2. 2.2. Rezistoare dependente

$SOLFD LLDOHYDULVWRDUHORU

Actualmente varistoarele sunt utilizate la reducerea supratensiunilor paraziteFHSRWVDSDUODLQWUDUHDFLUFXLWHORUVDXDFRPSRQHQWHORUHOHFWURQLFHÌQDFHVWVHQVSRWILH[HPSOLILFDWHXUPWRDUHOHXWLOL]UL

UHGXFHUHD VXSUDWHQVLXQLORU SR]LWLYH úL QHJDWLYH FH SRW DSUHD SH UH HD úLLQIOXHQ D IXQF LRQDUHD DSDUDWHORU VDX VLVWHPHORU HOHFWURQLFH DOLPHQWDWHGH OD UH HD9DULVWRDUHOH SRW IL FRQHFWDWH DWkW vQ SULPDUXO WUDQVIRUPDWRUXOXL GH UH HD FkW úL vQVHFXQGDU6HFRQHFWHD]DWkWvQSDUDOHOFXUH HDXDGDUúLvQWUHID]úLSRWHQ LDOXOGHSURWHF LH'H DVHPHQHD VH SRW FRQHFWD vQ SDUDOHO FX VHFXQGDUXO GDU úL vQWUH FHOHGRXERUQHDOHVHFXQGDUXOXLúLSRWHQ LDOXOGHSURWHF LH

- conectarea YDULVWRDUHORUODLQWUDUHDFRPSRQHQWHORUúLFLUFXLWHORUHOHFWURQLFH(exemplu circuitele digitale) pentru reducerea supratensiunilor parazite ce potDSUHDODLQWUDUHDDFHVWRUDúLSRWPRGLILFDIXQF LRQDUHDDFHVWRUD'HDVHPHQHDVXQWXWLOL]DWH OD SURWHF LD GLVSR]LWLYHORU VHPLFRQGXFWRDUH VHQVLELOH OD VXSUDWHQVLXQL(dispozitive MOS);

FRQHFWDUHD YDULVWRDUHORU vQ SDUDOHO FX FRQWDFWHOH PHFDQLFH úL VDUFLQLOHLQGXFWLYHSHQWUXDSURWHMD FRQWDFWHOHPHFDQLFH úL SHQWUXD UHGXFHSHUWXUED LLOH FHapar la comutarea sarcinilor inductive.

9DULVWRDUHOHVDXGRYHGLWHOHPHQWHRSWLPHGHSURWHF LHGDWRULWILDELOLW LLORUULGLFDWHúLUDSRUWXOXLIRDUWHEXQSHUIRUPDQ SUH 9DULVWRDUHOHFXR[LGGH]LQFSULQcoeficientul de neliniaritate αFXYDORULPDULVHDSURSLHFDSHUIRUPDQ HvQGRPHQLXOSURWHF LHLGHHOHPHQWHOHGHSURWHF LHVHPLFRQGXFWRDUHFXPDU ILGLRGHOH=HQHUVDXdiodele supresoare.

Varistoarele sunt utilizate în diferite domenii:• vQHFKLSDPHQWHLQGXVWULDOHVLVWHPHGHFRPXQLFD LLúLWUDQVPLVLLGHGDWHVXUVHúL

VLVWHPHGHDOLPHQWDUHHFKLSDPHQWHGHFRPXWD LHVLVWHPHGHDODUPúLFRQWUROWUDQVIRUPDWRDUHúLPRWRDUH

• vQHOHFWURQLFDGHODUJFRQVXPUHFHSWRDUH79úLYLGHRPDúLQLGHVSODWEDODVWelectronic SHQWUXOPSLOHFXGHVFUFULvQJD]H

• în industria de automobile.

