Powerex, Inc., 2 Hillis Sree, Youngwood, Pennsylvania 15697-18 (412) 925-7272 SC/GO/Diode POW--BOK Modules Applicaion Informaion 2. POW--BOK Module Mouning When mouning POW--BOK modules o a heasink, care should be aken o avoid applying uneven orque o he baseplae due o one sided ighening. I is recommended ha he mouning screws be ighened in he fashion shown in Figure 2.1. he device daa shee liss he maximum orque raing for boh he mouning screws and, where applicable, he erminal screws. he use of hermal compounds when mouning POW--BOK modules o heasinks is highly recommended o preven ho spos due o voids beween he package and he heasink surface. I is imporan o selec a hermal compound which has a sable characerisic over he operaing emperaure range and he lifeime of he equipmen. he compound should be applied in a very hin layer, applying a hin coaing wih a spaula or linless brush and wiping lighly o remove excess maerial. Anoher mehod is o place a predeermined minimal amoun a or along he cener of he conac area. hen in mouning, roaion and pressure will force he compound over he conac area and experience will indicae wheher he quaniy is sufficien as excess will appear around he edges of he conac area. Excess compound may be wiped away using a cloh weed wih aceone or alcohol. he use of hick consisency hermal compounds should be avoided, paricularly wih larger modules, since i may Figure 2.1 ➀ wo-poin mouning ype emporary ighening ➀ ➁ final ighening ➁ ➀ Mouning Screw Fasening Paern no compress evenly when he module is orqued. A number of manufacurers supply a wide variey of hermal grease and fluid ype compounds. Among hese are Wakefield, Dow-Corning, Alcoa, and hermalloy. In addion, some manufacurers offer alernaive hermal inerface pads which avoid he applicaion problems of greases. hese maerials, such as HEMSAE, are ofen available in pre-cu shapes ha accommodae many POW--BOK, module packages. ➁ I is recommended ha heasink surfaces be fla wihin ±1 mil/inch over he mouning area and have a surface finish of less han 64 microinches. I is also imporan o properly prepare he heasink mouning surface jusrior o module mouning. he heasink surface should be horoughly cleaned o remove any foreign maerial, oxides, or films. A saisfacory cleaning echnique is o polish he mouning area wih ➃ ➀ No. fine seel wool, followed by an alcohol or aceone rinse. 2.1 Gae Drive ecommendaions SCs have exraordinarily high power gain. For example, a 9 Ampere, 1 Vol SC is guaraneed o urn on if a 1 ma, 3 Vol gae drive is applied. his is a power gain of 3 x 15. he power gain is furher magnified as he required gae conrolled signal is a pulse only a few microseconds wide. ➂ ➁ Four-poin mouning ype emporary ighening ➀ ➁ ➂ ➃ final ighening ➃ ➂ ➁ ➀ o achieve reliable performance of he SC, a gae drive signal greaer han he minimum specified I G and V G values is required. Because of he diverse range of SC applicaions, a DC gae es condiion wih a resisive load was esablished for he basic gae parameers, I G and V G, found on a ypical daa shee. hese DC gae rigger parameers are no inended o reflec operaional applicaion requiremens. xxiii
Powerex, Inc., 2 Hillis Sree, Youngwood, Pennsylvania 15697-18 (412) 925-7272 SC/GO/Diode POW--BOK Modules xxiv he reason for he gae overdrive requiremen is he finie ime required o achieve full area conducion in he SC. his di/d problem, is especially criical in he firs few microseconds of urn-on, when only a very small percenage of he oal device area will be in conducion. he iniial conducion area is highly dependen upon gae-o-cahode geomery and he amoun of gae curren overdrive. Mos POW--BOK modules uilize SCs wih di-namic gae designs. he di-namic gae design provides an inegraed pilo