21. Between the peak point and the valley point of UJT emitter characteristics we have ....................... region

- Negative resistance
- Cut-off
- Saturation
- None of the above

22. Double fourier series analysis of PWM is

- Three dimensional functions
- One dimensional functions
- Two dimensional functions
- All of these

23. During the commutation period in 3 phase converter, overlap time is

- Dependent on the voltage
- Dependent on both the load current and load voltage behind the short circuit current
- Dependent on the load current
- Independent on both the load current and load voltage

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

- A low on - resistance switch can be added in parallel
- A high on - resistance switch can be added in series
- A high on - resistance switch can be added in parallel
- A low on - resistance switch can be added in series

25. For bidirectional operation of converters

- A parallel combination of controllable switch and capacitor is used
- A series combination of controllable switch and a diode is used
- A parallel combination of controllable switch and a diode is used
- A series combination of controllable switch and a capacitor is used

26. For similar carrier and modulating signals, the line current used in CSI is

- Identical to line current in VSI
- Identical to phase voltage in VSI
- Identical to line voltage in a VSI
- Identical to phase voltage in CSI

27. For sweptfrequency measurements, the input impedance of the mismatched transmission line would vary with frequency as the electrical length ofthe transmission line would

- Remains same with change in frequency
- Increase with frequency
- Decrease with frequency
- Either (a or b)

28. Harmonics in 3 phase inverters can be reduced by using

- Active filter
- Both passive and active filters
- Passive filter
- None of these

29. In a 3 phaseCSI, if the required line output voltages are balanced and 120 degreeout of phase, then the chopping angles are used to eliminate only theharmonics at frequencies

- 7
- 11
- 5
- All of these

30. In a load commutated DC - DC chopper, the capacitor has a

- Symmetric rectangular voltage across itself
- Symmetric trapezoidal voltage across itself
- Symmetric triangular voltage across itself
- Symmetric sinusoidal voltage across itself

MCQ Multiple Choice Questions and Answers on Power Electronics

Power Electronics Question and Answer