2 22.2 Rezistoare dependente

$SOLFD LLOHWHUPLVWRDUHORU37&

$SOLFD LLOHWHUPLVWRDUHORU37&VXQWIRDUWHQXPHURDVHFkWHYDGLQWUHHOHILLQGXUPWRDUHOHSURWHF LDvPSRWULYDVXSUDFXUHQ LORUúLDVXSUDWHPSHUDWXULLLQGLFDWRDUHde nivel, circuit de demagnetizare pentru tuburile cinescop color, termostate cuYDORULIL[HDOHWHPSHUDWXULLUHOHHGHWHPSRUL]DUHPVXUWRULGHWHPSHUDWXUúLPDLUDUFRPSHQVDUHDYDULD LHLFXWHPSHUDWXUDDDOWRUHOHPHQWHGHFLUFXLW

Cele prezentate la începutul capitoluluiGHDSOLFD LLSHQWUXWHUPLVWRDUHOH17&VHSRWDSOLFDúLvQFD]XOWHUPLVWRDUHORU37&RFODVLILFDUHXQLWDUDDSOLFD LLORUILLQGGHVWXOGHGLILFLOGHUHDOL]DW3HQWUXXQLWDWHDSUH]HQWULLYRPXWLOL]DDFHHDúLFODVLILFDUHúLYRPvPSU LDSOLFD LLOHGXSUHJLPXOGHOXFUXDOWHUPLVWRDUHORU37&vQUHJLPGHvQFO]LUHLQGLUHFWVDXvQUHJLPGHvQFO]LUHGLUHFW

8WLOL]DUHDvQUHJLPGHvQFO]LUHLQGLUHFW

D0VXUDUHDWHPSHUDWXULL7HUPLVWRDUHOH 37& SRW IL XWLOL]DWH OD PVXUDUHD WHPSHUDWXULL SHQWUX XQ

GRPHQLXFHFRUHVSXQGHSRU LXQLLFUHVFWRDUHDFDUDFWHULVWLFLL576HSRDWHXWLOL]DVFKHPD GH FRQHFWDUH vQ SXQWH SUH]HQWDW OD WHUPLVWRDUHOH 17& ÌQ SUH]HQWSURGXFWRULL QX UHDOL]HD] WHUPLVWRDUH 37& RSWLPL]DWH SHQWUX DFHDVW DSOLFD LH6HQVLELOLWDWHD IRDUWH PDUH D WHUPLVWRDUHORU 37& IDFH GLILFLO UHDOL]DUHD XQRUFDUDFWHULVWLFL WHUPLFH SUHFLV GHWHUPLQDWH ùL vQ FD]XO XWLOL]ULL 37&XULORU HVWHQHFHVDUHWDORQDUHDVFDOHLFDUDFWHULVWLFDWHUPLFILLQGQHOLQLDU

1(b) $SOLFD LLGHWLSVHVL]DUHDWHPSHUDWXULLDYHUWL]DUHúLSURWHF LH'HúL SULQFLSLLOH GH IXQF LRQDUH DOH WHUPLVWRDUHORU 37& vQ DVWIHO GH VLWXD LL

VXQW VLPLODUH FX DOH WHUPLVWRDUHORU 17& H[LVW úL XQHOH GHRVHELUL $VWIHO XQWHUPLVWRU 37& DF LRQHD] DVHPQWRU XQXL WHUPRVWDW UHDOL]kQG ³FRPXWDUHD´ OD RWHPSHUDWXU ELQH SUHFL]DW 3ULQFLSLXO GH IXQF LRQDUH vQ DVWIHO GH DSOLFD LL HVWHXUPWRUXO WHUPLVWRUXO VH PRQWHD] vQ FRQWDFW WHUPLF FX HFKLSDPHQWXO FDUH VHGRUHúWH V ILHSURWHMDW/DR WHPSHUDWXU QRUPDO UH]LVWHQ D WHUPLVWRUXOXL5T esteVF]XW 'DF DSDUH R VXSUDWHPSHUDWXU UH]LVWHQ D WHUPLVWRUXOXL GHSúHúWH EUXVFvaloarea Rb, acest fapt fiind utilizat în mod concret de schema sau de montajulrespectiv.

8QH[HPSOXGHDSOLFD LHHVWHSUH]HQWDWvQILJXUD2.118.Montajul din figura 2.118 este un circuit comparator. La temperaturi T<Tb

UH]LVWHQ D WHUPLVWRUXOXL HVWH 5T<Rb WHQVLXQHD OD LHúLUHD FRPSDUDWRUXOXL ILLQGVF]XW'XSFH5T a devenit mai mare ca Rb are loc comutarea comparatorului,tensiunea VoDYkQGRYDORDUHULGLFDWFDUHSRDWHFRPDQGDXQFLUFXLWGHDYHUWL]DUH

&LUFXLWXO SUH]HQWDW HVWH R YDULDQW PRGHUQL]DW D XQXL FLUFXLW FODVLF GHSURWHF LHODVXSUDWHPSHUDWXU>@SDJ

Cap.2 Rezistoare

2

+

-

+V

GND

R1

R2

Rb R3

Ro

Vo

RT

+θ

Vo

RT<Rb

RT > Rb

Tb T

Fig. 2.118 &LUFXLWGHVHVL]DUHDGHSúLULLWHPSHUDWXULL

RT +t°

D1BZX55C5V6

R2

470Ω

R1

91Ω

RL1

300ΩR25=25Ω

T1

BCY 58

D2BAY 44

+V13,5V

Fig. 2.119 &LUFXLWGHSURWHF LHODGHSúLUHDWHPSHUDWXULL>@

ÌQDFHDVWDSOLFD LH ODFUHúWHUHDWHPSHUDWXULLDUHORFEORFDUHD WUDQ]LVWRUXOXLúL GHFL vQWUHUXSHUHD FXUHQWXOXL SULQ ERELQD UHOHXOXL 5 L1, realizându-se astfelSURWHF LDGRULW

'LQ DFHHDúL FDWHJRULHGH DSOLFD LL IDFH SDUWH úL H[HPSOXO XUPWRU UHJODUHDWHPSHUDWXULLODPDúLQDGHVSODWDXWRPDW

.

