1) A carrier based PWM technique in CSI is composed of____________? a. A switching pulse generator and a shorting pulse generator b. A shorting pulse distributor c. A switching and shorting pulse combination d. All of these
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2) In a square – wave operation of 3 phase CSIs, the power values are on for___________? a. 60 degree b. 90 degree c. 120 degree d. 150 degree
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3) Ripple factor is the ratio of______________________? a. Rms value of the ac component of load voltage to the dc voltage b. Average value of the ac component of load voltage to the peak value of voltage c. Average value of the dc component of load voltage to the ac voltage d. Peak value of the dc component of load voltage to the ac voltage
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4) Form factor of a rectifier is the ratio of ______________? a. Root mean square value of voltage and current to its peak value b. Root mean square value of voltage and current to its average value c. Average value of current and voltage to its root mean square value d. Peak value of current and voltage to its root mean square value
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5) 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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6) 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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7) 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_____________________? a. both as forward characteristics b. both as reverse characteristics c. former as forward characteristics and later as reverse characteristics d. former as reverse characteristics and later as forward characteristics
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8) 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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9) With gate open, the maximum anode current at which SCR is turned off from ON condition is called____________? a. breakdown voltage b. peak reverse voltage c. holding current d. latching current
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10) 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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11) Bidirectional semiconductor device is___________? a. Diode b. BJT c. SCR d. TRIAC
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12) 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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13) An ideal diode is___________? a. Unidirectional b. Bidirectional c. Fixed voltage polarity d. Only (a) and (c)
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14) 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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15) The IGBT resulted in higher switching speed and lower energy losses. It can be used for___________? a. Uninterruptible power supplies b. Induction heating system c. Constant voltage and frequency power supplies d. All of these
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16) 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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17) To detect an over – current fault condition, the most reliable method is to connect a_____________? a. Current sensor across IGBT b. Voltage sensor across IGBT c. Current sensor in series with IGBT d. Voltage sensor in series with IGBT
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18) 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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19) The on – state voltage drop of IGBT consists of__________? a. Drop across the collector junction b. Drop across the drift region c. Drop across MOSFET portion d. All of these
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20) 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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