3URWHF LDODVXSUDWHQVLXQLSHOLQLDGHDOLPHQWDUH

Varistoarele cu oxid de zinc sunt utilizate în majoritatea cazurilor caGLVSR]LWLYH GH SURWHF LH OD WHQVLXQL SHULFXORDVH ,PSXOVXULOH GH WHQVLXQH SRW DYHDQDWXU GHWHUPLQLVW FLUFXLWH vQ UHJLP GH FRPXWD LH VDX SRW IL JHQHUDWH DOHDWRUIXOJHUH GHVFUFUL HOHFWURVWDWLFH HWF 3ULQFLSLXO SURWHF LHL OD VXSUDWHQVLXQHUHDOL]DWHGHYDULVWRUSRDWHILXUPULWvQILJXUD

Cap.2 Rezistoare

2

Aparatcare

trebuieprotejat

Zs

ZV

Zi

Ui

+

-

IV

UZ Is

Uo

Fig. 2.13ULQFLSXOGHUHDOL]DUHDSURWHF LHLODVXSUDWHQVLXQLFXYDULVWRDUH

&RQVLGHUPF VXUVDGHSHUWXUED LL LPSXOVDUH LPSHGDQ D=i ,PSHGDQ D=i

SRDWHFRQ LQH UH]LVWHQ DúL LQGXFWDQ DFRQGXFWRDUHORU úLDFDEOXULORUGHDOLPHQWDUH9DULVWRUXO FRQHFWDW vQ SDUDOHO FX FLUFXLWXO FDUH WUHEXLH SURWHMDW DUH LPSHGDQ D =V.,PSHGDQ DDSDUDWXOXLSURWHMDW=SVHFRQVLGHUIRDUWHPDUHúLQXVHLDvQFRQVLGHUDUH6XQWYDODELOHUHOD LLOH

βCIIZU

UUU

ii

ozi

+=

+=(2.209)

'DFWHQVLXQHDGHDOLPHQWDUHYDULD]FX∆UiFXUHQWXOYDDYHDYDULD LD∆I

( ) ( )βIICIIZUU iii ∆++∆+=∆+ (2.210)

Date fiind valorile mici ale lui β (pentru ZnO 0,03 ÷YDULD LDWHUPHQXOXLCIβHVWHPXOWPDLPLFID GHFHDDOXL8z'HFLRYDULD LHDOXL8i va produce oYDULD LHPDUHDOXL8zúLPXOWPDLPLFDOXL8O.

$FHODúLOXFUXSRDWHILREVHUYDWúLJUDILFvQILJXUDXQGHSXWHPFRPSDUDYDULD LDWHQVLXQLLODLHúLUHvQFD]XOXWLOL]ULLXQXLUH]LVWRUDúLDXQXLYDULVWRUE6HREVHUY YDORDUHD PXOW PDL PLF D WHQVLXQLL ∆UO vQ FD]XO XWLOL]ULL YDULVWRUXOXLTensiunea UO VH JVHúWH OD LQWHUVHF LD GLQWUH FDUDFWHULVWLFD YDULVWRUXOXL VDXUH]LVWRUXOXLúLGUHDSWDFDUHUHSUH]LQWFDUDFWHULVWLFDVXUVHL

i

i

Z

UUUI

−=)( (2.211)

'DFVXUVD8iQXHVWHXQLPSXOVFLHVWHRWHQVLXQHSHUPDQHQW FRQWLQXVDXDOWHUQDWLYVHVSXQHFYDULVWRUXOUHDOL]HD]RVWDELOL]DUHDWHQVLXQLLVXUVHL

3HUIRUPDQ DXQXLVWDELOL]DWRUHVWHDSUHFLDWSULQIDFWRUXOGHVWDELOL]DUH6

oo

ii

UU

UUS

/

/

∆∆

= (2.212)

FDUHVHGRUHúWHVDLEYDORULFkWPDLPDUL1HSURSXQHPVFDOFXOPVWDELOL]DUHDRIHULWGHYDULVWRUODYDULD LLOHVXUVHLGH

DOLPHQWDUHSUHVXSXQkQGFQXH[LVWVDUFLQVDXF=s este foarte mare.&XQRWD LLOHGLQILJXUDDYHP

αoioioi KUZUIZUU +=+= (2.213)

XQGH.úLα sunt parametrii varistorului.

