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Home » Most Important MCq on Power Electronics | Electrical Engineering
Question 1 A forward-biased PN junction acts as a/an
- Closed switch
Answer : Closed switch
Question 2 Leakage current flows through the thyristor in
- Forward conduction mode
- Reverse blocking mode
- Forward blocking mode
- Both forward and reverse blocking mode
Answer : Both forward and reverse blocking mode
Question 3 A step up chopper has input voltage 110 V and output voltage 150 V. The value of duty cycle is
Answer : 0.27
Question 4 A single phase full bridge inverter can operated in load commutation mode in case load consist of
- RLC underdamped.
- RLC overdamped.
- RLC critically damped.
Answer : RLC underdamped.
Question 5 A freewheeling diode is phase-controlled rectifiers.
- Stops rectifier operations
- Improves line power factor
- Is the reason for additional harmonics
- Is the reason for the sudden breakdown
Answer : Improves line power factor
Question 6 Find the average output of a semi-converter connected to a 220 V, 50 Hz power supply, and firing angle is 𝝅/𝟑
Answer : 148.55
Question 7 Which triggering is the most reliable?
- Forward voltage triggering.
- Gate triggering.
- dV / dt triggering.
- Thermal triggering.
Answer : Gate triggering.
Question 8 In a 3-∅ controlled bridge rectifier, the frequency of ripple in the output voltage depends on
- Power factor
- Supply frequency
- Voltage source
- Firing angle
Answer : Supply frequency
Question 9 Which semiconductor power device out of the following, is not a current triggering device?
Question 10 Which of the given device is the most suitable power device for a higher frequency (above 100 kHz) switching application
- Power MOSFET
Answer : Power MOSFET
Question 11 A half-wave rectifier circuit using an ideal diode has an input voltage of 10 sin ?t V; find the average and RMS value of output voltage?
- 3.18 V, 5V
- 3.68 V, 8V
- 4.18 V, 5V
- 4.68 V, 8V
Answer : 3.18 V, 5V
Question 12 A three phase full controlled converter can operate as a
- Converter for α = 0 to 1200
- Converter for α = 0 to 900
- Converter for α = 0 to 1800
- Converter for α = 0 to 600
Answer : Converter for α = 0 to 180 degree
Question 13 The advantages of SCS over SCR is
- Slow switching time and large VH
- Slow switching time and smaller VH
- Faster switching time and smaller VH
- Faster switching time and large VH
Answer : Faster switching time and smaller VH
Question 14 Leakage current flows through the thyristor in
- forward blocking mode.
- reverse blocking mode.
- both forward and reverse blocking mode.
- forward conduction mode.
Answer : both forward and reverse blocking mode.
Question 15 The minimum duration of the pulse in a pulse triggering system for thyristors should be at
- 10 μs
- 10 ms
- 30 ms
- 1 sec
Answer : 10 μs
Question 16 The triple frequency of a six-phase half wave rectifier for 220 V, 60 Hz input will be
- 2160 Hz
- 720 Hz
- 360 Hz
- 60 Hz
Answer : 360 Hz
Question 17 In a three-phase bridge rectifier, the maximum conduction of each thyristor is
Answer : 1200
Question 18 Which of the given regulator provide output voltage polarity reversal without the involvement of a transformer.
- Linear voltage regulator
- Shunt voltage regulator
- Buck-Boost regulator
- Series voltage regulator
Answer : Buck-Boost regulator
Question 19 A chopper converts
- AC to DC
- AC to AC
- DC to AC
- DC to DC
Answer : DC to DC
Question 20 PWM switching is used in voltage source inverters for the purpose of
- Controlling output current
- Controlling input voltage
- Controlling input power
- Controlling output harmonics and output voltage
Answer : Controlling output harmonics and output voltage
Question 21 Which of the given configurations is used for both regenerative and motoring breaking?
- First quadrant chopper
- Fourth quadrant chopper
- Third quadrant chopper
- Two quadrant chopper
Answer : Two quadrant chopper
Question 22 Power diode is
- Two terminal semiconductor device
- Three terminal semiconductor device
- Four terminal semiconductor device
- None of these
Answer : Two terminal semiconductor device
Question 23 The V-I characteristics of diode lie in the
- First quadrant
- Fourth quadrant
- The third and second quadrant
- The first and third quadrant
Answer : The first and third quadrant
Question 24 If a firing angle α of a single phase fully controlled rectifier feeding a constant DC current into the load is 600, Find the displacement factor of the rectifier
Answer : 0.5
Question 25 For a specific transistor, if the value of beta is equal to 400 and the Base current is 8mA, Find the value of Emitter current?
- 3.208 A
- 7.808 A
- 9.276 A
Answer : 3.208 A