Taking too long? Close loading screen.
    • Search for:

    1.Which king was first addressed as ‘Your Majesty’?

    1. Akbar
    2. Louis
    3. Victoria
    4. Henry VIII (Answer)

     

    2.Who is the founder of Greek historiography?

    1. Aristotle
    2. Herodotus (Answer)
    3. Thucydides
    4. Hippocrates

     

    3.Who became the first ever non Muslim woman elected to Pakistan’s senate?

    1. Krishna kumari (Answer)
    2. Sonakshi kumari
    3. Payal kumari
    4. Soni kumari

     

    4.Which monarch called himself as the Second Alexander?

    1. Akbar
    2. Ashoka
    3. Samudragupta
    4. Ala-ud-din Khilji (Answer)

     

    5.What is the national currency of Hong Kong?

    1. Taiwan dollar
    2. Yen
    3. Hong Kong dollar (Answer)
    4. Yuan

     

    .6When was the first petrol Car developed?

    1. 1885-1886 (Answer)
    2. 1887-1888
    3. 1888-1889
    4. 1889-1890

     

    7.Where is Headquarter of World Economic Forum is in————-?

    1. London
    2. Paris
    3. Cologny (Answer)
    4. Geneva

     

    8.What is the capital of Norway?

    1. Vienna
    2. Copenhegan
    3. Oslo (Answer)
    4. Berlin

     

    9.Dr Abdus Slam was born in which city of Pakistan?

    1. Lahore
    2. Multan
    3. Jhang (Answer)
    4. Khushab

     

    10.Members of Association Of Southeast Asian Nations (ASEAN) are————?

    1. 08
    2. 09
    3. 10 (Answer)
    4. 11

     

     

    11.Capital of Armenia is————-?

    1. Kampala
    2. Tbilisi
    3. Yerevan (Answer)
    4. Amman

     

    12.In a push – pull converter, the filter capacitor can be obtained as————?

    1. Cmin = V / ( Vr L f2 )
    2. Cmin= ( 1 – D ) V / ( Vr L f2 )
    3. Cmin= ( 1 – 2 D ) V / 32 ( Vr L f2 ) (Answer)
    4. Cmin= ( 1 – 2 D ) V / 42 ( Vr L f2 )

     

    13.MOSFET stands for————–?

    1. Metal – oxide semiconductor field effect transistor (Answer)
    2. Molybdenum – oxide semiconductor field effect transistor
    3. Metal – oxide silicon field effect transistor
    4. Metal – oxide semiconductor field effect transmitter

     

    14.In a flyback converter, the inductor of the buck-boost converter has been replaced by a————-?

    1. Flyback capacitor
    2. Flyback resistor
    3. Flyback transformer (Answer)
    4. Flyback transistor

     

    15.Advantages of Cuk converter is / are————-?

    1. Large number of reactive component
    2. Low stress on switch
    3. Low stress on capacitor
    4. None of these (Answer)

     

    16.A MOSFET, for its conduction uses————-?

    1. Only minority carriers
    2. Only majority carriers (Answer)
    3. Both minority and majority carriers
    4. None of these

     

    17.An RC snubber network used in BJT———-?

    1. Divert the collector current during turn – off
    2. Improves the reverse bias safe operating area
    3. Dissipates a fair amount of switching power
    4. All of these (Answer)

     

    18.The ac output voltage waveform of VSI and AC output current waveform of CSI respectively is

    composed of———–?

    1. High dv / dt, low di / dt
    2. Low dv / dt, low di / dt
    3. Low dv / dt, high di / dt
    4. High dv / dt, high di / dt (Answer)

     

    19.If energy is taken from the AC side of the inverter and sends it back into the DC side, then it is known

    as———–?

    1. Motoring mode operation
    2. Braking mode operation
    3. Regenerative mode operation (Answer)
    4. None of these

     

    20.A combination of synchronized leading edge and trailing edge modulation has also been used to

    control a————?

    1. Boost single – phase power factor converter
    2. A buck dc – dc converter to reduce ripple in the intermediate dc bus capacitor

     

     

    1. Both A. and B. (Answer)
    2. None f these

     

    21.Regulator sampling PWM is usually used in———–?

    1. High power inverters
    2. Rectifiers
    3. Low power inverters
    4. Only A. and B. (Answer)

     

    1. a 3 phase VSI SPWM to use a single carrier signal and preserve the features of PWM technique, the

    normalized carrier frequency should be————?

