B.TECH - Semester 8 power semiconductor drives Question Paper 2008 (may)
Practice authentic previous year university questions for better exam preparation.
- Draw the torque-speed characteristics of an induction motor drive and mark the region of operation clearly. What are the different speed control methods of induction motors?
- List the three different component of load torque and define them.
- With the help of neat schematics give the classification of DC drives.
- Define steady state stability of Electric Drives. What are the criteria for steady state stability of Drives? PART - B Answer one full question from each module.
- (b) Write a short note on steady state stability of electric drives.
- Draw the block diagram of a closed loop converter fed DC motor and list its advantages over open loop.
- Write notes on : (c) Draw the schematic of chopper resistance control in rotor circuits and compare it with conventional rotor resistance control.
- With a simple circuit explain the principle of slip power recovery scheme. What are its advantages?
- (b) Explain the slip power recovery scheme at sub synchronous and super synchronous speed control of 3 phase slip ring induction motor.
- (a) What is the use of torque speed characteristics of a motor? Discuss about the torque speed characteristics of fan, centrifugal pump, compressor, hoist.
- (i) Motor speed at the firing angle of $45^{\circ}$ and torque of 12 Nm . (ii) Developed torque at firing angle of $30^{\circ}$ and speed of 800 rpm .
- Write notes on : (a) Advantages and disadvantages of Current source inverters.
- Write notes on : (b) Difference between voltage and current source inverters.
- Distinguish between controlled and uncontrolled rectifiers. List different control strategies for electric drives and describe them.
- What is the principle of operation of cycloconverters? Discuss circulating mode cycloconverters and blocking mode cycloconverters.
- List the different operating modes of DC motor used for variable speed applications. With the help of a neat graph, list the conditions for four quadrant operation of a separately excited DC motor.
- Write a short note on dual converters and their role on speed control operations.
- Draw the equivalent circuit of a cycloconverter and explain its principle of operation with classification. What are its advantages and disadvantages. Write the output voltage equation of a cycloconverter and name each variable mentioned. List any six applications of a cycloconverter.
- (c) Explain four quadrant operation of a DC motor driving a hoist Load. Module - 2
- (a) A $200 \mathrm{~V}, 1500 \mathrm{rpm}, 10 \mathrm{~A}$ separately excited DC motor has an armature resistance of 1 ohm . It is fed from a single phase full converter with an AC voltage source of $230 \mathrm{~V}, 50 \mathrm{~Hz}$. Armature current is continuous. Calculate
- (b) Discuss the need for speed control of DC motors. The speed of a separately excited DC motor is controlled using a single phase fully controlled bridge converter. With the help of relevant waveforms obtain the expressions for speed in continuous conduction mode.
- (a) Draw the schematic of a single phase semi converter and single phase full converter drives feeding an armature circuit. Discuss their quadrant operations with the help of current waveforms and obtain the expression for average field voltage.
- (b) Write a short note on single phase dual converter drives.
- (a) Draw and explain family of speed torque characteristics of slip ring induction motor with respect to variations in rotor resistance.
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