by mt m hnh ci tin.

Hnh 4.2: M hnh ci tin ca chuyn mch (1)

Bng cch thm vo t in, khi mt chuyn mch c m, nng lng d tr trong cc

cun dy s khng to ra in p v cng, nhng np cho t in 1C . Nng lng ny s

khng thay i qua li gia in dung 1C v in cm 1L sau khi t in p cc i, v

c tiu th bi 1R . Dao ng ny tt dn v gim v khng khi kt thc.

Bng cch gii phng trnh vi phn bc hai, chng ta bit c tn s ca dao ng ny

l:

11

12

1

CLf

= (4.2)

in p cc i gia cc u cui ca ti l:

1

10max2

C

LiV = (4.3)



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Trong , 0i l dng in trc khi chuyn mch m v du l do sc phn in ng

(EMF: electromotive force: sc in ng) ca in dn.

Mch trn xem nh hon ho, nhng khi chng ta xem qua phn ngun ca mch ny, th

khng th b qua in cm ca cp cung cp ngun. Cng vn ny sinh l khi chuyn

mch m, nng lng c lu tr trong in cm ca dy dn cn gii phng; ngc li

c mt in p v cng c to ra trong dy. Khi , m hnh ny c ci tin nh hnh

4.3 sau:

Hnh 4.3: M hnh ci tin ca chuyn mch (2)

vn thc t, n ph hp vi phng php m hnh cp theo l thuyt truyn dn. Khi

cp b ngn v mt in, ngha l:

2


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22

32

1

CLf

= (4.6)

V 2R , 2L , 2C nh hn nhiu so vi 1R , 1L , 1C , v do tn s vng 3f ti phn

ngun cao hn nhiu so vi tn s 1f c to ra ti phn ti.

Chng ta bit rng in cm ca dy v in dung k sinh phi c xem xt t phn tchtrn. Trong trng hp cc tr, khi c hai in dung k sinh v in cm ca dy rt nh, s

cng hng tn s rt cao c d on bi cng thc trn khng xut hin trong kt qu

o. Nguyn nhn l do mt vi h s ch yu trong khi hnh thnh mt dao ng.

Bng cch m phng trn my tnh, chng ta bit rng dao ng s c to ra ch nu thi

gian chuyn mch ngn. Chng ta nh ngha tham s sau:

LC

P

2

1 = (4.7)

l t s ca thi gian qu ca chuyn mch i vi chu k ca dao ng gi nh.

Bng cch p dng tham s thay i trong m phng, chng ta c cc kt qu theo sau.

Hnh 4.4 trnh by dng sng ca dao ng khi 11 =P .

Hnh 4.4: Dng sng ca dao ng khi 11 =P

Hnh 4.5 trnh by dng sng ca dao ng khi 101 =P .



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Khi iu kin theo sau c tha mn, dao ng s tr thnh mt qu trnh qu phng

trong mch RLC.

251>P (4.8)

l mt tiu chun trnh dao ng. Chng ta phi la chn 1P ln hn 25. Dng

sng qu ny c th c thy trong Hnh 4.6.



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Tr khng s quyt nh thi gian suy gim ca dao ng. Dao ng ny s suy gim mt

cch nhanh chng nu in tr ln. Hnh 4.7 ch ra s so snh gia hai cu hnh khi

= 5.02R v =52R .

Hnh 4.7: So snh dng sng ca dao ng khi 202 =P v 2

Tiu chun tng t c th t c bng cch m phng. Chng ta nh ngha 2P nh

sau:

RC

P=2 (4.9)

2P phi c chn nh hn 2 trnh dao ng.

S thay i t ngt ca dng in cng l mt h s quyt nh bin ca dao ng.

Hnh 4.8 trnh by s so snh gia cc s thay i dng in sai khc.



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Hnh 4.8: So snh dng sng ca dao ng vi s bin i dng in sai khc

Kt lun: dao ng c th c chn bi th tc theo sau:

Tng thi gian qu ca chuyn mch

Chn thm s suy gim lm tt dn dao ng.

Lm gim s thay i t ngt dng in bng cch chn mt cu hnh mng tt.

2.4 MT

2.4.1 Cu trc ca mt

Khi m t mt mt c trng, vi thut ng c s dng trong kt ni vi mt

s c nh ngha u tin mt cch r rng. Chng ta s dng thut ng theo sau trong

ti liu ny:

Vng: l mt vng quay hon chnh ca dy dn. Thng thng mi vng trong

ng c nam chm vnh cu DC (mt chiu) bao gm mt b dy dn, v mi dy dn

c bao bc bng vt liu cch in tch ri tng dy vi nhau.

Cun dy: Mi cun dy bao gm nhiu vng, v phn cui ca cc cun dy c

hn dnh vo b gp in. N c xem nh l cun dy phn ng in.



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Rto: l phn quay bn trong ca Stato. Khe ct dc theo b mt ca rto cha cun

dy phn ng in. Rto cn c gi l phn ng.

B gp in: l mt b chuyn mch c c lp rp bng mt vng cc on kim

loi ng hay cn c gi l thanh ng. Khi rto quay gia cc cc v i qua mt gc

c bit, lc qun tnh s lm cho chi qut tip xc vi thanh ng k tip, v vy lc in

t c gn vo rto gi cng hng.

Trc: c dng chuyn i phn quay sang ti qua mt ng ren xoy c. Mt

vng sinh t c gn c nh trn trc. Do vy, IC cm bin Hall trong b SCU c th

pht hin phn quay ca trc.

Chi qut: Thng thng, n c lm t than ch graphit v c h s in tr thp.

Nh thanh y l xo pha sau, n gi vic tip xc vi b gp in khi n trt trn b mt

ca n.

V: l mt hnh tr kim loi rng v c np. N cng cn c gi l khung hoc

lp bc. Trong hu ht cc mt, cc t trit ghp v cc b cm bin c tch hp bn

trong b mt np.

Stato: l mt phn hnh tr xung quanh rto nhm to ra trng t. Trng t c th

c to ra bi mt dng in trong cun dy stato hoc bng mt nam chm vnh cu,

nhng y chng ta ni n stato s dng nam chm vnh cu. Cc cc lun phin giahng bc v hng nam xung quanh stato. Nu ch c mt cp cc cc bc v nam i

vi stato, chng ta gi n l mt 2 cc. Stato c gn vo thnh trong v mt.

Hnh 5.1 n 5.3 trnh by cc hnh nh v mi b phn ca mt.