RT1

+θ RT2

+θ RT3

+θ

~220V

Ua≅4V

K

30°60°90°

UC

Rp

T1

RL

25Ω

R

RTfi

RT1 RT2 RT3

Tb1 Tb2 Tb3 TN3

(90°C)TN2

(60°C)TN1

(30°C)θ(°C)

Fig. 2.120 Utilizarea termistoarelor PTC la reglarea temperaturii.

&RPSRQHQWHúLFLUFXLWHSDVLYH Note de curs

3

În acest ciUFXLW UH]LVWHQ D GH VDUFLQ 5L VH DIO vQ FXSODM WHUPLF VWUkQV FXtermistoarele PTC RT1-RT3, fiecare corespunzând unei temperaturi prestabilite careWUHEXLH UHJODW(OHPHQWXO GH FRQWURO DO FXUHQWXOXL SULQ UH]LVWHQ D GH VDUFLQ HVWHtriacul T1 /D R DQDOL] VLPSOLILFDW SXWHP FRQVLGHUD WULDFXO FD XQ FRPXWDWRUcaracterizat prin parametrul tensiune de prag Up. Atât timp cât tensiunea deFRPDQG8c este mai mare ca Up triacul conduce curentul electric. În caz contrarWULDFXOHVWHEORFDWDYkQGRUH]LVWHQ SUDFWLFLQILQLW5ROXOWHUPLVWRDUHORUHVWHGHDVHVL]D FUHúWHUHD WHPSHUDWXULL úL D FRPDQGD EORFDUHD WULDFXOXL OD R DQXPLW

WHPSHUDWXU 6H REVHUY F .pTi

pac RR

RUU

+= &kW WLPS WHPSHUDWXUD HVWH PLF

YDORDUHDUH]LVWHQ HLWHUPLVWRUXOXLHVWHúLHDFRERUkWDVLJXUkQGRYDORDUH8c>Up. Laatingerea temperaturii de basculare TbiUH]LVWHQ DWHUPLVWRUXOXLFUHúWHVHPQLILFDWLYFRQGXFkQG OD EORFDUHD WULDFXOXL $VWIHO VH vQWUHUXSH DOLPHQWDUHD UH]LVWHQ HL GHVDUFLQúLJHQHUDUHDGHFOGXUvQFHWHD]'XSXQWLPSWHPSHUDWXUDWHUPLVWRDUHORUYDVFGHDúLWULDFXOYDLQWUDGLQQRXvQFRQGXF LH3ULQDVWIHOGHFLFOXULGHSRUQLUHRSULUHDDOLPHQWULLUH]LVWHQ HLVHUHDOL]HD]GXSXQWLPSUHJODMXOWHPSHUDWXULL'HRELFHLVHXWLOL]HD]PDLPXOWHWHUPLVWRDUHFDUHSRWILVHOHFWDWHSULQFRPXWDWRUXO.

3HQWUX DOHJHUHD WHUPLVWRDUHORU VH YD FRQVLGHUD OD OLPLW 8c=Up

pTfi

pap RR

RUU

+= GHXQGHUH]XOWYDORDUHDUH]LVWHQ HL WHUPLVWRDUHORU vQSXQFWXOGH

IXQF LRQDUH 5Tfi 6H REVHUY GLQ ILJXUD 2.120 F WHPSHUDWXUD GH EDVFXODUH DWHUPLVWRUXOXLYDILDOHDVFHYDPDLPLFFDWHPSHUDWXUDQRPLQDOGHUHJODUH7N.

8WLOL]DUHDvQUHJLPGHvQFO]LUHGLUHFW

D8WLOL]DUHDWHUPLVWRDUHORU37&FDSURWHF LHODVXSUDVDUFLQLUn termistor PTC conectat în serie cu un circuit electronic sau cu un alt

FRQVXPDWRU DF LRQHD] FD R VLJXUDQ UHXWLOL]DELO UHVHWDELO SURWHMkQGconsumatorii împotriva suprasarcinilor accidentale care ar putea fi: supracurent,VXSUDWHQVLXQHVDXVXSUDWHPSHUDWXU

UA

RT +t°

6DUFLQ RS

Fig. 2.1213URWHF LDODVXSUDVDUFLQLFXWHUPLVWRU37&

ÌQDLQWHGHDGHVFULHvQGHWDOLXPRGXOGHXWLOL]DUHDWHUPLVWRDUHORUvQDSOLFD LLFRQFUHWHHVWHQHFHVDUVVHGHILQHDVFFk LYDWHUPHQL

Cap.2 Rezistoare

4

3ULQGHILQL LHSXWHUHDHOHFWULFLQMHFWDWvQWHUPLVWRUHVWH3 5,2 , unde R esteUH]LVWHQ D WHUPLVWRUXOXL vQDLQWHGHEDVFXODUH OD WHPSHUDWXUD DPELDQW7a. PutereaGLVLSDWGHWHUPLVWRUHVWH3 '7b-Ta) unde Tb este temperatura de basculare iar Ta

HVWH WHPSHUDWXUD DPELDQW úL ' HVWH FRHILFLHQWXO GH GLVLSD LH DO WHUPLVWRUXOXL5HXQLQG FHOH GRX UHOD LL VH RE LQH 5,2=D(Tb-Ta UHOD LH YDODELO SHQWUXtemperaturi ambiante mai mici sau egale cu Tb.