&RPSRQHQWHúLFLUFXLWHSDVLYH Note de curs

3

I

U

Rezistor R

UI =

i

ii

Z

UU ∆+

i

i

Z

U

UiUo

∆Uo ∆Ui

I

U

Varistor I=KUαi

ii

Z

UU ∆+

i

i

Z

U

UiUo

∆Uo ∆Ui

(a) (b)Fig. 2.29DULD LDWHQVLXQLLODLHúLUHvQFD]XOXWLOL]ULLXQXLUH]LVWRUD

úLDXQXLYDULVWRUE

3ULQGLIHUHQ LHUHRE LQHP

( )11 1 −− +=⋅+= αα αα oioooioi UKZdUdUUKZdUdU (2.214)

3ULQWUHFHUHODYDULD LLILQLWHúLvPSU LUHOD8iRE LQHP

−+

∆=

+

∆=

∆

i

oi

i

o

o

o

i

oi

i

o

o

o

i

i

U

UU

U

U

U

U

U

UKZ

U

U

U

U

U

U ααα

(2.215)

/DXOWLPDUHOD LHVDDMXQVvQORFXLQG IKUo =α úL oii UUIZ −=5H]XOW

( ) xxUU

UUS

oo

ii

ββ

βαα −−=⋅−−=

∆∆

= 111

/

/(2.216)

cu parametrul i

o

U

Ux = .

În cazul unui rezistor α úLUH]XOW6 3HQWUXYDULVWRDUHUH]XOWvQJHQHUDO6!De exemplu, pentru varistoare din SiC cu α SUHVXSXQkQG[ UH]XOW6 LDUSHQWUXYDULVWRDUHSHED]GH=Q2FXα UH]XOW6

'DFVHFRQVLGHUúLVDUFLQDFRQHFWDW vQSDUDOHOFXYDULVWRUXOVHSRDWHDUWDFIDFWRUXOGHVWDELOL]DUH6HVWH

( )y

yxS

++−−=

11αα (2.217)

cu i

o

U

Ux = úL

I

Iy s=

Cap.2 Rezistoare

4

Exemplu. &RQVLGHUPYDULVWRUXO9/$$ +DUULV 6HPLFRQGXFWRU 3UHVXSXQHP R WHQVLXQHperturbatoare Ui = 3000V.D&RQVLGHUPLPSHGDQ DVXUVHL=i = 50Ω, iar ZV = 8Ω.Calculul curentului presupune rezolvarea sistemului neliniar:

−=

=

i

oi

o

Z

UUI

KUI α

'HUHJXOSHQWUXUH]ROYDUHVHIDFDSUR[LPD LLVXFFHVLYHDSHOkQGODJUDILFHOHGLQFDWDORDJH

(VWLPPFXUHQWXOSHUWXUEDWRUSULQFLUFXLW AI 52850

3000 ≅+

= úL8o = 52⋅8=416 V.

3HQWUXYDULVWRUXO9/$$UH]XOWGLQFDWDORJOD$WHQVLXQHD8≅ 325V.

Curentul recalculat AI 5,5350

3253000 =−= , deci aproximarea curentului la valoarea de 52 A

HVWHDFFHSWDELO&GHUHDGHWHQVLXQH8R = Zi⋅I = 2675 V.E'DFLPSHGDQ DVXUVHLHVWH=i = 5ΩGHRULPDLPLFFDvQH[HPSOXODQWHULRUSUHVXSXQHPFXUHQWXOSULQFLUFXLWODRYDORDUHJKLFLWGHRULPDLPDUH, $/DDFHVWFXUHQWWHQVLXQHD

varistorului este Uo 95HFDOFXOP AI 5225

3903000 =−= , foarte aproape de valoarea

SUHVXSXV3HQWUXXQUH]LVWRUGHΩXWLOL]DWvQORFXOYDULVWRUXOXLUH]XOWWHQVLXQHD

VUo 185058

83000 ≅

+⋅=

Fig. 2.3 Caracteristici U(I) ale varistoarelor utilizate în exemplul de calcul, [35].