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Hnh 5.1: Np mt bao gm chi qut v mch trit

Hnh 5.2: Rto ca mt

Hnh 5.3: V mt v b phn stato



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Mt chng ta s nghin cu l mt nam chm vnh cu c hai cc, 8 cun dy phn ng.

Trong mt ny, c tnh lun c mch trit. Mt t in c mc sun vi cc u cc ca

mt trong khi hai t in kia ni cc u cc vi v mt. y, chng ta gi t in

mc sun l t trit mc sun, hai t cn li l hai t trit ni t. Mch trit in hnh cminh ha trong Hnh 5.4.

Hnh 5.4: Mch trit v v tr ca n

2.4.2 M hnh ca cun dyL thuyt m hnh ha mt cun dy c da trn vic gi s rng cun dy l mt hp

en 4 cc. Phng php ny c tm thy trong mt s ti liu trnh by m hnh cun

dy trong mt AC (xoay chiu). Cun dy c xem nh mt s kt hp ca cc in tr,

cc cun cm v cc t in.

u tin, chng ta o tr khng gia hai cc cun dy mt. Php o c thc hin

trong phm vi tn s t 42Hz n 5MHz. Mi lin h gia in cm tng ng v tn s

c ch ra trong Hnh 5.5. in cm tng ng ca mt cun dy trong 1MHz bng 1/8

gi tr o c 42Hz. Kt qu ny cho thy rng m hnh cun dy ny tn s cao (HF)

th phc tp hn m hnh mch RL mc ni tip tn s thp (LF).



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Hnh 5.5: in cm tng ng theo tn s ca mt cun dy trong mt DCNn tng ca m hnh l mch RL mc ni tip. Mt b cm bin c trng cho in cm

ghp t cm v h cm trong s cc cun dy. in tr c gii thiu m hnh ha

in tr ca dy dn. Mc d gi tr s thay i i vi hiu ng b mt v hiu ng ln

cn nhng tn s khc nhau, y n c xem nh gi tr trung bnh c nh.

L do ti sao in cm gim tn s cao l do in dung lin im r nh hng n s gia

tng tn s. in tr cn ca t in k sinh cng cn c xem xt. Bng cch chn thm

mch RC ni tip mc song song vi mch RL gc, chng ta c mt phin bn chnh ca

m hnh cun dy.

Trong th tc tip theo, chng ta xem xt n tn hao st trong AC. Mt in tr c mc

song song vi mch RC c trng cho s tn hao ny. N lm cho tr khng u cui n

u cui thp hn mt gi tr hp l.

Sau , xem xt n in dung k sinh. N hnh thnh gia cun dy v li st cng nh

gia cun dy v v. Bng cch mc thm mt mch chui RC ni tip gia cc v t,

in dung k sinh v in mi tn hao qua ng truyn xung t c xem xt.

Chng ta c m hnh u tin cho mt cun dy tn s cao nh Hnh 5.6 ch ra:



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Hnh 5.6: Mch tng ng tn s cao ca mt cun dy (1)

M hnh ny c ph duyt qua php o tr khng ca u cui n u cui v u cuin t m c thc hin trn mt mt th nghim. cho chnh xc, mch trit

c b i.

Vic chn gi tr ca cc thnh phn ny cho m hnh th r rng l quan trng v kh

khn. Ngn ng MATLAB c s dng so snh gi tr tr khng c tnh ton i

vi kt qu o. Bng cch iu chnh ng cong, chng ta cp nht m hnh cun dy vi

cc gi tr iu chnh. Th tc ny c gi l phng php back-annotation. N cng c

th c thc hin bng cc k thut s. Chng ta tng mt ca cc im tn s xung

quanh tn s cng hng tng chi tit. Bi v vic qun cc cun dy v s phn b

in dung k sinh th khng ng u, nn tn s cng hng khng ging nhau gia cc

kt qu kim tra tr khng. Sai lch trong khong 10%. y chng ta s dng kt qu

kim tra in hnh m hnh ha cun dy.

Cc ng cong ca tr khng o c nh ch ra trong Hnh 5.7:



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(a) u cc vi t (b) u cc vi u cc

Hnh 5.7: ng cong c tnh ca tr khng (o c)

Cc tn s cng hng c th d dng quan st c qua php o. C hai tn s cnghng quan st c. M hnh c to ra bng hai mch LC song song c mc ni tip.

N c ch ra trong Hnh 5.8.

Hnh 5.8: Mch tng ng tn s cao ca mt cun dy (2)

Bng cch o, c lng ban u ca cc tham s in tr v phn khng c th t c.

Phm vi tn s t DC n 100Hz, ta c c = 45.0DCR , HLLF 260= .

V cc tn s cng hng nm ti 1.2MHz v 6MHz (bng php ngoi suy), chng

ta c c c lng ban u ca cc tham s phn khng, 1L , 1C , 2L v 4C .

Chng c th c quyt nh bng cch gii phng trnh sau:



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Trong , L l in cm c n v l HF, c th suy on bng 1/3 LFL .

Gi tr ca 3R v 6R on c qua cng thc:

63 RRR += (5.4)

Trong , R l in tr dy dn ti tn s cao. N c th c on bng 2 ln

DCR .

Gi tr ca 1R v 4R c khi to bng tr khng nh ti hai tn s cng

hng.

Bng cch s dng kt qu o tr khng ca u cc vi t, c th quyt

nh in dung khung cun dy 2C v 3C .

Cc gi tr ny l cc gi tr c khi to i vi phng php back-annotation. Tip

tc thay i chng trong mi vng th nghim cho n khi kt qu tnh ton tng ng tt

vi php o. M hnh cui cng ca cun dy mt c ch ra trong Hnh 5.9

Hnh 5.9: M hnh tn s cao ca mt cun dy trong mt DC

i vi m hnh ny, tr khng c tnh ton ca u cc vi u cc v u cc vi t

theo tn s c minh ha di y:



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(a) u cc vi t (b) u cc vi u cc

Hnh 5.10: ng cong c tnh tr khng (m phng)

M hnh ny cho thy s tha thun rt tt vi kt qu th nghim. Mch ny c ng

gi thnh mt m hnh macro v c th c ng dng trong tng lai.

2.4.3 M hnh ha s o chiu

Khi mt c lc xon, rto bt u quay v s o chiu xy ra. Bn pha ca o chiu

ca mt DC c ch ra trong Hnh 5.11. Sau pha (d), mt trong pha (a) lp li v dn

n mt chu k mi khc.

