Diret Torque Control of BLDC Drives for Eletril Vehile Applition Gopl Krishn Nik B 1, Blji Gutt 2 1 PG student, EEE Deprtment, Gudlvlleru Engineering College (JNTUK), Gudlvlleru, AP, In 2 Assistnt professor, EEE Deprtment, Gudlvlleru Engineering College, Gudlvlleru, AP, In Astrt-Brushless DC (BLDC) motors re ommonly used for severl industril pplitions euse of their smll size, high torque nd high effiieny. This pper presents Diret torque Control of rushless DC (BLDC) drive y using Hysteresis urrent ontrol tehnique to extend the voltge pity of tteries per hrge in eletri vehile pplitions. In the onventionl urrent ontrol method, the urrent is still drwn from the tteries even when the motor is turned off. To void tht lekge urrent, it is fed to zero rossing detetor. By using Hysteresis omprtor it produes high swithing frequeny, whih produes ripple torque. But in this tehnique only urrent ontrol is possile. The proposed method redues the Torque ripple y ontrolling the inverter swithing instnts nd high swithing frequeny y using ret torque ontrol. The modeling, simultion nd ontrol of the BLDC motor is done y using the MATLAB/SIMULINK. Keywords:-Brushless DC(BLDC)motor, Hysteresis ontroller, Eletri vehile (EV),Buk Converter(step down),current Soure Inverter(CSI), Zero Crossing Detetor. I. INTRODUCTION Eletri Vehile (EV) is n emerging tehnology in the modern world euse of the ft tht it mitigtes environmentl pollutions nd t the sme time inreses fuel effiieny of the vehiles. Bttery-powered eletri vehiles re one of the solutions proposed to tkle the energy sster nd glol wrming. However, the high initil ost, short driving rnge, long hrging (refueling) time, nd redued pssenger nd rgo spe hve proved the limittion of ttery-powered EVs. The effiieny of the ttery is very importnt, euse the eletri motor uses the exess power of the engine to hrge ttery. If the engine genertes more power thn the driver then it provides dtionl power to ssist the driving. BLDC drives re widely used for driving purpose. BLDC motor is trtionlly defined s permnent mgnet synhronous motor with trpezoidl Bk EMF wveform shpe. BLDC motors do not use rushes for ommuttion, insted, they re eletronilly ommu-tted. The urrent ommuttion is done y solid stte swithes, whih elimintes rush mintenne nd sprking ssoited with them. BLDC motors re one of the motor type s fst gining the interest of the reserhers. This motor ttrts muh interest due to its etter speed, high dynmi response, high effiieny, long operting life, noiseless opertion nd power density, omptness, high torque potentil for steep slope or rod ontions, high reliility, roust-ness for eletri vehile nd offers resonle ost. BLDC motors re used in industries suh s Industril Automtion equipment nd Instrumenttion, Applines, Automotive, Airrft, Consumer, Mel. BLDC motors re ville mny fferent power rtings, whih ffer from very smll motor s used in hrd sk drives to lrge motor used in eletri vehiles. II. CONSTRUCTION OF BLDC MOTOR In onstrution point of view BLDC motor hs two min prts one is the sttor (sttionry prt) nd rotor (rotting prt) in whih the mgneti field generted y sttor nd rotor rottes t the sme frequeny, hene eliminting the slip whih is normlly seen in indution mhine. The sttor hs rmture winngs on sttor nd rotor hs permnent mgnets. Fig 1. Outer Rotor nd Inner Rotors IJRASET 2014: All Rights re Reserved 409
BLDC motors hve lifelong exittion from permnent mgnets mounted on rotor surfe. There re two si rotor designs inner rotor design nd outer rotor design s shown in fig 1. For the outer rotor design, the winng re loted in the ore of the motor. The rotor mgnets surround the sttor winngs nd ts s n insultor, reduing the rte of het ssiption from the motor. This design opertes t lower duty yles or t lower rted urrent nd it is used in low speed motors. The enefit of this design is reltively low ogging torque. For the inner rotor design, the sttor winng surround the rotor nd is fixed t motor housing. The