Electronics and Communication Engineering  Power Electronics
Exercise :: Power Electronics  Section 4
36. 
A single phase half wave converter is feeding a resistive load. Output dc power is P_{dc} and total power delivered to load is P_{ac} then 
A. 
P_{dc} = P_{ac} for all values of firing angles  B. 
P_{dc} = P_{ac} if firing angle is less than 180°  C. 
P_{dc} < P_{ac} for all values of firing angles  D. 
P_{dc} < P_{ac} if firing angle is less than 180° 
Answer: Option D
Explanation:

37. 
Which of the following devices exhibit negative resistance characteristics? 
A. 
UJT  B. 
PUT  C. 
Both UJT and PUT  D. 
UJT, PUT and SBS 
Answer: Option C
Explanation:

38. 
In integral cycle control of ac regulators, the period of integral cycle control, i.e., (m + n) T should be 
A. 
less than mechanical or thermal time constant of the system  B. 
more than the mechanical or thermal time constant of the system  C. 
more or less than the mechanical or thermal time constant  D. 
very high 
Answer: Option A
Explanation:

39. 
All other parameters remaining the same, a 3 phase bridge inverter with 180° mode of operation 
A. 
has the same peak thyristor current as in 120° mode of operation  B. 
has higher peak thyristor current than in 120° mode of operation  C. 
has lower peak thyristor current than in 120° mode of operation  D. 
any of the above 
Answer: Option B
Explanation:

40. 
As compared to BJT, MOSFET has 
A. 
lower switching losses and higher conduction losses  B. 
higher switching losses and higher conduction losses  C. 
higher switching losses and lower conduction losses  D. 
lower switching losses and lower conduction losses 
Answer: Option A
Explanation:
