Roll No.......................

[Total No. of Pages: 03Total No. of Questions: 10]

B. '{'echo (Sem. - 6th)ELECTRIC DRIVES AND UTILIZATION

SUB.TECT CODE: EE - 304Paper ID : [A0420]

[Note: Please fill subject code and paper ID on OMR]

Maximum Marks: 60Time: 03 Hours

Instruction to Candidates:

1) Section - A is Compulsory.2) Attempt any Four questions from Section - B.3) AtWmptany Two questions from Section - C.

Q1)

i)

j)

Section - A

(lOx 2 = 20)

a) Suggest suitable type of motors with reasons for textile mill and papermill drives.

b) Why projection welding is considered superior to spot welding?

What is comfort air conditioning?c)

d) Why single phase system is preferred for main line railway service?«

What is anodizing and Faraday constant?e)

f).

110 Volt lamp develops 16 c.p. and lamp of same material and workingat same efficiency develops 25 c.p. on 220 Volt. Compare diameter andlength of filaments.

g)

h)

-

What do you under stand by polar curve? .Why are indirect furnaces not built in large sizes?

What is the role of condenser and choke used in fluorescent lamp? .

A suburban electric train has a m~imum speed of 70 kmph. The schedulespeed including a station stop of.30 seconds is 45 kmph. If the accelerationis 1.5 kmphps.Find the value of retardation when the ,average distancebetween stops is 4km. .

M-157 [1859] P.T.O.

. Section - B ;

(4 x 5 =20),

Q2) (a) Derive an expression for the mo~or torque driving a rolling mill whenequipped with fly wheel.

(b) A trolley wire of a tramway is suspended from two poles 40 metersapart. If the diameter of the wire is 1 cm. and weight per meter is 0.5 kg.Fin4 its sag if the tension applied is 500 kg. Find also the total length ofwire required.

Q3) (a) Why a drooping characteristic of supply voltage is essential formaintaining steady are in electric welding and how this characteristic isobtained in case of d.c. source.

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(b) An illumination on the working plane of 75 lux is require'd in a room72 m x 15 m in size. The lamps are required to be hung 4 m above thework bench. Assuming a suitable space height ratio, a utilization factorof 0.5, a lamp efficiency of 14 lumens per watt and candle powerdepreciation of20% estimate the number, rating and disposition oflamps.

Q4) Compare D.C. and A.C. 'systemsof railway electrification from the view of

lnain line and.suburban line railway service.

Q5) Draw electric circuit of a refrigerator and explain its-working. How can

temperature inside tHerefrigerator be adjusted.

Q6) (a)

(b)

Explain various factors to be considered while designing street lighting.. .

Find the thickness of the copper deposited on a plate area of 0.00025 m2during electrolysis if a current of one ampere is passed for 100 minutes.Density of copper is 8900 kg/m3 and E.C.E. of copper is 32.95 x 10-8kg/C.

Section - C

(2 x 10 =20)-

Q7) (a) Explain what do you unqerstand by.'continuous', 'short time','intermittent' rating of an electric machine.

M-157 2

(b) A 3 phase arc furnace is used to melt 4.3 tones of steel in one hour.Determine the average kW and kVA input to the furnace, arc voltage,arc resistance and p.f: of the current drawn from the supply.

Given

Specific heat of steel = 0.12 K ca1/kg./°C

Latent heat steel = 8.89 K cal/kg.rC

. Melting point of steel = 1370°CInitial temperature of steel = 19.1°c

Overall efficiency of furnace = 50%

Input current = 5700A

Resistance of transformer referred to secondary and reactance of thetransformer referred to secondary are 0.008 and 0.014 ohm respectively..

Q8) Explain the working of a fluorescent tube with the help of the circuit diagramgiving the function of various parts. How stroboscopic effect is eliminated influorescent tube lighting.

Q9) (a)

(b)

M-157

Explain the working of ~entral air coqditional system.

An electric train has quadrilateral speed time curve as follows:

(i) Uniform acceleration from re,stat 2 Kmphps for 30 seconds.

(ii) Coasting for 50 seconds.

(iii) Uniform braking to rest for 20 seconds.

If the train is moving up a gradient of 10/1000, train resistance is40N. / Tone, Rot~tional inertia effect 10% of dead weight and durationof stop 30 seconds. Find the schedule speed.

. D~I~~

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