giao trinh thi nghiem dien tu cong suat

V0121 Gio Trnh Th nghim in T Cng Sut TTCN in

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1. Gii thiu in t cng sut l mt ngnh mi ca in t. Trong mt thi gian di, thut ng in t c ni n ch v kha cnh iu khin h thng. L do ca vn ny l v cc n in t ban u gi thnh thp khng c kh nng cp dng cho ti hot ng. iu ny c ngha l v phng din iu khin h thng gim c gi thnh v tit kim c khong khng gian chim ch nhng v

phng din dng ti vn phi c thit lp da trn sbin i v in. n nm 1949, chuyn tip PN mi ca bn dn c pht minh. iu ny gip hon tt kh nng to c dng ti ln v phng din in. T y n cho ra i mt lnh vc mi : in t cng sut.Tuy nhin iu ny khng ch khng

nh v mt nng lng m cn c v mt in t iu khin tng ng. Mt cch c bn c th ni rng in t cng sut l nhng g dng bin i, ha trn v phn phi nng lng in bng cng c in t.

Nhng b phn phi hoc chuyn ti nng lng c th c sp xp phn chia nh sau:

Hnh 1.1.1 Hnh trnh by dng nng lng qua s chuyn i ca cc b chuyn i nng lng in ( S = ngun , L = ti )


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Nu bn mun mt ti DC hot ng trn ngun AC chnh ca chng ti bn cn mt tng gia ngun nng lng v ti, n chuyn i dng xoay chiu ngha l chnh lu. Chng ta gi tng ny l b chnh lu.

Trng hp ngc li khi bn mun mt ti AC hot ng( v d nh motor ) t ngun cung cp l DC. iu ny c ngha l bn phi chuyn i thnh dng in AC.H thng bn mong mun thc hin vic ny c gi l Inverter ( b nghch lu ).B inverter ny c th thay i c c bin v tn s. i vi mt ng c khng ng b, iu ny s dn n vic c th thay i c c dng in ( ngu lc) v tc . i vi ngun AC, ta c th thay i bin v tn s t ngun AC ny sang ngun AC khc bng b chuyn i AC ( AC converter). Trong trng hp tn s vo f1 bng tn s ra f2 gi l b bin i AC trc tip. i vi ngun DC, ta c th thay i bin v cc tnh ca ngun DC bng b chuyn i DC ( DC converter). Trong trng hp nu chuyn i trc tip t in p DC U1 thnh in p DC U2 m khng qua h thng in p AC th c xem l b chuyn i trc tip DC.

Nhng ch cho phn k thut o lng

Chiu ca dng in v in p: Chiu ca dng in v in p trong cc mch o lun th lun lun c v t mt im n im tham chiu. im tham chiu thng c k hiu l im ni t.

o dng: Dng in c o gin tip thng qua in p ri trn in tr. Thang o dng in cn phi tnh ton tng ng vi thang o ca in p. Tt c cc in tr c o c gi tr 0,5 vi dung sai 10%.

Thang o thi gian ca my hin sng: Trong vic hin th s lin quan AC, trc thi gian c xc nh theo mt gc o. My hin sng c th c iu chnh tng ng vi cc gc o da vo trc to gc.


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Nhng ch khi lm vic vi Power Board Ngun cung cp cho Power Board B ngun 3 pha ng ra c cch ly vi

ngun cung cp

th d dy N t ngun cung cp 12VAC khng c ni vi dy N ca ngun cung cp chnh ( v l do an ton ) v cng khng c ni vi t ca ngun 15V.C hai u khng ni t ca ngun 15V c vi kt ni v in vi ngun cung cp chnh. iu ny

dn n vic to cho n c kh nng o lng vi mt my hin sng tiu chun m khng

cn dng mt bin th cch ly. Trong cc bi tp khc nhau GND ca 15V c minh ho l im ni n N hoc c ni vi cc

m ca b chuyn i dng in . Ngun 3 pha l ngun cung cp m trong pha L2 v L3 c to ra mang tnh gi lp( h thng ly ngun chnh l mt pha to

ngun 3 pha). B ngun ba pha hot ng c thng qua mch cu.

phn bit gia cc ngun cung cp ring bit v tng cng cch in gia dng 3 pha v ngun cung cp AC, cc ng dy c t tn l L1, L2, L3 v N.

Th d khi L1 v N ni dy khng ng, s xy ra ngn mch, cu ch F2 hoc cu ch F3 ca ngun 3 pha s t, cc cu ch ny c th c thay th m khng cn m mch. Cc cu ch bo v mch in trong Power Board, v d F1, c t bn trong mch v ch c th thay th bng cch m np y pha sau. Tuy nhin, nhng cu ch ny ch t nu c mt li trong mch ny v s khng t khi ni dy sai.


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S phn phi dng trn Power Board

Tn gi Power Board c th c s dng trong bn v k thut.

Chiu mi tn ch s phn phi cc tn hiu

th d chiu mi tn L1 ch rng tn hiu L1 c ni dy ti nhng im

kh c nhau trn Power Board.

Nu mt gic cm c ni vi L1 s c

biu din bi mt mi tn n ( xem hnh 1.1.4 bn phi). Tng t i vi N v +15V.

Ni t (GND) c k hiu l nh hnh H 1.1.4 bn phi.

im ci t ca chit p Nu in p ci t c yu cu cho mt s

th nghim, th d nh cc b chuyn i iu chnh c, nhng in p ny c ly t

cc chit p ci t. cc chit p phi c

gn cht vo cc im ph thuc khc nhau

vo dy in p ci t.

Kt ni cc u ni t 2mm n 4mm. u ni 2mm c dng trn board cng sut phi c kt ni n cc u ni 4mm c

dng ph bin trong cc thit b o, c th ni vi cc thit b o bn ngoi.Cc u chuyn i ny c gn trn board cng sut.

Cc panel chuyn i ny c hiu lc cho tay tri hay tay phi.Cc panel bao gm mt cp c 2 loi chuyn i t 2mm sang 4mm v mt u ni t tip nhn c 2 cm. u ni

t ny c ni t bn trong.


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2. Chnh lu khng iu khin

2.1 Mch chnh lu bn k 1 pha khng iu khin M1U

2.1.1 Tng qut

Cch n gin nht ca vic i dng xoay chiu thnh dng mt chiu l s dng trng thi m v trng thi tt ca diode. Hnh 2.1.1 minh ha cho 1 mch nh vy.

Diode V1 chuyn sang trng thi dn khi in p chnh Us vt in p ngng ca diode. Trong khong thi gian dn ny, dng mt chiu Id chy qua in tr RL .Diode V1 kha li khi in p chnh Us ri xung di ngng in p ca diode.

Nh vy diode ch cho php dng in chy qua trong khong thi gian ng vi bn k dng ca in p chnh. Bin ca dng in c xc nh bi gi tr ca in tr ti RL. Dng sng ca n ng dng vi bn k dng ca in p chnh t vo.

Hnh 2.1.1.1 Mch chnh lu bn k mt pha khng iu khin M1U


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Hnh 2.1.1.2 Dng sng dng v p trong mch chnh lu bn k 1 pha khng iu khin M1U i vi ti thun tr

2.1.2 Phn th nghim Th nghim 1

o dng v p mch chnh lu bn k khng iu khin M1U i vi ti thun tr

Tin trnh thc hin

Thit lp mch in nh trnh by hnh 2.1.2.2 vi boar cng sut.

Chuyn Trigger ca my hin sng sang ( Line/ )

o dng sng cc gi tr thay i sau :

- in p chnh Us

- in p ng ra chnh lu Ud

- Dng in ng ra Id ( khi in p ri trn Rm )

V cc dng sng trn cc biu cho hnh 2.1.2.3 v 2.1.2.4


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Cu hi :

Hy so snh Us v Ud . Bng cch no lm cho 2 in p ny c s khc nhau v s khc nhau ny xut pht t u ?

Tr li :

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S dng my hin sng tnh ton o dng

Mt dng in c gi tr 0,2A/div c yu cu th hin trong biu hnh 2.1.2.4. Hy tnh ton nhng gi tr thit lp cn thit trn my hin sng.

- Yu cu : 0,2A/div

- Cho bit : Rm = 0,5

U=R.I ..

= ..

0,2A/div ................V/div


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Th nghim 2

o dng v p mch chnh lu bn k khng iu khin M1U i vi ti hn hp RL

Tin trnh thc hin

Thit lp mch th nghim nh trnh by hnh 2.1.2.5

Ch kt ni ti th nht ( mch in c cun dy ni tip vi in tr )

o dng sng cc i lng thay i sau :

-in p ng ra Ud

- Dng in ng ra Id ( khi in p ri trn Rm )

V dng sng c ch r trn biu hnh 2.1.2.6


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Cu hi 1:

S lch pha gia dng in v in p c th nhn thy c trn my hin sng. Hy cho bit gi tr lch pha ny v nguyn nhn to ra ?

