Diploma-Diploma Mechanical Engineering 1st Year BEE-031 : ELECTRICAL TECHNOLOGY (Indira Gandhi National Open University (IGNOU), New Delhi-2013)
DIPLOMA IN MECHANICAL ENGINEERING (DME)
Term-End Examination - June, 2013
BEE-031 : ELECTRICAL TECHNOLOGY
Time : 2 hours Maximum Marks : 70
Note : Answer five questions in all. Question no. 1 is compulsory.
1. Select the correct answer from the given alternatives : 7x2=14
(a) RMS value of fully rectified sinwave is :
(i) Vm/ 2 (ii) 2 Vm/∏ (iii) Vm/∏ (iv) Vm / √2
(b) Which of the following motor is suitable for Traction ?
(i) DC shunt motor
(ii) DC compound motor
(iii) DC series motor
(iv) None of above
(c) Maximum efficiency of transformer occurs when :
(i) Iron loss = 0
(ii) Copper loss = 0
(iii) Iron loss = Copper loss
(iv) None of above
(d) At resonance frequency, a R-L-C series circuit has :
(i) Zero lagging power factor
(ii) Zero leading power factor
(iii) Unity power factor
(iv) None of above
(e) A Reciprocal network is consists of :
(i) Only unilateral elements
(ii) Only bilateral elements
(iii) both unilateral and bilateral elements.
(iv) None of above
(f) A 3-phase Induction motor developed maximum torque when slip is :
(i) S = 0
(ii) S = 1
(iii) S = ∞
(iv) S=R2 / X2
here R2 and X2 are Rotor resistance and reactances.
(g) A transformer has negative voltage regulation only at :
(i) Lagging power factor loads
(ii) Leading power factor loads
(iii) Unity power factor loads
(iv) All of the above.
2. (a) Derive resonance frequency for R - L - C series circuit. Write significance of power factor. 7
(b) Find current in 10Ω resistor using Superpositon Theorem. 7
3. (a) Define the following 6
(i) Armature Reaction
(ii) Back EMF
(b) A DC shunt motor connected with 250 Volt DC supply takes 20 A current and running at 1000 r.p.m. When a resistance of 2 Ω is inserted in armature circuit calculate its speed, Assume armature resistance of motor is 0.5 Ω.
4. (a) Draw and explain phasor diagram of real transformer at 0.8 pf leading load. 7
(b) Explain working principle and applications of Auto transformer. 7
5. (a) Draw Torque - slip characteristics of 3 - phase Induction motor using suitable torque relations. 7
(b) Discuss various methods of speed control used for 3 phase Induction motor. 7
6. Discuss the following : 4x31/2=14
(a) Armature reaction in Alternators
(b) MMF method of voltage regulation calculation
(c) 3 phase rotating magnetic field
(d) Synchronous condenser
7. Write short notes on any two of the following : 7x2=14
(a) V - curves of synchronous motor
(b) Parallel operation of Alternators
(c) Starters for 3-phase Induction motor
| Earning: ₹ 8.70/- |