Rezultatele pot fi sintetizate în tabelul 2.23.

&RPSRQHQWHúLFLUFXLWHSDVLYH Note de curs

5

Tabelul 2.23 Sinteza rezultatelor din exemplul de calcul7HQVLXQHDSHUWXUEDWRDUHODLHúLUH8o

,PSHGDQ DVXUVHL&RPSRQHQWXWLOL]DWOD

SURWHF LH50 Ω 5 Ω

Rezistor liniar R=8Ω 416 V 1850 VVaristor 325 V 390 V

3URWHF LDFRQWDFWHORUUHOHHORUúLDFRPXWDWRDUHORU

ÌQWUHUXSHUHD XQXL FLUFXLW LQGXFWLY SURGXFH R VXSUDWHQVLXQH GDWRULW IHQRPHQXOXL GH DXWRLQGXF LH $FHDVW VXSUDWHQVLXQH SRDWH DPRUVD XQ DUF HOHFWULFFDUH SRDWH GLVWUXJH FRQWDFWHOH FRPXWDWRUXOXL úL JHQHUHD] SHUWXUED LLHOHFWURPDJQHWLFH &RPXWDWRUXO . HVWH GH RELFHL XQ UHOHX ILLQG SRVLELO FKLDUVXGDUHDODPHOHORUUHOHXOXLúLGHFLGHIHFWDUHDLUHYHUVLELO DDFHVWXLD3HQWUXSURWHF LDFRQWDFWHORUVHXWLOL]HD]XQYDULVWRUFDUHOLPLWHD]VXSUDWHQVLXQHDvQWUHFRQWDFWHODRYDORDUHODFDUHQXPDLDSDUHDUFXOHOHFWULF3HQWUXDHUODSUHVLXQHQRUPDO vQFkPSXQLIRUP DFHDVW WHQVLXQH HVWH GH FFD 9GDU SRDWH VFGHD vQ DQXPLWH FRQGL LLSkQOD÷ 60V.

VaristoUXOVHSRDWHFRQHFWDvQSDUDOHOFXVDUFLQDLQGXFWLY VDXFXFRPXWDWRUXOsau releul K.

UA

K

RV

L

R

UA

K

RVL

R

(a) (b)Fig. 2.43URWHF LDFRQWDFWHORUHOHFWULFHFXYDULVWRDUH

/DvQWUHUXSHUHDFLUFXLWXOXLFXUHQWXOSULQVDUFLQDLQGXFWLY QXSRDWHVVXIHUHYDULD LLEUXúWHúLDUHvQSULPXOPRPHQWDOvQWUHUXSHULLYDORDUHDGHUHJLPSHUPDQHQWVF]kQGH[SRQHQ LDO

La deschiderea comutatorului K, la bornele sarcinii inductive, reprezentateSULQ JUXSDUHD VHULH /5 DSDUH R VXSUDWHQVLXQH FX YDORDUHD PD[LP

t

ILU

∆∆

⋅=∆ max FDUHHVWHGHUHJXOPDLPDUHFDWHQVLXQHDGHDOLPHQWDUH8A (12 -

99DULVWRUXOWUHEXLHVDVLJXUHODQLYHOXOFRPXWDWRUXOXLRWHQVLXQHVXESUDJXOGHSURWHF LH8p3HQWUXVFKHPDGLQILJXUDDvQVLWXD LDFHDPDLGHIDYRUDELOeste necesar ca Ap UUU −≤∆ max , sau varistorul trebuie ales astfel ca tensiunea la

bornele sale, UV V ILH PDL PLF GHFkW 8p-UA. La varianta din figura 2.175 (b)

Cap.2 Rezistoare

6

varistorul este montat la bornele comutatorului el fiind ales astfel ca tensiunea labornele sale UVVILHPDLPLFGHFkW8p.

