Protection of insulated gate bipolar tr. t.

Transcription

1 ndn nsr Sc Sept-Oct 2000 SO 457 d' -475 V n n nstllue of Scence Protecton of nsulted gte bpolr tr t short crcut nsls ors gmst G NARAYANAN S R MURALDHARA A S ANAN Dep9"lffSe()n'30600f ES<C66tnF Ph - x 9-S()' eml vrm@eescemetn Receved on AuguS! Abstrct 'Cl Engneerng ndn n;''u; ~f Scence~ B~~~"; ~~~NARA YANAN* ~~~~ted re b;polr ~sstors (?BTs) e wdely used n power electronc converters Two GST gte drve cr velo ~ ~ 0 protectmg ~e devces g3n~t short crcut by sensng ther colleclor--emuer vollge, hve been de ~ or owvojt~e devces One uses dls~~le components whle the other uses n e drve Me33S3 Tlese CrCUts re smple rehble nd useful for prctsng engneers 80th the crcuts te tested "ghly' h' b'll to protect the de both UlUUU lor eu ty VceS gms, 'ypes of fulls nmely hrd swtched fult (HSf) nd full under lod (FULl under d~ffe~enl Cl~Ul condltjo~ The test results brng out the nfluence of DC bus voltge nd fult nductnce on the short~ ~lrcun trnsents From ths method cm be rrved t for estmtng fult nductnce usng devce current nd devce oltge under fult The o~ervoltge spkes due to shut down followng fult delecton re qute low Ths vndctes the de~lgn of the lo~ stny lduc~~ bus~br used A smple gte drve crcut cpble of short-crcul protecton nd sndwch bus-br Wth low prsluc nductnce hold the key to mprove the relblty of GBT-bsed conveners Keywords nsulted gte bpolr trnsstors shon-crcut currents L ntroducton nsulted gte bpolr trnsstors (lgbts) re wdely used n power electronc systems lke unnterruptble power supples (UPS) motor drves nd ctve power flters To mke these syslems rugged the power devces used n them must be protected gnst short crcut A fult my occur when prtculr devce s n conducton Ths s tenned s 'fult under lod' (FUL) Alterntvely, the devce my tum on nto fult Ths s clled 'hrd swtched fult (HSF) The devce hs to be protected gnst both knds of fults Fsl swtchng devces lke GBTs cnnot be protected by fuses crcut brekers etc They cn only be protecled by tmely fult detecton followed by quck shut down of the gle drve'-'o Ths must be done wthn the short-crcut wthstnd tme (sd of the GBT whch s lo!!s for most devces"-'s Also t must be ensured tht no further drve s provded tll the fult s clered Any soluton provded to mprove the relblty of power converters musl tself be smple nd effectve to be of ny prctcl use Hence dfferenl ssues concernng short-crcut protecton of GBTs re dscussed nd the ones of rellvely hgher sgnfcnce re dentfed Two smple GBT gte drve crcuts hvng only the essentl fetures of fult protecton scheme re developed for low-voltge devces These re tested thoroughly to check ther effectveness n protectng devces from both types of fults over rnge of bus voltges nd fult nduclnces