SC conneced from anode o gae of he main SC. he pilo SC provides rapid urn on of a significanorion of he main SC secion of he device. Di-namic gae devices allow he use of sof gae drive for mos applicaions. However, applicaions sill exis even wih di-namic gae devices which require hard gae drive. Figure 2.2 illusraes sof and hard gae drive waveforms and provides recommended gae curren and volage levels. Noe ha gaerigger parameers are emperaure dependen, wih he required gae parameers increasing in magniude as emperaure decreases. hus, he selecion of drive levels should be made for he lowes operaing emperaure anicipaed for he equipmen. Hard gae drive is required for high repeiive di/d applicaions ypical of capaciive loads, heavy indusrial phase conrol operaion wih inducive load, and sysems where elecrical noise is roublesome requiring gae signal suppression circuiry. Gae Curren Gae Curren I is also necessary o increase he gae drive ampliude for pulse widh less han 2 microseconds. his is due o he need for he SC o receive a finie amoun of charge o urn-on. Addiional gae drive recommendaions and precauions are enumeraed here: A. GENEA CONSIDEAIONS Gae he SC when he anode volage is posiive. Allowing a posiive gae while he SC becomes reverse biased limis device reliabiliy. Design he gae firing sequence such ha he snubber nework across he SC is charged prior o gae riggering. his gives good di-namic gae acion. Figure 2.2.9 I GM I G.1 I GM r 2µs.9 I GM I G I G I G.1 I G r I GM Hard and Sof Gae Drive Waveforms A. HAD GAE DIVE dig d "Back Porch" I GM = 3 o 5 x I G dig > 1A/µs d.1µs < r 1µs Anode Curren Conducion ime ime (No o Scale) B. SOF GAE DIVE I GM 2µs o Anode Curren Conducion ime ime (No o Scale) I GM = 1.5 o 3 I G dig >.5A/µs d r ~1µs If a DC gae signal is used in a muli-phase sysem a sof gae drive signal does no give good di-namic gae acion. No snubber discharge is possible afer ime zero which resuls in poor di-namic gae acion. In addiion, POW--BOK modules have high noise immuniy characerisics, meaning hey do no false rigger a very low gae currens. For his paricular applicaion, hard gae drive is required. he gae drive circuiry should have a 1 o 2 Amp average. 1 Vol diode in series wih he gae and across he gae o cahode erminals as shown in Figure 2.3. hese will eliminae wo possible SC failure modes. he diode in series will preven negaive gae curren flow while he diode across he gae-o-cahode limis he reverse gae volage by clamping. Minimize average gae power dissipaion. Do no use excessive gae drive or excessively long gae pulses. emember ha SCs require more gae curren o rigger under narrow pulse widh and Figure 2.3 Gae Pulse Inpu gae Diode Proeced Gae Circui * May also employ a zener diode of appropriae raing o provide proecion agains excessive forward gae volage ransiens in addiion o he reverse volage proecion. * G A SC K
Powerex, Inc., 2 Hillis Sree, Youngwood, Pennsylvania 15697-18 (412) 925-7272 SC/GO/Diode POW--BOK Modules low juncion emperaure operaing condiions, refer o Figure 2.4. Boh excessive overdrive or weak underdrive can defea he operaion of he di-namic amplifying gae. Inducive loads can be roublesome if he gae drive is insufficien in ampliude or widh. ecommended pracice is he use of picke fence or hard gae drive. A picke fence is a high frequency gae signal varying from 1 o 15kHz, 2 o 5 microseconds wide, wihin a 6Hz envelope such ha he SC is coninuously gaed. he average gae curren raing is mainained wihin device raing. In hard gae drive circuis, he back porch anicipaes worse case power facor; making he gae pulse widh wide enough o insure SC laching and holding. Preven noise pickup in he gae signal connecions wising ogeher he gae and he cahode poenial