Tr li :


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o dng sng cc i lng thay i sau :

-in p ng ra Ud

- in p cun dy UL

V dng sng trn biu cho hnh 2.1.2.7

Ghi ch :

in p ng ra Ud v in p cun dy UL khng c im tham chiu chung. V vy cc tn hiu phi c o ln lt hoc th t ca mch in phi c thay i.

Cu hi 2 :

in p ng ra Ud i khi l m khi bn nhn vo biu hnh 2.1.2.7. Bn hy gii thch cho c 2 phn in p dng v m xut hin ti ng ra ca mch chnh lu?

Tr li :


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...

Hy kt ni li nhnh b song song vi ti nhnh a n ng ra ca mch chnh lu.

V dng sng trn biu cho hnh 2.1.2.8

Ghi ch :

Phn in p ng ra c gi tr m c hiu nh l vng thi gian in p m.Vng ny c th ngn chn khi s dng mt diode hi phc.

Cu hi 3:

Diode hi phc c tc dng g i vi dng in qua ti in tr - cun dy?

Tr li :


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Ghi ch:


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2.2 Mch chnh lu cu mt pha khng iu khin B2U

2.2.1 Tng qut

Mch in c s dng nhiu nht bin i trc tip dng din AC l mch chnh lu cu khng iu khin B2U. Vi mch ny, 4 diode c kt ni nhau to thnh dng cu.

im a c in th dng hn so vi im b ng vi bn k dng. iu ny c ngha l dng in c th chy t bin th qua diode V1, qua ti RL v diode V4 ri tr li bin th. im b c in th dng hn im a ng vi bn k m.Mt dng in k tip s chy qua diode V3 , ti RL v diode V2. in p ng ra Ud v dng in ti Id lun cng chiu nhau. Kt qu ta c dng mt chiu qua ti.

Hnh 2.2.1.1 Minh ha 2 kiu mch thng dng


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Hnh 2.2.1.2Dng tn hiu trong mch chnh lu cu khng iu khin B2U

2.2.2 Phn th nghim

Th nghim 1

o dng v p trong mch chnh lu cu khng iu khin B2U i vi ti thun tr.

Tin trnh th nghim

Thit lp mch in nh trnh by hnh 2.2.2.1 vi board cng sut

( xem hnh 2.2.2.2 )

o dng sng cho cc i lng thay i sau:

-in p ng ra Ud

-Dng ti ng ra Id

-Dng qua diode Iv2

-Dng qua diode Iv4

V dng sng trong biu cho hinh2.2.2.3 v 2.2.2.4


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Cu hi :

Hy cho bit s lng xung trn mch in B2U ( s lng xung l s xung in p trn phn DC trong mt chu k )?

Tr li :

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Th nghim 2

o dng in v in p cho mch chnh lu cu khng iu khin B2U i vi ti hn hp R-L

Tin trnh thc hin

Thit lp mch in nh trnh by hnh 2.2.2.5.B qua 2 in tr o 0,5 vi u cm 2mm

o dng sng in p ng ra Ud v dng ti Id


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2.3 Mch chnh lu 3 pha hnh tia khng iu khin

2.3.1 Tng qut

Mch im gia 3 xung khng iu khin M3U thng c ni n nh l mch im gia dng 3 pha .Ging nh mch im gia n xung M1U, y l mch chnh lu na sng. in p ng vo UL1, UL2 ,UL3 c cng im tham chiu vi in p ng ra Ud, tn ca n l dy dn N.

Mch in c thit lp lm sng t mt iu rng dng in ch c th chy qua 1 trong cc diode khi in p pha tng ng ln hn Ud.

Ghi ch :

Nhn L1....N thay th cho L1.....N nhm mun nhn mnh rng c mt s cch ly v in gia li

in v mch chnh lu.

Hnh 2.3.1.1 Mch chnh lu hnh tia 3 pha khng iu khin M3U


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Hnh 2.3.1.2 in p ng vo v ra trong mch chnh lu hnh tia 3 pha M3U

Biu 2.3.1.2 chng t rng in p 3 pha chng ln nhau mi pha n ca in p ch vt tri

hn trong mt thi gian ngn ca chu k.Khi in p 3 pha c chnh ng 120, phn vt tri ca in p pha cng tri qua mt gc ng bng 120. in p pha UL1 l in p cao nht, c lin h n chu k ca n, bt u ng t 30 n 150.

iu ny c ngha l diode V1 khng th dn in ti thi im khi UL1 qua trc 0, m ch khi UL1 c gi tr l 0,7V ln hn UL3 hoc UL1 c gc pha ln hn 30.

Diode V1 sau ti dng DC Id n gc pha 150. K tip n lt V2 tip tc ti dng v

UL2 c in p pha ln nht trong khong t 150 n 270.T 270 n 300 th lp li in p pha vt tri cho UL3 v diode V3 ti dng Id . Nh vy mi diode ti dng trong 1/3 chu k . Khi 1 diode chuyn dng c hiu l mt s chuyn mch.Chng ta ni rng dng in chuyn mch t V1 sang V2 ti 150.

Khc vi dng in trong mch in im gia n xung khng iu khin M1U, dng in ny khng th c hnh thnh t mc 0. Chng ta bo rng y l dng in khng gin on.

Nu 3 diode c kt ni sao cho m cc c im ni chung , s rt gn c th c m rng sang M3UC. Nu cc diode c ni chung ti dng cc, vn s c gii quyt c th mch M3UA.


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2.3.2 Phn th nghim

Th nghim

o dng in v in p cho mch im gia 3 xung khng iu khin M3U i vi ti thun tr

Tin trnh thc hin

Thit lp mch in nh hnh 2.3.2.1 vi board cng sut ( xem hnh 2.3.2.2)

Bt cng tc M3/B6 sang v tr M3

t ngun cung cp 3 pha sang chc nng ni cu

V dng sng cho cc i lng bin i sau :

- in p pha UL1,UL2 v UL3

- in p ra tng ng Ud

- Dng ng ra Id

V dng sng trong biu cho hnh 2.3.2.3.v 2.3.2.4

Ghi ch :

S dng chc nng trigger ca my hin sng :

Trc tin cho hin th in p pha UL1 trn mn hnh v chc nng trigger chuyn sang v tr LINE.

Cc mc t l thi gian phi c chn la cho ph hp. Mt chu k phi tri rng ra 10 chia. iu ny cho ta c mt t l 36/ chia( 1 chia = 1 ) .


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Hnh 2.3.2.2 Minh ho kt ni mch o lng hnh 2.3.2.1 board cng sut


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in p pha UL1...............V/div

in p pha UL2...............V/div

in p pha UL3...............V/div

in p ng ra Ud..................V/div


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Dng in ng ra Id...............A/div ..........V/div

Cu hi 1:

C bao nhiu xung trong mch M3U ?

Tr li :

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Cu hi 2 :

Cch no trong 2 cch rt gn M3UA hay M3UC c ng dng cho mch in( hnh 2.3.2.1)?Cho bit l do !

Tr li :

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2.4 Mch chnh lu cu 3 pha khng iu khin B6U

2.4.1 Tng qut

Mch cu 6 xung khng iu khin B6U cn c gi l mch cu dng 3 pha khng iu khin cng c th c xem nh mt dng ni tip ca 2 mch im gia 3 xung khng iu khin M3U d dng cho vic tm hiu hn.

Hnh 2.4.1.1 trnh by s m t ny

Cc diode V1, V3 v V5 to thnh mch M3U cung cp mt in p dng cho ng ra l Ud1 so vi im gia N ca bin th. Chng ta cng ni n mch M3UC bi v cc m cc ca 3 diode to thnh 1 im ni chung cho mch chnh lu.

Khi cc diode V4, V6, v V2 mc theo hng ngc chiu vi in p pha, kt qu dn n mt in p m Ud2 xut hin ng ra cho mch M3U ny. Mch ny cng ging nh mch M3UA v dng cc ca cc diode to thnh 1 im ni chung cho mch chnh lu. in p tng ng ra Ud c cho bi s phi hp ca 2 mch im gia ny.Dng mch cu by gi c c ud = ud1 ud2.( u l gi tr tc thi khc vi U l gi tr trung bnh tnh ton )

Hnh

2.4.1.1 Mch in ni tip ca 2 mch M3U trong 1 mch B6U


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Hnh 2.4.1.2 mch cu 6 xung khng iu khin thng dng


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2.4.2 Phn th nghim Th nghim

o cc dng in v in p trong mch cu 6 xung khng iu khin B6U.

Tin trnh thc hin

Thit lp mch in nh trnh by hnh 2.4.2.1

ng cng tc M3/B6 sang v tr B6

t ngun cung cp 3 pha sang chc nng kt ni dng cu ca ngun 3 pha

o dng sng cc gi tr bin i sau :

-in p ng ra Ud

-in p trn cc diode Uv4, Uv6, Uv2

-Dng in qua cc diode Iv4, Iv6, Iv2

V dng sng vo biu cho hnh 2.4.2.2 .......2.4.24

Ghi ch :

S dng chc nng trigger ca my hin sng :

Trc tin cho hin th in p pha UL1 trn mn hnh v chc nng trigger chuyn sang v tr LINE.

