Power Electronics Multiple Choice Questions and Answers

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

1. Symmetric rectangular voltage across itself
2. Symmetric trapezoidal voltage across itself
3. Symmetric triangular voltage across itself
4. Symmetric sinusoidal voltage across itself

32. In a three phase converter, the number of notches per cycle is

1. Three
2. Six
3. One
4. Nine

33. In a UJT, the p-type emitter is ........................ doped

1. Heavily
2. Moderately
3. Lightly
4. None of the above

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

1. Switches between -1 / 2 and +1 / 2
2. Switches between -1 and +1
3. Zero
4. Switches between 0 and +1

35. In current commutated DC - DC choppers, the voltage spike appears across the load when

1. The capacitance voltage adds to the supply voltage
2. Both (a and b)
3. Voltage across the commutating inductances collapses
4. None of these

36. In EMCsignal, the source delivers maximum power to the input of transmissionline when the transmission line input impedance

1. Greater than the source resistance
2. Smaller than the source resistance
3. Is equal to the source resistance
4. None of these

37. In radiative coupling, the emitter radiation field

1. Decays as R, where R is the separation distance between the emitter and the receptor
2. Decays as 1 / 2 R, where R is the separation distance between the emitter and the receptor
3. Decays as 1 / R, where R is the separation distance between the emitter and the receptor
4. Decays as 2R, where R is the separation distance between the emitter and the receptor

38. In single phase VSI, the harmonic which is not present is

1. 3rd
2. 5th
3. 2nd
4. 7th

39. LISN is a device used to measure conducted emissions. LISN stands for

1. Line impedance stabilization network
2. Line integrated stored network
3. Line integrated stabilization network
4. Laser integrated stabilization networking

40. Power electronics essentially deals with control of a.c. power at .....................

1. Frequencies above 1000 kHz
2. Frequencies less than 10 Hz
3. Frequencies above 20 kHz
4. 50 Hz frequency