leads o he SC and use eiher wised pair wire from he gae pulse amplifier or a coax ype shielded cable. ocae he gae wires as close as possible o he SC bu away from magneics and high curren carrying members of he power circuis. Of course, he gae signal leads should be as shor as possible. Minimize dela delay ime beween SCs using hard gae drive wih as high a gae curren rise ime, (di G /d), as possible. Figure 2.4 GAE IGGE CUEN, I GM, (ma) 14 12 1 8 6 4 2 Minimum Pulsed Gae rigger Parameers for a ypical SC SC MINIMUM GAE UN-ON CHAACEISICS POWEEX DI/NAMIC GAE DESIGNS I G @ 125 o C I G @ -4 o C SC I G = 15 ma, 25 o C @Vp = 12V I GM VS p, j V GM VS p, j V G @ 4 o C V G @ 25 o C V G @ 125 o C I G @ 25 o C 1 2 5 1 2 5 1 2 56 SQUAE WAVE PUSE WIDH,, (µsec) Always use a resisor in series wih each gae lead if riggering more han he SC from he same source. Generally, 1 o 25 ohms is used o diminish inpu gae cahode impedance variaions. Use single poin riggering if gaing more han one device from he same source. B. HIGH di/d OPEAION 7. 6. 5. 4. 3. 2. 1. Design for wors case di/d and include all capaciance and snubber discharge currens in deermining he SC di/d sress level. rea SC daa shee di/d raings like volage raings. Good engineering applicaion pracice dicaes a 2 o 1 safey facor for reliable operaion. Minimize gae drive rise ime. Minimize or eliminae shun capaciance and series inducance in he gae circui GAE IGGE VOAGE, V GM, (VOS) Figure 2.5 GAE CUEN, (I g ) GAE CUEN, (I g ) Normal Gae Curren and Gae Inversion Waveforms A. NOMA GAE CUEN IME, () B. GAE INVESION IME, () o preven gae curren inversion and resulan di/d sress. Be aware ha high di/d can require open circui gae source volage upward of 4 Vols o preven gae curren inversion and assure reliable operaion. Gae curren inversion or gae drive exincion occurs when high anode di/d causes he insananeous gae cahode volage o exceed he gae-o-source volage. efer o Figure 2.5. C. OW di/d OPEAION Use DC gae drive when possible o minimize urn-on delay ime. When using repeiive pulse/picke fence gae drive, maximize duy cycle o reduce xxv
Powerex, Inc., 2 Hillis Sree, Youngwood, Pennsylvania 15697-18 (412) 925-7272 SC/GO/Diode POW--BOK Modules urn-on delay ime and laching curren effecs. D. VEY OW ANODE VOAGE OPEAION Be aware ha he SC amplifying gae srucure may no funcion a very low anode volage. Observe urn-on behavior if anode volage is less han 1 Vols. Assure adequae rigger curren by driving wih peak gae curren in excess of five imes he I G specificaion of he SC. 2.2 Deermining Power osses Proper applicaion of SCs, GOs, and diodes requires ha users deermine device power losses and provide adequae cooling o keep juncion emperaures wihin raed values. For sandard phase conrol applicaions, his process is grealy simplified by using he daa shee curves of power dissipaion and maximum allowable case emperaure versus average curren. Use of hese curves and explanaions of he componens of device power dissipaion were explained in he aings and Characerisics secion. I is ofen required o calculae he roo mean square (MS) and/or average value of a waveform from peak currens, pulse widhs, phase angles, ec., in order o deermine device power losses. Figure 2.6 provides definiions and formulas for calculaing MS and average values of ypical power conrol waveforms. In some pracical applicaions, he power waveform is a shorulse a a low duy cycle or some oher irregular shape. In many of hese siuaions i is no adequae o deermine he average power dissipaion and average juncion emperaure. Proper applicaion requires ha he peak operaing juncion emperaure does no exceed he maximum allowable juncion emperaure. he procedure for deermining he peak juncion emperaure is o plo