Cc mc t l thi gian phi c chn la cho ph hp. Mt chu k phi tri rng ra 10 chia.

iu ny cho ta c mt t l 36/ chia( 1 chia = 1 ) .


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in p ng ra Ud ..................V/div

in p diode UV4 ..................V/div

dng diode IV4........................A/div V/div

in p diode UV6 .V/div

Dng in diode IV6 ............A/div ..V/div


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in p diode UV2 .V/div

Dng in diode IV2 ............A/div ..V/div

Cu hi 1:

Khi no diode V2 na phn di ca mch cu dn in, nhng diode no na trn mch cu c th cho dng chy qua sau ?

Tr li:

...

Cu hi 2 :

Trong mc 2.4.1, chng ta gii thch rng gi tr thi gian ca in p ng ra chnh lu ud c cho bi ud1- ud2. Ti sao gi tr hiu dng Ud12 khng bng Ud1- Ud2 ?

Tr li :


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..

Ghi ch :


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2.5 Gi tr trung bnh s hc v gi tr hiu dng trong chnh lu khng

iu khin

2.5.1 Tng qut

Khi kho st mch chnh lu,gi tr hiu dng thng ch v in p xoay chiu ng vo. Tuy vy , n l lng trung bnh tnh ton, cho nn phn in p DC th c ch dng cho in p ng ra ca mch chnh lu. phn bit chnh xc gia 2 gi tr ny, ch vit tt U1rms c dng trong trng hp ny l gi tr hiu dng ca in p xoay chiu ng vo , ch vit tt Udar l gi tr tnh ton ca in p DC.V vy n quan trng cho vic chn la dng c o hp l o lng cc mch chnh lu.

Bng 2.5.1.1 Bng tr gip chn la dng c o lng

Gi tr hiu dng ca in p v dng in hnh sin

-Dng c o lng c cng c bng st di chuyn c

-ng h vn nng in t to c gi tr hiu dng -Cp nhit vi cng c in p DC -Dng c o lng c cng c bng st thay i c

cc thang o AC

Gi tr hiu dng ca in p v dng in khng sin


-ng h vn nng in t to c gi tr hiu dng -Cp nhit vi cng c in p DC

Gi tr trung bnh tnh ton ca in p , dng in sin v khng sin


-ng h vn nng thng thng c cc thang o DC -My hin sng c cng tc AC/DC


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2.5.2 Phn th nghim

Th nghim

o gi tr trung bnh cng tnh ton v gi tr hiu dng trong cc mch chnh lu khng iu khin

Tin trnh thc hin

Thit lp ln lt cc mch in khc nhau nh trnh by hnh 2.5.2.1

o nhng i lng bin i sau bng dng c o lng thch hp:

-Gi tr hiu dng in p AC ng vo U1rms

-Gi tr hiu dng ca in p ng ra Ud rms

-Gi tr trung bnh tnh ton ca in p ng ra Ud ar

Ghi kt qu o vo bng 2.5.2.1

Ghi ch:

Mch in cn thit lp c trnh by hnh 2.1.2.2 (trang 7), hnh 2.2.2.2 ( trang 17), hnh 2.3.2.2( trang 24), hnh 2.4.2.1( trang 29 ), nhng khng cn o in tr.

Trong nhng mch chnh lu dng 3 pha,ngun 3 pha cng phi c t hot ng vi 1 mch cu c b phn iu chnh pha. Hn na, cng tc chn la M3/B6 phi c t theo ngun cung cp.


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Trang 35

Xc nh cc gi tr sau y v chuyn chng vo bng 2.5.2.2


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Bng 2.5.2.2

Cu hi 1:

So snh gi tr hiu dng rms ca in p ng ra Ud vi gi tr trung bnh ton hc cho cc mch in ring bit.Bn c th rt ra c kt lun g t mi quan h mt thit gia gn sng v mc DC?

Tr li:

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Cu hi 2:

Mt ti r nhnh DC tip nhn mt in p DC ca ngun UE = 230V, c thc hin bi mch B2U ti im ni E1 v E2 ca cun dy kch thch. Hy cho bit bin th cn phi cung cp in p th cp US l bao nhiu c c gi tr ny?

Tr li :

Hnh 2.5.2.2

Tnh ton :


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Ghi ch :


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2.6 S xung v gn sng trong mch chnh lu khng iu khin

2.6.1 Tng qut S tng quan ca cc mch chnh lu M1U,B2U,M3U v B6U khng ch khc nhau v mi quan h gia in p ng vo v in p ng ra m cn dng sng in p ng ra ca chng.

Cc in p tng hp xut hin cc ng ral s phi hp ca in p DC l tng Ud v in p gn sng Urip .

T s ca gn sng v phn DC l mt tiu chun o lng v cht lng ca mch chnh lu. Cht lng ny c ch r bng h s gn sng %.

Cng thc ng dng : rip = Urip rms / Ud ar

Vic xc nh hp l gi tr hiu dng ca in p gn sng vi thit b o lng, phn in p DC ca in p ng ra chnh lu Ud phi c thc hin cng lc.Vn ny c th thc hin vi 1 t

in.Minh ha hnh 2.6.1.1, s dng mch M1U lm v d.

Mt tiu chun khc cho mch chnh lu l tn s ca in p gn sng frip. Trong cc mch chnh lu,

tiu chun ny thng c ch r bng s xung gi l p ( s ln p mch ). S xung l s bn k in p DC xut hin trong 1 chu k ca ngun in p AC.

Hnh 2.6.1.1 Mch in xc nh in p gn sng.


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2.6.2 Phn th nghim

Th nghim o s xung v gn sng trong cc mch chnh lu khng iu khin.

Tin trnh th nghim

Thit lp ln lt cc mch in khc nhau nh trnh by trong hnh 2.6.2.1

o cc i lng bin i sau vi dng c o lng thch hp :

-Gi tr trung bnh tnh ton ca in p ng ra Ud ar

-Gi tr hiu dng ca in p gn sng Urip rms

Dng t in C1= 47F t panel ti ca board cng sut n phn in p DC

o dng sng ng ra ca cc mch in ring l.

Ghi cc kt qu o vo bng 2.6.2.1

Ghi ch :

Mch in cn thit lp c trnh by hnh 2.1.2.2 ( trang 7), hnh 2.2.2.2( trang17), hnh 2.3.2.2( trang 24), hnh 2.4.2.1( trang 29) nhng khng o in tr.

Trong nhng mch chnh lu dng 3 pha, Ngun 3 pha phi t vn hnh vi mch cu n b hiu chnh pha. Mt khc, cng tc chn la M3/B6 phi c t theo ngun cung cp.

M1U B2U M3U B6U Ud ar/V

Urip rms/V H s gn sng

S xung p

Bng 2.6.2.1


- 100 -


- 101 -


- 102 -


- 103 -

Ghi ch:


- 104 -

3. Chnh lu c iu khin

3.1 Mch chnh lu 1 pha bn k c iu khin M1C

3.1.1 Tng qut

Nu mun tc ng n bin in p ng ra ca mch chnh lu, ta cn dng n nhng van c th iu khin c, l Thyristor. Vi s h tr ca thyristor, mt mch chnh lu c th c thit lp

m vic kch dn 1 van c lm tr v v th mt phn in p ng ra b ct b. iu ny c hiu l iu khin pha cc cng bng hiu ng chnh lu. NHng mi quan h c bn c th c gii thch khi dng mt mch in ch vi 1 thyristor. y l mch im gia n xung c iu khin M1U. Mch in ny t c s dng trong thc tin nhng n chun mc gii thch nguyn l hm s ca chnh lu c iu khin v cu trc mch qu n gin.

in p xoay chiu Us c cp cho ti RL thng qua thyristor. Thyristor ch dn in khi in th ti Anode dng hn in th ti cathode v nu n nhn c 1 xung kch dngVGC ti cc cng ngay thi im tng ng.

Hnh 3.1.1.1 Mch im gia n xung c iu khin M1C


- 105 -

Hnh 3.1.1.2 Dng tn hiu trong mch im gia n xung c iu khin M1C

Ti thi im t0 in p US thay i cc tnh,ti y 1 diode bnh thng s dn in. Chng ta mun ni n y l thi im kch dn t nhin. i vi thyristor, y li l thi im kch dn u tin c th thc hin c.

Ti thi im t1, US c gi tr dng nhng thyristor khng dn in.Ton b in p xoay chiu US t ln thyristor gi l in p ngt.Mc d n thu nhn in p nhng thc t n b ngt.Chng ta ni rng thyristor tip nhn in p trng thi ngt.

Ti thi im t2, thyristor tip nhn 1 xung kch dn UGC v chuyn sang trng thi dn.Khong chuyn tip - c hiu nh gc kch - c lm tr bi gc iu khin so vi im kch dn t nhin.Trong th = 90.