    1. Multiple of two
    2. Odd multiple of three (Answer)
    3. Odd multiple of five
    4. Odd multiple of seven

     

    23.In square wave operation mode of 3 phase VSI, the VSI

    1. Can control the load voltage
    2. Cannot control the load voltage
    3. Cannot control the load voltage except by means of dc link voltage (Answer)
    4. Cannot control the load voltage except by means of dc link current

     

    24.For commutation in three phase PAC, normally balanced three phase voltages VR, VY and VB are

    connected to the three legs of the converter via————–?

    1. Three inductances (Answer)
    2. Three capacitances
    3. Three resistance
    4. Three transistors

     

    25.If all the SCR’s of 3 phase PAC is replaced by diodes, they would be triggered————-?

    1. 120 degree after the zero crossing of the corresponding line voltages

     

     

    1. 60 degree after the zero crossing of the corresponding line voltages (Answer)
    2. 120 degree before the zero crossing of the corresponding line voltages
    3. 60 degree before the zero crossing of the corresponding line voltages

     

    26.The ability of an electronic system to function properly in its intended electromagnetic environment

    and should not be a source of pollution to that electromagnetic environment is known as————?

    1. Susceptibility
    2. Emission
    3. Interference
    4. Electromagnetic compatibility (Answer)

     

    27.The opposite of susceptibility is———–?

    1. Immunity (Answer)
    2. Emission
    3. Interference
    4. Electromagnetic compatibility

     

    28.The output current in PWM DC – DC converters is equal to———–?

    1. Average value of the output inductor current
    2. Product of an average inductor current and a function of duty ratio
    3. Either A. or B. (Answer)
    4. None of these

     

    29.A step – down choppers can be used in———–?

    1. Electric traction
    2. Electric vehicles
    3. Machine tools
    4. All of these (Answer)

     

    30.In a lossless inverter, the average power absorbed in one period by the load must be———-?

     

     

    1. Equal to the average power supplied by the dc source (Answer)
    2. Greater than the average power supplied by the dc source
    3. Lesser than the average power supplied by the dc source
    4. Equal to the average power supplied by the ac source

     

    31.The ac voltage controller can be used for ———–?

    1. Lighting and heating control
    2. On – line transformer tap changing
    3. Soft starting
    4. All of these (Answer)

     

    32.In a full bridge VSI, in order to avoid the short circuit across the DC bus and the undefined AC output

    voltage condition, the modulating technique should ensure that———–?

    1. Top switch of each leg is on at any instant
    2. Bottom switch of each leg is on at any instant
    3. Either A. or B. (Answer)
    4. None of these

     

    33.The phase angle of gate signal in TRIAC can be shifted by using————-?

    1. A capacitor
    2. A variable resistor
    3. An inductor
    4. Only (a) and (b) (Answer)

     

    34.In the SPWM, the modulating signal is———–?

    1. Square
    2. Sinusoidal (Answer)
    3. Triangular
    4. Saw – tooth

     

     

    35.A TRIAC can be turned on with————–?

    1. Positive voltage at the gate terminal
    2. Negative voltage at the gate terminal
    3. Either (a) or (b) (Answer)
    4. None of these

     

    36.The transfer function of PWM is generally developed in————–?

    1. Time domain
    2. Frequency domain
    3. Either A. or B. (Answer)
    4. None of these

     

    37.DIAC and TRIAC both are semiconductors devices and conduct in——————–?

    1. DIAC conducts in forward direction and TRIAC conducts in reverse direction
    2. Both conducts in forward direction
    3. Both conducts in reverse direction
    4. Both conducts in either direction (Answer)

     

    38.The Graetz bridge makes excellent use of ————–?

    1. Current transformer
    2. Potential transformer
    3. Power transformer (Answer)
    4. SCR

     

    39.In constant frequency PWM, at perturbation the amplitude of the sinusoidal component is a———–?

    1. Linear function
    2. Non linear function
    3. Constant function
    4. None of these (Answer)

     

     

    40.If the firing angle becomes negative, then the rectifier begins to work as—————?

    1. A rectifier
    2. An inverter (Answer)
    3. A chopper
    4. A regulator

     

    41.In variable frequency, PWM gain

    1. Phase lead helps to increase the phase margin of the control loop (Answer)
    2. Phase lag helps to increase the phase margin of the control loop
    3. Phase lead helps to decrease the phase margin of the control loop
    4. Phase lag helps to decrease the phase margin of the control loop

     

    42.In a 3 phase half wave rectifier, when firing angle is less than 90 degree, then the average dc output

    voltage becomes——————?