2 458 G NARAYANAN et t 2 ssues n short-crcut protecton of Mll's The mjor spects of the short-crcut protecton of GBTs re dscussed n ths secton Also, the essentl fetures of smple gte drve crcut re shown 2 Fult-sensng Sensng fult s the prmry step n short-crcut protecton of devce Ths cn ether be bsed on the devce current 9-6 or on the voltge drop cross the devce tem 6 2 Bsed on devce current The drop cross resstor n seres wth the devce s good mesure of the devce current However, the use of n externl resstor mkes the power-crcut lyout clumsy Certn new devces re becomng vlble wth n-bult seres resstors 6 rrespectve of the resstor used, ether nternl or externl, the drop cross t s qute low ( few Os of mv) Ths lowmgntude sgnl s prone to nose problems The protecton scheme s very much senstve to the lyout of the drve crcut nd ts connecton to the power crcut Alterntvely, defned frcton of the devce current s mde to flow through lrge resstnce, nternl to the power devce or the devce drver The drop cross ths resstnce s used for fult-sensng s n ntellgent power modules nd few devce drvers 7-8 A very recent technque for fult detecton uses drop cross the nductor between the emtter power termnl nd ts semconductor contct nsde the csng The Kelvn emtter termnl (drve sde emtter termnl) cn be regrded s the semconductor contct pont tself Thus the voltge drop between the power nd Kelvn emtter termnls gves mesure of d/dt Ths s ntegrted to get n estmte of the collector current, whch s then used for protecton 9' 0 As ths nductnce s very low (only few nnohenres), the voltge cross t s lso low Ths mkes fult-sensng prone to nose problems s erler Further, the use of ntegrtor complctes the gte drve crcutry 22 Bsed on devce voltge The on-stte drop cross n GBT s low under norml condtons n cse of fult, the devce comes out of sturton, nd the drop cross t ncreses Ths cn be used to detect fult Ths method, usng the collector emtter voltge of the devce, s known s `desturton technque' The collector emtter voltge (vc E) s convenent to use s fr s the mgntude s concerned The devce current nd the on-stte drop re not proportonl n cse of n GBT unlke n the cse of MOSFET Besdes, the drop lso depends on the rte of rse of the devce current Doubts hve been expressed n the lterture regrdng the detecton of fults, especlly soft fults wth low d/d, usng ths technque 9- Hence, ts effectveness n fult detecton must be determned by thorough testng 22 Fult current lmtng To reduce the current n the event of fult, the gte emtter voltge cn be djusted dynmclly t cn be reduced below the norml level, but stll bove the threshold voltge to control

3 PROTECTON OF NSULATED GATE BPOLAR TRANSSTORS AGANST SHORT CRCUT 459 the fult current Once reduced sutbly, t must remn clmped t the sme level tll the gte drve s shut down Severl crcuts hve been reported n the lterture for such lmtng of fult current 2-6' 9' C ncorporton of fult current lmtng ncreses the component count nd the complexty of the gte drve crcutry The performnce of the drve crcut s qute senstve to certn prmeters n the fult current-lmtng crcut 23 Shut down The gte pulse s shut down n the cse of fult The shutdown leds to n overvoltge due to the lrge dldt nd the prstc nductnce n the bus-br f n excess, ths overvoltge cn dmge the devce Hence ether the d/ct or the prstc nductnce or both hve to be reduced for ths 24 Nondegrdton of the norml operton The short-crcut protecton mechnsm, ncorported n the gte drve crcut, must not deterorte the norml performnce of the drve There must be no nusnce trp Also, conducton nd swtchng losses of the devce must not ncrese pprecbly 25 Fetures of smple short-crcut protecton scheme Whle fult detecton, sfe shut down nd nondegrdton of norml performnce re bsolutely essentl for ny fult protecton scheme, fult current lmtng nd gte clmpng cn be done wy wth for smplcty From the dscusson n Secton 2, fult detecton bsed on v ce sensng s the smplest for the purpose Such smple short-crcut protecton scheme s consdered n ths work Two gte drve crcuts wth these fetures re developed One of them uses dscrete components, whle the other uses n C drver Motorol MC3353 These re presented n the next secton 3 Proposed JGBT gte drve crcuts The gte drve crcut- uses dscrete components for fult detecton nd protectve cton (Fg ) The gte drve sgnl, generted by the controller, frst psses through n HP30 optocoupler 9 for glvnc solton, nd then through drve stge The drve stge provdes dequte drve for proper swtchng of the devce Ths stge conssts of buffers nd trnsstor brdge The on- nd off-stte gte-emtter voltges re VGE(oN) = +5 V nd %/GROFF) = 5 V respectvely The gte resstnces re R oon) = RG(0}-F) = 22 for Semlcron SKM50GB- 23D s prescrbed n the devce dt sheet' A fst recovery dode (MUR WOE) nd n LM339 comprtor re used for fult-sensng A reference (desturton voltge) of 62 V s provded to the comprtor Whenever the drop cross the devce s greter thn 62 V, the comprtor output goes low The output of the comprtor nd the solted gte drve sgnl re used to generte sttus sgnl Ths sgnl s hgh under norml condton, nd s low under fult The sttus sgnl (BLANK seconds (blnkng tme) fter s held hgh s long s the gte drve s low, nd lso for the low-to-hgh trnston of the drve sgnl to llow for the norml turn-on operton The