dvntge of the design is the ility to ssipte het thus retly impts its ility to generte torque nd its lower inerti nd these re used in high speed pplitions. Sttor ommodtes 3-ϕ winngs nd the no of sttor slots is hosen depenng on the rotor poles, winng onfigurtion, phse numer. A frtionl slots/pole design is preferred to minimize ogging torque. The winng slots re uilt into the sttor nd rotting mgneti field is provided y the urrent polrity hnges in the slot winngs. The hnge of urrent polrity must e in ordne to the rotor mgneti field, whih requires the position of the rotor. Hll Effet sensors re fixed on the sttor to provide this informtion. Solid stte swithes re used for urrent ommuttion whih elimintes the need of rushes. A. Opertion of BLDC The fundmentl working priniple of BLDC motor is sme s tht of onventionl DC Motor with the permnent mgnets pled in the rotor nd oils in the sttor. Hving the rmture winngs on sttor helps the ondution of het from the winngs. As the winng is sent on rotor, the rotor opper losses re negligile. The oil winngs re eletrilly seprte from eh other whih llows them to turn on nd off in sequene tht retes rotting mgneti field. The rotor position is to e determined so tht exittion of the sttor field lwys leds to the genertion of torque. The rotor is not eletrilly onneted to the sttor thus preventing ring phenomen whih use ron to e produe hene mking insultion filure. Fig 2. BLDC motor ross setion nd phse energizing sequene Here the ommuttion instnts re determined y the rotor position nd the position of the rotor is deteted either y position sensors or y sensor less tehniques. For this mostly we re using two types of sensors they re Hll Effet sensors nd Optil position sensors. These sensors re pled on shft. The signls from these sensors tht generlly used in BLDC motor drive to energize the pproprite sttor winngs. The permnent mgnets used in BLDC motor it helps to keep the inerti low. The k e.m.f mplitude of the BLDC is proportionl to the rotor speed. TABLE II. Hll Signls nd Phse Sequene Swithin g sequene Seq. no Position sensors Swith losed Phse urrent H 1 H 2 H 3 A B C 0 0-60 0 0 1 0 0 Q 1 Q 4 + - Off 60 0-120 0 1 1 1 0 Q 1 Q 6 + Off - 120 0-180 0 2 0 1 0 Q 3 Q 6 Off + - 180 0-240 0 3 0 1 1 Q 3 Q 2 - + off 240 0-300 0 4 0 0 1 Q 5 Q 2 - off + 300 0-360 0 5 1 0 1 Q 5 Q 4 off - + The ir gp flux-density wve form is essentilly squre wve, w.r.t the rotor position. Beuse of firing the k e.m.f wveform tkes on trpezoidl shpe. The k e.m.f indued in eh phse re similr in shpe nd re spled y 120 0 w.r.t eh other. By injeting retngulr urrent pulses in eh phse tht oinides with the rest of the k e.m.f wve form in tht phse, it is possile to otin lmost onstnt torque from the BLDC motor. IJRASET 2014: All Rights re Reserved 410
Fig 3. Three phse Bk E.M.F nd Torque wve forms The mplitude of the phse k e.m.f is proportionl to the rotor speed, whih is given y E = kϕ ω m (1) Where k = onstnt depends on the no.of turns in eh phse, ϕ = permnent mgnte flux, ωm = mehnil speed. During ny 120 0 intervl, the instneous power is onverted from eletril form to mehnil form, it is given y P o = ω m T e = 2 EI (2) So the out put torque n e written s T e = 2 kϕ I = T e = k t I (3) Where k t = torque onstnt, T e = out put toque A BLDC motor mthemtil equtions n e derived similr to DC mhines where there re two equivlent iruits, i.e. eletril nd mehnil equtions. Figure 4 shows the si loks of BLDC motor tht ontins three phse sttor iruit nd mehnil prt. Applying Kirhhoff s voltge lw for the three phse sttor loop winng iruits yields Fig 4. 3-ϕ Brushless DC mhine equivlent iruit nd mehnil model. v v ir ir L L e (4) v e (6) ir L e (5) Where, v = instntneous of phse voltge IJRASET 2014: All Rights re Reserved 411