Ti thi im t3, thyristor vn trng thi dn, dng ti Id chy qua v in p ngt Uv th rt nh, 1V l in p c c trn thyristor.

Ti thi im t4, in p US chuyn xung bng 0.Dng in Id cng bng 0 v thp hn dng duy tr ca thyristor. Thyristor b ngt.

Trong v d ca chng ta ,v vy dng ti Id chy qua t gc = 90 n = 180. chng ta ni rng gc dn ca dng in l 90.


- 106 -


- 107 -

Nhng ng dng sau cho ti thun tr :

= 180 -

Ti thi im t5, cc tnh in p li o ngc mt ln na. Thyristor tip nhn in p trng thi

ngt chiu nghch v th c gi l trng thi ngt nghch.

Cu trc ca mch to in p kch dn khng c tm hiu chi tit y. N s c nghin cu mc 3.3.

3.1.2 nh hng ca cc loi ti khc nhau trn hot ng ca b bin i

Thyristor tip nhn xung kch t s iu khin pha ti cc cng. Gc iu khin l

= 90

Khi thyristor c kch dn, in p Ud lp tc chuyn n gi tr ngng ca in p chnh US. Dng in khng tng t ngt bi v tnh cm khng lm tr hon s tng ca dng in. Nng lng tch ly ca cun dy c hnh thnh ti thi im m in p US qua trc 0. Sau dng in gim dn. Tuy nhin khi dng in cha bng 0, thyristor cng cha b ngt v Ud t c in th ng vi bn k m ca in p chnh.Dng in khng gim di mc dng duy tr ca thyristor cho n khi Ud tr nn m, nguyn nhn lm thyristor b ngt.Nng lng trong cun dy bng 0 ti thi im ny. Lc thyristor ngt, in p Ud cng bng 0.


- 108 -

Hnh 3.1.2.2 Dng sng tn hiu trong mch M1C vi ti R-L ( m t l tng )

3.1.3 Phn th nghim

Nhng lu v o lng:

Chc nng iu chnh gc kch dn W iu khin pha cc cng th phi trng thi khng hot ng. thc hin th n phi c chuyn sang v tr tt bn phi.

o lng trong phn th nghim ny, vic iu khin pha cc cng i hi 1 in p iu khin

trong dy +U. V vy t im o in th ca ng h o gia +10V v 0V

Ni ng ra ca ng h o in th n ng vo iu khin +U ca gc pha iu khin I.S ca bin th kch xung phi c ch r thay th cho in p kch dn.V d I1 l ch vit tt cho bin th kch xung 1 iu khin pha cc cng I. Mt im ni ca bin th kch c biu th bi 1 im. im kt ni ny phi c ni n cc cng. im ni th 2 phi c ni n cathode. My hin sng phi s dng phn trigger chc nng LINE cho tt c cc biu dng sng.Nu in p chnh US v in p ng ra Ud khng c im lin h chung, chng phi c o ring bit ln lt.


- 109 -

Th nghim 1

o dng in v in p mch im gia n xung c iu khin M1C.

Tin trnh thc hin

Thit lp mch in nh trnh by trong hnh 3.1.3.1 vi board cng sut

(xem hnh 3.1.3.2)

Ghi ch:

S dng thyristor 1 t cu pha n I

t 1 gc iu khin = 90

Ni in tr thun lm ti

o dng sng cc gi tr bin i sau:

- in p chnh US

- in p ng ra Ud

V dng sng vo biu cho hnh 3.1.3.3


- 110 -


- 111 -

Chuyn mch o hnh 3.1.3.1 n board cng sut

Hnh 3.1.3.2


- 112 -


- 113 -

in p chnh US..V/div

in p ng ra Ud.V/div

Cu hi:

Cho bit gi tr dng in v ln gc dn dng trn ti thun tr ti gc iu khin l 90

Tr li:

..


- 114 -

Th nghim 2

S nh hng ca thnh phn ti cm khng i vi hot ng ca mch M1C.

Tin trnh thc hin

Hy ni mch in ni tip gm cun cm, in tr ti v in tr o lng xem nh 1 ti

o dng sng cc gi tr bin i sau vi gc iu khin l 90

-in p chnh US

-in p ra Ud

-in p cun dy UL

-Dng ti Id

V dng sng vo biu c cho hnh 3.1.3.5 v hnh 3.1.3.6


- 115 -

in p chnh US............V/div

in p ng ra Ud...V/div

in p cun dy UL.V/div

Dng ti Id.A/div .V/div


- 116 -

Cu hi 1: Cho bit gi tr ln nht ca gc dn dng v l thuyt i vi trng hp ti hn hp?

Tr li:

..

Cu hi 2:

Bn gii thch th no v vn c nhng phn in p m xut hin ng ra ca mch M1C khi mt ti tr cm c ni vo?

Tr li:

..

Cu hi 3:

in p no c s dng cun dy (in p thun ty AC, in p thun ty DC, hay in p tng hp)?

Tr li:

..


- 117 -

Cu hi 4:

So snh Id v UL ( hnh 3.1.3.6)

a) Ti thi im no in p cun dy thay i du ca n ?

b) Gi tr UL m trong bao lu ?

c) Trong khong thi gian no cun dy pht sinh nng lng v khi no n tiu tn ht nng lng?

Tr li:

a)

..

b)

..

c)

..


- 118 -

Ghi ch:


- 119 -

3.2 Mch chnh lu cu 1 pha c iu khin B2C

3.2.1 i cng

c th iu khin in p ra Ud ca mt mch cu 2 xung bng phng php iu khin pha(iu khin gc m), mch ny cn c nhng khabn dn iu khin c.H.3.2.1.1 trnh by mt mch in lai ny.

Vi 4 Thy-rt-to ta c th iu khin thi gian (m)tr trong c hai bn k dng v m ca

din p ngun Us. Thy-rt-to V1 v V4 dn dng Id trong bn k dng, cn V2 v V3 dn trong bn k m.

c c dng in qua ti, cc Thy-ris-to V1 v V4 phi dn ng thi. V2 v V3 cng phi nh vy trong bn k m. iu ny c ngha l cc cp Thy-ris-to cng dn phi ng thi nhn c xung iu khin.

Mch iu khin thch hp c gii thch chi tit trong mc 3.3.

H.3.2.1.1 Mch cu hai xung iu khin B2C


- 120 -

3.2.2 Phn Th Nghim

Th nghim 1

o dng v p trong mch cu hai xung iu khin B2C

Phng php

Mc mch in nh trong hnh 3.2.2.1.

Ch : S dng mch cu mt pha I v mch iu khin pha I.

Chnh gc k = 1440.

Dng mt in tr thun lm ti.

Kho st trn dao ng k cc bin s sau:

- in p ra Ud

- Dng qua Thy-ris-to IV2 v IV4

V cc ng cong tng ng vo cc s n gin ha trong hnh 3.2.2.2 v 3.2.2.3.


- 121 -


- 122 -

Th nghim 2 Tc dng ca ti in cm ln c tnh ca mch B2C

Phng php Mc mch ti gm mt in tr ni tip vi mt in cm(H 3.2.2.4). Kho st trn dao ng k cc bin s sau:

- in p ra Ud

- Dng in ra Id

- in p hai u cun dy UL V cc ng cong tng ng vi cc s cho trong hnh 3.2.2.5 v 3.2.2.6.


- 123 -


- 124 -

Cu hi 1 :

Bn xung iu khin c quan h v pha nh th no?

Tr li:

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. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Cu hi 2 :

Bn c nhn xt th no v hin tng cun dy i lc lm vic nh mt my pht?

Tr li:

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. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .


- 125 -

3.3 Mch iu khin pha

3.3.1Tng qut

c th vn hnh mt mch cu hai xung iu khin han tan B2C, bn cn mt mch iu khin cung cp bn xung iu khin c lp v in, trong c hai cp, mi cp gm hai xung ng b vi nhau.Hai cp lch nhau v pha 1800.

Nhng xung iu khin ny cn phi ni thng trc vo in p ngun.Chng cng phi thay i v

pha bng mt in p lch Uin. thc hin c iu ny, bn cn c mt mch theo s khi nh sau:

H.3.3.1.1 S nguyn l mch iu khin

Tng ng b

Tng to in p lch

Tch knh 1 Cch ly in th 1

To xung Cch ly in th 2

Tch knh 2


- 64 -

H.3.3.1.2 Thc hin mch iu khin pha dng trong BO CNG SUT

Mt my pht in p rng ca bt u vo thi im in p ngun i ngang qua im khng trong tng ng b. in p ny lun lun bt u sn ln ca n ng vo thi im khng ca in p ngun.Ngai ra, nhng tn hiu iu khin cho bn k dng v bn k m cng c pht ra tng ny.