4 460 G NARAYANAN et l " UPS 0 STATUS T c--c e 0 +5V 'PUT 2N2222 5K 6K8 +5V (L 0K V 40 _ N44 lt +5 rar K5 330E 5V MLR 00E 82 6V V t K2 >,5)5_ DRVE 'KS P ' N r ' ' o l 62V 6V 680E 2N2906 K2 K2 2N E +5V Rg(oll) '448 Roo) N448 2N2906 2N2222 K2 688E 6V E- 62%' FG GHT gte drve crcut- dscrete component verson blnkng tme must be suffcently lrger thn the worst cse turn-on tme to vod nusnce trp When the gte drve s hgh, the sttus sgnl goes low whenever the comprtor output goes low fter the end of blnkng tme Ths sttus sgnl s ANDed wth the drve sgnl on the solted sde Thus, fult s detected nd the drve s shut n the cse of fult The sttus sgnl s fed bck to the centrl protecton crd or the controller through nother HP30 optocoupler Ths sgnl s useful to prevent gte pulses from beng fed further to the devce tll the clernce of the fult 0 =x= 3 N448 5V K N448t 82K N22 2,6 K K 00u -r Ou FG 2 solted power supply for gte drve crcut-

5 PROTECTON OF NSULATED GATE BPOLAR TRANSSTORS AGANST SHORT CRCUT V +5V 2N2906 K P30 0u V STAR'S \ 6 K2 8K T 470E MUR00E * r-- k-- C +5V n T t 47P N448 Reou) -SV r O!--N,\,- 2 5, K N V - MC3353 L4 B K& HP30 N448 Rg(off) 78Nt 5K '' K , V DRVE > 0u o W;ts r<serse -W *- 473 rff " FG 3 GBT gte drve crcut- MC3353 verson The power supply for the solted sde shown n Fg 2 conssts of flybck converter 2-2 wth lner regultor t the output for voltge regulton The gte drve crcut-, shown n Fg 3, uses HP30 for soltng the gte drve However, nsted of dscrete components, ths crcut uses n C drver MC3353 for fult-sensng, provdng blnkng tme, nd shuttng down the gte pulse nd genertng sutble sttus sgnl n the event of fult The sttus sgnl s lso solted usng HP30 s n the erler cse The C drver MC3353 hs n bsolute mxmum voltge swng of 20 V Hence, the swng between V GE(oN) nd VGE0DET) must be less thn 20 V Therefore, VGEoN) = +4 V nd VGEoFe = 5 V re used n ths crcut The solted sde of crcut- requres bpolr supply The power supply conssts of flybck converter wth bpolr output nd two lner regultors (Fg 4) 4 Testng for protecton gnst short crcut Both the gte drve crcuts re tested for protecton gnst HSF nd FUL (Fgs 5, 5y)The GBT used s SEMKRON SKM50GB23D, whch s 50 A, 200 V, hlf-brdge module tn' > E 4 47u FG 4 solted bpolr power supply for gte drve crcut-

6 462 G NARAYANAN etl PWW Sttus- Zenerl Ms crd D Cl R +5V OND PWM2 Sttus-2 Gte Drve Crd Zener re crd 2 D2 C2 R2 Shortng wre () PW`4 Sttus- +5V GND PWM2 Sttus-2 (b) FG 5 Expermentl setup to test for protecton gnst ) Hrd-swtched fult (HSF) nd b) Fult under lod (FUL) C, C pf, 400V electrolytc cpctors; Q, D, Q2, D2 SEMKRON SKM50GB23D GBT hlf-brdge module; R, R2 0K, 25 W wre wound resstors (for voltge blncng) The connectons between the DC bus cpctors nd the devce re mde usng sndwch bus-br wth low prstc nductnce The tests re crred out over rnge of DC bus voltges nd lso rnge of fult nductnce The test procedure nd the results re presented n ths secton 4 Hrd-swtched fults (HSF) The testng crcut for protecton gnst HSF s s shown n Fg 5 The test devce s turned on wth ts complementry devce shorted The DC bus voltge s set t the requred level Gte drve s ppled to the test devce The gte drve crcut must shut down the drve fter the blnkng perod ((BLANK) The fult current nd the voltge cross the devce re recorded usng storge osclloscope

