M.Sc. (Semester (CBCS) Examination Mar/Apr-2018
Electronics
POWER ELECTRONICS
Time: 2½ Hours
Max. Marks: 70
Instructions: Attempt five questions. Q. 1 and 2 are compulsory. Answer any three questions from Q.3 to Q.7. Figures to the right indicate full marks.
Q.1
Choose the alternatives given below.
08
In three phase full converter the thristers are fired at the interval of rad.



600
The single phase dual converter provides the output voltage with polarity.
equal
opposite
equal but opposite
none of these
In extension angle control the displacement and power factors are
leading
lagging
equal
both a b
In mid-point cycloconverter the output frequency reduces in the ratio
5:1
1:6
1:5
6:1
In single phase bidirectional controller with inductive load, for power control PF angle θ must be firing angle
greater than
equal to
less than
none of these
The AC voltage controller have the advantage of
power control flexibility
lighting control
AC magnet control
none of thee
In mode operation of the dual converter is same as the full converter.
circulating current
continuous current
non circulating current
discontinuous current
McMurray Bedford half bridge inverter is also called commutatedinverter.
voltage
complementary
voltage source
current
State True or false.
06
In three phase bridge inverter firing is delayed by 600 from earlier firing.
The McMurray Bedford half bridge inverter is called voltage commutated voltage source inverter.
In PWM modulation control the lower order harmonicscan be reduced by increasing number of pulses per half cycle.
Page 2 of 2
SLR-UJ-323
In single phase bidirectional controller, firing pulses of two thyristers are kept 1800 apart.
Single phase step up cycloconverter gives the output frequency greater than input supply frequency.
In multiphase chopper each chopper handles a constant load current when it ON.
Q.2
Attempt any two. (Short Questions)
10
State the difference between symmetrical and asymmetrical configuration of semiconverter.
Write a note on single phase full wave half controlled bridge rectifier with R load.
Write a note on multiphase chopper.
Explain McMurryhalf bridge inverter.
04
Q.3
Explain operating principle of single phase bridge inverter.
07
Write a note on integral cycloconverter.
07
Q.4
Explain in detail class E chopper.
07
Explain single phase full controlled bridge rectifier with resistive load.
07
Q.5
With neat circuit diagram and waveform explain the McMurry fully bridge inverter.
07
Explain in detail AC chopper.
07
Q.6
Explain with suitable waveform single phase unidirectional controller.
07
Explain PWM inverters.
07
Q.7
Explain single phase half controlled rectifier with R-L load.
07
Explain Microcontroller based firing schemes.
07