i = instntneous of phse urrent e = instntneous of phse k-emf voltge R = r-phse resistne L = -phse indutne M= mutul indutne The eletromgneti Torque is given y T e = (e i + e i + e i ) / ω m (7) The sussion hs onentrted on the opertion of BLDC mhine s motor. It n however operte eqully well s genertor in some speil pplitions. III. CONVENTIONAL CONTROL SYSTEM It is simple method tht n offer these requirements is the use of urrent ontrol tehnique. Figure 5 shows the struture of urrent ontroller for BLDC motor. The ontrol of urrent n e estlished y ontrolling the three-phse urrent t its referene suh tht Fig 5. Struture of Conventionl Current Control drive for BLDC motor. it will stisfy the equtions (4).As shown y Fig. 5, the motor urrents need to e ontrolled stisfying to their referenes (i *, i *nd i *). The genertions of referene urrents re sed on the torque demnd (i.e. Iref =Te,ref x G 1 ) nd deoded signls (H 1, H 2 nd H 3 ) whih re derived from the Hll Effet signls (H 1, H 2 nd H 3 ) s given in Tle. I TABLE I: Derivtion of Deoded Signls sed on Hll Signls Hll Effet signls Deoded Signls H 1 H 2 H 3 H 1 H 2 H 3 0 0 0 0 0 0 0 0 1 0-1 +1 0 1 0-1 +1 0 0 1 1-1 0 +1 1 0 0 +1-1 0 1 0 1 0 +1-1 1 1 0 0 +1-1 1 1 1 0 0 0 IJRASET 2014: All Rights re Reserved 412
Eh phse urrent is ontrolled using 2-level hysteresis omprtor, whih is responsile to produe pproprite swithing sttus to e fed into the inver-ter, either to inrese or derese the phse urrent suh tht its error (or urrent ripple) is restrited within the hysteresis nd (HB).In suh wy, the referene urrent for eh phse will hve the sme pttern wveform with the respetive deoded signls. In the onventionl urrent ontrol method, the urrent is still drwn from the tteries even the referene urrent is set to zero. As the phse urrent needs to e regulted IGBTs/MOSFETs in the inverter,. When the torque pedl is relesed (T e,ref = 0) nd one the tul motor torque is ompletely redued to zero. This setion presents urrent loking strtegy to void wste of energy from the ttery (due to the urrent drwn) when the torque pedl is relesed (i.e. T e, ref = 0) for eletri vehile pplitions. This simply n e estlished with minor mofition on the originl struture of urrent ontrol (shown in Fig. 5) Using hysteresis omprtor s shown in Fig. 6 within the hysteresis nd t round zero Amperes (A). To lok the urrent drwn from the ttery, the proposed urrent loking strtegy will turn OFF ll. By referring to the Fig. 6, the tivtion of urrent loking strtegy requires the solute vlue of torque demnd, T e,ref nd phse urrents (i, i nd i ) whih re then fed into zero rossing detetor nd hysteresis omprtor, respeti-vely. Fig 6. Conventionl urrent loking strtegy sed on hysteresis omprtor The tivtion to swith OFF ll IGBTs/MOSFETs in urrent soure inverter will perform if the torque produ-tion, Te nd torque demnd, Te,ref derese to zero. For lerer piture, the ontion of the tivtion is illustrted in Fig 7. Otherwise, norml swithing oper-tion to keep the urrent (or torque) to e regulted within the hysteresis nd will perform. Fig 7. Bloking Strtegy is Ativted if Te nd T e,ref Derese to IV. BLOCK DIAGRAM COMPONENTS A. Current Controller Hysteresis ontrol is one of the simplest losed-loop ontrol shemes. A referene sine wve urrent is omp-red with the tul phse urrent. When the urrent exeeds presried hysteresis nd, the upper swith in the inverter ridge is turned off IJRASET 2014: All Rights re Reserved 413
nd the lower swith is turned on, nd the urrent strts to dey. As the urrent rosses the lower nd limit, the lower swith is turned off nd the upper swith is turned on. The tul urrent is fored to trk the sine referene within the hysteresis nd y k nd forth (or ng-ng) swithing of the upper nd lower swithes. The inverter then essentilly eomes urrent soure with pek-to-pek urrent ripple, whih is ontrolled within the hysteresis nd. In hysteresis ontrol, the vlue of the ontrolled vrile is fored to sty within ertin limits round its referene vlue. By ompring with PWM tehnique, hysteresis urrent ontroller is preferred, onsidering its performne, fst retion mximum urrent limit nd insensile to lod prmeter vritions. Due to lk of oorntion mong invidul hysteresis ontrollers of