7 PROTECTON OF NSULATED GATE BPOLAR TRANSSTORS AGANST SHORT CRCUT 463 SO ov 2 SO ov ) -,, N ' - ' - _ - t sst e COW, Sre +2 sm 4 / r--r- "dlm'hd t $ s - b) A so OT 2 00V 'V Srn / - 6 -,, 0', S A c) SO O 2 00V f _ t tredeof / 0/550 A V, 2 l tl - l / Sno $ A - / - t t_ FG 6, Testng o f drve crcut- for protecton gnst HSF t dfferent bus voltges wth L= 200 nh t ) VD c= 400 V nd c) 4, = 600 V Chnnel Fult current ( dvson or 50 mv corresponds to 00 A) Chn- 200 V, b) Voc = nel 2 Devce voltge

8 464 G NARAYANAN et t ) SO 500V Pt t Pr L v n W, Snl S l l le l l l - l l t l s l! *_555 *54 b) 0 SO OV 2 00V t- 4 00W 200W, Sn9+2_rgr, Al A ; 555) Fs eso 0--0-sjssetoot - L4 t - FG 7 Testng of drve crcut- for protecton gnst HSF t dfferent bus voltges wth L = 200 nh t ) Vrx 200V,b)VDc =400 V nd c) Voc = 600 V Chnnel Fult current ( dvson or 50 mv corresponds to 00 A) Chnnel 2 Devce voltge The complementry devce s frst shorted wth short wre nd slck just enough to put the current probe on The test s conducted t dfferent DC bus voltges rngng from 00 V to

9 PROTECON OF NSULATED GATE BPOLAR TRANSSTORS AGANST SHORT CRCUT V et t set rrrrrr ses t SO OV 2 00V S "VdrsH \ S %00nmemel 44,,zS S504--e C) SO OV 2 00V rreen-g-r! L eeter ; ' FG 8 Testng of drve crcut- for protecton gnst HSF t dfferent fult nductnces t VDc=600 V t ) ph Chnnel Fult current ( dvson or 50 mv corresponds to 00 A) L= 750 nh, b) j = 5 ph nd c) L= 34 Chnnel 2 Devce voltge

10 466 ) G NARAYANAN et l t sow soosv ens' +2_ STO --l -e--- l-ot t b) c) L 046 " mp"406% - t4 - O - $ Pt - s FG 9 Testng of drve crcut- for protecton gnst HSF t dfferent fult nductnces t Vtr=600 V t ) L= 750 nh, b) L = 5 "LH nd c) L = 34M Chnnel Fult current ( dvson or 50 mv corresponds to 00 A) Chnnel 2 Devce voltge