(a) Trc khi o chiu (b) Bt u o chiu



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(c) Trong khi o chiu (d) Ngng o chiu

Hnh 5.11: Bn pha trong s o chiu mt DC

Trc khi o chiu, dng in tch gia cc ng dn song song trong vng xon mt

nh trong Hnh 5.11(a). Khi bt u o chiu, mt trong nhng cun dy ca mi trnh t

trong mt c lm ngn trc khi o chiu dng in trong cun dy . Nng lng

c lu tr trong cun dy s to ra mt s tng vt in p gia cc phn cui o chiu.

Mt vi tnh hung khc xy ra khi ngng o chiu. C ba cun dy trong hai ng dn

song song khi mt trong khi o chiu. Thm mt cun na tham gia ng dn song

song trong pha (d). S thay i t ngt ca dng in trong cun dy dn n mt in p

kch thch nh trong Hnh 5.11(d).

Cc ngun nhiu ny kch thch cp mt qua mt ng dn tn s cao nh Hnh 5.12

trnh by. Dng in ch chung ny s l nhiu bng rng v bc x hiu qu t cp

mt.

Hnh 5.12: Dng in ch chung c to ra nh th no

Mt mch n gin c s dng m phng s thay i t ngt ca lu lng dng

trong ng truyn nng lng xy ra khi o chiu. Php o hm theo phng php ton

hc cng c a ra nhm gii thch s to ra EMI t quan im v nng lng.



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Hnh 5.13: M hnh o chiu c n gin ha

Mi s o chiu c m hnh ha khi m hoc ng chuyn mch nh c ch ra trong

hnh trn, 1S c m v c ng bi ngun in p. Khi 2L c lm ngn, n cng

tin trnh vi khi bt u o chiu.1

S

m c trng cho tin trnh ngng o chiu. y, chng ta c s d on ca lu lng dng vo 1L v 2L .

Hnh 5.14: Kt qu m phng ca dng in trong cun dy

By gi, chng ta a ra mt o hm s dng l thuyt mch. Chng ta cng chia dng

sng thnh 4 pha, trong pha (a), dng ca 1L ang tng ln; trong pha (b), dng bt u

gim; trong pha (c), dng tip tc gim; trong pha (d), dng thay i t ngt. Chng ta

khai trin n theo trc thi gian nhn c r hn.

Hai ng tim cn c minh ha bng ng nt t l hai gi tr dng in ti hn nu

chu k di.



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Hnh 5.15: Cc pha ca dng in nht thi

Bn pha ca dng in ny thay i tng ng vi bn pha ca s o chiu c minh

ha trong Hnh 5.11.

Trong pha (a), dng in gim t HI n LI , khng th t ti gi tr ti hn v chu k bt

u mt ln na sau khong thi gian ny. Hng s thi gian ca vic gim theo hm m l

1 , trong :

Trong pha (b), dng in bt u tng.

Trong pha (c), dng in tng t LI n HI , gi tr ti hn cng khng bao gi t ti

c.

Hng s thi gian ca vic tng theo hm m l 2 , trong :

Trong pha (d), khi 1S c m, dng in c s thay i t ngt. Gi s dng in trong

1L v 2L l 1I v 2I tng ng, cn trc v sau khi qu l 0t v +0t .

Ti thi im 0t , theo nh lut KCL, ta c:

Theo nh lut KCL, ta c phng trnh ny:



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Ly tch phn phng trnh trn cn t 0t n +0t v xt thy rng dng in trong cun

cm khng th bng v cng, do :

Chng ta c th c gi tr dng in ti +0t , bng cch s dng phn thit lp trong Hnh

5.13,

Khi ny sinh mt cu hi, nh chng ta bit, cun cm l mt thnh phn lu tr nng

lng, nng lng c lu tr trong t trng c thit lp bi dng in. Nng lng

th nng l:

Chng ta thy rng cc nng lng c lu tr trong 1L v 2L th khng bng trc v

sau 0t . Phi chng nh lut bo ton b ph v? Cu tr li l: Mt in p qu ln (nu

chuyn mch l l tng th in p khng xc nh) c thm vo cun cm vo thi

im m dng in b buc phi thay i. Nng lng ny c tiu th bi cc

thnh phn khc trong mch hoc bin i thnh cc pht x. Ni cch khc, phn thctrong tn hiu khng mong mun lun l ngun ca EMI.

2.4.4 Phn tch s vn hnh

Chng ta bit t phn trc, thay v chuyn mch l s o chiu, v m hnh i vi cun

dy c. Sau , y thit lp mt m hnh i vi mt vn hnh trong ch lun

chy, tc l, mt in p khng i c cung cp n mt. Bng vic b qua thnh phn

ng hc, tc rto c thit lp mt gi tr c nh i vi mi m phng.

V in cm thay i theo tn s, ta thit lp cc m hnh i vi tn s thp v i vi tns cao tng ng.

Hnh 5.16 a ra mt m hnh mt trong tn s thp. EMF c xem xt trong m hnh,

bi v n nh hng ng k n bin dng in.



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Hnh 5.16: M hnh tn s thp ca mt mt

Kt qu m phng ca dng in trong cp mt c trnh by trong Hnh 5.17.

Hnh 5.17: Kt qu m phng ca dng in ch sai khc

S dng u d dng in (Tektronix A6302), b khch i dng in (TektronixAM503B) v my hin sng (YOKOGAWA DL1540), chng ta c c kt qu o ca

dng in c cho trong Hnh 5.18. Chng ta c th thy c mt s ph hp gia php

o v m phng.



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Hnh 5.18: Dng in DM c o vi si cp di 3m (0.2A/div 0.5ms/div)

D on v tnh cht tn s cao i vi s vn hnh ca mt da trn m hnh cun dy

c tn s cao m c thit lp di y. tn s cao, tn s o chiu thp hn nhiu.

Chng ta gi s rng s o chiu lun lun xy ra trong mt cun dy m khng gy ra

bt c s sai khc no v sc phn in ng c xem xt nh mt gi tr c nh.

Hnh 5.19 trnh by mt m hnh ca mt trong tn s cao.



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Hnh 5.19: M hnh tn s cao ca mt mt

Ta s dng chuyn mch c trng cho s o chiu. Trong m phng, ta nh du v

ca mt nh vt qui chiu, v mi cun dy bn trong mt ang di ng n vt qui

chiu. Trong min thi gian, nh cao nht ca in p trong cc cun dy xut hin khi

mt bt u ngng o chiu. Ph ca nhiu o chiu c trnh by trong Hnh 5.20.

