Characteristics: Triac - nptel

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LOAD R 1 V 1 C 1 C D 1 R R 2 Fig. 4.16: Triac triggering circuit using a diac. In this circuit as Vi increases voltage across C 1 increases due to current flowing through load, R 1 , R 2 and C 1 . The voltage drop across diac D 1 increases until it reaches its break over point. As D 1 conducts a large current pulse is injected into the gate of the triac. By varying R 2 the firing can be controlled from zero to virtually 100%. Exercise 4.5 1) Fill in the blank(s) with the appropriate word(s) i. A Triac is a ________________ minority carrier device ii. iii. iv. A Triac behaves like two ________________ connected thyristors. The gate sensitivity of a triac is maximum when the gate is ________________ with respect to MT 1 while MT 2 is positive with respect to MT 1 or the gate is ________________ with respect to MT 1 while MT 2 is negative with respect to MT 1 A Triac operates either in the ________________ or the ________________ quadrant of the i-v characteristics. v. In the ________________ quadrant the triac is fired with ________________ gate current while in the ________________ quadrant the gate current should be ________________. vi. The maximum possible voltage and current rating of a Triac is considerably ________________ compared to thyristor due to ________________ of the two current carrying paths inside the structure of the triac. Version 2 EE IIT, Kharagpur 28
vii. viii. To avoid unwanted turn on of a triac due to large dv ________________ are used dt across triacs. For “clean turn ON” of a triac the ________________ of the gate current pulse should be as ________________ as possible. Answer: (i) bidirectional; (ii) anti parallel; (iii) positive, negative; (iv) first, third; (v) first, positive, third, negative (vi) lower, interaction; (vii) R-C shubbers; (viii) rise time, small. Version 2 EE IIT, Kharagpur 29
Page 1 and 2: Module 1 Power Semiconductor Device
Page 3 and 4: Instructional objects On completion
Page 5 and 6: A A p n - G K p n + n + (a) G (b) K
Page 7 and 8: Where I I +I is the total reverse l
Page 9 and 10: 4.4 Steady State Characteristics of
Page 11 and 12: V g V g max A E c d R g • S 2 P g
Page 13 and 14: Answer: (i) gate; (ii) break down,
Page 15 and 16: I av Amps 120 100 φ = 180° φ = 1
Page 17 and 18: Average Gate Power dissipation (P G
Page 19 and 20: Delay time (t d ): After switching
Page 21 and 22: The reverse recovery charge Q rr is
Page 23 and 24: 1 2 V 2 V V ( ∝) πω π i i H E
Page 25 and 26: G I G MT1 ( - ) I G N 2 I G I G N 3
Page 27: A 200 Bidirectional ON state curren
Page 31 and 32: Lesson Summary • Thyristor is a f
Page 33 and 34: 1. Explain the effect of increasing
Page 35 and 36: Answers to Practice Problems Versio
Page 37 and 38: Since V g = 10 - i g R is tangent t
Page 39: 5. As soon as THA is turned on the

Characteristics: Triac - nptel

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