11 PROTECTON OF NSULATED GATE BPOLAR TRANSSTORS AGANST SHORT CRCUT V n steps of 00 V The oscllogrms correspondng to drve crcut- re presented for DC bus voltges of 200 V, 400 V nd 600 V n Fgs b, b nd c, respectvely The sme results correspondng to drve crcut- re shown n Fgs 7, b nd c, respectvely Chnnels nd 2 pertn to the fult current nd the collector emtter voltge, respectvely One dvson corresponds to 00 A n the cse of Chnnel, nd s mentoned n the fgures n the cse of Chnnel 2 The complementry devce s then shorted wth ncresng lengths of wre nd ncresngly hgher loop res so s to ncrese the fult nductnce The short-crcut test s crred out for dfferent vlues of fult nductnce wth DC bus voltge of 600 V The test results correspondng to drve crcuts- nd H re shown n Fgs 8 nd 9, respectvely Pror to the fult, the bus voltge s supported by the test devce nd there s no current through the devce Soon fter the pplcton of the gte drve, for short durton (round 00 ns), there s no sgnfcnt ncrese n the current, whle the voltge cross the devce drops Ths drop s essentlly cross the nductve elements n the crcut" Subsequently, the current strts rsng rpdly, nd the voltge lso ncreses n concert wth the current The rte of rse of current s ntlly hgh, nd decreses grdully wth the current sturtng t bout 250 A (5 tmes the rted current of the devce) The crcut senses fult s voltge cross the devce contnues to remn hgh even fter the blnkng perod, nd shuts down the drve Durng the turn-off of the devce, there s n overvoltge spke Fnlly, the voltge settles down to V the current grdully decys to zero Though most devces hve short-crcut wthstnd tme of 0 ps, t s preferble to shut down the drve wthn sy 2-3 gs to vod ny dverse effect on the lfe nd the long-term relblty of the devce 4 The blnkng tme remns prctclly ndependent of the fult nductnce nd bus voltge wth crcut- However, wth crcut-, the blnkng tme s hgher when the loop nductnce s lrger MC3353 hs n nternl current source of 270 AA Blnkng tme s equl to the tme tken by ths current source to chrge the 47 pf cpctor connected to pn 8 of the C to the desturton voltge of 65 V Though the chrgng rte s expected to be constnt, t seems to be ffected by the condtons n the power crcut nd gets reduced when the fult nductnce s hgher On the other hnd, wth gte drve crcut-, the blnkng tme mechnsm s ndependent of the trnsents n the power crcut 42 FUL The testng crcut for protecton gnst FUL s s shown n Fg 5b n ths test, fult s creted by shortng the lod whle the devce s n conducton The testng s crred out t dfferent bus voltges nd wth dfferent vlues of fult nductnce s erler The expermentl oscllogrms correspondng to drve crcut- re presented for 200 V, 400 V nd 600 V n Fgs 0, b nd c, respectvely Those correspondng to crcut- re presented n Fgs, b nd c, respectvely Fult nductnce L= 06 gh n both these cses The results wth L= 24 ph correspondng to crcuts- nd H re shown n Fgs 2 nd 3, respectvely Once the lod s shorted, the fult current strts ncresng The voltge cross the devce lso ncreses s shown When the devce voltge crosses the reference, the drve crcut senses fult nd shuts down the gte drve There s n overvoltge spke durng the turn off s before The devce voltge settles down to Vpc nd the current grdully decys to zero

12 468 ) b) so G NARAYANAN l 4O0 00W Snl t O 5002, Sng4 ;-- L ;# MM m% ***** POO / ' v o '*'l''''l''''ll''ll''l l + ' c) SO 0' V 4 SOO S no le dr l l l e A " "SMMM" ""2"M"MM t LslsosgkmplLlmLhoLpplk4444L sstwrwyomme 0 2 FG 0 Testng of drve crcut- for protecton gnst FUL t dfferent bus voltges wth L = 06 ph t ) VDc= 200 V, b) VDc =400 V nd c) VDc = 600 V Chnnel Fult current ( dvson or 50 mv corresponds to 00 A) Chnnel 2 Devce voltge

13 PROTECTON OF NSULATED GATE BPOLAR TRANSSTORS AGANST SUORT CRCUT 469 so 00V redelps bmdsrrrt, sow soog, s - - W 0 / b) SO 200V S0 5002,, Srtg 5 c) 50 _ S V 8!8 'Ll d - e -- - sov sop, Sne J STD 2 FG, Testng of drve crcut- for protecton gnst FUL t dfferent bus voltges wth L= 06 ph t ) Voc= c = 600 V Chnnel Fult current ( dvson 0 50 mv corresponds to 00 A) Chn- 200 V, b) Voc=400 V nd e) VD nel 2 Devce voltge