    1. Positive (Answer)
    2. Negative
    3. Zero
    4. None of these

     

    43.Transformer utilization factor is a measure of the merit of a rectifier circuit. It is the ratio of————-

    –?

    1. AC input power to the transformer volt – amp rating required by secondary
    2. AC input power to the transformer volt – amp rating required by primary
    3. DC output power to the transformer volt – amp rating required by secondary (Answer)
    4. DC output power to the transformer volt – amp rating required by primary

     

    44.A carrier based PWM technique in CSI is composed of————?

    1. A switching pulse generator and a shorting pulse generator
    2. A shorting pulse distributor
    3. A switching and shorting pulse combination
    4. All of these (Answer)

     

     

    45.In a square – wave operation of 3 phase CSIs, the power values are on for———–?

    1. 60 degree
    2. 90 degree
    3. 120 degree (Answer)
    4. 150 degree

     

    46.Ripple factor is the ratio of———————-?

    1. Rms value of the ac component of load voltage to the dc voltage (Answer)
    2. Average value of the ac component of load voltage to the peak value of voltage
    3. Average value of the dc component of load voltage to the ac voltage
    4. Peak value of the dc component of load voltage to the ac voltage

     

    47.Form factor of a rectifier is the ratio of ————–?

    1. Root mean square value of voltage and current to its peak value
    2. Root mean square value of voltage and current to its average value (Answer)
    3. Average value of current and voltage to its root mean square value
    4. Peak value of current and voltage to its root mean square value

     

    48.Silicon controlled rectifier can be turned on————?

    1. By applying a gate pulse and turned off only when current becomes zero (Answer)
    2. And turned off by applying gate pulse
    3. By applying a gate pulse and turned off by removing the gate pulse
    4. By making current non zero and turned off by making current zero

     

    49.TRIAC is a semiconductor power electronic device which contains————?

    1. Two SCR’s connected in reverse parallel (Answer)
    2. Two SCR’s connected in parallel
    3. Two SCR’s connected in series
    4. Two BJT’s connected in series

     

    Page 12

    50.The curve between V and I of SCR when anode is positive w.r.t cathode and when anode is negative

    w.r.t cathode are known as———————?

    1. both as forward characteristics
    2. both as reverse characteristics
    3. former as forward characteristics and later as reverse characteristics (Answer)
    4. former as reverse characteristics and later as forward characteristics

     

    51.An SCR can be used———–?

    1. as static conductor
    2. for power control
    3. for speed control of dc shunt motor
    4. All of these (Answer)

     

    52.With gate open, the maximum anode current at which SCR is turned off from ON condition is called—

    ———?

    1. breakdown voltage
    2. peak reverse voltage
    3. holding current (Answer)
    4. latching current

     

    53.A crowbar is a circuit which is used to protect a————-?

    1. voltage sensitive load from excessive dc power supply output voltages (Answer)
    2. current sensitive load from excessive dc power supply output voltages
    3. voltage sensitive load from excessive ac power supply output voltages
    4. current sensitive load from excessive ac power supply output voltages

     

    54.Bidirectional semiconductor device is———–?

    1. Diode
    2. BJT
    3. SCR

     

    Page 13

     

    1. TRIAC (Answer)

     

    55.A full wave rectifier with resistive load produces———–?

    1. Second harmonic
    2. Third harmonic
    3. Fifth harmonic
    4. Do not produce harmonics (Answer)

     

    56.An ideal diode is———–?

    1. Unidirectional
    2. Bidirectional
    3. Fixed voltage polarity
    4. Only (a) and (c) (Answer)

     

    57.The input current waveform of a bridge controlled rectifier when the load is perfectly filtered is——–

    —?

    1. Sine wave
    2. Square wave (Answer)
    3. Saw – tooth wave
    4. Trapezoidal wave

     

    58.The IGBT resulted in higher switching speed and lower energy losses. It can be used for———–?

    1. Uninterruptible power supplies
    2. Induction heating system
    3. Constant voltage and frequency power supplies
    4. All of these (Answer)

     

    59.The advantage of using free – wheeling diode in half controlled bridge converter is that

    1. There is always a path for the dc current independent of the ac line (Answer)
    2. There is always a path for the ac current independent of the ac line

     

    Page 14

     

    1. There is always a path for the dc current dependent of the ac line
    2. There is always a path for the ac current independent of the ac line

     

    60.To detect an over – current fault condition, the most reliable method is to connect a————-?