device power dissipaion versus ime by muliplying insananeous curren values by corresponding forward volage values obained from he device daa shee on-sae curren volage characerisic curve. he peak juncion emperaure is hen calculaed using he ransien hermal impedance curve. For irregular waveforms, his procedure is edious. For he purpose of calculaing peak juncion emperaure, he irregular power waveshape can be approximaed by a recangular waveshape having an idenical value of peak power and wih a pulse widh such ha he average power is also idenical. Figure 2.7 illusraes his square wave approximaion echnique. ranslaion ino recangular power pulses of power ensures a wors case approximaion since a recangular waveform will always have an equal or greaer effec on emperaure as an arbirary waveform of equal peak and average values. Afer deerminaion of he equivalen recangular power waveform, he ransien hermal impedance curve can be used along wih he equaions presened in Figure 2.8 o deermine he peak juncion emperaure. 2.3 Volage aings and Overvolage Suppression he volage raing of an SC, GO, or diode mus be seleced high enough o wihsand anicipaed volage ransiens as well as he repeiive peak forward and reverse volages imposed upon he device by he applicaion circui. I is common pracice wih SCs and diodes o provide a volage safey facor of wo imes he maximum high line condiion circui volage. able 2.1 provides device volage raing recommendaions for common circui volages. able 2.1 ecommended Device Volage aings ecommended Device Supply Volage Volage aing (V AC(MS) ) (V M, V DM ) 12 4 24 8 48 16 575 2 Unanicipaed volage ransiens which exceed he blocking volage raings are probably he mos frequen failure mode for SCs and diodes. Because volage breakdown ends o occur a he surface of he device, he energy required o cause damage can be xxvi
Powerex, Inc., 2 Hillis Sree, Youngwood, Pennsylvania 15697-18 (412) 925-7272 SC/GO/Diode POW--BOK Modules quie small. echniques o proec agains volage ransiens include: 1. edesign he circui operaion and/or physical layou o remove or minimize he source of he ransien. 2. Suppress he ransien by absorbing he energy in an appropriaely designed C snubber circui locaed across he device or across he source of he ransien. Design of a snubber for a specific device and applicaion involves rade offs beween many conflicing requiremens. Figure 2.9 illusraes an C snubber used wih an SC and provides general recommended snubber componen values. Care mus be aken in selecing he acual C snubber componen values o insure heir capabiliy o handle peak currens wihou overheaing or adding addiional ransiens o he circui. 3. Use nonlinear resisive elemens such as selenium ransien suppressors, zener diodes, or meal oxide varisors (MOVs) in shun wih he device being proeced. Mainain shor leads beween he ransien suppressor and he device. 4. Occasional severe ransiens can someimes be bes limied by a solid-sae crowbar circui which shors he line and absorbs he ransien energy unil a fuse or circui breaker can be opened. 2.4 ypical Applicaions POW--BOK modules are uilized in a wide variey of applicaions. he circui configuraions and criical parameers for a number of common phase conrol applicaions are given Figure 2.1. Figure 2.6 Definiions and Formulas for Calculaing MS and Average Values of ypical Power Conrol Waveforms f() a b MS Value = MS Value Form Facor = Average Value b b 1/2 1 1 [ f() 2 d] Average Value = f()d b a a b a a Half-Sine Waveform Square Waveform 2 (1) I AV = Ip (3) I MS = P 2 1.57 I (2) I MS = AV 2 [ p ] (4) I AV = (5) I MS = I AV (6) I MS = p Phase Conrol Half-Sine Waveform Phase Conrol Full-Wave Sine Waveform 2 (7) I AV = 2 [ 1 + COS ] (8) I MS = 2 1 + Sin 2 2 (9) I AV = (1) I MS = [ 1 + COS ] 2 1 + Sin 2 2 = riggering Angle 2 = Conducion Angle xxvii