Trong tng to in p lch sau y, in p rng ca c so snh vi in p lch Uin.Nu in th

ti u vo khng o dng hn tn hiu ti u vo o ca b so snh th in th ti u ra ca n l +U. Ngc li, nu in th ti u vo o ln hn, th in th ti u ra l 0V. iu ny to ra

mt tn hiu c dng sng vung, tc mt xung vung lun lun c sn ln trng vi im khng ca

in p ngun v do lun lun ng b vi in p ngun.Sn xung ca n c th dch chuyn ti hay lui gia hai im khng ca mt bn k ty theo in p lch Uin.

Tn ny cn phi c gia cng c th thay i thi im kch m Thy-ris-to.

Tn hiu ny c kt ni vi cc tn hiu iu khin cho bn k dng v bn k m qua mt cng V trong B tch knh. B ny cho chng ta nhng tn hiu trong hai bn k dng v m c lp vi nhau.

Cui cng, nhng tn hiu kch m Thy-ris-to c a vo mt bin p iu khin trong b cch ly in th, b ny c nhim v to ra ln lt hai xung iu khin ng b ring bit.Tuy nhin, ng thi in p iu khin UGC cng c tng ln bng cch ng v ct in cm truyn.


- 65 -

3.3.2 Phn th nghim

Th nghim

o dng chy ca cc tn hiu trong mch iu khin pha trong BO CNG SUT

Phng php

Mc mch in nh trong hnh 3.3.2.1.

Chnh in p iu khin bng +6V nh chit p chnh tr s t.

Quan st trn dao ng k cc tr s:

- in p ngun US

- in p iu khin UI 1

- in p iu khin UI 2

V cc ng biu din trong cc s cho H.3.3.2.2 va 3.3.2.3.

Ch : Chit p iu chnh gc mM trong mch iu khin pha phi khng hot ng. Phi xoay

nm iu chnh ht c v bn phi lm th nghim ny.

V0121 Gio Trnh Th nghim in T Cng Sut Khoa in

- 66 -


- 67 -

Cu hi 1:

Nu cu chnh lu mt pha II c iu khin bng phng php iu khin pha I, th nhng in p

V1,V2,V3,V4 phi tun theo nhng iu kin no (bng 3.3.2.1) ?

Tr li :

V1:

V2:

V3:

V4:

H.3.3.2.1


- 68 -

Ch :


- 69 -

3.4 Mch chnh lu cu 1 pha bn iu khin 3.4.1 Tng Qut Nu bn mun iu khin in p ra ca mt mch chnh luu cu hai xung bng phng php iu khin pha, bn s phi dng hai van bn dn c iu khin. Mt van phi iu khin c trn ng dng in tng ng vi bn k dng ca in p ngun, van kia cng phi nh vy tng ng vi bn k m. C hai cch lm iu ny. Hnh 3.4.1.1 v 3.4.1.2 trnh by hai mch in tng ng. Cc van bn dn 1,2,3,4 to thnh cc cp nhnh Nu c hai van c iu khin ca cu thuc v H.3.4.1.1 Mch chnh lu cu bn iu mt cp nhnh, th ta gi l mch chnh lu cu khin hai cp nhnh B2HZ bn iu khin hai cp nhnh B2HZ.

Cp nhnh cn li ch cha hai Diode thng (khng iu khin). Mch ny trc y c gi l mch chnh lu cu bn iu khin bt i xng v hai cp nhnh c cu to khc nhau- bt i xng. Tuy nhin, nu c hai cp nhnh u c van iu khin, th mch ny c gi

l mch chnh lu cu hai xung mt cc B2HC. V c hai cc m ca hai van c iu khin to thnh mt cc

ca in p mt chiu, cho nn trong k hiu tn ca

mch c thm mt ch

C. Mch ny trc y c gi l mch chnh H3.4.1.2 Mch chnh lu cu hai xung lu bn iu khin i xng v c hai cp nhnh c cu Cc B2HC

cu to ging nhau.

C hai bn k dng v m u c th iu khin c trong c hai mch chnh lu cu bn iu

khin. Nu mch ngai l mt ti thun tr, thin p ra Ud c cng dng sng nh dng sng trong mch chnh lu cu iu khin han tan B2C. Tuy nhin nu ti c tnh in cm th hai Diode trong mch B2HZ hay mt Diode v mt van iu khin trong mch B2HC tc dng nh mt nhnh phc hi trong vng in p m ca ti.

Do trong mch chnh lu cu bn iu khin, mt khng c vng in p m trn ti.


- 70 -

3.4.2 Phn th nghim

Cc iu lu trong cc th nghim sau:

Chit p iu chnh gc mM trong mch iu khin pha phi khng hot ng. N phi c vn ht v bn phi trong th nghim ny. Mch iu khin pha cn mt in p iu khin trong thang o +U thc hin nhng php o trong mc ny. Do , hy chnh chit p t 0V n +10V. Ni ng ra ca chit p vi ng vo iu khin +U ca mch iu khin pha I. S bin p chnh lu phi c qui nh theo s Thy-ris-to thay v theo in p iu khin.

V d, I1 l bin p chnh lu 1 trong mch iu khin pha I. Mt mi ni ca bin p

chnh lu c nh du bng mt im. Mi ni ny phi c ni vo cc cng (G) . Mi ni th hai phi c ni vo Ca-tt (K). My dao ng k nn ni vo NGUN in.

Nu in p ngun US v in p ra Ud khng c im chun chung, th chng phi c o ring r.

y ch kho st mch chnh lu cu bn iu khin hai cp nhnh B2HZ nh mt v d v mch

chnh lu bn iu khin.

Th nghim

o dng v p trong mch chnh lu cu bn iu khin hai cp nhnh B2HZ.

Phng php

Mc mch in nh trong hnh 3.4.2.1 vi BO CNG SUT (cng xem H3.4.2.2). Ch dng ti l mt in tr thun.

Chnh gc m bng 360.

Kho st trn dao ng k cc bin sau:

- in p ra Ud

- Dng qua Thy-ris-to IV2

- Dng qua Diode IV4

V cc ng cong vo cc biu d cho sn H.3.4.2.3 v 3.4.2.4.

Ch :

Chit p iu chnh gc mM trong mch iu khin pha phi khng hot ng. Phi chnh ht v bn phi trong th nghim ny.


- 71 -


- 72 -


- 73 -


- 74 -

By gi ni ti c tnh in cm.

Quan st trn dao ng k cc bin sau y:

- in p ra Ud

- Dng in ra Id

- Dng qua Thy-ris-to IV2

- Dng qua Diode IV4

V cc ng cong vo s cho

H.3.4.2.5 v 3.4.2.6


- 75 -

Cu hi 1 :

Ti sao dng in chy qua Diode V4?

Tr li :

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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- 76 -

Cu hi 2 :

Hai xung iu khin I1v I2 phi c quan h v pha nh th no?

Tr li:

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. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Cu hi 3:

Ti sao chng ta o nhng dng in m Iv2 v Iv4 ?

Tr li:

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- 77 -

3.5 Mch chnh lu c iu khin 3 pha hnh tia M3C

3.5.1 Tng qut

Ging nh mch chnh lu khng iu khin 3 pha hnh tia M3U, mch chnh lu c iu khin 3 pha hnh tia M3C cng l mt b chnh lu n sng. N cng c gi l mch chnh lu 3 pha c im gia.

Mt Thy-ris-to ch c th dn dng khi in th cc dng ca n ln hn in th cc + ca in p ra Ud.

Tuy nhin cc Thy-ris-to khng th t n dn , m phi ch c mt xung iu khin vo thi im tng ng vi gc m. Cc xung iu khin 3 Thy-ris-to cng lch nhau 1200 in ging nh cc

in p pha UL1 , UL2 , U L3.

H3.5.1.1 Mch chnh lu c iu khin 3 pha hnh tia M3C


- 78 -

H.3.5.1.2 in p ra ng vi gc k = 600

Nu ta ga s l Thy-ris-to V1 ang dn, UL1 c t ng ra v do xc nh in p catt. Thi gian sm nht Thy-ris-to V3 dn tip theo V1- l vo thi im c. Thy-ris-to V5 mi n tn thi im e mi dn, cn V1 th bt u dn thi im h hay a. Nhng thi im a,c v e c gi l tng ng vi gc kch t nhi = 00

. l thi im m in p ca mt pha ln hn in p ca pha c ng cong giao ct vi n, Do Thy-ris-to tng ng vi pha ny c th dn in. H.3.1.5.2 v ng cong in p ra ng vi gc k = 600. iu ny c th minh xc c:

Thi im a: Thy-ris-to V5 ang dn. Nu trong mch M3U (dng Diodes ?

khng iu khin)

th Diode

V1 s dn. Cn trong mch ny th khc, Thy-ris-to V1 ch dn khi c xung iu khin, m xung ny li xut hin tr hn mt thi gian ng v = 600. Do Thy-ris-to V5 vn tip tc dn cho n khi cc tnh ca in p t vo n o chiu ( vi ti thun tr, U = 0V => I = 0A => di mc dng duy tr => Thy-ris-to b kha). Do Ud = 0. Thi im b: Vo thi im ny, V1 nhn xung iu khin, Ud t ga tr UL1. Thi im c: Nu l nhng Diode thng th V3 s dn. Nhng y V3 vn cn kha nn dng vn tip tc chy qua V1 cho n khi in p o chiu Thi im d: Vo thi im ng v = 600 xung iu khin ca V3 xut hin. Ud t ga tr UL2, V c nh th