Curentul de comutare ("trip current") Ic este definit ca fiind curentulPLQLPJDUDQWDWFDUHSURGXFHEDVFXODUHDWHUPLVWRDUHORUúLSRDWHILFDOFXODWFX

( )[ ]ε+−⋅= abc TTDRI2 (2.180)

FX5UH]LVWHQ DWHUPLVWRDUHORUOD7b iar ε (°&HVWHRPDUJLQHGHVLJXUDQ GDWRUDWabaterilor în definirea valorilor TbúL7a.

Curentul de non – comutare Inc ("non-trip current" sau "hold current") esteGHILQLWFDILLQGFXUHQWXOPD[LPJDUDQWDWODFDUHWHUPLVWRUXOQXEDVFXOHD]FRPXW6HGHILQHúWHSULQ

( )[ ]ε−−= abnc TTDRI2 (2.181)FXDFHHDúLVHPQLILFD LHDPULPLORUFDPDLvQDLQWH

ÌQFD]XOFRQHFWULLXQXLWHUPLVWRU37&vQVHULHFXRUH]LVWHQ GHVDUFLQ5S,GDWRULWIRUPHLFDUDFWHULVWLFLLFXUHQWWHQVLXQHDWHUPLVWRUXOXL37&VXQWSRVLELOHWUHLSXQFWHGH IXQF LRQDUH&DUDFWHULVWLFDHOHFWULF DVDUFLQLL HVWHRGUHDSWQXPLW úLGUHDSW GH VDUFLQ LDU SXQFWHOH GH IXQF LRQDUH UHSUH]LQW LQWHUVHF LD GLQWUHFDUDFWHULVWLFDWHUPLVWRUXOXLúLGUHDSWDGHVDUFLQYH]LILJXUD2.122). Punctele M1úLM3VXQWSXQFWHGHIXQF LRQDUHVWDELOHvQWLPSFH02 este instabil.

UA

UA/RS M1M2

M3

RS

PTC

B

0U

I

ITerm.=ISarcin

I=f(U)=(UA-U)/RS

Fig. 2.122'HILQLUHDSXQFWHORUGHIXQF LRQDUHvQFD]XOFLUFXLWXOXLVHULHWHUPLVWRU±UH]LVWRU

La aplicarea unei tensiuni de alimentare UA circuitului serie din figura 2.121echilibrul se atinge în punctul M1, la un curent relativ ridicat. Echilibrul seVWDELOHúWHvQSXQFWXO03QXPDLGDFYkUIXO%DOFDUDFWHULVWLFLL,8DWHUPLVWRUXOXLVHVLWXHD]VXEGUHDSWDGHVDUFLQ$FHVWOXFUXVHSRDWHvQWkPSODvQWUHLVLWXD LLUA FUHúWH WHPSHUDWXUD DPELDQW FUHúWH UH]LVWHQ D GH VDUFLQ VFDGH 3ULQstabilirea echilibrului în punctul M3 VH H[SOLF úL SURWHF LD UHDOL]DW GHtermistoarele PTC.

&RPSRQHQWHúLFLUFXLWHSDVLYH Note de curs

5

În mod normal, în punctul M1UH]LVWHQ DWHUPLVWRUXOXLHVWHPLFLDUFXUHQWXOWUHEXLH V DLE R YDORDUH PDL PLF GHFkW FXUHQWXO GH QRQFRPXWDUH QRQWULScurrent) IncGHILQLWDQWHULRUÌQDFHODúLWLPSFHDPDLPDUHSDUWHDWHQVLXQLLVHDSOLFsarcinii RS2VXSUDVDUFLQFDUHYDFRQGXFHODGHSúLUHDFXUHQWXOXLGHFRPXWDUH,cYD vQFO]L UDSLG WHUPLVWRUXO SHVWH WHPSHUDWXUD GH EDVFXODUH LDU UH]LVWHQ DWHUPLVWRUXOXLYDFUHúWHSURWHMkQGDVWIHOFLUFXLWXO

3URWHF LDODVXSUDWHQVLXQHFDX]DWGHFUHúWHUHDWHQVLXQLLGHDOLPHQWDUHSRDWHILXUPULWvQILJXUD2.123.