+ + + Powerex, Inc., 2 Hillis Sree, Youngwood, Pennsylvania 15697-18 (412) 925-7272 SC/GO/Diode POW--BOK Modules Figure 2.7 Square Wave Approximaion of Irregular Power Waveforms (A) ACUA POWE INPU (B) EQUIVAEN POWE INPU P pk P pk Power Inpu (Was) P avg Power Inpu (Was) P P avg ime N = P avg P pk Figure 2.8 Basic oad Curren aing Equaions oad Condiion Waveform of Power oss a Juncion Waveform of Juncion emperaure ise ( = eference emp.) Soluion for Jucion emperaure θ = Seady-Sae hermal esisance θ(1 ) = ransien hermal Impedance a ime 1 θ(2 1 ) = ransien hermal Impedance a ime ( 2 1 ), ec. Coninuous oad P IME j IME j = P θ j P = θ Single oad Pulse P 1 1 2 1 2 1 = P Z θ(1 ) 2 = P [Z θ(2 ) Z θ( ) ] 2 1 P = 1 Z θ(1 ) Shor rain of oad Pulses (Equal Ampliude) P 1 2 3 4 5 1 3 5 1 2 3 4 5 1 = P Z θ(1 ) 3 = P [Z θ(3 ) Z θ( ) + Z θ( ) ] 3 1 3 2 5 = P [Z θ(5 ) Z θ( ) + Z θ( )], ec. 5 1 5 2 rain of Unequal Ampliude oad Pulses P P 2 P 4 1 2 3 4 5 3 5 1 1 2 3 4 5 1 = P Z θ(1 ) 3 = P Z θ(3 ) P Z θ( ) + P 2 Z θ( ) 3 1 3 2 5 = P Z θ(5 ) P Z θ( ) + P 2 Z θ( ) P 2 Z θ( ) + P 4 Z θ( ) 5 1 5 2 5 3 5 4 ong rain of Equal Ampliude oad Pulses (Approx. Soluion) Overload Following Coninuous Duy (Non-Pulsed) Overload Following Coninuous Duy (Pulsed) (Approx. Soluion) P P P CD P P CD P > P CD j IME θ j = P [ + (I ) Z θ( + p ) Z θ() + Z θ( ) ] p j P = θ p + (1 ) Z θ( + p ) Z θ() + Z θ( ) p O = P CD θ + (P O P CD )Z θ(o ) O P CD θ P O = Z θ(o ) + P CD { p P CD p P O } O = P CD θ + P [ ] Z θ( O ) + (1 )Z θ( + ) Z θ() + Z θ( ) O + P CD ( θ -Z θ(o ) ) P = Z p θ(o ) + (1 )Z θ( + ) Z θ() + Z θ( ) p p xxviii
Powerex, Inc., 2 Hillis Sree, Youngwood, Pennsylvania 15697-18 (412) 925-7272 SC/GO/Diode POW--BOK Modules Figure 2.9 C Snubber Circui and ecommended Snubber Componen Values ecommended Snubber Circui Values SC S C S Module Curren S C S aing (A) (Ω) (µf) 25-6 1.1 9-13 1.2 Figure 2.1 Noaion Circui Circui Configuraions and Criical Parameers for Common Phase Conrol Applicaions Schemaic Waveforms Peak everse Max. Volage SC Volage SC Diode Max. oad Volage Avg. E a = MS oad Volage wih Delayed Firing Max. Average SC Curren Avg. Amps. Con. Period Max. Average Diode Curren Avg. Amps. Con. Period 1-1-1-H ~ E a = 2 (1 + COS) 2 E a = ( - + 1/2Sin 2) 2 18 o 1-1-1-H Wih Free- Wheeling Diode ~ (1 + COS) 2 Very Ind. oad Convenional 2 18 o ( ).54 21 p o 2-1-1-C 2.8 2E P 2 (1 + COS) 18 o 2-1-1-C 2.8 2 2 (1 + COS) (I dc = K) 18 o 2-1-1-C Wih hyrisor in D C Circui 2.8 2 (1 + COS) 2 36 o for 2-1-1-C.5( ) 18 o <18 o Half Conrol 4-1-1-B and ~ 2 (1 + COS) 18 o for 4-1-1-B.26(2 ) 18 o <18 o Full Conrol 4-1-1-B ~ 2 (1 + COS) (I dc = K) 18 o xxix
Powerex, Inc., 2 Hillis Sree, Youngwood, Pennsylvania 15697-18 (412) 925-7272 SC/GO/Diode POW--BOK Modules Figure 2.1 Circui Configuraions and Criical Parameers for Common Phase Conrol Applicaions (Coninued) Circui Noaion Schemaic Waveforms Peak everse Max. Volage SC Volage SC Diode Max. oad Volage Avg. E a = MS oad Volage wih Delayed Firing Max. Average SC Curren Avg. Amps. Con. Period Max. Average Diode Curren Avg. Amps. Con. Period 4-1-1-B Wih E' hyrisor MS and. 2Ep (1 + COS) 2Ep 36 o p.5 18 o <18 o 3-1-1-Y I D 3 3 2 3 3 2 (COS) (I dc = K).33 I D 12 o 3-1-1-Y Wih Free- Wheeling Diode I D 3 3 2 3 3 2 (COS) (<<3 o ) 3 [1 + 2 COS( + 3 o )] (3 o <<15 o ).33 I D 12 o Size o.33 I D <12 o 6-1-1-B Wih Full Conrol I D 3 3 3 3 (COS).33I D 12 o 6-1-1-B Wih Full Conrol and I D 3 3 3 3 3 3 2 (COS) (<<6 o ) (1+ COS 3 2 2 Sin) (6 o <<12 o ).33 I D 12 o Size o.33 I D <12 o 6-1-1-B Half Conrol and 3 3 3 3E p (1 + COS).33 I D 12 o.33 I D Size o.33 I D 12 o <12 o I D AC Swich I MS E a = E a = 2 ( + 1/2Sin 2) 18 o xxx