- 79 -

H.3.5.1.3 in p ra khi ti c tnh in c m


- 80 -

Vi ti thun tr, dng sng ca dng in ging vi dng sng ca ca in p ra Ud; nhng

c van ang dn trc thi im m ca van k tip mt gc 300. V vi gc k = 1500 , in p tng ng c cc tnh m nn Thy-ris-to tng ng s khng dn. Do , gii hn ca gc k i vi ti thun tr s t 00 n 1500. S liu i vi ti c tnh in cm c ct ngha trong hnh 3.5.1.3. Trong hnh ny, ta ga s ti c R nh v L ln v gc kch c tng ln t t. in cm ca ti bo

m rng trong mi trng hp s c dng in chy lin tc ngay c khi in p phn cc ca pha

tng ng o cc tnh. V Thy-ris-to tng ng s vn c dn cho n khi n c tip sc bi Thy-ris-to k tip: lc ny dng in c chuyn qua Thy-ris-to k ti = 150 :Trong khi Thy-ris-to V5 cn

ang dn, th Thy-ris-to V1 bt u dn. Hai Thy-ris-to cng dn trong mt khang thi gian ngn to ra mt ngn mch gia UL1 v UL3. ULl c tr s tm thi l 230V, UL3 c tr s l 84.1V.Mt in p chuyn mch UC = -145.9V c t vo V5 nh dng ngn mch tng hp y dng I5 xung di tr s ca dng duy tr lm V5 b kha li. V1dn v tip qun dng in = 600 : nh hng ca dng in ln dng sng ca Ud c trnh by y.in p ra c nhng an m. Dng in chuyn

t pha 2 sang pha 3. Dng ngn mach chuyn mch c to ra bi UL3 = 325V v UL2 = 162.5V; do n chy sang V3 (I3) lm V3 b kha. V5 dn v tip qun d = 900 : Mc d chng ta vn c dng Id dng, nhng in p ra ca chnh lu l han tan xoay chiu ( ng cong in p nm c trn v di trc hanh). Tuy nhin, trng hp l tng ny ch xy ra khi tr s ca in tr R ca ti l khng ng k. T

thi im Thy-ris-to dn cho n thi im m ng cong in p ct trc hanh, cun dy nhn nng lng t ngun v tr li cho ngun trong thi gian cn li ca chu trnh dn nh mt my pht. Ta c th thy r = 00 n 900, th mch vn hnh nh mt b chnh lu, v cng tng th in p mt chiu ng ra cng gim v b = 900. Ch chnh lu chm d = 900 ( v tr gii hn ca ch chnh lu). Tuy nhin, v mt l thuyt th gc kch c th tin = 1800 (H3.5.1.2). iu kin tin quyt duy nht dng in c th chuyn sang nhnh k tip l : in p ca Thy-ris-to k tip phi dng hn in p ca Thy-ris-to trc. Trong khang t a n d, UL1 ln hn UL3, trong khang t c n g, UL2 ln hn UL1, v.v

3.5.2 Phn th nghim Ch trong nhng php o sau y: Mch iu khin pha cn mt in p iu khin trong thang o +U thc hin nhng php o trong mc ny. Do , hy chnh chit p t 0V n +10V. Ni ng ra ca chit p vi ng vo iu khin +U ca mch iu khin pha I,II v III. S bin p chnh lu phi c qui nh theo s Thy-ris-to thay v theo in p iu khin. V d, I1 l bin p chnh lu 1 trong mch iu khin pha I. Mt mi ni ca bin p chnh lu c nh du bng mt im. Mi ni ny phi c ni vo cc cng (G) . Mi ni th hai phi c ni vo Ca-tt (K). My dao ng k nn ni vo NGUN in. Nu in p ngun US v in p ra Ud khng c im chun chung, th chng phi c o ring r.


81

Th nghim o dng v p trong mch chnh lu c iu khin 3 pha hn tia M3C

Phng php

Ni mch in nh trong H.3.5.2.1 vi BO CNG SUT (xem H.3.5.2.2). Bt cng tc M3/M6 qua M3. Ni cu chnh lu vo b ngun 3pha cp in cho mch. Chnh mch ng b ca mch iu khin pha II qua L2 bng cng tc L1/L2. Ni cu vo my pht xung trong mch iu khin pha I.

Chnh nm iu khin gc mM trn mch iu khin pha I v II sao cho 3 Thy-ris-to ln lt

bt u dn vo ng cc thi im lch nhau khang 1200 ca in 3 pha.

Tin hnh nh sau: Kho st trn giao ng k UL1 v Ud. Chnh gc k = 900. Sau bn c th chnh cc xung n ca Ud c cng gc kch v bin nhM bng cc chit p tng ng. ( c th c sai s do sai s ca cc phn t mch gy ra). Ch : Trong mch chnh lu 3 pha, gc k khng tnh t im 0 ca UL1 m phi tnh t giao im ca UL1 v UL3. Nu mun tnh t im 0 ca UL1 th gc o c phi tr i 300.

? Kho st trn dao ng k cc bin sau y ng vi gc k = 900, v = 1200: - in p ra Ud - Dng in qua ti Id

H.3.5.2.1


82

H.3.5.2.2 chuyn mch o n BO CNG SUT


83


84

Cu hi 1:

Cc xung iu khin I1, I2, I3 phi c quan h v pha nh th no ?

Tr li :

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85

Cu hi 2 :

Trong php o no th dng mt chiu Iout b gin an ?

Tr li:

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Cu hi 3 :

Ti sao dng in khng b gin an ti gc k = 450?

Tr li:

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Cu hi 4 :

Mt in cm nh hng nh th no n s gin an ca dng in trong mch ti?

Tr li:

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86

Ch :


87

3.6 Mch chnh lu iu khin 3 pha hnh tia lm vic trong ch nghch lu:

3.6.1 Tng qut

in p ra ca mch chnh lu c th c tr s m (xem mc 3.5, H3.5.1.3). Chng ta gii thch vic mt b bin i c thit k chnh lu sau li chuyn qua ch nghch lu. iu ny c th hnh dung c khi xt mt b bin i iu khin mt ng c DC, chng hn mt cu trc.

Ga s ng c c cp dng in nh mc v in p phn ng dng nn ngu lc nng ti.ng c lm vic ch ng Nu ta tng gc kch ln th dng qua ng c s gim i v ngu

lc ca ng c hu nh bin mt. n mt tr s no moment cn s ln hn moment tc ng ca ng c. Ti s h xung t t v ko ng c quay theo chiu ngc li. V vy, chng ta a ra khi

nim v ti nng-h. ng c tr thnh my pht ( dng v p c cc tnh ngc chiu). Ch nghch lu tng ng vi gc k t 900 n 1200. H3.6.1.1. trnh by chi tit vn ny.

c v n chu mt moment cn do ti tc dng ln.


88

H3.6.1.1 Mch chnh lu 3 pha hnh tia M3C lm vic trong ch nghch lu


89

Trong H.3.6.1.1, ta gi s rng mch chnh lu lm vic nh mt ngun p m c in tr trong tng icao. Mch ny d thc hin trn BO CNG SUT v gn nh tng ng vi trng hp ng c quay ngc chiu c cp trc y.

Khi tng gc kch ga tr trung bnh ca Ud ngy cng m hn nhng lun lun ln hn in p UB ca bnh in. Do , dng Id vn cn dng. Chng ta c th thy rng cc iu kin c th chuyn mch thnh cng c tha mn i vi cc gc kch c v. in p ca Thy-ris-to tip

qun dng in ln hn in p ca Thy-ris-to dn trc n. Trong qu trnh chuyn mch xy ra hin tng ngn mch lm Thy-ris to k tip b kha. Tuy nhin, tnh hnh tr nn xu i khi chng ta

tng gc kch ln tr s gii hn 1800. Ch ta trnh by mt v d trng hp g = 1780 . in p qua Thy-ris-to tip qun UL3 ch l Uc = 19.7V ln hn UL2 . Do to ra c dng ngn mch

cn thit kha V3 v s chuyn mch sang V5 thnh cng. Khi gc kch bng 1800 , th hai in p ny bng nhau, do khng c in p cn thit chuyn mch. Tnh trng cn xu hn na i vi Thy-ris-to cn c kha l: in p chuyn mch n nh tr nn dng sau thi im 1800 .

H.3.6.1.1 cng cho thy cc mi quan h ng vi trng h = 1820 . in p UL2 tng mau trong khong sn ln ca xung . Nu by gi V5 dn, th s chuyn mch s khng thnh cng v in p t vo V3 l theo chiu dng in.