7UHEXLH IFXW UHPDUFD F DOHJHUHD FRQFUHW D YDULVWRUXOXL SUHVXSXQHFXQRDúWHUHD YDORULL HOHPHQWHORU / 5 D WLPSXOXL GH FRPXWDUH D FXUHQWXOXL SULQYDULVWRUúLVDUFLQvQPRPHQWXOvQWUHUXSHULLFLUFXLWXOXLHWF2DOHJHUHVLPSOLILFDWDvaristorului se face astfel ca la tensiunea de alimentare UAYDULVWRUXOVVHJVHDVFvQ UHJLXQHD FXUHQ LORU GH IXJ LDU OD FXUHQWXO GH YkUI JHQHUDW GH GHVFKLGHUHDcomutatorului K, tensiunea de limitare (“clamping voltage”) UV V FRUHVSXQG

UHOD LLORUSUH]HQWDWHDQWHULRUILLQGFkWPDLPLFSRVLELO ÌQ OLSVDDOWRUGDWHVHSRDWHconsidera curentul prin varistor ca fiind egal cu curentul de regim permanent prinVDUFLQDLQGXFWLY,0, înainte de deschiderea comutatorului K. Se va alege un varistor

FDUHVSHUPLWGLVLSDUHDHQHUJLHLDFXPXODWHvQERELQ 20

2

1ILW ⋅⋅= .

Exemplu. Ca exemplu de calcul se va prezenta modalitatea de alegere a unui varistor pentruSURWHF LDXQXLFRPXWDWRUYDULVWRUFRQHFWDWFDvQILJXUD2.5 (a). Se va exemplifica cu varistoare dinJDPD6,29SHED]GHR[LGGH]LQFDOHILUPHL6LHPHQV

UA

K

RV

L

R

(a) (b)Fig. 2.5DFRQHFWDUHDYDULVWRUXOXLEIRUPDFXUHQWXOXLGXSGHVFKLGHUHDFRPXWDWRUXOXL.

&RQVLGHUPXUPWRDUHOHGDWHTensiunea de alimentare UA=24V;,QGXFWDQ D/ +5H]LVWHQ DERELQHL5 Ω;Curentul prin circuit I0=1A;7HQVLXQHDGHOLPLWDUHQLYHOXOGHSURWHF LH91XPUXOGHFRPXWULLPSXOVXUL 6;3HULRDGDGHUHSHWL LHDLPSXOVXULORU7 V

ÌQWUHUXSHUHDXQXLFLUFXLWLQGXFWLYFXERELQHSURYRDFDSDUL LDODERUQHOHERELQHLDXQRU

WHQVLXQLvQDOWHÌQERELQDIRVWvQPDJD]LQDWHQHUJLD 20

2

1ILW ⋅⋅= . La întreruperea circuitului

DFHDVW HQHUJLH HVWH WUDQVIHUDW FDSDFLW LL SDUD]LWH & DIODWH vQ SDUDOHO FX ERELQD $FHDVWFDSDFLWDWHSRDWHILFKLDUFDSDFLWDWHDSDUD]LWDERELQHL

&RPSRQHQWHúLFLUFXLWHSDVLYH Note de curs

7

'DFSUHVXSXQHP& S)IUFRQVLGHUDUHDSLHUGHULORUSXWHPVFULH 220 2

1

2

1UCIL ⋅=⋅ ,

de unde V200000 ==C

LIU . Pentru reducerea acestei tensiuni ce apare la bornele bobinei

VHXWLOL]HD]XQYDULVWRUFRQHFWDWvQSDUDOHO$OHJHUHD YDULVWRUXOXL GLQ SXQFWXO GH YHGHUH DO WHQVLXQLL GH IXQF LRQDUH úL D FXUHQWXOXL

maxim6HDOHJHXQYDULVWRUFXWHQVLXQHDFRQWLQXPD[LP8MDYkQGRYDORDUHLPHGLDWVXSHULRDU

FHOHLGHDOLPHQWDUH3HQWUXSURGXVHOH6LHPHQVH[LVWYDULVWRDUHFXWHQVLXQHDHJDOFX96XQWmai multe tipuri de produse disponibile.

