M.Sc. (Semester (CBCS) Examination Oct/Nov-2017
Electronics
POWER ELECTRONICS
Day Date: Tuesday, 21-11-2017 Max. Marks: 70
Time: 10.30 AM to 01.00 PM
Instructions: Attempt five questions.
Q. and are compulsory.
Answer any three questions from Q.3 to Q.7.
Figures to the right indicates full marks.
Q.1 Choose the alternatives given below. 08
The voltage controller is used in speed control of Induction motor.
AC DC
Both a b None of these
In the operation of McMurry half bridge inverter is based on the
assumption that load current is during the communication period.
Varies Decreases
Increases Constant
In McMurry half-bridge inverter are the commutating components.
Capacitors Inductors
Both a b None of these
In case of step down cycloconverter the output frequency is
supply frequency.
Less than Greater than
Equal to None of these
The chopper is converter.
AC to DC DC to AC
AC to AC DC to DC
In three phase half wave controlled rectifier for interval the
average load voltage is given by
The is application of AC voltage controllers.
Lighting control Speed control of DC motor
AC magnet control All of these
In voltage source inverter output AC voltage depends on voltage.
Input AC Input DC
Both a b None of these
State True or false. 06
The RMS load voltage for integral cycle control is Vs
The rectifier is DC to AC convertor.
In phase operation of multiphase chopper, it turn on and off at a different
instant.
In symmetrical configuration of single phase full wave half controlled
bridge rectifier, angle for all the devices is − rad.
In McMurry Bedford communication the feedback diode are equally
effective in centre taped circuits catering for inductive loads.
In type A chopper, SCR is turned off when its current drops below its
holding current value for specific duration.
Q.2 Attempt any two. (Short Questions) 10
State the advantages disadvantage of unidirectional and bidirectional
controllers.
Write a note on single phase full wave full controlled bridge rectifier with
R load.
Write a note on class C chopper.
Explain integral cycle controller. 04
Q.3 Explain three to single phase cycloconverter. 07
Explain half controller bridge rectifier with free wheeling diode. 07
Q.4 Explain single phase full bridge inverter. 07
Explain step up and step down chopper. 07
Q.5 With neat circuit diagram and waveform explain the operation of full wave
controlled rectifier with inductive load.
07
Derive the relations for average output voltage and RMS output voltage full
wave controlled rectifier with inductive load.
07
Q.6 Explain with suitable waveform three phase unidirectional controller. 07
Explain McMurry full bridge inverter. 07
Q.7 Explain in detail single PWM and multiphase PWM inverters. 07
Explain in detail mid point and bridge type cycloconverter. 07