Chng ta nhn xt l: phm vi ca gc kch bng 1800 ch l l tng. Thc t tr s ny phi nh hn v nhng l do sau y:

Phi c mt in p chuyn mch m i vi Thy-ris-to cn kha. Thy-ris-to phi cn thi gian

kha v dng qua n khng th trit tiu ngay tc thi. Do khang cch an tan thng thng l

150 nh hn tr s l thuyt.


90

3.6.2Phn th nghim Cc iu lu trong cc th nghim sau: Mch iu khin pha cn mt in p iu khin trong thang o +U thc hin nhng php o trong

mc ny. Do , hy chnh chit p t 0V n +10V. Ni ng ra ca chit p vi ng vo iu khin +U ca mch iu khin pha I. S bin p chnh lu phi c qui nh theo s Thy-ris-to thay v theo in p iu khin.

V d, I1 l bin p chnh lu 1 trong mch iu khin pha I. Mt mi ni ca bin p chnh lu c nh du bng mt im. Mi ni ny phi c ni vo cc cng (G) . Mi ni th hai phi c ni vo Ca-tt (K). My dao ng k nn ni vo NGUN in. Nu in p ngun US v in p ra Ud khng c im chun chung, th chng phi c o ring r

V d

o in p v dng in trong ch nghch lu ca mch M3C

Phng php

Ni mch in nh trong hnh 3.6.2.1. Chnh ti sao cho in tr cp nhit PTC ca h iu khin sng (Lai 5125.5) v in tr 1k to thnh mt b phn p 10V.

V chc nng: B chnh lu hot ng nh mt ngun p m 10V v mt ni tr tng i cao. Mch s m phng s vn hnh ca mt ti hot ng nh my pht.

Vn cng tc M3/M6 qua B6 gim in p ra Ud. Chnh gc gii hn nghch lW mch iu khin pha I v II sao cho 3 Thy-ris-to c kch

nhng thi im gn bng 1200 .

iu ny c thc hin nh sau: Quan st trn giao ng k UL1 v Ud. Chnh gc k = 900 . Sau bn c th chnh tng xung ring

r ca Ud c cng gc kch v bin vi cc chit p tng W . ( c th c sai s do cc linh kin c sai s)

Ch :

Trong mch chnh lu 3 pha, gc k khng tnh t im 0 ca UL1 , m t giao im ca UL1 v UL3. Nu bn mun tnh t im 0 ca UL1 , th kt qa phi tr i 300 .

Chnh s ng b ca mch iu khin pha II bng cch vn cng tc L1/L2 qua L2. Quan st trn dao ng k cc bin s sau y ng vi gc k = 900 v =1500 :

- in p pha UL1 (L1/N) - in p ra Ud

o ga tr trung bnh s hc ca dng mt chiu Id ar.


91

Gii thch mch in:

Ngun cp in cho cu c chnh qua B6 do Ud s nh hn bnh thng. Ta chnh ti sao cho n bin thnh mt b phn p c in p ra m v ni tr tng i cao.

iu ny s m phng mt ti nng h (mc 3.6.1).

c tnh ca ti tc ng nh mt my pht l dng v p khc du. Dng Id trong trng hp ny dng s vn cn dng khi in p ca my pht i chiu. Nh vy chiu chy ca nng lng s l t ngun ti ti khi dng v p cng chiu; v t ti ti ngun khi dng v p ngc chiu.


92


93

Cu hi 1 :

Trong trng hp no th in p ra ca b chnh lu c tr s m?

Tr li:

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Cu hi 2 :

B chnh lu cng c th cho php mt dng in m chy qua hay khng?

Tr li:

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94

Ch :


95

3.7 Chnh lu cu 3 pha c iu khin B6C

3.7.1 Tng qut

V nguyn tc in p ra ca chnh lu cu 3 pha B6C cng cn c gi l chnh lu cu 6 xung c to ra ging nh trong mch chnh lu cu 3 pha khng iu khin B6U. C hai mch y c th c coi nh l s kt hp ca 2 mch chnh lu 3 pha hnh tia trong mt mch chnh lu bn

k dng, cn mch kia chnh lu bn k m.

Do c cc tnh khc nhau, tng ca hai in p chnh lu chnh l in p ra Ud.

Trong mch chnh lu cu 3 pha, iu quan trng l c 2 Thy-ris-to lun lun dn ng thi mt na trn v mt na di ca cu. Ch c nh vy th dng mt chiu Id mi c th chy t na trn ca cu, i qua ti , ri qua na di ca cu tr v ngun.

Nu cu ang hat ng, th mt Thy-ris-to s tip qun dng in t Thy-ris-to trc. Tuy nhin , nu

cu sp sa dn in, th hai Thy-ris-to phi ng thi nhn c xung kch. bo m cho iu ny xy ra ti mi thi im kch xung, cc Thy-ris-to phi nhn c hai xung kch cch nhau 600 . Lai xung ny c gi l xung 600 ni tip.

H3.7.1.1 Chnh lu cu 3 pha c iu khin B6C


96

H.3.7.1.2Hat ng ca mch chnh lu cu 3 pha c iu khin


97

Hnh 3.7.1.2 trnh by mi quan h quan trng nht, cc in p 3 pha v in p ra Ud. Cc in p pha c v vi cc xung kch, cc Thy-ris-to k hiu trong vung thuc v na trn

ca cu. Cc an tng ng vi in p ra Ud c v vi nt m trn cc ng cong in p pha.

Thi im a:

Thy-ris-to bt u m vo thi im UL1 c tr s dng va v UL2 c tr s m.Do phi cn mt xung kch cho V1 v V6 .

Thi im b:

Vo thi im ny UL2 phi c thay th bng UL3 c in th m, Thy-ris-to V2 cn mt xung kch. Cn Thy-ris-to V1 vn dn. N cng nhn mt xung mc d khng cn thit.

Thi im c:

Vo thi im ny UL1 phi c thay th bng UL2 c in th dng, Thy-ris-to V3 nhn mt xung kch. Cn Thy-ris-to V2 vn dn v vn nhn mt xung 600 ni tip.

Thi im d:

Thy-ris-to V5 dn v a UL3 vo cc dng, Thy-ris-to V4 vn dn trong bn k m.

Thi im e:

Gc kch tng t ngt t 450 ln 750, nn cc xung kch b chm li 300. Thy-ris-to V4 v V5 vn cn dn n thi im f.

Thi im f:

in p gia UL3 v UL1 bng khng v sau cc tnh b o ngc : c hai Thy-ris-to b kha v tip tc kha cho n thi im g. Ud tin v zero , in p ra bt u gin an.

Thi im g:

S thay i t nght ca gc kch ti e tr nn ng lu vo thi im ny ch sau mt thi gian tr

: Thy-ris-to V5 a UL3 vo cc dng, Thy-ris-to V6 a UL2 vo cc m.

Thi im h:

C hai in p tc ng UL3 v UL2 c cng tr s vo thi im ny, Ud sau thay i cc tnh :

C hai thy-ris-to u b kha.

Xung 600 ni tip cng c th c to ra bi b to xung chm dng trong BO CNG SUT. y, khng phi ch mt xung m l mt chm xung c truyn i vi iu kin l chm xung

phi ko di hn 600.


98

3.7.2 Phn th nghim

Th nghim

o dng v p trong mch chnh lu cu 3 pha B6C

Phng php

Lp mch in nh trong hnh.3.7.2.1.

ng cu chnh lu vo ngun 3 pha.

Chnh cng tc M3/B6 qua B6.

Chnh cng tc khu ng b trong mch iu khin pha II qua L2.

Chnh nm iu khin gc kM trn mch iu khin pha I v II sao cho 3 Thy-ris-to ln lt bt u dn vo ng cc thi im lch nhau khang 1200 ca in 3 pha.

Tin hnh nh sau:

Kho st trn giao ng k UL1 v Ud. Chnh gc k = 900. Sau bn c th chnh cc xung n ca Ud c cng gc kch v bin

nhM bng cc chit p tng ng. ( c th c sai s do sai s ca cc phn t mch gy ra).

Ch :

Trong mch chnh lu 3 pha, gc k khng tnh t im 0 ca UL1 m phi tnh t giao im ca UL1

v UL3. Nu mun tnh t im 0 ca UL1 th gc o c phi tr i 300.

Chnh gc k = 360.

Quan st trn dao ng k cc bin sau:

-

in p ra Ud

- Dng

in ra Id

- Dng qua Thy-ris-to IV4, IV6 v IV2

V cc ng cong vo s cho H.3.7.2.2 . . . . .3.7.2.4.


99


100


101

Cu hi:

Gii thch dng ca ng cong dng in qua Thy-ris-to.

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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102

Ch :


103

3.8 Tr trung bnh s hc v hiu dng ca dng in trong b chnh lu iu khin

3.8.1 Tng qut

Trong b chnh lu iu khin, nng lng cung

cp cho ti RL c th bm tng liu bng cch

iu khin pha. Do in p ngun c truyn

ti ti theo tng phn, nn s gia tng ca cc

lng nng lng l khng tuyn tnh .Khi gc

kch tng 200, t = 1400 l = 1600, th nng

lng tng ln t hn so vi khi gc kch cng

tng 200, nhng t = 700 l = 900 .

