1) Silicon controlled rectifier can be turned on
a. By applying a gate pulse and turned off only when current becomes zero
b. And turned off by applying gate pulse
c. By applying a gate pulse and turned off by removing the gate pulse
d. By making current non zero and turned off by making current zero
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Answer
Explanation
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ANSWER: By applying a gate pulse and turned off only when current becomes zero
Explanation:
No explanation is available for this question!
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2) TRIAC is a semiconductor power electronic device which contains
a. Two SCR’s connected in reverse parallel
b. Two SCR’s connected in parallel
c. Two SCR’s connected in series
d. Two BJT’s connected in series
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3) An SCR can be used
a. as static conductor
b. for power control
c. for speed control of dc shunt motor
d. all of these
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4) A crowbar is a circuit which is used to protect a
a. voltage sensitive load from excessive dc power supply output voltages
b. current sensitive load from excessive dc power supply output voltages
c. voltage sensitive load from excessive ac power supply output voltages
d. current sensitive load from excessive ac power supply output voltages
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Answer
Explanation
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ANSWER: voltage sensitive load from excessive dc power supply output voltages
Explanation:
No explanation is available for this question!
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5) A full wave rectifier with resistive load produces
a. Second harmonic
b. Third harmonic
c. Fifth harmonic
d. Do not produce harmonics
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6) The input current waveform of a bridge controlled rectifier when the load is perfectly filtered is
a. Sine wave
b. Square wave
c. Saw - tooth wave
d. Trapezoidal wave
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7) The advantage of using free - wheeling diode in half controlled bridge converter is that
a. There is always a path for the dc current independent of the ac line
b. There is always a path for the ac current independent of the ac line
c. There is always a path for the dc current dependent of the ac line
d. There is always a path for the ac current independent of the ac line
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Answer
Explanation
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ANSWER: There is always a path for the dc current independent of the ac line
Explanation:
No explanation is available for this question!
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8) Harmonics in 3 phase inverters can be reduced by using
a. Passive filter
b. Active filter
c. Both passive and active filters
d. None of these
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9) The most suited gate pulses given to the AC regulator with R - L load can be in the form of
a. Continuous signal
b. Large isolating pulse transformer
c. A train of pulses
d. None of these
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10) With increase in firing angle,
a. Both harmonic distortion and quality of input current increases
b. Harmonic distortion increases and quality of input current decreases
c. Harmonic distortion decreases and quality of input current increases
d. Both harmonic distortion and quality of input current decreases
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Answer
Explanation
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ANSWER: Harmonic distortion increases and quality of input current decreases
Explanation:
No explanation is available for this question!
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11) The power MOSFET device is a
a. Current controlled unipolar device
b. Voltage controlled unipolar device
c. Current controlled bipolar device
d. Voltage controlled bipolar device
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12) The conduction losses in IGBT is
a. More than that of MOSFET
b. Lower than that of MOSFET
c. Equal to that of MOSFET
d. Equal to that of BJT
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13) For a buck converter to reduce the conduction losses in diode
a. A high on - resistance switch can be added in parallel
b. A low on - resistance switch can be added in parallel
c. A high on - resistance switch can be added in series
d. A low on - resistance switch can be added in series
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Answer
Explanation
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ANSWER: A low on - resistance switch can be added in parallel
Explanation:
No explanation is available for this question!
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14) For bidirectional operation of converters
a. A parallel combination of controllable switch and a diode is used
b. A parallel combination of controllable switch and capacitor is used
c. A series combination of controllable switch and a diode is used
d. A series combination of controllable switch and a capacitor is used
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Answer
Explanation
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ANSWER: A parallel combination of controllable switch and a diode is used
Explanation:
No explanation is available for this question!
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15) Single phase VSI are mainly used in
a. Power supplies
b. Ups
c. Multilevel configuration
d. All of these
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16) Very large values of modulation index (greater than 3.24) lead to
a. Square AC output voltage
b. Sine AC output voltage
c. Triangular AC output voltage
d. Trapezoidal AC output voltage
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17) In single phase VSI, the harmonic which is not present is
a. 2nd
b. 3rd
c. 5th
d. 7th
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18) Double fourier series analysis of PWM is
a. Two dimensional functions
b. Three dimensional functions
c. One dimensional functions
d. All of these
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19) In bipolar modulation, the carrier is symmetric about zero with amplitude equal to Cm, the PWM output
a. Zero
b. Switches between - 1 / 2 and + 1 / 2
c. Switches between - 1 and + 1
d. Switches between 0 and + 1
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20) Unipolar modulation is generally used in
a. AC - AC converters
b. AC - DC converters
c. DC - AC converters
d. DC - DC converters
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21) The square wave operation of 3 phase VSI lines contains the harmonics. The amplitudes are
a. Directly proportional to their harmonic order
b. Inversely proportional to their harmonic order
c. Not related to their harmonic order
d. None of these
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Answer
Explanation
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ANSWER: Inversely proportional to their harmonic order
Explanation:
No explanation is available for this question!