three phses, very high swithing frequeny t lower modultion index my hppen [7]. The sdvntge of the hysteresis nd ontrol tehnique re the high nd unontrolled swithing. frequenies when nrrow hysteresis nd is used nd lrge ripples when the hysteresis nd is wider [8]. The unontrolled swithing frequeny mkes it ffiult to filter the ousti nd eletromgneti noise. The swit-hing method used here is the soft hopping method in whih only the upper swith is turned on nd off while the lower swith is left on. This method produes less torque ripple nd less swithing losses thn the hrd hopp-ing method. Only urrent ontrol is implemented here. The reson is tht if position ontrol is to e implemented in the sme wy s the torque nd the position ontrol, it would only e possile y onstntly reversing the rotor speed so tht the rotor ngle would sty within the hysteresis nd.. B. Retifier Retifier is n eletroni equipment; tht onverts lternting urrent to ret urrent (A.C-D.C), whih flows only in one retion. Mny pplitions of retif-iers, suh s power supplies for television nd omputer equipment, ros, where onstnt DC urrent (s would e produed y ttery) is required. In these pplitions the output of the retifier is urved y n eletroni filter (usully pitor) to generte stedy urrent. C. DC/DC Converter (Buk Converter) A uk onverter is voltge step down nd urrent step up onverter. The si opertion of the uk onverter hs the urrent in n indutor restrited y two swithes (usully trnsistor nd ode). Fig 8. DC /D.C (uk) onverter In this pper, the uk onverter is used for voltge step down purpose of retified D.C. the voltge is eing ontrolled depenng on the duty rtio (D). The gte signls re generted y using urrent speed wve forms of the motor. This ontrolled voltge is fed to the ttery. Output voltge of uk onverter V o = D V in (8) D. Current Soure Inverter (C.S.I) An inverter is n eletroni devie tht hnges ret urrent (DC) to lternting urrent (AC). The input voltge, output voltge nd frequeny, nd overll power hndling depend on the design of the prtiulr devie. The onverter is three phse DC to AC onverter nd it onsists of six solid stte semiondutor swithes s shown in Figure 9. Mosfets nd IGBT re the most ommon types of swithes used. In lower power pplition, Mosfets re preferred over IGBT. The power eletroni onverter is neessry to operte the BLDC mhine. Current ommuttion is done y six-step inverter. The three phse BLDC motor is operting in two phses-on fshion whih mens the two phses tht produe the highest torque re energized while the third phse is off, see Figure 2. The two phses re energized depends on the rotor position. Hll Effet position sensors re most frequently used. IJRASET 2014: All Rights re Reserved 414
The inverter is responsile for oth the Eletroni ommuttion nd urrent regultion. The ondution of every phse winng is determined y the rotor position where the position n e known from hll effet sensors tht provides three git output tht hnges every 60 degree (eletril degrees).the genertion of three gitized outputs (i.e. H1,H2 nd H3) from the sensor orng to the rotor position n e lso desried in Tle 2. Fig 9. Three-Phse DC /AC inverter. The power eletroni inverter must e ple of pplying positive, negtive nd zero voltge ross the motor phse terminls. Eh drive phse onsists of one motor terminl driven high, one motor terminl driven low, nd one motor terminl floting [6]. V. PROPOSED DIRECT TORQUE CONTROL TOPOLOGY In the onventionl urrent ontrol strtegy only urrent will e ontrolled, with high ripples in torque. The Diret Torque Control sheme is extended to BLDC motor drives to minimize the Torque Ripples. The eletro-mgneti torque nd the sttor flux linkge mplitude of the BLDC motor under 2-phse ondution mode n e ontrolled simultneously. Here we re going to redue the ripples in torque y using ret torque ontrol. Minly BLDC drive hs drwk of high torque pulstion. Bsilly it is used y two-omponents one is ripple torque nd nother one is ommuttion torque. The min omponents of