Hnh 5.20: Ph ca nhiu o chiu khi khng b trit (m phng)

Chng ta thy rng nh xp x tn s 5MHz trong ph ca nhiu khi o chiu ca mt.

N ph hp vi kt qu o dng CM ca mt bi v mt dao ng tn s 4.6MHz cng

c tm thy. Bin ca dao ng khong 3mA.



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Hnh 5.21: Nhiu o chiu chuyn i thnh dng CM (o c)

nh ny trong ph c trng cho ch cng hng, c thit lp cng vi in cm

trit, t in trit t v cun dy. S tng ln ca t in trit t s di nh ny hng

n mt tn s thp hn.

Ch cng hng khc c gim st trong dng DM ca mt, ta nhn thy ch

cng hng vi tn s 3.1MHz v bin xp x 3mA.

Cng hng ny c to ra bi in cm cp ca mt, t in trit mc sun trong mt

v bin tr trong b SCU. So snh vi dng CM, dng DM c din tch mch vng nh


Hnh 5.22: Nhiu o chiu chuyn i thnh dng DM (o c)


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hn nhiu nn lm cho n bc x khng hiu qu. Nhiu gy ra bi dng DM c b qua,

nhng dng DCM c chuyn i t dng DM ny c nh hng ng k.

Mch trit lm gim nhiu mt cch hiu qu. Kt lun ny c xc minh bng m phng

sau. Ph ca nhiu trc v sau khi trit c ch ra trong Hnh 5.21.

Hnh 5.23: Ph ca nhiu o chiu vi t trit t khc nhau (m phng)

Hnh 5.23 ch ra ba ng cong, ng cong cao nht l mc nhiu vi 47pF in dung

trit t v ng cong cao th hai c 47nF trit t. ng cong thp nht l kt qu m

phng vi 470nF t trit t. Do , trit c tha mn, 47nF ca t trit t l cnthit.

Tc ng ca vic gia tng t trit mc sun cng c nh gi. Hnh 5.24 trnh by hai

ng cong, ng cong cao hn l mc nhiu vi 470nF, v ng cong thp hn l kt

qu m phng vi 4700nF.



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Hnh 5.24: Ph nhiu o chiu vi t trit mc sun khc nhau (m phng)

Bng cch so snh ph ca in p nhiu trc v sau khi trit, chng ta bit rng mch

trit lm vic mt cch hiu qu trn tn s 1MHz. gn sng bn di 500kHz khng

thay i mt cch ng k trc v sau khi trit. Hnh 5.25 khng nh kt lun ny trong

min thi gian.

(a) Dng DM khng c trit (b) Dng DM c trit

(1.1mA/div 20 s/div) (1.1mA/div 20 s/div)

Hnh 5.25: So snh dng DM khi c v khng c t trit

Khi mt ang vn hnh, qu trnh o chiu tr thnh ngun nhiu chnh. Ta nhn thy

mt ch cng hng trong php o. y l mt ngun nhiu tim nng. V mt, mc

d gii hn v kch c, nhng n ng vai tr nh mt tip t. Cp mt ng vai tr nh



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mt ng-ten. Do , mt ng-ten n cc c hnh thnh. Tr khng n cc ca ng-ten

c th tnh ton c. Chng t c kh nng n gin ha m hnh bc x bi ng-ten n

cc.

Nhiu ny c th c loi b bng cch lm ngn c hai phn cui ca ngun nhiu, tc

l, vi s tip t ti c v mt v cc m ca ngun. Cu hnh h thng dy dn c nhhng i vi nhiu ny.

Mt c ch na ca ngun nhiu c trnh by y. N c gy ra bi nhiu khi o

chiu v s cng hng c xy dng dc theo mch vng minh ha trong Hnh 5.26.

Hnh 5.26: C ch ca dng CM trong mng tip t

Cng hng c hnh thnh thng qua in cm planeL trn mt phng kim loi, in

cm gL trong vt mt t, in cm 2212 , ww LL trong vt mt t, v in

dung trong vng mch ny. Bi v cp gia b SCU v mt ngn hn nhiu so vi

cp gia LISN (LISN: Line Impedance Stabilization Networks) v b SCU, do , ta c

1222 pp CC


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vng ny theo th t l 1pF. iu lm cho tn s cng hng gi nh bng

45MHz. Ngun nhiu tn s ny qu yu kch thch s cng hng. Khi c v

mt hoc cc m ca ngun c kt ni vi thn xe, tn s cng hng tnh ton

l khong 350kHz. Nu c "dy th ba" gia v mt v t ca b SCU, tn s cng

hng tnh ton l xp x 800kHz. Tn s cng hng thay i theo cu hnh dy dn, biv cc yu t dc theo vng mch cng hng thay i theo cu hnh dy dn.

2.4.5 Phn tch s nht thi

So snh vi s o chiu, tnh hung nghim trng hn xy ra khi mt khng kt ni vi

ngun. L do l nng lng c lu tr trong tt c cc cun dy s gii phng ra xung

quanh, trong khi cng lc s o chiu lin quan n mt cun dy. Mt in p pht x

dn in hnh c o v hin th di y.

Hnh 5.27: Pht x dn nht thi khi mt tt t ngt

Nhiu nht thi khi mt tt c mt ni dung nhiu tn s hn nhiu o chiu. Cc thnh

phn tn s chnh c phm vi ln n 200MHz. Nhng xung nht thi ny c th c lm

suy gim dp i, nhng xung ny cn c gi l xung E. Cc xung ny xut

hin nh dng in DM trong cp mt, v mc cao nht trong cc xung

ny l 110mA. c tnh thc nghim ca nhiu nht thi khi mt tt th to ra EMI cao

hn 20dB so vi nhiu o chiu.



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Vic d on nhiu ny l v cng kh khn, bi v n lin quan n tham s k sinh

ca mt ln n tn s rt cao. Cc tn s nh cao ny thay i vi mt khc nhau

ging nh du vn tay ca mt, n cn c gi l cc ch t nhin. ngn

chn nhiu ny, ta nn lm cho cp mt ngn hn v t in trit mc sun ln hn khi n

l dng in DM. Cu hnh dy dn dng nh khng nh hng i vi loi nhiu ny.Vic gim s thay i dng in nht thi s mang li li ch rt ln trong vic trit nhiu

nht thi.

2.4.6 Kt lun

V d on ca EMI ph thuc vo vic d on chnh xc dng in HF c hai ch

chung v sai khc, m hnh mt c bit hu ch v quan trng. Chng ta bt u m hnh

t cun dy v kt thc vi mt m hnh hon chnh i vi tn s thp v tn s cao.