UA

UA/RS M1

M3 PTC

B

0 U

I

M3'

UA’

RS

UA’/RS

RS

UA'>UA

Fig. 2.1235HDOL]DUHDSURWHF LHLODVXSUDWHQVLXQH

/DFUHúWHUHD WHQVLXQLLGHDOLPHQWDUHGH OD8A la UA′ GUHDSWDGH VDUFLQ VH

GHSODVHD] GHDVXSUD SXQFWXOXL GH PD[LP DO FDUDFWHULVWLFL ,8 D WHUPLVWRUXOXLSXQFWXO%úLDVWIHOSXQFWXOGHIXQF LRQDUHVHVWDELOHúWHGLQ01 în M3', termistorulSUHOXkQGFHDPDLPDUHSDUWHDFGHULLGHWHQVLXQHSURWHMkQGVDUFLQD

0RGXOGHUHDOL]DUHDSURWHF LHLODVXSUDWHPSHUDWXUSRDWHILXUPULWvQILJXUD2.124.

UA

UA/RS M1

M3

Ta

B

0 U

I

M3′

B′

Ta′

Ta′ > Ta

Fig. 2.1245HDOL]DUHDSURWHF LHLODVXSUDWHPSHUDWXU3URWHF LDHVWHUHDOL]DWSULQPRQWDUHDWHUPLVWRUXOXLvQFRQWDFWWHUPLFEXQFX

VDUFLQDFDUHVHSRDWHVXSUDvQFO]L$LFLDXIRVWXWLOL]DWHFXUEHOHSUH]HQWDWHDQWHULRUFDUH GHVFULXPRGLILFDUHD FDUDFWHULVWLFLL ,8 vQ IXQF LH GH WHPSHUDWXUD DPELDQW

Cap.2 Rezistoare

6

'DWRULWFUHúWHULLWHPSHUDWXULLDPELDQWH7a′ WHUPLVWRUXODUHQHYRLHGHPDLSX LQ

energie pentru a bascula (punctul B′). În acest fel caracteristica termistoruluiFRERDU VXE GUHDSWD GH VDUFLQ SXQFWXO GH IXQF LRQDUH VWDELOLQGXVH vQ 03

′ úLUHDOL]kQGSURWHF LDVDUFLQLL

5HDOL]DUHDSURWHF LHLODVXSUDFXUHQWSRDWHILXUPULWvQILJXUD2.125.

UA

UA/RS M1

M3'

RS

B

0 U

I

RS'

M3

RS' < Rs

Fig. 2.1255HDOL]DUHDSURWHF LHLODVXSUDVDUFLQVXSUDFXUHQW

8QVXSUDFXUHQWSRDWHDSUHDFDXUPDUHDXQHLVFGHULDYDORULLUH]LVWHQ HLGHVDUFLQFDX]DWGHH[HPSOXGHXQVFXUWFLUFXLWDOvQIúXUULORUXQXLPRWRUHOHFWULF

Prin rHGXFHUHD YDORULL UH]LVWHQ HL GH VDUFLQ OD 5S′ GUHDSWD GH VDUFLQ VH

VLWXHD] GHDVXSUD FDUDFWHULVWLFLL HOHFWULFH D WHUPLVWRUXOXL SURWHF LD UHDOL]kQGXVHSULQVWDELOLUHDSXQFWXOXLGHIXQF LRQDUHvQ03

′DúDFXPDIRVWSUH]HQWDWDQWHULRUAúD FXP D IRVW DPLQWLW OD vQFHSXWXO VHF LXQLL WHUPLVWRUXO 37& SRDWH IL

XWLOL]DWFDRVLJXUDQ UHVHWDELO2GDWFHWHUPLVWRUXO37&DEDVFXODWWHPSHUDWXUDVDGHSúLQG7búLUHDOL]kQG

SURWHF LDFLUFXLWXOXLHVWHQHFHVDU³UHVHWDUHD´SURWHF LHLDGLFUHYHQLUHDODVLWXD LDQRUPDO GH IXQF LRQDUH $FHVW OXFUX SUHVXSXQH vQWRDUFHUHD GH OD SXQFWXO GHIXQF LRQDUH03

′ (vezi figura 2.122) la punctul M1SULQFRERUkUHDGUHSWHLGHVDUFLQVXESRU LXQHDFXUEDWDFDUDFWHULVWLFLLWHUPLVWRUXOXL$FHVWOXFUXVHSRDWHvQWkPSODGDFWHQVLXQHDGHDOLPHQWDUHVFDGHODPHQ LQHUHDFRQVWDQWDVDUFLQLLYH]LILJXUD2.126DVDXGDFYDORDUHDUH]LVWHQ HLGHVDUFLQFUHúWHODWHQVLXQHGHDOLPHQWDUHFRQVWDQWFDvQILJXUD2.126 (b).

'HDLFLUH]XOWúLRSHUD LLOHSUDFWLFHFDUHVHIDFvQFD]XOvQFDUHRSURWHF LHFXWHUPLVWRU 37& vQ VHULH D IRVW DFWLYDW 'H FHOHPDL PXOWH RUL vQV vQWUHUXSHUHDWHQVLXQLLGHDOLPHQWDUHHVWHVLQJXUDYDULDQWSRVLELO

&RPSRQHQWHúLFLUFXLWHSDVLYH Note de curs

7

Ua′

UA/RS

M1′′

M3′

RS

PTC

B

0 U

I

UA′/RS

Ua′′

Ua′′ < Ua

′

UA

UA/RS

M3

RS

B

0 U

I

M1′

RS′>RS

(a) (b)Fig. 2.126 “Resetarea” termistorului PTC (a) prin reducerea tensiunii de alimentare;

ESULQFUHúWHUHDUH]LVWHQ HLGHVDUFLQ

'LQWUH PXOWLSOHOH GRPHQLL GH DSOLFD LH FDUH XWLOL]HD] SURWHF LD FXtermistoare PTC conectate în serie, amintim:

• WUDQVIRUPDWRDUHúLPRWRDUHHOHFWULFH• surse de alimentare;• difuzoare;• VLVWHPHGHLOXPLQDUHIOXRUHVFHQW• vQFO]LWRDUHúLERLOHUHPDúLQLGHVSODW• OLQLLGHWHOHFRPXQLFD LLFHQWUDOHWHOHIRQLFH• linii de transmisiuni de date (ISDN);• porturi ale calculatoarelor (USB, video, mouse, tastaturi, SCSI).

