Cochin University of Science and Techology (CUST) 2007 B.Tech Electronics and Communications Engineering Industrial and Power Electronics - Question Paper

Industrial and Power Electronics (November 2007)

1a. Draw and discuss the V-I characteristics of an SCR. Also describe Latching current and Holding current
b. elaborate the different methods to turn on an SCR. Also discuss the turn off characteristics of an SCR
2a. Draw the V_I characteristics of a TRIAC and discuss its working in every of the 4 modes using improper structures
b. discuss different voltage ratings of Thyristors
3a. Draw the circuit, waveforms and discuss operation of a single phase full converter with RL with voltage source as load
b. discuss the function of a free-wheeling diode, showing how it is connected in a circuit
4a. Draw the circuit of a three phase full wave rectifier with R load and discuss its working with suitable waveforms
b. The speed of a seperately excited d.c. motor is to be controlled in either direction. explain a suitable thyristor control scheme
5a. discuss with circuit diagrams and waveforms auxiliary commutation scheme for SCRs
b. discuss the working of a single phase parallel inverter. Bring out its salient features and limitations
6a. With circuit diagram, define the working of Jone's Chopper
b. Briefly discuss the concept of slip-power recovery scheme in the speed control of induction motors
7a. discuss the working of a buck-boost converter
b. A boost regulator has an input voltage of Vin=15V. The avg. output voltage is Vav=25V and avg. load current Iav=0.5A. If L=150 microH and C=200 microF Detemine i) duty cycle ii) ripple current in inductor iii) ripple voltage in capacitor. presume switching frequency as 25 KHz.
8a. discuss online and offline UPS with the help of block diagrams
b. discuss dv/dt and di/dt protection in thyristors
9a. provide the principle and characteristics of induction heating
b. discuss with diagrams the different kinds of resistance welding
10a.Explainthe principle and theory of dielectric heating
b. In non-destructive testing, explain the use of ultrasonics

Earning:   Approval pending.