Kt lun di y hng dn cho vic thit k EMC:

Nhiu o chiu xut pht t cc tia la in p gia cc cun dy v chi

qut khi cun dy ngng o chiu. Mch trit c th lm gim mc nhiu. Cc t

in trit ni t c tc dng ch yu.

Bc x pht ra t nhiu o chiu c th c loi b bng cch lm ngn c hai

phn cui ca ngun nhiu, tc l, vi s tip t tt c hai v mt v

cc m ca ngun in.

Nhiu o chiu gia u cui v v mt s bc x ra khng kh trong khi cp hot

ng nh mt ng-ten hiu qu. V vy, chng ta s gi cp mt cng ngn cng

tt. Quy nh ny cng rt hu ch ngn chn nhiu nht thi khi mt tt.

T in trit mc sun c tc dng trong vic trit nhiu nht thi.

2.5 RLE

Nhiu nht thi xy ra khi chng ta bt hoc tt b SCU. Ngoi ra cn do s chuyn

mch, m v ng ca rle cng dn n s thay i t ngt ca dng in hoc in

p. Bi v ti cm ng ca n dn n s thay i dng in ln hn, iu c hi. N c



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th gy tia la in gia cc dng in v ting n popping c nghe trong radio. Nhng

tnh hung ny cn phn tch nht thi.

2.5.1 M hnh ca rle

Th vin thnh phn trong PSPICE a ra mt m hnh macro cho rle, trong ctnh n c im k thut c kh. Tuy nhin, theo quan im EMC, vic bt hoc tt l

quan tm chnh, c bit trong qu trnh ng v m ca tip im in. V vy chng ta

b qua tc ng ca cc cun dy rle. Tr nn kh quen thuc vi mt chuyn mch,

rle c m hnh ha bi cc chuyn mch song song c trng cho cc tc ng ny

ln. in cm dn cng c tnh n. Cng ging nh trong phn trc, mt ci t c

thit lp xc nhn nh trnh by trong Hnh 6.1.

Hnh 6.1: Thit lp xc nhn tc ng ca rle

2.5.2 Phn tch nht thi khi ng rle

Gi s rng v ca mt c kt ni tt vi t. Trong tnh hung ny, c hai dng in

ch sai khc v ch chung c trnh by.

Khi rle hot ng, ba ch cng hng lin tip c thit lp. Vng mch Loop1 bao

gm in cm dy dn v t in trit mc sun bn trong mt; vng mch Loop2 bao gm



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t in u vo ngun, in cm dn ca rle, in cm ca cp mt v t in trit mc

sun ca mt.

Bi v hai t in trit ni t c kt ni vi v ca mt c tr khng thp tn s cao,

vng mch th ba c thit lp qua ng dn ny. Vng mch Loop3 bao gm t in

u vo ngun, in cm dn ca rle, in cm ca cp mt, t in trit mc sun camt, t in trit ni t v mng t. Dng in trong vng mch 3 l thnh phn chnh

ca dng in ch chung.

2.5.3 Phn tch nht thi khi m rle

Khi rle hot ng, vic ng in hnh l chui cc s kin ng v m nhanh c c t

s ny ln, s trt, s lc l v cc tp cht b mt. Hnh 6-3 trnh by ba vng mch

cng hng lin tip gii phng nng lng d tr trong cc cun dy. Cc vng mch

ny s ng gp cho dng in ch chung.

Hnh 6-3: Mch mt vi vng mch cng hng khi m rle

Vng mch Loop4 bao gm tt c cc cun dy trong mt v t in trit mc sun; vng

mch Loop5 c to thnh t cc chui kt ni ca in cm dy dn v t in trit mcsun bn trong mt; vng mch Loop6 bao gm cc chui in cm dy dn, t in trit

ni t v mng t.

Dao ng trong vng mch Loop4 s b p buc do s ph v ca varistor xt kim loi

(MOV: Metal Oxide Varistor). Nng lng s b tn x bi MOV nu bin gia cc u



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cc ca mt ln hn 33V. N cng cung cp mt ng dn cho dng in tn s cao vi

in dung ca n l 2500pF.

Mc d t trit mc sun c trong vng mch Loop5, in dung ca MOV l

yu t chnh xc nh tn s cng hng, bi v in dung ca MOV

thng thng c tnh theo nF, n nh hn so vi t in trit mc sun. in cm dy dnca cp mt cng quyt nh tn s cng hng ca vng mch Loop5. Tr khng ca

mng t l yu t chnh xc nh c im ca vng mch Loop6. Tr khng cao s

lm cho s cng hng suy gim nhanh hn. Hnh 6-4 trnh by kt qu m phng ca

dng in CM khi v mt ni t tt. Hnh 6-5 cho thy s pht x dn trong min tn s.

Hnh 6.4: M phng s nht thi ca dng CM trong min thi gian



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Hnh 6.5: M phng ph pht x dng CM vi v mt c ni t

Chng ta thy c su tn s cng hng trong ph, l 15kHz, 60kHz, 1.03MHz,

1.6MHz, 1.97MHz v 8.6MHz. thun tin, t tn chng t 1f n 6f . Cc 2f , 3f ,

5f c hnh thnh trong vng mch Loop1, Loop2, Loop3 khi rle ang ng, 1f , 4f ,

6f l trong Loop4, Loop6, Loop5 khi rle ang m.

Kt qu m phng c xc nhn bng cch o. Hnh 6-6 cho thy in p o

trn pin 1 v pin 4 ca rle, l u cui COM v u cui Normal Open ca chuyn

mch DPDT bn trong rle. Chng ta tm thy bn ch cng hng trong php o,

c tn s nh sau: 12.5kHz, 60kHz, 1.25MHz, 8MHz. Chng tng ng vi 1f , 2f , 3f

v 6f . Cc 4f , 5f khng c quan st bi v chng l dng CM chy qua dy ni

t. Qui nh ny chng minh rng m hnh ca chng ta l ng tin cy v cc ch cng hng chnh c bao gm trong m phng.

Hnh 6.6: in p o c trn pin1 v pin4 ca rle

2.5.4 Kt lun



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Chng ta c by ch cng hng t ph ca EMI, bn trong s xy ra

khi rle ang m, v ba xy ra khi rle ang ng. Bng s so snh gia cc cu hnh khc

nhau, chng ta c c kt lun sau y:

Cch thc n gin nht trit EMI l cch li mt vi khung xe c. Theo quan

im nhiu nht thi c to ra bi rle, th vic c lp v mt l c ch ngn

chn nhiu nht thi.