Exemplu. 6H YD H[HPSOLILFD FX DFHHDúL DSOLFD LH SUH]HQWDW vQ FXOHJHUHD GH SUREOHPH >@Problema 3.2.9 pag 76.

S VH DOHDJ XQ WHUPLVWRU 37& GLQ JDPD 3KLOLSV PRGHO 37& FXtemperatura de basculare Tb=140°&FDUHVSURWHMH]HXQGLIX]RUDOLPHQWDWGHODXQDPSOLILFDWRUDXGLRGDF

temperatura de lucru este Ta=25°C;curentul normal de lucru I≤0,5A;WHQVLXQHDPD[LPGHOXFUX8a=20V;FXUHQWXOGHVXSUDVDUFLQPD[LP,M=10A.

Datele electrice ale termistoarelor PTC 30 sunt prezentate în Tabelul 2.18.Deoarece Vmax≥UA UH]XOW F WHUPLVWRDUHOH GLQ DFHDVW FDWHJRULH FRUHVSXQG OD SULPD

H[DPLQDUHFHULQ HORU6HYDDOHJHXQWHUPLVWRUFDUHvQGHSOLQHúWHPLQLPDOFRQGL LLOH ,nc≥I (Int non trip în limba

HQJOH]vQWDEHOúL,max≥IM&RUHVSXQGHFRQGL LHLWHUPLVWRUXOXLFX525=1,1Ω.

Cap.2 Rezistoare

8

Tabelul 2.18 Date de catalog pentru termistoarele Philips 2322 66.4/5/6 model PTC 30, [33].

Conform figurii 2.123, în cazul unei supratensiuni echilibrul se va stabili în punctul M3′,

ODXQFXUHQW DSUR[LPDWLY HJDO FX FHO UH]LGXDO 6H SRDWH FDOFXOD úL WLPSXO QHFHVDU FRPXWULL SHbaza graficului din figura 2.127FXUEDQU$VWIHOVHFDOFXOHD]UDSRUWXO,M/Inc= 10/0.83 ≅úLGLQILJXUUH]XOWWLPSXOGHFRPXWDUHWb= 0,6 s.

Fig. 2.127 Timpul de comutare al termistoarelor PTC Philips 2322 66.4/5/6, [33].

7UHEXLHIFXWUHPDUFDFYDORULOHFXUHQ LORUGHFRPXWDUHQRQFRPXWDUHGHSLQGGHWHPSHUDWXUca în figura 2.128.

&RPSRQHQWHúLFLUFXLWHSDVLYH Note de curs

9

$VWIHO GDF WHPSHUDWXUD DPELDQW HVWH GLIHULW GH °& VH YD LQH VHDPD GH JUDILFHOHprezentate.

Fig. 2.1289DULD LDFXWHPSHUDWXUDDFXUHQ LORU,F,t), Inc (Int), Imax pentru termistoarele PTCPhilips 2322 66.4/5/6, [33].

2 (b) Demagnetizarea tuburilor cinescop colorDe foarte mult timp demagnetizarea tuburilor cinescop a fost una din

DSOLFD LLOHLPSRUWDQWHSHQWUXWHUPLVWRDUHOH37& LQkQGVHDPDGHQXPUXOPDUHGHreceptoare de televiziune sau monitoare care se produc.

7XEXULOHFLQHVFRSFRORUSRVHGvQVSDWHOHHFUDQXOXLRPDVFSHUIRUDWFDUHHVWH UHDOL]DW GH RELFHL GLQ PHWDOH FDUH VH SRW PDJQHWL]D IRDUWH XúRU PDWHULDOHPDJQHWLFH PRL 0DJQHWL]DUHD PúWLL SHUIRUDWH SRDWH IL SURGXV GH FkPSXULPDJQHWLFH H[WHUQH FXP DU IL PDJQH LL SHUPDQHQ L DL GLIX]RDUHORU ERELQHHOHFWURPDJQH L VDX FKLDU GH FkPSXOPDJQHWLF WHUHVWUX&D XUPDUH DPDJQHWL] ULLPúWLL SHUIRUDWH FDOLWDWHD LPDJLQLL VH vQUXW HúWH FXORULOH QHPDLILLQG SXUH VDXDYkQGORFLUL]D LLGHFXORDUH'LQDFHVWPRWLYWRDWHUHFHSWRDUHOHGHWHOHYL]LXQHVDXPRQLWRDUHOH FRORU VXQW SUHY]XWH FX R ERELQ GH GHPDJQHWL]DUH SODVDW vQ MXUXOWXEXOXLFLQHVFRS3ULQFLSLXOGHGHPDJQHWL]DUHGHJDXVVLQJvQHQJOH] FRQVWvQVXSXQHUHDPúWLLSHUIRUDWHODXQFkPSPDJQHWLFDYkQGLQL LDORDPSOLWXGLQHPDUHGDU GHVFUHVFWRDUH vQ WLPS &D XUPDUH PDWHULDOXO GLQ FDUH HVWH UHDOL]DW PDVFDSDUFXUJH FLFOXUL GH KLVWHUH]LV FX DPSOLWXGLQH GHVFUHVF WRDUH LDU PDJQHWL]DUHDUHPDQHQWHVWHDGXVODRYDORDUHFRQYHQDELOGHVF]XW