Vom opta pentru un varistor de tip disc cu diametrul de 10 mm model S10K20, cuparametrii:

7HQVLXQHPD[LPSHUPDQHQW8M(c.c.)=26V;7HQVLXQHPD[LPSHUPDQHQW8M(c.a.)=20V;7HQVLXQHDQRPLQDOP$8N=33 V;Curentul maxim nerepetitiv Inrp=500 A;3XWHUHDQRPLQDO3N=0,05 W;&DSDFLWDWHDSDUD]LW& S)

&DUDFWHULVWLFD8,DDFHVWXLYDULVWRUHVWHSUH]HQWDWvQILJXUD2.6.

Fig. 2.6 Caracteristicile U(I) pentru varistoarele Siemens utilizate în exemplul de calcul, [37].

&RUHVSXQ]WRU FXUHQWXOXL GH $ VH RE LQH WHQVLXQHD GH OLPLWDUH PD[LP 8c ("max.FODPSLQJYROWDJHGH9'HFLHVWHDVLJXUDWRYDORDUHGHOLPLWDUHDWHQVLXQLLFDUHFRUHVSXQGHFHULQ HORUGHSURWHF LH8C < 65 V.

/DvQWUHUXSHUHDFLUFXLWXOXLFXUHQWXOSULQERELQQXSRDWHVVXIHUHYDULD LLEUXúWHúLDUHvQSULPXOPRPHQWDOvQWUHUXSHULLYDORDUHDGHUHJLPSHUPDQHQW$VF]kQGGXSROHJHH[SRQHQ LDOvezi figura 2.5 (b).

Cap.2 Rezistoare

8

&RQVWDQWDGHWLPSDGHVFUHúWHULLFXUHQWXOXLHVWHVRR

L

+≈τ , cu RVUH]LVWHQ D³VWDWLF´D

varistorului. Valoarea lui RV GHYLQH GLQ FH vQ FH PDL PDUH SH PVXU FH FXUHQWXO VFDGH GHFLvaloarea lui τ QX HVWH FRQVWDQW ÌQ FDOFXOH VH QHJOLMHD] vQV DFHVW IDSW5H]LVWHQ D VWDWLF HVWHRV=55/1 =55 Ω.

5H]XOWSHQWUXFRQVWDQWDGHWLPSYDORDUHD

ms26,15524

1,0 =+

≈τ .

)RUPDGHXQGH[SRQHQ LDODFXUHQWXOXLSRDWHILHFKLYDODW³HQHUJHWLF´SHED]DILJXULL2.5EFXXQLPSXOVGHFXUHQWGUHSWXQJKLXODUGHGXUDWτFXDPSOLWXGLQHHJDOFXFHDDFXUHQWXOXLGLQPRPHQWXOLQL LDO3HED]DJUDILFHORUGLQILJXUD2.7VHFDOFXOHD]UHGXFHUHDDPSOLWXGLQLLFXUHQWXOXLPD[LPvQIXQF LHGHQXPUXOGHLPSXOVXULúLGHGXUDWDLPSXOVXOXLW≅τ.

Fig. 2.75HGXFHUHDFXUHQWXOXLPD[LPvQIXQF LHGHGXUDWDLPSXOVXOXLúLGHQXPUXOGHLPSXOVXULpentru varistoarele Siemens utilizate în exemplul de calcul, [37].