    1. Current sensor across IGBT
    2. Voltage sensor across IGBT
    3. Current sensor in series with IGBT (Answer)
    4. Voltage sensor in series with IGBT

     

    61.Harmonics in 3 phase inverters can be reduced by using———–?

    1. Passive filter
    2. Active filter
    3. Both passive and active filters (Answer)
    4. None of these

     

    62.The on – state voltage drop of IGBT consists of———-?

    1. Drop across the collector junction
    2. Drop across the drift region
    3. Drop across MOSFET portion
    4. All of these (Answer)

     

    63.The most suited gate pulses given to the AC regulator with R – L load can be in the form of————?

    1. Continuous signal
    2. Large isolating pulse transformer
    3. A train of pulses (Answer)
    4. None of these

     

    64.The maximum firing angle in the half wave controlled regulator is————-?

    1. 180 degree
    2. 190 degree

     

    Page 15

     

    1. 200 degree
    2. 210 degree (Answer)

     

    65.With increase in firing angle,

    1. Both harmonic distortion and quality of input current increases
    2. Harmonic distortion increases and quality of input current decreases (Answer)
    3. Harmonic distortion decreases and quality of input current increases
    4. Both harmonic distortion and quality of input current decreases

     

    66.n a phase controlled 3 phase ac voltage controller, the harmonic present is———-?

    1. 2nd (Answer)
    2. 3rd
    3. 5th
    4. 7th

     

    67.The power MOSFET device is a———–?

    1. Current controlled unipolar device
    2. Voltage controlled unipolar device (Answer)
    3. Current controlled bipolar device
    4. Voltage controlled bipolar device

     

    68.In dual converters—————-?

    1. Both rectifiers provides positive current to the load (Answer)
    2. Both rectifiers provide negative current to the load
    3. One rectifiers provide positive current to the load and the other negative current
    4. One rectifier provide positive current to the source and the other negative current to the load

     

    69.The conduction losses in IGBT is————?

    1. More than that of MOSFET
    2. Lower than that of MOSFET (Answer)

     

    Page 16

     

    1. Equal to that of MOSFET
    2. Equal to that of BJT

     

    70.For a buck converter to reduce the conduction losses in diode

    1. A high on – resistance switch can be added in parallel
    2. A low on – resistance switch can be added in parallel
    3. A high on – resistance switch can be added in series
    4. A low on – resistance switch can be added in series (Answer)

     

    71.Advantages of HVDC transmission over AC system is / are————?

    1. Reversal of power can be controlled by firing angle
    2. Very good dynamic behavior
    3. They can link two AC system operating unsynchronized
    4. All of these (Answer)

     

    72.For bidirectional operation of converters————?

    1. A parallel combination of controllable switch and a diode is used (Answer)
    2. A parallel combination of controllable switch and capacitor is used
    3. A series combination of controllable switch and a diode is used
    4. A series combination of controllable switch and a capacitor is used

     

    73.In rectifiers, load current flow is———?

    1. Unidirectional (Answer)
    2. Bidirectional
    3. Either (a) or (b)
    4. Non directional

     

    74.Due to non sinusoidal waveform of the input current, the power factor of the rectifier is————?

    1. Negatively affected by firing angle
    2. Negatively affected by distortion of the input current

     

    Page 17

     

    1. Positively affected by both firing angle and distortion of the input current
    2. Both (a) and (b) (Answer)

     

    75.Single phase VSI are mainly used in———–?

    1. Power supplies
    2. Ups
    3. Multilevel configuration
    4. All of these (Answer)

     

    76.The man made noise sources is / are————-?

    1. Motors
    2. Switches, radio interferences
    3. Computers, digital electronics
    4. All of these (Answer)

     

    77.Very large values of modulation index (greater than 3.24) lead to———–?

    1. Square AC output voltage (Answer)
    2. Sine AC output voltage
    3. Triangular AC output voltage
    4. Trapezoidal AC output voltage

     

    78.Any electrical signal present in a circuit other than the desired signal is known as————–?

    1. Noise (Answer)
    2. Distortion
    3. Interference
    4. All of these

     

    79.In single phase VSI, the harmonic which is not present is————?

    1. 2nd (Answer)
    2. 3rd

     

    Page 18

     

    1. 5th
    2. 7th

     

    80.In commutation PAC stands for——-?

    1. Permanent angle converter
    2. Phase angle converter (Answer)
    3. Phase angle commutation
    4. Phase and commutation

     

    81.Double fourier series analysis of PWM is————-?