Nu yu cu trn khng p ng c, tr khng gia v mt v mt t nn gi t

nht 10 dn trit c 20dB.

Vic gim cc t trit t s ngn chn ch cng hng trong ng dn CM vi

bin gim. Bng cch lm gim t in trit t n 1/1000 gi tr ban u, th

dng CM c th c trit n 40dB.

Thi gian chuyn mch c th nh hng ng k n s cng hng. Rle vi thi

gian tip xc lu hn to ra EMI thp hn tn s cao. Nhng thay i thi gian

chuyn mch, chng ta cn thay th rle ny bng MOSFET.

T in trit mc sun ch nh hng n nh cng hng tn s thp.

in cm dy dn ca cp mt nh hng hiu qu n tn s cng hng cao.

Varistor c in dung nh hng mnh m n nh ca ch cng hng 6f . S

dng varistor vi in dung nh hn s di chuyn cng hng theo hng tn scao hn thm ch l bin mt.

Tng cng cc t in u vo ngun s di cc ch cng hng 3f , 5f

hng ti mttn s thp hn.

Mch trit ca mt, khng phi cc cun dy trong mt, ch yu quyt nh c

im nhiu. Kt lun ny cng ng i vi nhiu c to ra bi PWM. Cc tham

s cun dy mt ch nh hng n nhiu o chiu.

2.6 IU CH RNG XUNG

Tn hiu PWM (Pulse Width Modulation) c s dng c c s iu khin tc

bin i trong vic tng v gim tc trong mt. Trong mt s sn phm, mc EMI



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vt xa quy nh do cc dng sng chuyn i. Bi v cc php o EMC lun c thc

hin trong "trng hp xu nht", b SCU c thit lp vn hnh trong 50% trng thi

PWM trong h thng o lng, iu ny lm cho n kh vt qua h thng o kim.

2.6.1 M hnh ha ca MOSFET

MOSFET l mt thit b chuyn mch c m hnh ha trong tiu lun ny nh l

mt chuyn i song song vi hai t in, th hin trong Hnh 7.1. T chuyn tip jC lin

quan n dng phc hi ngc v in dung kC nh l in dung k sinh gia cc mng

v t. C jC v kC c th o c. Thi gian bt v tt ca chuyn mch c thit lp

thng qua tham s trong m hnh chuyn mch c o trong th nghim.

Hnh 7.1: M hnh MOSFET cho tn s cao

2.6.2 Phn tch s vn hnh

Sau khi ny ln nht thi, rle s trong trng thi n nh. Lc ny, tt c cc rle cxem nh tr khng thp. MOSFET l mt thnh phn chuyn mch m lm cho in p v

dng in thay i t ngt.

Bi v MOSFET c mt tham s chuyn mch n nh hn so vi b o chiu, v d thi

gian nht thi, khong thi gian, nhiu gy ra bi sng PWM nh l nhiu bng thng hp.

Trong phn ny, ngi ta s dng mt sn phm thc s m phng v xc nhn m

hnh ca h trn mt chu k chuyn i PWM hon ton.

Tn s ca PWM l 100kHz, v tn s ny khng th thp hn 15kHz, nu khng th tpm c to ra. Do , mt yu t khc i vi s u tin cho tn s PWM cao l kch

thc ca b lc c th c gi nh. S dng Hnh 7.2 minh ha ca chuyn i PWM

nht thi.



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Hnh 7.2: Dng in mch vng qua it

Trong pha 1, MOSFET c bt trc tin. Dng t ngun chy qua mt sau i qua

MOSFET v tr li ngun. Trong pha 2, MOSFET tt, dng in trong cc cun cm

khng th thay i ngay lp tc, cc tnh ca in p qua cc cun cm s b o ngc do

lc in t khi di/dt


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(a) Dng it (b) Dng DM ti cp mt (c) Dng DM ti cp ngun v b SCU

(0.44A/div 2s/div) (4.4mA/div 5s/div) (0.22mA/div 10s/div)

Hnh 7.4: Dng sng dng DM khi mt ang chy trong ch PWM (o lng)

Chng ta thy mt gn sng nh b mp i xung ca dng sng dng it. N l do

mt ch cng hng mi m khng c trong sn phm thc. Ch cng hng ny

c to ra bi mt dy m rng a vo vng mch dng it ni vi ci kp ca u

d dng in. Ph ca cc dng DM cng c hin th trong Hnh 7.5.

(a) Dng it (b) Dng DM ti cp mt (c) Dng DM ti cp ngun-SCU

Hnh 7.5: Ph ca dng DM khi mt vn hnh trong ch PWM (o lng)

Dng it c mt mc cao nht trong cc tn hiu DM ny. N bt u t 100dBA ti

400kHz v theo dc -20dB/dec. Do s tng mnh bin ca dng it khong 100ns,

dc suy gim -20dB/dec di 3MHz.

Dng in DM ca cp mt l 70dBA ti 400kHz v theo sau mt dc suy gim

nhanh hn n -40dB/dec. Dng DM ti cp mt ngun l 20dBA 400kHz v cng

theo sau mt dc suy gim -40dB/dec.



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So vi dng it, ph ca cc dng DM ti cp mt v cp ngun-SCU gim

nhanh hn nhiu, iu ny lm cho dng it tr thnh ngun chnh ca bc x pht ra

thp hn 3MHz.

Trong Hnh 7.5 (a) v (b), c hai ng cong trnh by kt qu o khi v mt c

hoc khng c kt ni n mt mt phng kim loi. Ta nhn thy rng khi thay i cuhnh h thng dy dn, dng in ch sai khc l thay i khng ng k. iu ny thc

t do dng DM l mt dng chc nng. Ph ca cc dng DM lin quan n cu hnh mng

ca mch v gi tr cc thnh phn trong b SCU v mt. Ta cng c th tm thy t hnh

trn rng dng DM ch yu tp trung ti tn s thp. Kt lun ny c li xc nh mt

ngun nhiu.

Kt qu m phng v kt qu o ca dng it c so snh trong Hnh 7.7.

(a) Kt qu m phng (0.1A/div 1s/div) (b) Kt qu o lng (0.44A/div 2s/div)

Hnh 7.7: So snh dng it gia php o v m phng

2.6.3 Kt lunS nht thi ca tn hiu PWM gy ra hai ngun nhiu chnh bi v s gia tng bin mnh.

gim nh hng ca hai ngun nhiu ny l dng it v dng DM trong cp mt,

di y l kt lun hng dn khi thit k EMC:

1. Cc vng c vng di/dt cao phi cng nh cng tt. Bng cch gim din tch

vng xung 1/10, mc pht x s gim hn 20dB.