ripple torque re motor relted nd inverter relted. Motor relted omponents re produed y the non-idelities in the k e.m.f wve forms. Here Motor reltes ogging torque, inverter reltes ripple torque. Ripple torque is onsequene of the intertion of the rmture urrents with the mhine k e.m.f wve forms. Cogging torque produed y vrition of relutne used y the sttor slot openings s rotor rottes. Cogging torque n e redued y skewing nd y hoosing frtionl slot/pole motor design. Fig 10. Blok grm of proposed system The inverter relted ripple torque omponents deprture from the idel retngulr urrent profiles due to finite indutne. The inverter relted ripple torque is used y the Hysteresis ontroller euse whih produes high swithing frequeny urrent ripple. This high frequeny ripple is used y orresponng ripple in phse urrent. The k e.m.f relted omponent hs high frequeny; it is Six times of the eletril frequeny, orresponng to the six ondution intervls in eh yle. At low speeds they n ffet the performne of the drive, ut t high speeds it is not prolem s it is filtered out y lod inerti. This high frequeny torque ripple is redued y ontrolling the urrent nd rotor position. The seond omponent of inverter relted torque ripple is ommuttion torque ripple, it ours t every ommuttion instnt. The torque ripple genertes some of the urrents t ON/OFF position lmost never onstnt during the swithing instnts. Here IJRASET 2014: All Rights re Reserved 415
the urrent is ommutted from B - phse to C phse. The rte t whih the urrent uilds up in C phse is greter thn the rte t whih deys in B phse, whih results in urrent ripple in A phse nd resultnt ripple in torque prodution. This torque ripple depends on rotor speed nd soure voltge. This ommuttion ripple omponent is minimized y using urrent sensor in eh phse. Here D.C/D.C onverter ontrols the soure voltge, BLDC motor urrent nd tul speed (ω m ). Atul speed ompred with referene speed (ω*) nd is ontrolled using PI ontroller. The PWM ontroller genertes the swithing pulses to the uk onverter, whih ontrols the soure voltge. Fig 11. Ripple Torque Wve Forms In onventionl urrent ontrol only urrent ontrol is possile, ut hving lrge torque ripple s shown in ove fig 11.(ripple is nerly 1.4 N-m). VI. SIMULATION CIRCUITS AND RESULTS Fig 12. Simulink Blok Digrm of Overll System The ove figure.12 shows simultion grm of overll ontrolling system. It ontins. soure, d./d. onverter, inverter nd BLDC drive. Fig 13. Simulink Ciruit of Controlling Ciruit IJRASET 2014: All Rights re Reserved 416
Figure13 shows the simultion grm of inverter ontrolling system. It ontrols torque nd speed y ontrolling urrent nd rotor position. Fig 14. Hll Sensor Signls Figure 14 shows the hll signls re generted y the lekge flux t the pproprite rotor positions Fig 15. Bk E.M.F Wve Forms Figure 15 shows Bk E.M.F wve forms. Whih re spled y 1200 w.r.t eh other in 3-phse mhine. Fig 16. Motor Sttor Currents. Figure 16 shows 3-phse sttor urrents nd the urrent error ripple is restrited within the predefined nd gp. Fig.17. loking strtegy Motor lekge Currents Aove fig.17 wve forms shows lekge urrent of the motor. Current ripple is redued smll mount ompred to urrent ontrol 1A to 0.8 A. IJRASET 2014: All Rights re Reserved 417
Fig.18(). Torque wve forms The ove figure shows redued ripple torque wveforms. Fig18(). Torque Wve Forms The ove figure shows redued ripple torque wveforms (ripple is redued from 1.4 N-m to 0.12 N-m). Fig 19.Speed Wve Forms Aove figures 18 & 19 shows Torque nd speed wve forms, these re in positive nd negtive. It n e oserved s the speed nd torque dereses (during motor rking) the frequeny of the urrent wveforms dereses nd s the speed nd torque inrese (during motor elertion) the frequeny of the urrent wveforms inreses. By the opertion of BLDC motor it n however work s genertor. The polrity of Torque n e reversed y simply reversing the polrity of phse urrent wveforms w.r.t k e.m.f. wveforms. In regenertive reking it is used n dvntge, in vehile popultion. For exmple speil rrngements re needed in the power onverter to llow the energy returned y the mhine, s onventionl ode ridge retifiers re unle to feed k to the A.C. supply. In utomoile pplitions this sitution is onsiderly simplified y using the ttery s soure. TABLE 2: Performne Comprison Without Bloking Strtegy Current ontrol Diret Torque ontrol Torque Ripple 1.6 N-m 1.4 N-m 0.12 N-m Current Ripple 4.9 A 1 A 0.8 A IJRASET 2014: All Rights re Reserved 418