'H RELFHL ERELQD GH GHPDJQHWL]DUH HVWH DOLPHQWDW GLUHFW GH OD WHQVLXQHDDOWHUQDWLY D UH HOHL GH 9 &XUHQWXO SULQ ERELQ WUHEXLH V DLE LQL LDO RDPSOLWXGLQH GH FLUFD $ LDU GXS FLUFD XQPLQXW YDORDUHD FXUHQWXOXL WUHEXLH V

VFDGVXE,res = 2mA (vezi figura 2.130).

Cap.2 Rezistoare

10

Fig. 2.1293ULQFLSLXOUHDOL]ULLGHPDJQHWL]ULL

$FHVWOXFUXHVWHQHFHVDUSHQWUXFDLPDJLQHDVQXILHSHUWXUEDWGHFXUHQWXOUH]LGXDOSULQERELQDGHGHPDJQHWL]DUH,GHDODUILFDERELQDGHGHPDJQHWL]DUHV

ILH VFRDV FRPSOHWGLQFLUFXLW vQV DFHVW OXFUXSUHVXSXQHFRVWXULPDUL2 VROX LHIRDUWH EXQ úL HFRQRPLF R FRQVWLWXLH XWLOL]DUHD WHUPLVWRDUHORU 37& vQ VHULH FXbobina de demagnetizare.

Fig. 2.130(YROX LDvQWLPSDFXUHQWXOXLGHGHPDJQHWL]DUH

&RPSRQHQWHúLFLUFXLWHSDVLYH Note de curs

11

([LVWGRXYDULDQWHGHUHDOL]DUHDGHPDJQHWL]ULLFXWHUPLVWRDUH37&FXXQWHUPLVWRU37&VDXFXGRXWHUPLVWRDUH

La varianta cu un singur termistor se cRQHFWHD]HIHFWLYWHUPLVWRUXOvQVHULHcu bobina de demagnetizare, vezi figura 2.131.

PTC

+t°

220V~

Bobina dedemagnetizare

Fig. 2.131 Circuit de demagnetizare cu un singur termistor.

/D FRQHFWDUHD DOLPHQWULL WHUPLVWRUXO HVWH UHFH úL DUH UH]LVWHQ D PLF 3HPVXU FH WHUPLVWRUXO VH vQFO]HúWH FUHúWH úL UH]LVWHQ D OXL FXUHQWXO SULQ FLUFXLWscade, ajungând la valoarea curentului rezidual IRes.

Valoarea curentului rezidual IResSRDWHVSURGXFGLVWRUVLRQULDOHLPDJLQLLEUXP vQ VSHFLDO OD UHFHSWRDUHOH 79 FX GLDJRQDO PDUH 'LQ DFHVW PRWLY VHXWLOL]HD]PRQWDMXOFXGRXWHUPLVWRDUH37&ODFDUHXQXOGLQWHUPLVWRDUHDUHUROXOGH HOHPHQW GH vQFO]LUH 'LQ ILJXUD VH REVHUY F RGDW FX FUHúWHUHDWHPSHUDWXULL DPELDQWH DUH ORF úL VFGHUHD YDORULL FXUHQWXOXL UH]LGXDO 5ROXO FHOXLGHDO GRLOHD WHUPLVWRU HVWH WRFPDL GH D DVLJXUD R WHPSHUDWXU ULGLFDW SHQWUXWHUPLVWRUXODIODW vQVHULHFXERELQDGHGHPDJQHWL]DUH6HXWLOL]HD]GRXYDULDQWHde conectare, prezentate în figura 2.132.

RT2

+t

220V~

RT1

+t

R

K

Ld

(a)

RT2

+t

220V~

K

Ld

(b)

RT1 +t°

Fig. 2.132 &LUFXLWHGHGHPDJQHWL]DUHFXGRXWHUPLVWRDUH

La varianta din figura 2.132 D FHOH GRX WHUPLVWRDUH VH DIO vQ VHULH FXbobina de demagnetizare Ld'XSXQDQXPLWWLPSGHODFRQHFWDUHWHUPLVWRUXO5T1

SUHLD UROXOXQXL UH]LVWRUGH vQFO]LUHSHQWUX WHUPLVWRUXO5T25H]LVWRUXO5 DVLJXUpentru RT1 XQ FXUHQW FDUH vO PHQ LQH OD R WHPSHUDWXU ULGLFDW &HOH GRX

Cap.2 Rezistoare

12

WHUPLVWRDUHVXQWUHDOL]DWHvQDFHHDúLXQLWDWHFRQVWUXFWLYvQDúDIHOvQFkWvQWUHHOHVexiste un cuplaj termic bun.

