Power Electronics Mcqs - Set 3

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
Answer  Explanation 

ANSWER: All of these

Explanation:
No explanation is available for this question!


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
Answer  Explanation 

ANSWER: 120 degree

Explanation:
No explanation is available for this question!


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
Answer  Explanation 

ANSWER: Rms value of the ac component of load voltage to the dc voltage

Explanation:
No explanation is available for this question!


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
Answer  Explanation 

ANSWER: Root mean square value of voltage and current to its average value

Explanation:
No explanation is available for this question!


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
Answer  Explanation 

ANSWER: By applying a gate pulse and turned off only when current becomes zero

Explanation:
No explanation is available for this question!


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
Answer  Explanation 

ANSWER: Two SCR’s connected in reverse parallel

Explanation:
No explanation is available for this question!


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
Answer  Explanation 

ANSWER: former as forward characteristics and later as reverse characteristics

Explanation:
No explanation is available for this question!


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
Answer  Explanation 

ANSWER: All of these

Explanation:
No explanation is available for this question!


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
Answer  Explanation 

ANSWER: holding current

Explanation:
No explanation is available for this question!


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
Answer  Explanation 

ANSWER: voltage sensitive load from excessive dc power supply output voltages

Explanation:
No explanation is available for this question!


11)   Bidirectional semiconductor device is___________?

a. Diode
b. BJT
c. SCR
d. TRIAC
Answer  Explanation 

ANSWER: TRIAC

Explanation:
No explanation is available for this question!


12)   A full wave rectifier with resistive load produces___________?

a. Second harmonic
b. Third harmonic
c. Fifth harmonic
d. Do not produce harmonics
Answer  Explanation 

ANSWER: Do not produce harmonics

Explanation:
No explanation is available for this question!


13)   An ideal diode is___________?

a. Unidirectional
b. Bidirectional
c. Fixed voltage polarity
d. Only (a) and (c)
Answer  Explanation 

ANSWER: Only (a) and (c)

Explanation:
No explanation is available for this question!


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
Answer  Explanation 

ANSWER: Square wave

Explanation:
No explanation is available for this question!


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
Answer  Explanation 

ANSWER: All of these

Explanation:
No explanation is available for this question!


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
Answer  Explanation 

ANSWER: There is always a path for the dc current independent of the ac line

Explanation:
No explanation is available for this question!


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
Answer  Explanation 

ANSWER: Current sensor in series with IGBT

Explanation:
No explanation is available for this question!


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
Answer  Explanation 

ANSWER: Both passive and active filters

Explanation:
No explanation is available for this question!


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
Answer  Explanation 

ANSWER: All of these

Explanation:
No explanation is available for this question!


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
Answer  Explanation 

ANSWER: A train of pulses

Explanation:
No explanation is available for this question!