14 470 G NARAYANAN et l From the nstnt when the devce voltge crosses the reference voltge, short dely cn be notced n the oscllogrms before shut down tkes plce Ths s due to the dely n the dfferent,stges of the gte drve crcut The dely s slghtly lesser n the cse of crcut- whch uses the C drver Also, the dely s constnt wth crcut-, whle t vres from cse to cse n crcut- The sturton n the nput stge of the LM339 comprtor s responsble for ths n ny cse, the dely s only of the order of few 00 ns, whch s too smll to be of ny consequence n the protecton of the devce Thus, both the proposed drve crcuts protect the GBT effectvely gnst HSF s well s FUL They re effectve over wde rnge of bus voltges nd loop nductnces s demonstrted by the test results 5 Effect of DC bus voltge nd loop nductnce on short-crcut trnsents The lumped equvlent crcut of the test set-up for short-crcut protecton of GBTs s shown n Fg 4 The equvlent seres nductnce of the DC bus cpctors s denoted s LEn The dstrbuted prstc nductnce of the bus-br nd ts connectons cn be lumped nto n equvlent nductnce (Lys) The stry nductnce between the collector power termnl nd ts semconductor contct nsde, nd tht between the emtter power termnl nd ts semconductor contct nsde re represented by l< nd LE, respectvely These two cn be summed up s L, the vlue of whch s usully specfed n the devce dt sheets" The DC sde-loop nductnce LOC = LESL + LBW + L The nductnce correspondng to the shortng wre nd the swtch, f ny, s desgnted s Lump The totl nductnce of the short-crcut pth or the fult nductnce L= LESL + -43U5 + CE + The test results presented n the erler secton brng out the nfluence of the DC bus voltge nd tht of the loop nductnce of the short-crcut pth on the fult current nd devce voltge under fult 5 Effect of DC bus voltge Short-crcut trnsents correspondng to DC bus voltges of 200 V, 400 V nd 600 V re presented n Fgs 6, 7, 0 nd Wth ncrese n the DC bus voltge, the rte of rse of fult current ncreses However, the pek vlue of the fult current s ndependent of the bus voltge Also, the ntl dp n the devce voltge n the cse of HSF nd the overvoltge spke durng shut down remn prctclly unffected by the DC bus voltge 52 Effect of loop nductnce (L) Gven devce, 'CE s fxed Gven set of DC lnk cpctors nd bus-br rrngement LEs nd LEus re lso fxed Essentlly, L s vred by vryng Lump Short-crcut trnsents correspondng to dfferent vlues of fult nductnce (L) re shown n Fgs 8, 9, 2 nd 3, respectvely Wth ncrese n L, the rte of rse of fult current decreses n the cse of HSF, the dp n the devce voltge soon fter the turn-on ncreses wth ncrese n L The overvoltge spke t turn-off remns ndependent of Lump s shown by the oscllogrrns However, from the equvlent crcut n Fg 4, t cn be seen tht t depends on sm More dscusson on ths s provded n Sectons 53 nd 6

15 PROTECTON OF NSULATED GATE BPOLAR TRANSSTORS AGANST SHORT CRCUT 47 ) 50 v_ Ory 2 V 'WM MtS /4/ A - " b) J c) 200V 00W SOOQ, SrK ---- O FG 2 Testng of drve crcut- for protecton gnst FUL t dfferent bust voltges wth L= 24 }LH t ) VDc = 200 V b) VDc = 400 V nd c) VDc = 600 V Chnnel Fult current ( dvson or 50 mv corresponds to 00 A) nd Chnnel 2 Devce voltge 53 Estmton offult nductnce (L) The loop nductnce of the short crcut pth cn be estmted from the fult current nd the devce voltge under fult Ths cn be done for both types of fults The fult current cn be

16 472 G NARAYANAN t ), so OZ,' 2 oov -v- 4 oot 2 00W/ Snl orlreteor---essssmss S l l 6 ss sests-,sso- - 6 & b) V 2 S s 4 --e e--f-r ters 4 es- - - ' l l l l - l l l l l l S so 0V c) S 2 200V rsfrtr l l l l l r 4 O0 5002/ Sngl - =_ 6 -,j t t A S FG 3 Testng of drve crcut- for protecton gnst FUL t dfferent bus voltges wth L= 24 th t ) VDC =- 200V, b) VDc = 400V nd c) VDc = 600 V Chnnel Fult current ( dvson or 50 mv corresponds to 00 A) nd Chnnel 2 Devce voltge consdered to be constnt ntlly (zero n the cse of HSF) nd then to be rsng exponentlly Let the ntl rte of rse of the exponent be (d/don Let the dfference between the DC