Hnh 3.8.1.1 v 3.8.1.2 m t iu ny bng ca-

kch dng in p ra Ud trong mt mch chnh lu

M1C lm v d.

Quan h gia c tnh iu khi/ Ud0 v

gc k cng ni ln iu ny.

Hnh 3.8.1.3 trnh by quan h ni trn trong

mch chnh lu M1C vi ti thun tr.

Trong nhng mch in y, khng th dng

mt VOM thng thng o ga tr hiu dng

ca in p ra v ng cong in p c nhng

an khng sin. Do bn cn dng nhng

my o lai in ng hay in t. Tuy nhin,

ngay c nhng my o lai ny cng khng th

o chnh xc c nhng tr s ng vi g

rt ln. Ga tr cc i ca in p ra c gi l

in p DC l tng Ud0.


104

3.8.2 Phn th nghim

Th nghim

Xc nh c tnh iu khin ca cc b chnh lu iu khin M1C, B2C, M3C v B6C.

Phng php

Lp mch o cho nh trong hnh 3.8.2.1.

Xc nh ga tr trung bnh ca in p trn t v t s bin thin t 150 n 1800

.

in cc tr s tm c vo bng 3.8.2.1.

V ng cong kt qa vo trong hnh 3.8.2.2.


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Cu hi:

T s gia tr hiu dng v trung bnh s hc ca in p ra bin thin nh th no theo gc k ?

Tr li:

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4. B BIN I IN P XOAY CHIU

4.1. B BIN I IN P XOAY CHIU MT PHA W1C

4.1.1. Tng quan:

Phn ny chng ta dng iu khin in p xoay chiu mt pha (cng c bit n nh b bin i trc tip AC ) in hnh cho mch bin i in p xoay chiu.

Chng ta thng s dng TRIAC nh mt van trong th nghim o. V mt l thuyt th mch

c th cng c th c lp t vi hai thyristor mc i song. ( Hnh 4.1.1.1 trnh by hai mch c th dng trong iu khin ny ).


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TRIAC nhn tn hiu xung kch vi in p chnh n nh t cng iu khin pha I, xung kch

tr c th c iu chnh bng gc kch trong phm vi iu chnh t 00 180 0 . Hnh

4.1.1.2 ng vi gc kch = 900.

Nh trn hnh 4.1.1.2, c hai na chu k ca in p u b ct trong mch bin i in p xoay chiu 1 pha. Nu mch ny dng hai thyristor mc i song ging nh hnh 4.1.1.3. trong

mch ny ( khi c xung kch) Thyristor V1 dn trong chu k dng, Thyristor V2 dn trong chu k m. V vy Thyristor V1 nhn c xung kch t MBA xung mang tn hiu xung

dng. ( trong trng hp MBA xung 1 hoc 4 iu khin cng pha . Tng t nh vy, thyristor nhn xung kch trong chu k sng m ( MBA xung kch 2 hoc 3 ).


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Khi s dng TRIAC nh mt van bn dn, cng iu khin s c thay i cch du. (Hnh 4.1.1.4 ).

T 2 na chu k ca dng sng in p cn iu chnh, TRIAC phi nhn c xung kch trong c 2 na chu k. Nhng khng c MBA cp xung kch cho c 2 chu k v cc MBA c tch ring cho

mi na chu k ( hnh v ) . Tuy nhin, tn hiu iu khin c th nhn c bng cch u ni tip 2 MBAi (trong VD ny: FT3 v FT1).

Xt kha cnh khc, khi nhn vo hnh 4.1.1.2. chng ta c th thy rng dng in ra ca b bin i trc tip AC khng c dng sin, N khng ging vi dng in p u vo, sinh ra cng sut

phn khng, cng sut phn khng ny cn c th c gi l ,, Ha tn ,, .hay iu chnh cng sut

phn khng.

gii thch v loi cng sut cm ng c bit mt cch chi tit s vt qa gii hn ca phn ny. c mt s ti liu c a ra gii thch v vn ny. Tuy nhin c th ni rng vic tng

gc iu khin ng ngha vi tng cng sut phn khng ha tn. iu ny c ngha l dng in

u ra s cng xa di dng sin.


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PHN TH NGHIM

Th nghim

Tn hiu trn cng iu khin pha khng c tc ng ca b chng lu.

Trnh t tin hnh:

- lp t mch theo hnh 4.1.2.1

- Trn POWER BOARD Mc mt in tr 27 song song vi mt bng n si t ta

nhit. V iu chnh sng ca bng n.

- Xung kch m c ly t u ra ca hai MBA ni tip I3 v I1.

- t gc kch = 900.

-

Dng my hin sng quan st cc dng sng in p:

in p chnh Us

in p ra Uout

in p trn TRIAC UV1

in p cng UG

- V ng cong c tnh vo th H 4.1.2.2, H 4.1.2.3

Ch :

Gc kch w trn cng iu khin pha khng iu chng c. Chng ta nn dng li lcthch hp.


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Cu hi 1:

in p trn bng n ln nht ti gi tr gc kch l bao nhiu?

Tr li:

Cu hi 2:

Nu bng n c tng dn sng nn, khi gc iu khin s thay i nh th no?

Tr li:

Cu hi 3:

in p chnh xy ra hin tng mo dng, Khi kch TRIAC, Ti sao?

Tr li:


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4.2. IU KHIN THEO NHM XUNG

4.2.1. Tng quan:

gii thch phn 4.1 v ha tn cng sut phn khng c sinh ra trn cng iu khin pha

vi ti thun tr. Ha tn cng sut phn khng c th c gi mc thp, khi dng v p s

c dng gn sin v dng sin.

ti c iu khin VD- iu chnh l nng in tr hoc bp in, my un nc nng. chu k dng kch m TRIAC, ta nhn c xung ch nht, khi TRIAC kha,n in p ra bng 0. in p v dng in lun c dng sin. Phi iu chnh ha tn cng sut phn khng

mc thp nht. Ngc li vi cng tc ti trc i qua im 0, qu trnh ng ct cho kt qa c tnh dng hi dc v c chiu tng ln ti cng iu khin . Cc qu trnh ng ct sinh ra dao ng tn s cao c th to nn hin tng nhiu trn in p chnh v trn radio ti 1 s bc sng nht nh.


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Khi iu khin TRIAC trng thi xung thu c :

- Cng tc ang im 0.

- iu khin t do h sTtD on= .

- Chu k ng ct T trong phm vi 1 giy.

B so snh s pht ra tn hiu xung dng trong 1s khi so snh in p delta UD v in p iu chng

mt chiu. H s D chnh l h s iu chnh t do. Ti thi im pht xung dng l AND vi tn hiu in p ra bng 0.

tn hiu xung c sinh ra c di ca ph thuc vo bin ca in p mt chiu cung cp. Hot ng ca mch ph thuc vo tn s dao ng ca xung iu khin trong 1 chu k.

TRIAC c th c kch kha khi in p chnh i qua im 0 , c th iu chnh trong c chu k dao n sin. Mc ch ca phn ny l b so snh s to tn hiu xung vung c gi tr on/ off . cui cng

l 2 tn hiu l ,, AND LIKE ,, vic to ra nhm tn hiu ny nh vic pht kch TRIAC.


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PHN TH NGHIM:

Th nghim:

ng cong in p trn mch iu khin nhm xung vi b bin i in p xoay chiu 1 pha W!C

Trnh t tin hnh:

- lp t mch theo hnh 4.2.2.1

- t in p iu khin U = 7 V.

-

Dng my hin sng quan st cc dng sng in p:

in p chnh Us

in p ra Uout

- V ng cong c tnh vo th H 4.2.2.2,

in p chnh Us :

in p ra Uout :


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5. B IU CHNH IN P MT CHIU

5.1. IU CH RNG XUNG

5.1.1. Tng quan:

Phn ln cc loi iu kin tn s thng s dng bin i in p my pht v ng c DC s dng phng php iu ch rng xung ( PWM ). y vic tnh ton in p trung bnh ca xung in p b nh hng bi thi gian ng van ton v thay i theo chu k c nh T, Mt cch khc c th gi phng php ny l phng php iu ch thi gian tn ti xung.

VD, Bn c th iu kin in p trn ti vi phng php ny, vic tnh ton gi tr trung bnh

ca dng ti il s thay i theo h s D:

p dng cng thc sau: TtD on=


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Vi mch khuyh i thut ton n gin, vic chuyn mch iu ch xung c th c lp t

nh hnh 5.1.1.2 Mt b khuych i thut ton so

snh in p xoay chiu delta UD v in p iu khin Uctr. B khuych

i thut ton c s dng nh

mt b so snh.

Chc nng ca b so snh trn: Nu gi tr ca in p iu khin

Uctr ln hn gi tr ca in p

giao trinh thi nghiem dien tu cong suat

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