La montajul din figura 2.132 (b) este eliminat rezistorul auxiliar R,IXQF LRQDUHDFLUFXLWXOXLILLQGVLPLODUÌQILJXUD2.133VHREVHUYFvQOLSVDOXL5T1

YDORDUHD UH]LVWHQ HL OXL 5T2 corespunde punctului M1 LDU vQ SUH]HQ D OXL 5T1

punctului M2, asigurând astfel un curent mai mic prin circuit. De asemenea, seREVHUYFFHOHGRXWHUPLVWRDUHDXFDUDFWHULVWLFLGLIHULWH

R(log)

RT1

T1 T2 T

RT2

M2

M1

Fig. 2.133 Caracteristicile termistoarelor utilizate la demagnetizare.

'LQ SXQFW GH YHGHUH FRQVWUXFWLY FHOH GRX WHUPLVWRDUH VXQW UHDOL]DWH VXEIRUPGHGLVFXULFRQHFWDWH vQ DFHHDúL FDUFDV FRPSRQHQWD ILLQGXQGLVSR]LWLY FXtrei terminale, ca în figura 2.134.

Termistoaredisc

lamelearcuite

Fig. 2.134&RQVWUXF LDGLVSR]LWLYXOXLFXGRXWHUPLVWRDUHXWLOL]DWODGHPDJQHWL]DUH

F7HUPLVWRDUH37&SHQWUXSURWHF LDYROWPHWUHORUGLJLWDOH'00'LIHUHQ DSULQFLSDOvQWUHWHUPLVWRDUHOHSHQWUXSURWHF LDYROWPHWUHORUGLJLWDOH

úL WHUPLVWRDUHOH XWLOL]DWH vQ JHQHUDO OD SURWHF LH HVWH YDORDUHD IRDUWH UHGXV DFXUHQ LORUGHQRQFRPXWDUH,nc, respectiv de comutare Ic. În acest caz, la o tensiuneH[FHVLY DSOLFDW OD ERUQH WHUPLVWRUXO YD DF LRQD IRDUWH UDSLG SURWHMkQG DVWIHOcircuitul, vezi figura 2.135.

&RPSRQHQWHúLFLUFXLWHSDVLYH Note de curs

13

PTC

+t

I

Diodprotec LH

Circuite voltmetru electronic

Tensiunede

mVXUDW

I (mA)

t

Fig. 2.135 8WLOL]DUHDWHUPLVWRDUHORU37&ODSURWHF LDYROWPHWUHORUHOHFWURQLFH

Curentul de comutare IcSHQWUXDFHVWHWHUPLVWRDUHDUHYDORDUHDFXSULQVvQWUHP$ 5H]LVWHQ LQL LDO 5T25 HVWH FXSULQV vQWUH VXWH GH RKPL úL XQLW L GHNLORRKPL FUHVFkQG SXWHUQLF SkQ OD · 0Ω. Valoarea relativ mare aUH]LVWHQ HL LQL LDOH QX HVWH VXSUWRDUH GHRDUHFH FLUFXLWXO GH LQWUDUH SUH]LQWLPSHGDQ HFXYDORULPDUL

2 (d) Termistoare PTC pentru pornirea motoarelor electrice.$FHVWHWHUPLVWRDUHVXQWXWLOL]DWHvQFRQH[LXQHVHULHFXvQI úXUDUHDGHSRUQLUH

a motoarelor electrice. La pornirea motoarelor (de ex. motoare de frigider sau aleLQVWDOD LLORUGHDHUFRQGL LRQDWFXUHQWXOQHFHVDUvQvQIúXUDUHDDX[LOLDUGHSRUQLUHHVWHUHODWLYPDUHGXSSRUQLUHDFHVWFXUHQWQHPDLILLQGQHFHVDU7HUPLVWRUXO37&SRDWHFXVXFFHVVvQGHSOLQHDVFDFHVWHFHULQ HDGLFVDVLJXUHODSRUQLUHXQFXUHQWLPSRUWDQW LDU GXS SRUQLUH V VFRDW SUDFWLF GLQ FLUFXLW vQIúXUDUHD DX[LOLDU&RQHFWDUHDWHUPLVWRUXOXLSRDWHILXUPULWvQVFKHPDGLQILJXUD2.136.

∼

PTC

+t°

220V c.a.

ÌQIúXUDUHDSULQFLSDO ÌQIúXUDUHDGH

pornire motor

Fig. 2.136 Utilizarea termistoarelor PTC la pornirea motoarelor electrice.

Cap.2 Rezistoare

14

H&LUFXLWHGHvQFO]LUHWHUPRVWDWDWH7HUPLVWRDUHOH 37&SRW IL XWLOL]DWH FD HOHPHQWH GH vQFO]LUH SHQWUX OLFKLGH

aer sau mai nou pentru oglinzile automobilelor.$YDQWDMXO WHUPLVWRDUHORU ID GH HOHPHQWHOH UH]LVWLYH FODVLFH HVWH IDSWXO F SULQXWLOL]DUHD ORU VH UHDOL]HD] VLPXOWDQ úL WHUPRVWDWDUHD RELHFWXOXL vQFO]LW $VWIHOGXS FH WHPSHUDWXUD GH EDVFXODUH D IRVW DWLQV WHUPLVWRUXO GLVLS PDL SX LQ

FOGXU UH]LVWHQ DFUHVFkQGSXWHUQLF7HUPLVWRUXOHVWHXWLOL]DW vQDFHVWFLUFXLWDWkWFDHOHPHQWGLVLSDWLYGDUúLFDHOHPHQWUHJXODWRUYH]LILJXUD2.137.

