page 2 | Power Electronics and Drives MCQ

Q21. A resistance \(R_C\) (along with parallel connected diode) is connected in series with a capacitor \(C\) to form a dynamic equilization network. The purpose of this resistance \(R_C\) is _______.

limits charging current

limits discharging current

limits both charging and discharging currents

none of the above

Q22. Power semiconductor device that combines the characteristic of BJT and MOSFET is

GTO

FCT

IGBT

MCT

Q23. What is the output voltage \((V_{dc})\) of the three-phase full converter?
Take \(V_m\) as the phase voltage.

\(V_{dc} = \frac{V_m3\sqrt{3}}{\pi} \:\cos \alpha\)

\(V_{dc} = \frac{V_m3\sqrt{3}}{2\pi} \:\cos \alpha\)

\(V_{dc} = \frac{V_m\sqrt{3}}{2\pi} \:\cos \alpha\)

\(V_{dc} = \frac{V_m\sqrt{3}}{\pi} \:\cos \alpha\)

Q24. A semiconverter feeding an RLE load operates in

first quadrant only

first and second quadrants

first and third quadrants

first and fourth quadrants

Q25. A single phase full-wave half-controlled bridge converter feeds an inductive load.The two SCRs in the converter are connected to a common DC bus. The converter has to have a freewheeling diode

because the converter inherently does not provide for free-wheeling

because the converter does not provide for free-wheeling for high values of triggering angles

or else the freewheeling action of the converter will cause shorting of the AC supply

or else if a gate pulse to one of the SCRs is missed, it will subsequently cause a high load current in the other SCR.

Q26. single phase full wave thyristor converter is supplying an RL load. The supply voltage is 200 V, and triggering angle is 60º. If the load is drawing a constant current from the source the output voltage will be

75 V

90 V

135 V

110 V

Q27. Statement 1: Diode rectifier is controllable<br> Statement 2: Thyristor based rectifier is controllable<br> Which of the above statement is false ?

Both Statement 1 and statement 2

Only Statement 2

Only statement 1

None

Q28. What is the output voltage \((V_{dc})\) of a single-phase full converter (fully controlled bridge rectifier)?

\(V_{dc} = \frac{V_m \sqrt 3}{\pi}\cos \alpha\)

\(V_{dc} = \frac{2V_m}{\pi}\cos \alpha\)

\(V_{dc} = \frac{3V_m}{\pi}\cos \alpha\)

\(V_{dc} = \frac{3V_m}{2\pi}\cos \alpha\)

Q29. A boost converter is used to obtain a 50 V output from a 40 V DC source. Find the duty cycle.

10%

20%

90%

80%

Q30. In a type A chopper, source voltage is 200 V dc, on period = 150 \(\mu sec\) and off period = 100 \(\mu sec\), and load RLE consist of R = 6 \(\Omega\), L = 8 mH, E = 60V. The output current of the chopper will be,

20A

10A

6A

4A

MCQ

POWER ELECTRONICS & DRIVES