B.Tech-B.Tech Electrical Engineering 7th Sem 7EE4 Utilization of Electrical Power 7E4174(Rajasthan Technical University-2011)
7E4174
B. Tech. VII Semester (Main/Back) Examination, Nov-Dee-2011
Electrical Engineering
7EE4 Utilization of Electrical Power
Time: 3 Hours
Maximum Marks: 80
Min. Passing Marks : 24
Unit - I
Q.1. a) Briefly describe the principle of induction heating at high frequency and highlight a few applications of the eddy current heating. [8]
b) A piece of an insulating material is to be heated by dielectric heating. The size of the piece is 12cm x 12cm x 3cm, A frequency of 20 MHz is used and the power absorbed is 450W. If the material has a relative permittivity of 5 and a power factor of 0.05. Calculate the voltage necessary for heating and current that follows in the material. [8]
OR
Q.1. a) Discuss the principle of Arc welding and the difference between carbon and metallic Arc welding and their relative merits. Compare the A.C. and D.C. systems of metallic Arc welding. [8]
b) A slab of insulating material 130cm2 in area and 1 cm thick is to be heated by dielectric heating. The power required is 380 W at 30 MHz. Material has a relative permittivity of 5 and p.f. of 0.05. Absolute permittivity =8.854x 10-12 F/M. determine the necessary voltage. [8]
Unit - II
Q.2. a) Two lamp posts are 14m apart and are fitted with 200 c.p. lamp each at a height of 5 m above the ground. Calculate: [8]
i) Illumination mid - way between them.
ii) Illumination under each lamp.
b) Describe with the help of a neat diagram the construction and working of a high pressure mercury vapour lamp. [8]
OR
Q.2. a) Compare the metal filament lamp with discharge lamp. What is the advantage of coiled coil? Describe principle of operation, construction and working of a sodium discharge lamp. [8]
b) A small light source with intensity uniform in all directions is mounted at a height of 8 meters above a horizontal surface. Two points A and B both lie on the surface with point a directly beneath the source. How far is B from A if the illumination at B is only 1/12 as great as at A? [8]
Unit - III
Q.3. a) Explain the term 'Polarization', 'Throwing Power' and 'Electro-Deposition'. How are zinc and copper refined from their base metal electrically. [8]
b) In a copper sulphate voltameter, the copper cathode is increased in weight by 0.055 kg in 2 hours, when the current was maintained constant. Calculate the value of this current. Given:
Atomic weight of copper = 63.5;
atomic weight of hyclrogen = 1;
atomic weight of silver = 108;
electro - chemical equivalent of silver = 111.8x 10-8 kg/C. [8]
OR
Q.3. a) Calculate the thickness of copper deposited on a plate area of 2.2 cm2 during electrolysis if a current of 1 A is passed for 90 minutes.
E.C.E. of copper =32.95xl0-8 kg/c and density of copper = 8900 kg/m3 [8]
b) Describe in detail the process of nickel- electro plating in industry, giving the composition of electrolyte used. What are the. factors on which the quality of electro plating depends? [8]
Unit - IV
Q.4. a) Discuss the suitability of D.C. series motor for its application in electric locomotive for traction duty. [8]
b) A train is required to run between two stations 2 km apart at a schedule speed of 36 km/h. The duration of stops being 20 seconds. The braking retardation is 2.7 km/h/s. Assuming a trapezoidal speed - time curve, calculate the acceleration if the ratio of maximum speed to average speed is 1.2. [8]
OR
Q.4. a) A suburban train run with an average speed of 36 kmph between two stations 1.8 km apart Values of acceleration and retardation are 1.8 km/h/s and 3.6 km/ph/ps. Calculate the maximum speed of the train assuming trapezoidal speed-time curve. [8]
b) What is tractive effort of a train and what are its functions? Derive an expression for the tractive effort developed by a train unit. [8]
Unit - V
Q.5. a) Discuss the advantages of series - parallel starting against the ordinary rheostatic starting for a pair of D.C. traction motors. [8]
b) A multiple - unit train weighing 210 tonnes is equipped with 6 motors giving a total tractive effort of 82800 N. The motors operate at a line voltage of 600V and each motor takes an average current of 200 A during starting. Series - Parallel control is used for starting. The full line voltage is applied to each motor when the speed reaches 38.6 km/h. Resistance of each motor is 0.1 ohm. Calculate :
Energy supplied during the starting period. [8]
OR
Q.5. a) What are the advantages and disadvantages of the regenerative braking of electric traction motor? [8]
b) State with sketches the three important methods of transmission of mechanical power from traction motor to the driving wheels. [8]
| Earning: ₹ 6.10/- |
