# Home / ECE / Power Electronics :: Section 1

### ECE :: Power Electronics

1. A cycloconverter can be

2.  A. step down B. step up C. step down or step up D. none of the above   3. In the below figure the average load current is 15 A. The rms value of transformer secondary current is 4.  A. 15 A B. 10.61 A C. 7.5 A D. 14.14 A   5. In a 3 phase fully controlled converter the firing frequency is

6.  A. 3 times the line frequency B. 6 times the line frequency C. 9 times the line frequency D. 12 times the line frequency   7. Two thyristor of same rating and same specifications

8.  A. will have equal turn on and turn off periods B. will have equal turn on but unequal turn off periods C. may have equal or unequal turn on and turn off periods D. will have unequal turn on and turn off periods   9. The amount of dielectric heating is inversely proportional to frequency.

10.  A. True B. False   11. A semiconverter feeding an RLE load operates in   13. The phenomenon of overlap in converter operation due to

14.  A. source resistance B. source inductance C. both source resistance and source inductance D. high value of firing angle   15. A thyristor has a maximum allowable junction temperature of 120°C and the ambient temperature is 40°C. If thermal resistance is 1.6° C/W, the maximum allowable internal power dissipation is

16.  A. 20 W B. 50 W C. 92 W D. 128 W   17. For a 12 pulse operation, the two 6 pulse units are fed by

18.  A. Y - Y and Y - Y transformers B. Δ - Δ and Δ - Δ transformers C. Y - Y and Y - Δ transformers D. Y - Δ and Y - Δ transformers   19. In a single phase full wave converter (M - 2 connection) feeding a highly inductive load, the firing angle for each thyristor is a in the respective half cycle. The period of conduction of each thyristor is

20.  A. p - a B. p C. p + a D. p - 2a   