www.ijrset.om Volume 2 Issue XII, Deemer 2014 VII. CONCLUSION This pper presents simultion results of Diret Torque Control of rushless DC (BLDC) drive y using Hysteresis urrent ontrol tehnique to extend the voltge pity of tteries per hrge in eletri vehile pplitions. In the onventionl urrent ontrol method, the urrent is still drwn from the tteries even when the motor is turned off. To void tht lekge urrent, it is fed to zero rossing detetor. By using Hysteresis omprtor it produes high swithing frequeny, whih produes ripple torque. But in this tehnique only urrent ontrol is possile. The proposed method redues the Torque ripple y ontrolling the inverter swithing instnts nd high swithing frequeny y using Diret Torque ontrol. The simultions of the ret torque ontrol were performed using MATLAB/Simulink. REFERENCES [1] Ahmd Fiz Noor Azm, Auzni Jin, Nor Azzi Ngtimn, M.H Jopri, Mustf Mnp, Adeline Lukr Herlino, Nor Fezh Alis urrent ontrol of ld drive for ev pplition,ieee 7th Interntionl Power Engineering nd Optimiztion Conferene (PEOCO2013), Lngkwi, Mlyssi. 3-4 June,2013. [2] Lefley, P., L. Petkovsk, nd G. Cvetkovski. Optimiztion of the design prmeters of n symmetri rushless DC motor for ogging torque minimiztion in Power Eletronis nd Applitions (EPE 2011), Proeeng of the 2011-14thEuropen Conferene on 2011. [3] Bhri N., Jin A., Adullh A. R. nd Othmn M. N., Modeling nd Simultion of Torque Hysteresis Controller for Brushless DC Motor Drives, IEEE Symposium on Industril Eletronis nd Applitions ISIEA, 2012. [4] Myer, J.S. nd O. Wsynzuk, Anlysis nd modelling of single-phse rushless DC motor drive system, Energy Conversion, IEEE Trnstions on, 1989. 4(3): p. 473-479. [5] Jin, A., Idris, N. R. N., Ytim, A. H. M., Sutikno, T. nd Eluluk, M. E. An Optimized Swithing Strtegy for Quik Dynmi Torque Control in DTC-Hysteresis-Bsed Indution Mhines, IEEE Trnstions on Industril Eletronis,2011, Vol. 58, pp. 3391-3400. [6] Norhzilin Binti Bhri; Jin, Auzni in; Adullh, Adul Rhim in; Md Nzri in Othmn; Mnp, Mustf in, "Modeling nd simultion of torque hysteresis ontroller for rushless DC motor drives," Industril Eletronis nd Applitions (ISIEA), 2012 IEEE Symposium on, vol., no., pp.152,155, 23-26 Sept. 2012 [7] Hendershot, J.R nd T. Miller. Design of Brushless Permnent Mgnet Motors. Oxford: Mgn Physis Pulitions & Oxford Siene Pulition, 1994. [8] Ching-Tsi, P. nd C. Ting-Yu, An improved hysteresis urrent ontroller for reduing swithing frequeny. Power Eletronis, IEEE Trnstions on, 1994. 9(1): p. 97-104. [9] KS Low M.F Rhmn nd K.W Lim. Approhes to the Control of Torque nd Current in Brushless D Drive,2002. Gopl Krishn Nik. B Reeived his B.Teh degree in Eletril nd Eletronis Engineering from Chirl Engineering College, Chirl, ffilited to JNTU, Kkind in 2009. He is pursuing M.Teh in the deprtment of Eletril nd Eletril Engineering with speiliztion in Power Eletronis nd Eletri Drives in Gudlvlleru Engineering College, Gudlvlleru, A.P, In. His reserh interests inlude Power Eletroni Converters nd Drives. BALAJI GUTTA hs reeived his B.Teh degree from Gudlvlleru Engineering ollege, Gudlvlleru under J.N.T.University, Hyderd in the yer 2002. M.Teh degree with the speiliztion of Eletril Drives nd Control from Ponherry Engineering College in the yer 2006. At present he is working s n Assistnt Professor in Gudlvlleru Engineering ollege, Gudlvlleru. His res of interest re Eletril Mhines nd Drives, Power Eletronis, Eletril Ciruits, nd Control Systems. IJRASET 2014: All Rights re Reserved 419