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2. Nu c th, s dng tn s lm vic l 70kHz, bi v cc thnh phn sng hi th

nht v th hai nh hn cc tn s thp nht theo yu cu ca CISPR-25.

3. Nu c th, iu chnh tn s chuyn mch trong 100Hz. N s lm phng ph

EMI.

4. Nu cc iu khon nu trn khng th tha mn c, gii php khc l vicxon cc ng trong PCB (s hy b ln nhau gia cc dng). N c th hin trong

Hnh 7.12.

Hnh 7.12: Phng php gim nhiu c xut bng cch xon ng i

5. Trng hp s dng mt b SCU nha bc kim loi chc chn s lm gim mc

EMI di 2MHz, nhng iu th tn km.

6. trit bc x pht ra trn 2MHz, k thut u tin l c lp v mt vi thnxe. Nu chng ta s dng bao bc cch in hoc vt nha, in dung gia v mt v thn

xe nn c gi di 5pF. Nu iu kin ny c tha mn, pht x dng CM l khng

ng k.

7. Nu cc iu khon nu trn khng th c tha mn, thc hin cn bng dy

dn bng cch xon chng.

8. Nu dng CM c to ra, nhng chng ta c th hn ch chng trong mt

khu vc nh bng cch thm vo mt "dy th ba" gia v mt v t ca b SCU, gidy ngn v chy dc theo hai dy dn khc. xut ny hiu qu nht khi v mt v cc

m ca ngun c kt ni vi thn xe.

9. iu khon tip theo l di cc nh cng hng ra ngoi bng thng quan trng.

Bng cch lm gim chiu di dy dn gia mt v b SCU hoc s dng varistor vi



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in dung nh hoc thay th varistor bng cc it, tn s cng hng cp mt s rt cao

hoc thm ch s bin mt.

Chng 3:

PHP O SO SNH

3.1 THIT LP O

Chng ta s dng thit lp th nghim c cng nhn cho php o so snh, nh trong

Hnh 8.4.

Hnh 8.4: Thit lp o

Trong qu trnh o, mt hot ng trong ch PWM hoc trng thi lun lun bt. i

vi chiu di dy dn v cch b tr cp, ta c cu hnh nh sau:

di cp mt: 0.06m

cao cp mt pha trn mt phng kim loi: 0.05m

di cp ngun-SCU: 1mBa tnh hung c kim tra. Mt l t cp mt trn b mt ca kim loi phng. Tnh

hung khc l lm gim di ca cp ngun-SCU n 0.1m. Tnh hung th ba l

tng chiu di cp ca mt n 0.66m. Bin th nghim tip theo l cu hnh dy

dn. Bng cch thay i kt ni gia cc m ngun v mt kim loi, kt ni gia v



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mt v mt phng kim loi v xut phng php dy th ba gia t ca SCU v v

mt, chng ta c tm cu hnh t setup1 n setup8 nh trong Bng 8.1 sau.

Setup

Kt nim ngun v mt kim

loi

V mt v mt kim

loi

Dy th ba gia t ca

SCU v mtM Ngn M Ngn M NgnSetup1 x x xSetup2 x x xSetup3 x x xSetup4 x x xSetup5 x x xSetup6 x x xSetup7 x x xSetup8 x x x

Bng 8.1: Kt ni theo cu hnh dy dn khc nhau

3.2 CC KT QU O BC X PHT RA

3.2.1 o vi phn cc khc nhau

So snh u tin c thc hin vi s phn cc khc nhau. Trong qu trnh ci t o,

tnh hung xu nht l ng-ten c t vung gc vi cp ca mt. Hai php o c

thc hin vi phn cc dc v phn cc ngang. Kt qu o c ch ra trong Hnh 8.7.

(a) Kt qu o phn cc ngang



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(b) Kt qu o phn cc dc

Hnh 8.7: So snh kt qu gia php o phn cc ngang v dc khi mt vn hnh trong ch

PWM vi cu hnh dy dn l setup5.

Bng cch so snh, ta thy sai khc t nht 3dB. Do , chng ta s ch s dng cc kt qu

o dc so snh v tng hp khng c s sai khc.

3.2.2 So snh gia cc ch vn hnh khc nhau ca mt

Php so snh ny l gia cc trng in t mt mt vn hnh trong ch lun lun

chy v t mt mt ang trong ch PWM.

(a) Mt vn hnh trong ch lun lun chy



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(b) Mt vn hnh trong ch PWM

Hnh 8.8: So snh cc kt qu ca php o khi mt vn hnh trong ch lun lun chy

v trong ch PWM, vi cu hnh dy dn l setup4.

Trong trng hp ny, chng ta c th thy rng mt vn hnh trong ch PWM bc x

nhiu hn khi vn hnh trong ch lun lun chy v i km vi cc nh c nh du.

Bng vic loi b cc nh ny, s khng c s khc bit gia cc cng trng. iu

ny ng vi l thuyt rng hai tn hiu khng thch ng c th chng chp ln nhau c.

R rng l mt vn hnh trong ch PWM pht x nhiu bng rng t b phn o

chiu ca mt v nhiu bng hp t tn hiu PWM. Nhiu bng hp ti thiu l 25dB ln

hn nhiu bng rng.

3.2.3 So snh gia cc cu hnh dy dn khc nhau

S so snh ny l s bc x pht ra gia cc cu hnh dy dn khc nhau.

(a) Cu hnh dy dn l setup1



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(b) Cu hnh dy dn l setup2

(c) Cu hnh dy dn l setup4

Hnh 8.9: So snh ca bc x pht ra vi cc cu hnh dy dn khc nhau khi mt angvn hnh trong ch PWM

Trong php so snh ny, chng ta c th thy rng s khc nhau gia cc trng thp hn

2MHz l khng ng k. Khi c tm thy trong setup1 xung quanh 9MHz, v setup2

xut hin hai khi xung quanh 5MHz v 9MHz, trong khi setup4 th i cng vi hai khi

trong phm vi 350kHz v 9MHz.

Khi 9MHz c nh trong tn s nhng thay i trong mc, vi setup2 mc ca n l 4dB

cao hn setup1, v vi setup4 th khong 15dB ln hn trong setup1.



