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T355- Utilization of Electrical Energy

1 (a) Discuss the Speed-time curve for main-line service of electric train

(b) The distance between two stops is 5km apart. A train has schedule speed of 50kmph.

The train accelerates at 2.5kmphps and retards 3.5kmphps duration of stop is 55 Sec.

determine the crest speed over the run assuming trapezoidal speed time curve.(Or)

(c) Derive the expression for a trapezoidal speed time curve of an electric train

(d) A suburban electric train has a maximum speed of 75kmph. The schedule speed

including a station stop of 25sec is 48kmph. If the acceleration is 2kmphps, the

average distance between two stops is 4km. determine the value of retardation.

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2 (a) Derive the expression for the distance between the stops and speed at the end of the

coasting period for a quadrilateral speed-time curve

(b) The distance between two stops is 1.2km apart. A schedule speed of 40kmph is

required to cover that distance. The stop is of 18 seconds duration. The values of

acceleration and retardation are 2 kmphps and 3 kmphps respectively. Then determine

the maximum speed over the run. Assume a simplified trapezoidal speed-time

(or)

(c) Derive the expressions for a trapezoidal speed time curve of an electric train?

(d)A train is required to run between two stations 2 km apart at a scheduled speed of 36

kmph, the duration of the stops being 20 seconds. The braking retardation is 2.7

kmphps. Assuming a trapezoidal speed- time curve, calculate the acceleration if the

ratio of maximum speed to average speed is 1.2.

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3 (a) Explain clearly regenerative braking when used for dc series traction motor

(b) What are the advantages of electric braking over mechanical braking?(or)

(c) Explain the various types of electric braking. State the conditions to

be fulfilled to each method of braking

(d) Explain why a dc series motor is ideally suited for traction purpose.

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4 (a) Describe how plugging, rheostat braking and regenerative braking are

employed with DC series motor

(b) What are the various electric traction systems in India? Compare them.

(or)

(c) Explain the speed time curve for a main line service and derive theexpression

12

1+

1 =

3600

1

Where the symbols have their usual meaning.

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5 (a) Write a short note on mechanics of train movement.

(b) The speed-time curve of a train consists of

i). Uniform acceleration of 6 km/hr/s for 26 seconds;

ii). free running for 10 minutes;

iii). Uniform deceleration of 6 km/hr/s to stop the train;iv). A stop of 5 minutes.

Find the distance between stations, the average, and scheduled speeds

(or)

(c) Discuss about electric traction system in India. How it is different from distribution

system.

(d) Describe how plugging and rheostatic braking are employed with DC motors.

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6 a) Derive the expression for the tractive effort for a train on a level track.

b) An electric train of weight 250 tonne has eight motors geared to driving wheels,

each is 85cm diameter. The tractive resistance is of 50 per tonne. The effect of

rotational Inertia is 8% of the train weight the gear ratio is 4 to 1 and gearing

efficiency is 85percent determine the torque developed by each motor to accelerate

the train to a speed of 50Kmph in 30 Seconds up a gradient of 1 in 200.

(or)

c) Explain the dead weight, effective weight and adhesive weight in a locomotive

d) A 2300 tone train proceeds down a gradient of 1 in 100 for 5 minutes,

during which period, its speed gets reduced from 40kmph to 20kmph by

application of regenerative braking, find energy returned to the lines, if

the tractive resistance is 5kg/ tone, rotational inertia 10% .

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7 a) Explain briefly the tractive effort required while the train is moving up thegradient and down the gradient

b) An electric train has an average speed of 42 kmph on a level track between stops 1.4

km apart. It is accelerated at 1.7 kmphps and is braked at 3.3 kmphps. Assumingtractive resistance as 10 N per ton, allowing 10 percent for rotational inertia, and

efficiency of motors 85 percent: (i) Estimate the specific energy consumption (ii)Draw the speed time curve.