    1. Two dimensional functions (Answer)
    2. Three dimensional functions
    3. One dimensional functions
    4. All of these

     

    82.In the operation and control of both naturally commutated and forced commutated SCR base

    converter, commutation plays an important role. The converters is / are ———–?

    1. AC – DC
    2. DC – DC
    3. DC – AC
    4. All of these (Answer)

     

    83.In bipolar modulation, the carrier is symmetric about zero with amplitude equal to Cm, the PWM

    output

    1. Zero
    2. Switches between – 1 / 2 and + 1 / 2 (Answer)
    3. Switches between – 1 and + 1
    4. Switches between 0 and + 1

     

    84.In a 3 phase VSI out of eight valid states, the number of valid states that produce zero ac line voltages

    is/are———?

     

    Page 19

     

    1. One
    2. two (Answer)
    3. Three
    4. Four

     

    85.The square wave operation of 3 phase VSI lines contains the harmonics. The amplitudes are————

    ?

    1. Directly proportional to their harmonic order
    2. Inversely proportional to their harmonic order (Answer)
    3. Not related to their harmonic order
    4. None of these

     

    86.In a three phase voltage source inverters————?

    1. Only amplitude of voltage is controllable
    2. Only phase is controllable
    3. Both amplitude and phase is controllable
    4. Amplitude, phase and frequency of voltages should always be controllable (Answer)

     

    87.Under harmonic free load voltages, the 3 phase VSI————-?

    1. Does not contains second harmonic (Answer)
    2. Does not contains third harmonic
    3. Does not contains fifth harmonic
    4. Does not contains seventh harmonic

     

    88.Double edge modulation eliminates certain harmonics when the reference is a———-?

    1. Sine wave (Answer)
    2. Square wave
    3. Triangular wave
    4. Trapezoidal wave

     

    Page 20

     

    89.For similar carrier and modulating signals, the line current used in CSI is———-?

    1. Identical to line voltage in a VSI (Answer)
    2. Identical to line current in VSI
    3. Identical to phase voltage in VSI
    4. Identical to phase voltage in CSI

     

    90.The carrier which are commonly used in constant – frequency PWM is————–?

    1. Sawtooth carrier
    2. Inverted sawtooth carrier
    3. Triangle carrier
    4. All of these (Answer)

     

    91.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

    1. 5
    2. 7
    3. 11
    4. All of these (Answer)

     

    92.A capacitive load in voltage source inverters generates —————-?

    1. Small current spikes and can be reduced by using an inductive filter
    2. Large current spikes and can be increased by using an inductive filter
    3. Small current spikes and can be increased by using an inductive filter
    4. Large current spikes and can be reduced by using an inductive filter (Answer)

     

    93.In a three phase converter, the number of notches per cycle is————?

    1. One
    2. Three
    3. Six (Answer)
    4. Nine

     

    Page 21

     

    94.The main objective of static power converters is to————?

    1. Obtain an dc output waveform from a dc power supply
    2. Obtain an ac output waveform from a dc power supply (Answer)
    3. Obtain an dc output waveform from a dc power supply
    4. Obtain an ac output waveform from a ac power suppl

     

    95.During the commutation period in 3 phase converter, overlap time is————-?

    1. Dependent on the load current
    2. Dependent on the voltage
    3. Dependent on both the load current and load voltage behind the short circuit current (Answer)
    4. Independent on both the load current and load voltage

     

    96.The control method used for PWM dc – dc converter is————–?

    1. Voltage mode control
    2. Current mode control
    3. Hysteric control
    4. All of these (Answer)

     

    97.Between the incoming and outgoing devices in voltage commutation

    1. Large overlapping takes place
    2. Small overlapping operation
    3. No overlapping operation (Answer)
    4. None of these

     

    98.The average value of the output voltage in a step – down dc chopper is given by———-?

    1. V 0 = V s
    2. V 0 = D V s (Answer)
    3. V 0 = V s / D
    4. V 0 = V s / ( 1 – D )

     

    Page 22

     

    99.The effects of EMI can be reduced by————?

    1. Suppressing emissions
    2. Reducing the efficiency of the coupling path
    3. Reducing the susceptibility of the receptor
    4. All of these (Answer)

     

    100.Choppers is a—————?

      1. AC – DC converters
      2. AC – AC converters
      3. DC – AC converters
      4. DC – DC converters (Answer)
    Post Views: 1,433
    Was this article helpful?
    YesNo