17 PROTECTON OF NSULATED GATE BPOLAR TRANSSTORS AGANST SHORT CRCUT 473 bus voltge nd the voltge cross the devce t tht nstnt be AV Ths s the drop cross the sum of nductnces LEsL, Lgus nd /tom> Both AV nd (d/do N cn be mesured from the oscllogrms Now, the vlue of the fult nductnce cn be estmted s per eqn () AV(dldON+ () Le s vlble from the dt sheets" The vlues of L quoted n Fgs 6-3 re bsed on such n estmton 6 Overvoltge spkes nd bus-br desgn Overvoltge spkes occur durng swtchng due to prstc nductnce nd hgh d/d These must be decresed by reducng d/dt or the prstc nductnce or both Reducng d/d mens ncresng the gte resstnces, whch leds to ncrese n losses Hence ths s not desrble However, reducng prstc nductnce by usng sndwch bus-br s move n the rght drecton The sndwch bus-br must preferbly be desgned n such wy tht the spkes re tolerble even wth the worst &Mt expected The worst d/dt occurs durng shut down followng fult detecton The overvoltge spke then s yrdstck for the desgn of the bus-br The expermentl results n Fgs 6-3 show the spkes to be qute low (bout 20 V n the cse of HSF nd bout 50 V n the cse of FUL) vndctng the desgn of the bus-br Reducng the fult current before the shut down cn lso reduce the overvoltge spke But ths requres gte clmpng, whch mkes the drve crcut complex s mentoned erler Further, ths s not very essentl s the expermentl results demonstrte Reducton n the stry nductnce by proper desgn of the bus-br s dequte to keep the spkes wthn tolerble lmts 7 Selecton of gte resstnces Selecton of gte resstnces s very crtcl n the desgn of gte drve crcut For norml operton, the gte resstnces re selected bsed on the swtchng losses, stress on the devces, etc usng the chrcterstcs n the devce dt sheet Durng fult nd subsequent shut down, the stress on the devce s expected to be hgher Hence, one my consder usng hgher vlues of gte resstnces thn those used under norml condtons to decrese the stresses Ths secton ttempts to fnd n nswer to the queston whether such n ncrese s requred Wth ncrese n gte resstnces, the swtchng losses ncrese Durng test t ws found tht ncresng Rc(Qr,) from 22 to 47 Q resulted n nusnce trps t hgher bus voltges nd lod currents Thus, such n ncrese clerly deterortes the norml performnce As mentoned n the prevous secton, the voltge spkes cn be dequtely hndled by proper desgn of bus-br t s nether necessry nor desrble to ncrese the gte resstnces to control the voltge spkes Further, f &or s low, the turn-on tme s less nd hence the blnkng tme cn lso be less Ths decreses the dsspton n the devce under fult Dependng on the devce technology, the vlue of gte resstnces nd gte voltge, the fult current cn rse to very hgh vlue ntlly nd then reduce subsequently to lesser vlue The ntl pek fult current