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Hnh 8.10: Kt qu ca phng php o bc x vi setup7

3.2.4 So snh nh hng ca dy th ba i vi cc cu hnh dy dn khc

nhau thy c s ci thin ca dy dn th ba, s so snh sau y c thc hin:

(a) setup1 (b) setup5

Hnh 8.11: So snh gia setup1 v setup5

i vi setup1, dy dn th ba khng cho thy mt s khc bit r rng. y l v dng

CM b kha trong setup1.



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Hnh 8.12: So snh gia setup2 v setup6S so snh ny ch ra rng i vi setup2, dy dn th ba c trit 2dB i vi

mt khi xung quanh 9MHz. S sai khc ny th r rng hn s sai khc trc

nhng dy th ba to ra mt khi khc na xut hin trong tn s 800MHz v c

kch thch bi tn hiu PWM vi 32dB V/m.


Hnh 8.13: So snh gia setup4 v setup8



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Vi dy dn th ba c a vo setup4, hai khi xung quanh 9MHz v 340kHz c trit

mt cch hiu qu. Trong s trc suy gim khong 12dB, cn trong s sau th hon

ton khng xut hin.

3.2.5 So snh hiu ng ca mn chn i vi cc cu hnh dy dn khc nhau

Bng s so snh bc x pht ra c thc hin khi b SCU c v khng c mn chn,chng ta khng nh v tr ca ngun nhiu. Chng ta thy rng t Hnh 8.14, bng cch

che chn b SCU, bc x pht ra t 150kHz n 2m th c trit mt cch quyt lit ti

thiu 10dB. S so snh ny chng t rng dng DM bn trong SCU l ngun chnh ca

EMI trong tn s thp.

(a) setup1 c SCU khng c che chn



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(b) setup1 c SCU c che chn

Hnh 8.14: So snh gia b SCU c chn v khng c chn i vi setup1

T Hnh 8.15, chng ta nhn thy cc nh ring bit b i vi mc thp nu cu hnh dy

dn l setup2. L do l dng DM ring c chuyn i thnh dng CM chy qua mt kim

loi. Do , s bc x c to ra bi s chuyn i dng CM th khng c bao bc. Thnghim ny khng nh c ch dng CM m c chuyn i t dng DM to ra EMI.

(a) setup2 c SCU khng che chn (b) setup2 c SCU che chn

Hnh 8.15: So snh gia SCU c v khng c che chn i vi setup2

Thc ra th ph ln hn 2MHz thay i mt cch ng k m c th gy ra bi mt s tip

xc ngu nhin gia l chn v v mt m ng vai tr nh dy th ba.



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KT LUN CHUNG

Tiu lun bn v cc m hnh ring l ca cc sn phm sunroof trong phm vi tn

s t 150kHz n 100MHz. Bt u vi vic tm hiu cc thng s k sinh bng cch s

dng phng php back-annotation. S dng m hnh thit lp, trnh by nhiu tholun v nh hng no s xy ra qua s thay i ca cc tham s. Thc hin phn tch qu

v phn tch vn hnh. y cng s dng kt qu cc php o t mt trung tm kim

tra c cp quyn chng minh gi thuyt. Cc c ch ny ca cc ngun nhiu c

lm sng t.

Cu hnh dy dn l tham s u tin la chn. L do l n c nh hng ln i

vi dng CM m tr thnh ngun nhiu chnh ln hn 2MHz, v cu hnh dy dn hu nh

c th p dng c v yu t chi ph. Kt ni t thn xe n v mt v kt ni t thn xen cc m ca ngun cho ta c bn cu hnh dy dn. Nhiu o chiu nh hng t

nht i vi cu hnh ny. Nhiu CM chuyn i t dng DM trong cp mt c th c

trit bng cch thm vo dy dn th ba hoc thm ch b loi tr bi cp mt ngn hn

hoc varistor c in dung nh. Nhiu nht thi gy ra khi mt chuyn qua trng thi tt

th kh c lm suy gim ngoi tr bng cch thc hin cp mt ngn hn v thc hin

thay i bin thin dng nh nhng.

Kt ni tt ti c hai bn v gi cp mt ngn l cu hnh ti u.Cu hnh ti u th hai l vic cch li v mt vi thn xe.

Bn cnh , thm mt s tham s c th thit k sn sng cho vic lm gim EMI hn

na. Sau y l danh sch cc tham s c ch.

1. Cu hnh mng trong b SCU ng vai tr mt rle quyt nh cho hiu lc ca

EMI.

2. Vic b i t in ng vo chuyn mch loi tr c nhiu gy ra bi chuyn

mch.

3. Lm cho in dung trit t v in dung trit mc sun cng ln cng tt hoc

thc hin mt dng mch trit khc.

4. trnh cc ch cng hng ri vo bng tn radio, ta c th x l bng cch

dch tn s cng hng.



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Tp tiu lun phn tch mt s im quan trng trong cng ngh tng thch in t trong

h thng thit b sunroof t ng ca xe c. y l mt trong nhng kin thc cn thit cho

vic bo dng, vn hnh tt h thng ny trong xe c.

Em xin trn trng cm n Thy gio PGS.TS. Tng Tn Chin tn tnh hng

dn, truyn t nhng kin thc qu gi, cung cp ti liu tham kho cho em.

Trong qu trnh lm tiu lun, tuy ht sc c gng song chc chn khng trnh

khi nhng sai st. Rt mong nhn c s gp ca Thy, v cc bn hc vin trong lp

ni dung ca tiu lun c hon chnh hn.

Hc vin thc hin

Trn Th Phng Hoi Ngc



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MC LC

TI LIU THAM KHO



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1. TS. Tng Tn Chin, Tng thch in t, NXB Gio Dc Vit Nam.

2. Dongsheng Zhao, EMC study of an automotive application, University of

Twente, 2004.

3. M. R. Feusse, Modeling Conducted Emission Transient due to DC MotorSwitching in Automotive Application, Master Thesis, Michigan State University,

2001.

4. Adam KEMPSKI, Robert SMOLENSKI, Decomposition of EMI Noise into

Common and Differential Modes in PWM Inverter Drive System , University of

Zielona Gora, Institute of Electrical Engineering, Poland.

5. K. M. Muttaqi, M. E. Haque, Electromagnetic Interference Generated from Fast

Switching Power Electronic Devices.

6. G. Grandi, D. Casadei, A. Massarini, High Frequency Lumped Parameter Model

for AC Motor Windings.

Documents

Tieu Luan EMC Ngoc Cao Hoc K21 Nop Thay