(or)

c) Derive an expression for specific energy output on level track using a

simplified speed time curve

d) A train weighing 450 tonnes is going down a gradient of 20 in 1000, it isdesired to Maintain train speed at 50kmph by regenerative braking.Calculate the power fed in to the line and allow rotational inertia of 12%

and efficiency of conversion is 80%. Traction resistance is 50 N/tones.

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8 a) Explain the terms dead weight, effective weight and adhesive weight in alocomotive

b) An electric train weighing 200 tonnes has 8 motors geared to driving

wheels; each wheel is of 80 cm diameter. Determine the torque developedby each motor to accelerate the train to a speed of 48 km/hr in 30

seconds up a gradient of 1 in 200. The tractive resistance of 50

Newtons/tonne, the effect of rotational inertia is 10% of the train weight,the gear ratio is 4 in 1 and gearing efficiency is 80%.

(or)

c) Describe the procedure for calculating the specific energy consumption of an electric

train.

d) Explain the termsi). coefficient of adhesion

ii). tractive effort

iii). Gradient

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9 a) What is coefficient of adhesion? How does it affect slipping of the driving wheel of a

traction unit?b) Derive an expression for the tractive effect developed by a train unit.

(or)

c) What is specific energy consumption of a train? Discuss various factors affecting it.d) Differentiate between adhesive weight and total weight of an electric locomotive.

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10 a) Describe the procedure for calculating the specific energy consumption

of an electric train.

b) A 400 tonne goods train is to be hauled by a locomotive up a gradient of 2%with

acceleration of 1 km/hr/sec, coefficient of adhesion 20%, track resistance 40

newtons/tonne and effective rotating masses 10% of the dead weight. Find the weight

of the locomotive and the number of axles if the axle load is not to increase beyond 22

tonnes.

(or)

c) Derive the expression for the tractive effort for a train on a level track.

d) An electric train of weight 250 tonne has eight motors geared to drivingwheels, each is 85cm diameter. The tractive resistance is of 50 per

tonne. The effect of rotational Inertia is 8% of the train weight the gear

ratio is 4 to 1 and gearing efficiency is 85 percent determine the torque

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developed by each motor to accelerate the train to a speed of 50Kmph

in 30 Seconds up a gradient of 1 in 200.

11 a) Define and explain the following terms:

(i) MHCP (ii) MSCP (iii) MHSCP (iv) Solid angle

b) What are polar curves? How it is useful to an illumination engineer.

(or)

c) A lamp fitted with 120 degrees angled cone reflector illuminates circular area of 200meters in diameter. The illumination of the disc increases uniformly from 0.5- meter

candle at the edge to 2- meter candle at the centre. Determine

(i) The total light received(ii) Average illumination of the disc(iii)Average candlepower of the source.

d) What is Photometry? Explain its use in illumination engineering.

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12 a) State and explain about the laws of Illumination. Derive the relation between E, Land I

for a uniform diffused source.

b) A small light source with intensity uniform in all directions is mounted at a height of 10

meters above a horizontal surface. Two points A and B both lie on the surface with

point A directly beneath the source. How far the point B from the point A if the

illumination at point B is only 1/10 as great as at point A(or)

c) A lamp having a uniform candle power of 200 in all directions is provided

with a reflector which directs 60 % of total light uniformly on to a circulararea of 10 m diameter. The lamp is hung 6 meters above the area. Calculate

the illumination (i) at the center (ii) at the edge of the surface with and

without the reflector. Determine also the average illumination over the areawithout reflector.

d) Explain any one method of measuring a brightness of light source

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13. a) Explain with connection diagram the operation of the low-pressure

fluorescent lamp and state its advantages.b) Explain working and construction of LED lighting system and list out

Merits and Demerits of LED lighting System.

(or)

c) Discuss the flood lighting with suitable diagrams.d) What do you understand by discharge lamp? Explain the construction and working of

high-pressure mercury lamp.