18 474 G NARAYANAN et l L Le LEst 8 L E Lb, FG 4 Lumped equvlent crcut under fult (speak) cn be s hgh s twce the stedy vlue 8 t ncreses wth ncrese n Rc, (0FF)3 The stedy fult current slghtly decreses wth ncrese n Ro wn)7 However, ths s not very sgnfcnt n the present work, the gte resstnces hve been chosen for good performnce under norml condtons Hgher vlues re not used to reduce the stress under fult The expermentl results show tht ncrese n gte resstnces s not essentl for effectve fult protecton Also, t my not be dvsble to ncrese them for the resons stted bove 8 Concluson Two GBT gte drve crcuts cpble of protectng the devces gnst short crcut re presented These re shown to be effectve n protectng the devces gnst both hrd-swtched fult s well s fult under lod under dfferent crcut condtons The test results brng out the nfluence of the DC bus voltge nd the fult nductnce on the short-crcut trnsents Both the crcuts use collector emtter voltge for sensng fult Though the collector emtter voltge gves only corse dstncton between the fult nd the norml condtons, the test results estblsh tht t s suffcent for protectng the devces effectvely A smple gte drve crcut lke the ones proposed nd well-desgned low-stry nductnce bus-br form cost-effectve soluton to mprove the relblty of GBT-bsed power converters References CHOKHAWALA, R CATT, J AND PELLY, B Gte drve consdertons for GBT modules, EEE-AS '92 Conf Rec, 992, Houston, Texs, pp BLAABERG, F AND PEDERSEN, J K An optmum drve nd clmp crcut desgn wth controlled swtchng for snubberless PWM-VS-GBT nverter leg, EEE- PESC '92 Conf Rec, 992 Toledo, Spn, pp CHOKHAWALA, R AND CASTNG, G GBT fult current lmtng crcut, EEE-AS '93 Conf Rec, 993, Toronto, Cnd, pp CHOKHAWAA, R, CM-F, J AND CRALY, L A dscusson on GBT short crcut behvour nd fult protecton schemes, EEE-APEC '93 Conf Re, 993, Sn Dego, Clforn USA, pp

19 PROTECTON OF NSULATED GATE BPOLAR TRANSSTORS AGANST SHORT CRCUT 5 CHOKHAWALA, R AND SDMAN, S, Swtchng voltge trnsent protecton schemes for hgh current GBT modules, EEE-APEC '94 Conf Rec, 994 Orlndo, Flord, USA pp ECKEL, H G AND SACK, L Expermentl nvestgton on the behvour of GBT t short crcut durng the on stte, EEE-ECON '94 Conf Rec, 994, Bologn, tly, pp NAND, P K 475 Study of short crcut performnce of GBT nd development of bse drves for GBT, ME Project Report Deprtment of Electrcl Engneerng, ndn nsttute of Scence, Bnglore, nd, GBT gte drver crd Lbortory document, Power Electroncs Group Deprtment of Electrcl Engneerng ndn nsttute of Scence Bnglore, nd, JOHN, V, SUF B-S AND LPO, T A Fst-clmped short-crcut protecton of GBTs EEE Trns, 999 A JOHN, V, SUH, B-S AND LPO, T A Hgh-performnce ctve gte drve for hgh-power GBTs EEE Trns 999 A-35, 08-7 SEMKRON Product Hndbook, SEMKRON nterntonl, Nurenberg Germny, Oct RGT000M2 Prelmnry Dt Sheet No PD-9924, nterntonl Rectfer, July RGT0025M 2 Prelmnry Dt Sheet No PD-9925, nterntonl Rectfer July RGT0050M2 Prelmnry Dt Sheet No PD-9926 nterntonl Rectfer, July RGT0075M2 Prelmnry Dt Sheet No PD-9927 nterntonl Rectfer, July MC3353 dt sheet nd pplcton nformton, Motorol nc, Mono, E R t A new generton of ntellgent power devces for motor drve pplctons, EEE-AS Conf Rec, MS '93, 993, Toronto, Cnd, pp ADAMS, J Usng the current sensng R22X gte drve Cs, Applcton note AN- 04 nterntonl Rectfer, June HCPL-300/30 techncl dt sheet, Hewlett-Pckrd Co ' 22 SKBNSK, G AND DVAN, D M 23 CAPONET, M C, PR0F440, F, DE DONCKER, R W AND TENCON, A Lecture Notes, Short-term ntensve course on Recent trends n power electroncs nd drves, Dec 2-3, 998, Centre for Contnung Educton, ndn nsttute of Scence, Bnglore nd Lecture notes, Short-term ntensve course on Swtched mode power converson, July 3-7, 2000, Centre for Contnung Educton, ndn nsttute of Scence, Bnglore nd Desgn methodology nd modelng of low nductnce plnr bus structures EPE"93 Conf Rec, 993, Brghton, UK, pp Low stry nductnce bus br desgn nd constructon for good EMC performnce n power electronc crcuts, leee-pesc '2000 Conf Rec, June 8-23, 2000, Glwy, relnd pp 96-92