Deemed University 2010 B.Tech Electrical and Electronics Engineering University: Lingayas University Term: III Title of the : Electromechanical Energy Conversion - Question Paper

Roll No. ..

 

Lingayas University, Faridabad

Examination May, 2010

Course: B.Tech. Year: II^nd.

Semester: III Paper Code: EE-205E

Subject: Electromechanical Energy Conversion

[Time: 3 Hours] [Max. Marks: 100]

 

Before answering the question, candidate should ensure that they have been supplied the correct and complete question paper. No complaint in this regard, will be entertained after examination.

 

Note: Attempt any Five Questions. All questions carry equal marks.

Q-1. (a) Explain role of magnetic materials in Electrical Engineering w.rt following terms: (8)

(i) Cold rolled grain oriented steel.

(ii) Retentivety

(iii) Magnetic Friction

(iv) Hard Magnetic material

(b) What is hysterics and eddy current loss? Why is it important to know before selecting a particular material for a particular application? (5+2=7)

(c) The total core loss of a specimen of silicon steel is found to be 1500 w at 50Hz. Keeping the flux density constant the loss becomes 3000w. When the frequency is raised to 75 Hz. Calculate separately the hysteresis and eddy current loss at each of these frequencies. (5)

Q-2. (a) For an attracted armature relay define the following: (8)

(i) Field energy (ii) Co-energy

Express the force on the armature of a current excited relay in terms of co-energy.

(b) Explain the principle of energy conversion with a block diagram of a general diagram of a general process. (8)

(c) Define what is coupling field reaction? Why is it essential for electromechanical energy conversion? (4)

Q-3. (a) Explain the construction of a single phase transformer with a neat sketch. (8)

(b) Draw the equivalent circuit of a single phase transformer defining all the parameters. (5)

(c) A 20 KVA, 2500/500 volt, single phase transformer has the following parameters. (7)

H.V winding r₁ = 8 , x₁ = 17

L.V winding r₂ =0.3, x₂ = 0.7

Find the voltage regulation and secondary terminal voltage at full load for a power factor of (i) 0.8 lagging (ii) 0.8 leading.

Q-4. (a) Explain the working principle of a current transformer and its area of application. Can it be used for bulk power transfer? Justify your answer. (10)

(b) What is auto transformer? Discuss its limitation and advantages over two winding transformers. Write the area of applications. (10)

Q-5. (a) What is the importance of a starter for starting a d.c motor? Explain the working of a 4 point starter with a neat sketch. (8)

(b) Derive a torque equation of a d.c shunt motor. (7)

(c) An 8-pole generator has 500 armature conductors and has a useful flux per pole of 0.065 wb. What will be the e.m.f generated if it is lap connected and runs at 1000 r.p.m? Also what must be the speed at which it is to be driven to produce the same e.m.f if it is wave connected? (5)

Q-6. (a) Develop an equivalent circuit model of a 3-induction motor (8)

(b) Explain the star-delta starting technique of a 3-induction motor with a neat sketch. (7)

(c) A 3-induction motor has a 4-pole, star- connected stator winding. The motor runs on a 50 Hz supply with 200v line to line voltage. The rotor resistances and standstill rotor reactance per phase are 0.1 and 0.9respectively. The ratio of rotor to stator turns in 0.67 calculate (i) total torque developed at 4% slip; (ii) Maximum torque (5)

Q-7 (a) Discuss the working principle of a stepper motor and give its applications. (10)

(b) Single phase induction motor is not self starting Justify your answer with any one of the theories. (10)

Q-8. (a) What is voltage regulation? Explain the Potier triangle method of voltage regulation of a 3-alternator. (10)

(b) Derive the e.m.f equation of a 3-alternator considering short pitched, distributed stator winding. (10)

Roll No. ..

 

Lingayas University, Faridabad

Examination December, 2009

Course: B.Tech. Year: II^nd.

Semester: III Paper Code: EE-205E

Subject: Electromechanical Energy Conversion

[Time: 3 Hours] [Max. Marks: 100]

 

Before answering the question, candidate should ensure that they have been supplied the correct and complete question paper. No complaint in this regard, will be entertained after examination.

 

Note: Attempt any Five Questions. All questions carry equal marks.

Q-1. (a) Explain role of magnetic materials in Electrical Engineering w.rt following terms: (8)

(i) Cold rolled grain oriented steel.

(ii) Retentivety

(iii) Magnetic Friction

(iv) Hard Magnetic material

(b) What is hysterics and eddy current loss? Why is it important to know before selecting a particular material for a particular application? (5+2=7)

(c) The total core loss of a specimen of silicon steel is found to be 1500 w at 50Hz. Keeping the flux density constant the loss becomes 3000w. When the frequency is raised to 75 Hz. Calculate separately the hysteresis and eddy current loss at each of these frequencies. (5)

Q-2. (a) For an attracted armature relay define the following: (8)

(i) Field energy (ii) Co-energy

Express the force on the armature of a current excited relay in terms of co-energy.

(b) Explain the principle of energy conversion with a block diagram of a general diagram of a general process. (8)

(c) Define what is coupling field reaction? Why is it essential for electromechanical energy conversion? (4)

Q-3. (a) Explain the construction of a single phase transformer with a neat sketch. (8)

(b) Draw the equivalent circuit of a single phase transformer defining all the parameters. (5)

(c) A 20 KVA, 2500/500 volt, single phase transformer has the following parameters. (7)

H.V winding r₁ = 8 , x₁ = 17

L.V winding r₂ =0.3, x₂ = 0.7

Find the voltage regulation and secondary terminal voltage at full load for a power factor of (i) 0.8 lagging (ii) 0.8 leading.

Q-4. (a) Explain the working principle of a current transformer and its area of application. Can it be used for bulk power transfer? Justify your answer. (10)

(b) What is auto transformer? Discuss its limitation and advantages over two winding transformers. Write the area of applications. (10)

Q-5. (a) What is the importance of a starter for starting a d.c motor? Explain the working of a 4 point starter with a neat sketch. (8)

(b) Derive a torque equation of a d.c shunt motor. (7)

(c) An 8-pole generator has 500 armature conductors and has a useful flux per pole of 0.065 wb. What will be the e.m.f generated if it is lap connected and runs at 1000 r.p.m? Also what must be the speed at which it is to be driven to produce the same e.m.f if it is wave connected? (5)

Q-6. (a) Develop an equivalent circuit model of a 3-induction motor (8)

(b) Explain the star-delta starting technique of a 3-induction motor with a neat sketch. (7)

(c) A 3-induction motor has a 4-pole, star- connected stator winding. The motor runs on a 50 Hz supply with 200v line to line voltage. The rotor resistances and standstill rotor reactance per phase are 0.1 and 0.9respectively. The ratio of rotor to stator turns in 0.67 calculate (i) total torque developed at 4% slip; (ii) Maximum torque (5)

Q-7 (a) Discuss the working principle of a stepper motor and give its applications. (10)

(b) Single phase induction motor is not self starting Justify your answer with any one of the theories. (10)

Q-8. (a) What is voltage regulation? Explain the Potier triangle method of voltage regulation of a 3-alternator. (10)

(b) Derive the e.m.f equation of a 3-alternator considering short pitched, distributed stator winding. (10)