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Power Electronics
Comments
Question
In a thyristors are
i
=
kv
a
. The value of
a
is
Options
A. about 0.5
B. about 2
C. about 5
D. about 20
Correct Answer
about 5
Power Electronics problems
Search Results
1. In a 3 phase bridge inverter with 180° mode of operation the numbers of thyristors conducting at one time are
Options
A. 1
B. 2
C. 3
D. 4
Show Answer
Scratch Pad
Discuss
Correct Answer: 3
2. A single phase half wave rectifier circuit has a free wheeling diode. The free wheeling diode will conduct only if
Options
A. load is purely resistive
B. load is purely inductive
C. load is combination of R and L
D. load is purely inductive or combination of R and L
Show Answer
Scratch Pad
Discuss
Correct Answer: load is purely inductive or combination of R and L
3. A voltage V
BB
is applied across the terminals of a UJT. The emitter voltage at peak point is
Options
A. hV
BB
B. (h + 1) V
BB
C. hV
BB
+ V
D
D. V
D
Show Answer
Scratch Pad
Discuss
Correct Answer: hV
BB
+ V
D
4. In an ordinary thyristor
Options
A. turn on and turn off times are equal
B. turn on time is more than turn off time
C. turn off time is more than turn on time
D. turn on time may be equal, less than or more than turn off time
Show Answer
Scratch Pad
Discuss
Correct Answer: turn off time is more than turn on time
5. A 3 phase fully controlled bridge converter is fed by a 3 phase system having phase voltage
v
= V
m
sin ?
t
. The firing angle is
a
. The dc output voltage is
Options
A.
B.
C.
D.
Show Answer
Scratch Pad
Discuss
Correct Answer:
6. A single phase cycloconverter feeds a resistance heating load. The heating power is provided by
Options
A. only the fundamental component of output wave
B. only higher harmonics in the output wave
C. both fundamental and higher harmonics in the output wave
D. either (a) or (b)
Show Answer
Scratch Pad
Discuss
Correct Answer: both fundamental and higher harmonics in the output wave
7. A full bridge inverter is fed by a battery of 30 V. The rms value of output voltage is
Options
A. 15 V
B. 15
2
V
C. 30 V
D. 30
2
V
Show Answer
Scratch Pad
Discuss
Correct Answer: 30 V
8. Which of the following devices exhibit negative resistance characteristics?
Options
A. UJT
B. PUT
C. Both UJT and PUT
D. UJT, PUT and SBS
Show Answer
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Discuss
Correct Answer: Both UJT and PUT
9. Natural commutation can be used in :
Options
A. DC circuits only
B. AC circuits only
C. both AC and DC circuits
D. none of the above
Show Answer
Scratch Pad
Discuss
Correct Answer: AC circuits only
10. The gate lead, in a thyristor is welded to :
Options
A.
p
layer to which anode is connected
B.
n
layer nearest to the anode terminal
C.
p
layer nearest to the cathode terminal
D. outside
n
layer
Show Answer
Scratch Pad
Discuss
Correct Answer:
n
layer nearest to the anode terminal
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