Electronics Engineering (Semester 7)
Total marks: 80
Total time: 3 Hours
(1) Question 1 is compulsory.
(2) Attempt any three from the remaining questions.
(3) Draw neat diagrams wherever necessary.
Q1) Attempt any four from the following :
Why separately excited DC motor is widely used as compared to DC shunt motor? Explain.
Give advantages of regenerative braking of DC motor compared to other methods of braking?
Explain why V/F control is popular in AC induction motor control.
Give advantages of high frequency induction heating as compared to conventional methods of heating.
Compare SMPS with linear regulated power supply.
Explain the effect of source inductance in single-phase converter working in rectifier
mode. Draw relevant output voltage waveforms. Give equations which can be used
to determine overlap angle and output DC voltage.
In a 3-phase full converter working in rectifier mode, input supply is 440V(L-L), 50Hz. If firing angle $\alpha = \pi/4$ and load current is 20 A constant with load voltage = 370 V,
determine source inductance $Ls$ and overlap angle $\mu$.
Explain the steps involved in space vector modulation (SVM) technique used in three-phase voltage source inverter.
Explain using block diagram and transfer function, working of PI controller for DC-DC converter.
Give details of the state – space averaged model of DC – DC buck converter 10
operating in continuous conduction mode.
A separately excited DC motor armature winding is supplied power using single-phase 10
full bridge converter working on 250V, 50Hz mains supply. If $Ra = 0.1Ω$ and armature
current is 50 A, find the firing angle of the converter at 700 RPM. Assume that field
winding is supplied with rated DC voltage and motor ratings are 110V DC, 1000 RPM
and 75A .
Explain rotor resistance method of speed control of three-phase wound rotor induction motor. Draw speed-torque characteristics and give disadvantages of this technique.
Explain the following regions as related to V/F control of AC induction motor
- i) Content torque
- ii) Content power
Draw variations in applied voltage and motor current over entire operation from low
speed to double the rated speed of the motor.
Q6) Write short notes on
Battery charging circuit and its working
Selection of battery capacity in UPS.
Constant torque and content power regions in control of separately excited DC motor.