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22) Under harmonic free load voltages, the 3 phase VSI
a. Does not contains second harmonic
b. Does not contains third harmonic
c. Does not contains fifth harmonic
d. Does not contains seventh harmonic
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23) For similar carrier and modulating signals, the line current used in CSI is
a. Identical to line voltage in a VSI
b. Identical to line current in VSI
c. Identical to phase voltage in VSI
d. Identical to phase voltage in CSI
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24) In a 3 phase CSI, if the required line output voltages are balanced and 120 degree out of phase, then the chopping angles are used to eliminate only the harmonics at frequencies
a. 5
b. 7
c. 11
d. All of these
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25) In a three phase converter, the number of notches per cycle is
a. One
b. Three
c. Six
d. Nine
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26) During the commutation period in 3 phase converter, overlap time is
a. Dependent on the load current
b. Dependent on the voltage
c. Dependent on both the load current and load voltage behind the short circuit current
d. Independent on both the load current and load voltage
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Answer
Explanation
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ANSWER: Dependent on both the load current and load voltage behind the short circuit current
Explanation:
No explanation is available for this question!
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27) Between the incoming and outgoing devices in voltage commutation
a. Large overlapping takes place
b. Small overlapping operation
c. No overlapping operation
d. None of these
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28) The effects of EMI can be reduced by
a. Suppressing emissions
b. Reducing the efficiency of the coupling path
c. Reducing the susceptibility of the receptor
d. All of these
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29) In radiative coupling, the emitter radiation field
a. Decays as 1 / R, where R is the separation distance between the emitter and the receptor
b. Decays as R, where R is the separation distance between the emitter and the receptor
c. Decays as 1 / 2 R, where R is the separation distance between the emitter and the receptor
d. Decays as 2R, where R is the separation distance between the emitter and the receptor
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Answer
Explanation
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ANSWER: Decays as 1 / R, where R is the separation distance between the emitter and the receptor
Explanation:
No explanation is available for this question!
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30) In EMC signal, the source delivers maximum power to the input of transmission line when the transmission line input impedance
a. Is equal to the source resistance
b. Greater than the source resistance
c. Smaller than the source resistance
d. None of these
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31) For swept frequency measurements, the input impedance of the mismatched transmission line would vary with frequency as the electrical length of the transmission line would
a. Decrease with frequency
b. Remains same with change in frequency
c. Increase with frequency
d. Either (a) or (b)
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32) Voltage commutation circuit can be converted into a current commutation by interchanging the positions of
a. Diode and capacitor
b. Capacitor and SCR
c. Inductor and capacitor
d. Capacitor and load
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33) In a load commutated DC - DC chopper, the capacitor has a
a. Symmetric triangular voltage across itself
b. Symmetric rectangular voltage across itself
c. Symmetric trapezoidal voltage across itself
d. Symmetric sinusoidal voltage across itself
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34) In current commutated DC-DC choppers, the voltage spike appears across the load when
a. Voltage across the commutating inductances collapses
b. The capacitance voltage adds to the supply voltage
c. Both (a) and (b)
d. None of these
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35) LISN is a device used to measure conducted emissions. LISN stands for
a. Line integrated stabilization network
b. Line impedance stabilization network
c. Line integrated stored network
d. Laser integrated stabilization networking
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36) The output power of the cascaded amplifier / attenuator system can be determined using
a. Actual gain of amplifier
b. Actual gain of amplifier and attenuator
c. Gain in dB of amplifier and attenuator
d. Actual gain of attenuator
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37) An SCR is made up of silicon because
a. silicon has large leakage current than germanium
b. silicon has small leakage current than germanium
c. silicon has small leakage voltage than germanium
d. silicon has large leakage voltage than germanium
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Answer
Explanation
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ANSWER: silicon has small leakage current than germanium
Explanation:
No explanation is available for this question!
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38) AC power in a load can be controlled by using
a. two SCR’s in parallel opposition
b. two SCR’s in series
c. three SCR’s in series
d. four SCR’s in series
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39) The switching function of semiconductor devices can be characterized with
a. Duty ratio only
b. Frequency only
c. Duty ratio and frequency
d. Duty ratio, frequency and time delay
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40) The quadrant operation of BJT is represented by
a. 1
b. 2
c. 3
d. 4
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