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14. a) Estimate the number and wattage of lamps which would be required to illuminate a

work space of 60m x 15m by means of lamps mounted 5 meters above work plane. Theaverage illumination required is 100 Lux, coefficient of utilisation is 0.4 luminous

efficiency is 16 lumens per watt. Assume space height ratio of unity and candle power

depreciation of 20%.b) Define the terms

i) Space-height Ratio

ii) Utilisation factoriii) Maintenance factor

(or)

c)Two similar lamps having uniform intensity of 500 candle power in all directions below

the horizontal are mounted at a height of 4 meters what must be the maximum spacing

between the lamps so that the illumination on the ground mid -way between the lamps

shall be atleast one half the illumination directly entered the lamp

d) Define the Termsi) Illumination

ii) Solid angle and relation between solid angle and plain angle

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15. a) Explain the construction and working of Mercury vapour lamp with a

neat diagram. Mention its applications.

(or)

b) Explain with a neat diagram the working and operation of a Sodium

vapour lamp. Mention its application.

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16 a) Discuss briefly the various methods of welding.

b) What are the advantages of coated electrodes in welding process?

(or)

c) What do you understand by electric heating? What are the advantages over othermethods of heating?

d) What are the characteristics of heating elements? Explain the design of heatingelements in resistance heating.

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17 a) Discuss the important features of electric arc welding and resistance welding.

b) Compare the A.C and D.C systems of metallic arc welding.

(or)

c) Discuss the important features of resistance heating and induction heating.

d) Explain the merits and application of dielectric heating.

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18 a) Discuss the features of DC arc welding system.

b) Explain the advantages of AC arc Welding machines.

(or)

c) Discuss the different methods of electric heating and their relative merits.d) Discuss the differences between carbon and metallic arc welding and give their relative

merits and demerits.

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19 a) With a neat sketch explain the working principle of coreless type induction furnace.

b) Discuss various methods of temperature control in the resistance heating.

(or)

c) What is a resistance welding? What are its limitations?

d) Describe briefly the various types of arc welding processes used in industry.

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20 a) What are the advantages of electric heating? Give classification of various

electric heating methods along with brief account of their working

principles (or)

b) Describe with neat sketches various methods of electric resistance welding.

c) The power required for dielectric heating of a slab of resin 150 cm 2 in area

and 2cm thick is 200 watts at a frequency of 30x106 Hz. The material has arelative permittivity of 5 and power factor of 0.05. Determine the voltage

necessary and current flowing through the material. If the voltage is limited

to 600 V, what will be the value of the frequency to obtain the same heating?

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21 a) Describe the construction and working of a Dry Cell?

b) Explain the configuration of Off-line interactive UPS?(or)

c) Explain the selection process and design of a UPS?d) Explain the difference between primary and secondary batteries?

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22 a) Explain thei) lead acid storage cell

iii) Lithium ion Battery

(or)

b) What is UPS? Classify the groups of UPS?c) Why is an Inverter/UPS based stand by power preferred over a diesel generator- set?

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23 a) What are effects of quick or fast charging or high energy recovery from battery?

b) What do you mean by depth of discharge? How does it affect the life of a battery?

(or)

c) Design a standby ups based power supply for 230v, 2.5 kw , 50hz, 0.8pf load for ahalf-hour back-up period. The input dc bus voltage is 120v?

d) Explain the difference between primary and secondary batteries?

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24 a) Explain the configuration of an Off-line Preferred UPS?

b) Explain the difference between primary and secondary batteries?

(or)c) Explain the configuration of an online inverter, preferred type?

d) Why is an inverter/UPS based stand by power preferred over a diesel generator- set?

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25 a) Define the Primary Batteries and its Examples?b) Define the Secondary Batteries and its Examples?

c) Why off-line interactive UPS is cheap and online UPS is costlier(or)

d) Describe the construction and working of a Dry Cell?

e) Explain the nickel/Cadmium Battery Construction and working

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