5H]XOWSHQWUXRGXUDWDLPSXOVXOXLGHPVúLXQQXPUGHLPSXOVXUL6) un factorGH UHGXFHUH GH &XUHQWXOPD[LP QHUHSHWLWLY SHQWUX DFHVW YDULVWRU HVWH GH $5H]XOWcurentul maxim care poate fi suportat de varistor IMAX=0,006⋅500=3A >1 A. Deci, acest varistorcorespunde din punctul de vedere al curentului maxim suportat.

(QHUJLDDEVRUELWGHYDULVWRUFDOFXODWSHED]DLPSXOVXOXLGUHSWXQJKLXODUGHGXUDWτ este:

mJ3,691026,1155 30 =⋅⋅⋅=××= −τIUW CMAX

&RPSRQHQWHúLFLUFXLWHSDVLYH Note de curs

9

9DULVWRUXO WUHEXLH V DEVRDUE vQ FHOPDL GHIDYRUDELO FD] WRDW HQHUJLD vQPDJD]LQDW vQ

ERELQ mJ5011,05,02

1 20 =⋅⋅== LIW <WMAX=69,3 mJ, deci varistorul poate absorbi

HQHUJLDFHGDWGHERELQvQPRPHQWXOvQWUHUXSHULLFLUFXLWXOXLSolicitarea în regim permanent9DULVWRUXOSULPHúWHRHQHUJLHGHP- OD ILHFDUH7 V$FHDVWD FRUHVSXQGHXQHLSXWHULPHGLL

mW510

05,0===

T

WP L < PN P: 'HFL YDULVWRUXO DOHV QX HVWH vQFUFDW WHUPLF SHVWH

OLPLWDDGPLVLELO6HSRDWHGHWHUPLQDSHULRDGDPLQLPGHUHSHWL LHD LPSXOVXULORU7minGLQFRQGL LDGHDQXGHSúL

SXWHUHDQRPLQDO5H]XOW s5,220

50min ===

N

L

P

WT .

ÌQPRG DVHPQWRU DF LRQHD] úL YDULVWRDUHOH FDUH VH FRQHFWHD] OD ERUQHOHvQIúXUULL VHFXQGDUH D WUDQVIRUPDWRDUHORU VDX YDULVWRDUHOH FDUH SURWHMHD]

"comutatoare" electronice cum ar fi tranzistoare, tiristoare, triace.În mod similar, se pot proteja contactele de colector (perii) ale motoarelor

HOHFWULFHSULQFRQHFWDUHDXQXLYDULVWRUvQSDUDOHOSHILHFDUHvQI úXUDUHDURWRUXOXL&KLDUúLPRWRDUHOHGHFXUHQWDOWHUQDWLYIUSHULLSRWILSURWHMDWHFXYDULVWRDUH

OD DSDUL LD XQRU VXSUDWHQVLXQL FDUH SRW V OH GLVWUXJ L]ROD LD vQIúXUULORU6XSUDWHQVLXQL OD DFHVWH PRWRDUH SRW V DSDU OD RSULUHD ORU úL PDL UDU vQ WLPSXOpornirii.

R

S

T

Motor conexiune Y Motor conexiune ∆Fig. 2.80RGXOGHFRQHFWDUHDYDULVWRDUHORUSHQWUXUHDOL]DUHDSURWHF LHLPRWRDUHORUWULID]DWHvQ

conexiune stea sau triunghi.

În figura 2.8 a fost prezentat modul de conectare a varistoarelor în cazulPRWRDUHORU WULID]DWH FX vQIúXUULOH FRQHFWDWH vQ VWHD < VDX WULXQJKL ∆). Pentru

conexiunea stea (Y) tensiunea la bornele varistorului este lU3

1 în timp ce la

conexiunea triunghi (∆) tensiunea este Ul, Ul ILLQG WHQVLXQHD GH OLQLH D UH HOHLtrifazate (380 V).