Power Electronics Trivia Questions And Answers
Characteristics of Power Electronic devices, phase control, bridge converters, choppers and inverters, basic concepts of adjustable speed drives.
- 1.Triacs cannot be used in a.c voltage regulator for a
- A.
Resistive load
- B.
Back e.m.f load
- C.
Inductive load
- D.
Resistive inductive load
- 2.In a step-down cyclo converter commutation required is
- A.
Natural
- B.
Forced
- C.
Depends on power
- D.
None of these
- 3.Cyclo converter can be considered as a.c-a.c converter with conversion of
- A.
1 stage
- B.
2 stage
- C.
3 stage
- D.
None of these
- 4.Inverters are used in
- A.
Induction heating
- B.
UPS
- C.
None of these
- D.
Both
- 5.Commutation overlap in the phase controlled ac to dc converter is due to
- A.
Load inductance
- B.
Harmonic content of load current
- C.
Switching operator in the converter
- D.
Source inductance
- 6.Which of the following devices should be used as a switch in a low power switched mode power supply(SMPS)
- A.
GTO
- B.
MOSFET
- C.
TRIAC
- D.
THYRISTOR
- 7.A converter which can operate in both 3-phase and 6-pulse modes is a
- A.
1-phase full converter
- B.
3-phase half wave converter
- C.
3-phase semi converter
- D.
3-phase full converter
- 8.In d.c choppers per unit ripple is maximum when duty cycle alpha is
- A.
0.1
- B.
0.3
- C.
0.5
- D.
0.7
- 9.The most suitable device for high frequency inversion in SMPS is
- A.
BJT
- B.
IGBT
- C.
MOSFET
- D.
GTO
- 10.Which of the following doesnot cause permanent damage of an SCR
- A.
High current
- B.
High rate of rise of current
- C.
High temperature rise
- D.
High rate of raise of voltage
- 11.A 4-quadrant chopper cannot be operated as
- A.
1-quadrant chopper
- B.
Cyclo converter
- C.
Inverter
- D.
Bi-directional rectifier
- 12.Power diodes has characteristics of
- A.
High power,high speed
- B.
Low power,low speed
- C.
Low power,high speed
- D.
High power,low speed
- 13.IGBT is use for applications in
- A.
Low power
- B.
Medium power
- C.
High power
- D.
None of these
- 14.Turn-on and Turn-off times of transistor depend on
- A.
Static characteristics
- B.
Junction capacitance
- C.
Current gain
- D.
None of these
- 15.Which one of the following is used as the main switching element in a switched mode power supply operating in 20khz to 100khz range?
- A.
Thyristor
- B.
MOSFET
- C.
TRIAC
- D.
UJT
- 16.When an UJT is used for triggering an SCR, the waveshape of the voltage obtained from UJT circuit is a
- A.
Sine wave
- B.
Saw-tooth wave
- C.
Trapezoidal wave
- D.
Square wave
- 17.In a 3-phase semi-converter, for firing angle less than or equal to 60degrees, free wheeling diode conducts for
- A.
30 degrees
- B.
60 degrees
- C.
90 degrees
- D.
0 degrees
- 18.In a 1-phase full converter, if load current is I and ripple free, than average thyristor current is
- A.
1/2*I
- B.
1/3*I
- C.
1/4*I
- D.
I
- 19.Power electronic device with poor turn-off gain is
- A.
A symmetrical thyristor
- B.
A conventioanal thyristor
- C.
Power bipolar junction transistor
- D.
Gate turn-off thyristor
- 20.Modern ac-dc converters employ self commutated devices like GTOs of IGBTs instead of thyristors inorder to achieve
- A.
Low reactive power loading on the source
- B.
Better efficiency in conversion
- C.
Low switching frequency operation of devices
- D.
Cost reduction in converter realization
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