Question

(i) (ii) Draw the structural diagram of a Gate Turn-Off (GTO) thyristor. [7%] Explain the operation of GTO and clearly state the voltage and frequency range for its application [15%] State four advantages of GTOs when compared to conventional thyristors. (iii) [8%] (b) Consider the single-phase full bridge rectifier shown below where R=6 12, L = 6 mH, E = 60 V and the ac source voltage is 230 V, 50 Hz. * * 13 பண்பு 14* (i) For continuous conduction, find the average value of the output voltage (V.) and average load current (I.) for a firing angle delay 50°. [20 %] In the case that the third thyristor (T3) gets open circuited due to a fault, find the new values of the average output voltage (V.) and average load current (I.). Consider the output current to be continuous and that the firing angle delay is 50°. [30 %] Sketch well-labelled waveforms for the input voltage (vs) and the output voltage (v.) during the period 0 to 37 radians. Indicate the conduction of various thyristors. [20 %] (iii)

Answer 1

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a.)
① Structural Diagram of (GTO) thyrinter? GITO Gate Turn off thyrister. Gate Cathode a N ot ['N+ 7 Cathode Gate J2 →N 644 Anode o Anode Pront Highly doped N → Moderate doping Symbol Anode (+) Grate & cathed -

It is a three junction device. 10 J, Junction between prof anode and N. (1) Junction J, is anode Tinition. @ J2 (0) Tinction beteen pt of gate and N ② J₂ (6) Junetion between pt of gate and Nt of cathode. 3 (1) Junction Is in cathod Junction. (WIt has three terminals- 0 Anode ② Cathode ③ Gare. (*) gt in four loyer device. (1) Operation of GI TO:- GITO is a part of a thynter family Thysinter use as ideas switch, It has capability to blocking thousand woit in off state and good conducting thousand amp. current in an atate. GITO can be turned on by applying the gate rignal and GTO can be turn off by a ove gate signal - Two tran diter analogy - INGITO One NPN and one PNP tramidters are back to back comected Anode qe SE 1B PNP Gate. Go Turn on HNPN Turnoff VIER o cathode

Tum ON Mechamerm :- when we apply poditive gode pulse to gate terminal wirt cathode then GTO will on. - when anoce in comected to the terminal and cathode in cometed to negative terminal then an emilter cerment If start following through PNP transiter, and when we apply the gate pulse to the bene of NPN then NPN tanrister will on. and when PNP and NPN both tranciater will on, then G To will on. and start current following through between gate and cathode Turn off mechonim : when we apply negative pule to gale terminal writ cathodle then GTO will off when we opply -ve pulse into the base of NPN trominter then it will oppore or reduce the collects cement Tes which make NPN tramuter off, and OUR GTO will also off - GTO is fully controlloble device which can be turn on and turn off by gate signal. - GTO in 10 times farter then ser

V-1 charochematics I 'ONstake .. . ove gake pake (GTOOPP) - - -- - rue gake pule (GITO ON) VBR T VBF forward blockory' state Revene blocking i state - Va Voltage saty up to 5 kn frequency sengers uptotes 200-5ooth (iii) four ad Advantage of GTO compored to conventioned thynnten (a) It in 10 timer farter then ser pa . ton = anoree ch) gt in completely confrollable. On compared to other thynister ce) turn off time in very len as compared to other thynunter ed! It's operating frequeey in very high on compared to other therinter (e) G To has high voltage blocking capability and high over consent capability.

b)

i.)
for Aug) Vineta Vm Sinut Rma. Vield At T2 ) }R: 62 0801, Soth 1 AT Vroue Lu 6mH AT I GOV=E firing angle delay = x (1) Continous conduction for 2:50 ta Varage #Van Sumut det | Um sinut det wt Vila /27 ---- AT' - Smoldkust - + - TAX --- -> wt +- TIT2 1 Thawt w 1 = m ( - Cassett Von -CoreT46)- Cost] hot an :m & Cosa - Cos (Ttar] = m (Cesa- (- Costi] [Ces (tr) = + Coax) - Vm & Cos da Cose] I Vo (Arg) : 2vm Cord Vrms: 230V Vm=230x12 TVm = 325.26 volt

Volav) = 0Vm Cosa Vm2 325.26rolt x= 50 Cood - Cosso - 0.6428 Vocavg): 2x325.20 x 0.6422 vo (Ang) = 133.08 volt! Apply are: -VoCAU) + To Caug. R+VL (Arg) + E=0 NolAra)= To Avg. R+ Vil Aug) + E. V. (Arg)=0 V (Arg)= L . d I So Ang voltage acesta acroda inducter in alway zero Vo(Aug) = To caus). RTE (133.88) = TO CAVg). 6 + 60 6 to Aug) = 133.08-60 6 IA) = 73.08 ToCAUS)4308 So coy) = 12.18 Amp 6