Most Important MCq on Power Electronics | Electrical Engineering

Multiple Choice Questions (MCQ), Power Electronics

Question 1 A forward-biased PN junction acts as a/an

  1. Thyristor
  2. Closed switch
  3. Amplifier
  4. Chopper
Answer : Closed switch

Question 2 Leakage current flows through the thyristor in

  1. Forward conduction mode
  2. Reverse blocking mode
  3. Forward blocking mode
  4. 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

  1. 0.32.
  2. 0.67.
  3. 0.45.
  4. 0.27.
Answer : 0.27

Question 4 A single phase full bridge inverter can operated in load commutation mode in case load consist of

  1. RL.
  2.  RLC underdamped.
  3.  RLC overdamped.
  4.  RLC critically damped.
Answer : RLC underdamped.

Question 5 A freewheeling diode is phase-controlled rectifiers.

  1. Stops rectifier operations
  2. Improves line power factor
  3. Is the reason for additional harmonics
  4. 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

  1. 178.52
  2. 248.05
  3. 148.55
  4. 198.49
Answer : 148.55

Question 7 Which triggering is the most reliable?

  1. Forward voltage triggering.
  2. Gate triggering.
  3. dV / dt triggering.
  4. Thermal triggering.
Answer : Gate triggering.

Question 8 In a 3-∅ controlled bridge rectifier, the frequency of ripple in the output voltage depends on

  1. Power factor
  2. Supply frequency
  3. Voltage source
  4. Firing angle
Answer : Supply frequency

Question 9 Which semiconductor power device out of the following, is not a current triggering device?

  1. Thyristor
  2. Triac
  3. G.T.O
  4. MOSFET
Answer :MOSFET

Question 10 Which of the given device is the most suitable power device for a higher frequency (above 100 kHz) switching application

  1. SCR
  2. Power MOSFET
  3. GTO
  4. BJT
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?

  1. 3.18 V, 5V
  2. 3.68 V, 8V
  3. 4.18 V, 5V
  4. 4.68 V, 8V
Answer : 3.18 V, 5V

Question 12 A three phase full controlled converter can operate as a

  1. Converter for α = 0 to 1200
  2. Converter for α = 0 to 900
  3. Converter for α = 0 to 1800
  4. Converter for α = 0 to 600
Answer : Converter for α = 0 to 180 degree

Question 13 The advantages of SCS over SCR is

  1. Slow switching time and large VH
  2. Slow switching time and smaller VH
  3. Faster switching time and smaller VH
  4. Faster switching time and large VH
Answer : Faster switching time and smaller VH

Question 14 Leakage current flows through the thyristor in

  1. forward blocking mode.
  2.  reverse blocking mode.
  3.  both forward and reverse blocking mode.
  4.  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

  1. 10 μs
  2. 10 ms
  3. 30 ms
  4. 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

  1. 2160 Hz
  2. 720 Hz
  3. 360 Hz
  4. 60 Hz
Answer : 360 Hz

Question 17 In a three-phase bridge rectifier, the maximum conduction of each thyristor is

  1. 1200
  2. 900
  3. 300
  4. 600
Answer : 1200

Question 18 Which of the given regulator provide output voltage polarity reversal without the involvement of a transformer.

  1. Linear voltage regulator
  2. Shunt voltage regulator
  3. Buck-Boost regulator
  4. Series voltage regulator
Answer : Buck-Boost regulator

Question 19 A chopper converts

  1. AC to DC
  2. AC to AC
  3. DC to AC
  4. DC to DC
Answer : DC to DC

Question 20 PWM switching is used in voltage source inverters for the purpose of

  1. Controlling output current
  2. Controlling input voltage
  3. Controlling input power
  4. 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?

  1. First quadrant chopper
  2. Fourth quadrant chopper
  3. Third quadrant chopper
  4. Two quadrant chopper
Answer : Two quadrant chopper

Question 22 Power diode is

  1. Two terminal semiconductor device
  2. Three terminal semiconductor device
  3. Four terminal semiconductor device
  4. None of these
Answer : Two terminal semiconductor device

Question 23 The V-I characteristics of diode lie in the

  1. First quadrant
  2. Fourth quadrant
  3. The third and second quadrant
  4. 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

  1. 0
  2. 0.5
  3. 1
  4. 1.5
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?

  1. 4.308
  2. 3.208 A
  3. 7.808 A
  4. 9.276 A
Answer : 3.208 A