RT +t°

U

Fig. 2.137 8WLOL]DUHDWHUPLVWRDUHORU37&FDHOHPHQWGHvQFO]LUHFXWHPSHUDWXUFRQWURODW

2 (f) Indicatoare de nivelUtilizarea termistoarelor PTC în circuite de sesizare (indicare) a nivelului

IOXLGHORU VH ED]HD] SH DFHODúL SULQFLSLX SUH]HQWDW OD DSOLFD LLOH VLPLODUH FXWHUPLVWRDUHOH 17& úL DQXPH SH IDSWXO F vQ OLFKLG FRHILFLHQWXO GH GLVLSD LH DOtermistoarelor este mai mare ca în aer. În cazul termistoarelor PTC, curentul deIXQF LRQDUHFDUHVHVWDELOHúWHSULQWHUPLVWRUHVWHPDLPDUHDWXQFLFkQGWHUPLVWRUXOHVWHLPHUVDW vQ OLFKLG ID GH VLWXD LD FkQG GLVLS vQ DHU ÌQ PRG HFKLYDOHQW UH]LVWHQ DWHUPLVWRUXOXL LPHUVDW vQ OLFKLG HVWH PDL PLF ÌQ ILJXUD 2.138 a fost prezentat unLQGLFDWRU GH QLYHO FXPDLPXOWH WHUPLVWRDUH 37& SODVDWH SH YHUWLFDO vQ IOXLGXO DOFUXLQLYHOVHPVRDU&XUHQWXOSULQFLUFXLWHVWHRLQGLFD LHDQLYHOXOXLIOXLGXOXL

+t°

U

+t°

+t°

+t°

A

Fig. 2.138 Utilizarea termistoarelor PTC în indicatoare de nivel a lichidelor.

$FHDVW VROX LH FRQVWUXFWLY HVWH vQWkOQLW OD XQHOH DXWRPRELOH úL SUH]LQWDYDQWDMXO ID GH VROX LD FODVLF FX SOXWLWRU F QX FRQ LQH HOHPHQWH PHFDQLFH vQPLúFDUHDYkQGDVWIHORILDELOLWDWHVXSHULRDUJ5HDOL]DUHDXQHLWHPSRUL]ULvQWkU]LHUL

&RPSRQHQWHúLFLUFXLWHSDVLYH Note de curs

15

Când un termistor PTC este conectat în serie cu bobina unui releu, releulHVWH DQFODQúDW DF LRQDW LPHGLDW GXS FRQHFWDUHD WHQVLXQLL XUPkQG V ILHGH]DFWLYDWGXSXQWLPSWLPSvQFDUHWHUPLVWRUXOVHvQFO]HúWH

PTC

+t°

UABobinreleu

(a) (b)Fig. 2.139D5HDOL]DUHDXQHLWHPSRUL]ULEHYROX LDvQWLPSDFXUHQWXOXL

7HQVLXQHD DSOLFDW OD ERUQH WUHEXLH V GHSúHDVF YDORDUHD FH FRUHVSXQGHPD[LPXOXL FDUDFWHULVWLFLL 8, D WHUPLVWRUXOXL SHQWUX FD WHUPLVWRUXO V SRDWEDVFXOD &XUHQWXO SULQ WHUPLVWRU DUH R HYROX LH GHVFUHVFWRDUH vQ WLPS ,QL LDOFXUHQWXO SULQ WHUPLVWRU HVWH FRQVWDQW DSRL SHPVXU FH WHUPLVWRUXO EDVFXOHD]WUHFHvQVWDUHDGHUH]LVWHQ PDUHúLFXUHQWXOVFDGHSURJUHVLYSkQ ODRYDORDUHODFDUH VH VWDELOHúWH HFKLOLEUXO WHUPLF )RUPD FDUDFWHULVWLFLORU vQ IXQF LH GH WLPSGHSLQGH GH WHPSHUDWXUD DPELDQW GH WHQVLXQHD DSOLFDW úL GH FDUDFWHULVWLFLOHWHUPLVWRUXOXLUHOHYDQWHSHQWUXUHJLPXOWHUPLFFDSDFLWDWHDWHUPLFúLFRHILFLHQWXOGHGLVLSD LH

'DFWHUPLVWRUXOVHFRQHFWHD]vQSDUDOHOFXUHOHXODQFODQúDUHDDUHORFGXSXQWLPSWLPSQHFHVDUWHUPLVWRUXOXLSHQWUXDVHvQFO]L

K6XUVGHFXUHQWFRQVWDQW&RQHFWkQGXQWHUPLVWRU37&vQSDUDOHOFXXQUH]LVWRUHVWHSRVLELOVVHDVLJXUHSULQUH]LVWRUXOGHVDUFLQ5VXQFXUHQWDSUR[LPDWLYFRQVWDQW

RT +t°

UA

Rp

RS

Fig. 2.140&LUFXLWSHQWUXVWDELOL]DUHDFXUHQWXOXLSULQUH]LVWHQ DGHVDUFLQ5S.

/DRFUHúWHUHDWHQVLXQLLGHDOLPHQWDUH8ADUHORFRFUHúWHUHDFXUHQWXOXLSULQUH]LVWRUXO5SúLFDXUPDUHRFUHúWHUHDWHQVLXQLLODERUQHOHWHUPLVWRUXOXL$FHDVWWHQVLXQHPULW IDFH FD SULQ HO V FLUFXOH XQ FXUHQWPDLPLF FRPSHQVkQG DVWIHOFUHúWHUHDGHFXUHQWSULQ5S