University Of Pune Question Paper
S.E. (Mechanical) (Semester – II) Examination, 2011
ELECTRICAL TECHNOLOGY
(Common to Mech. S/W, Industrial, Production, Prod. S/W)
(2003 Course)
Time : 3 Hours Max. Marks : 100
Instructions : 1) Answer any 3 questions from each Section.
2) Answers to the two Sections should be written in separate
books.
3) Neat diagrams must be drawn wherever necessary.
4) Black figures to the right indicate full marks.
5) Your answers will be valued as a whole.
6) Use of electronic pocket calculator is allowed.
7) Assume suitable data, if necessary.
SECTION – I
1. a) Draw sectional view of two pole d.c. machine (label the various parts). 6
b) A shunt motor takes 20 A at 220 V and run at 1500 rpm. Motor has armature
resistance 0.5Ω and field resistance 110Ω . If machine has stray losses = 150 W.
Calculate
i) Back emf
ii) Mechanical power develop
iii) Gross torque developed
iv) Loss torque
v) Net torque
vi) BHP. 8
c) States the necessity of a starter in D.C. motors. 4
OR
2. a) State the various speed control methods used for d.c. series motor. Explain
any one of them with diagram. 6
b) A d.c. shunt motor runs at 1000 rpm by drawing 8 A current at no load from
250 V supply. If motor has armature and field winding resistances 0.2Ω and
250Ω respectively. Calculate the speed when motor takes 50 A. (Assume
flux remains constant) 8
c) Draw only electrical and mechanical characteristics of d.c. shunt motor. 4
3. a) The three phase power is measured by a two wattmeter method. The reading
of wattmeters are W1 = 2000 W and W2 = 500 W. Calculate the total power
and power factor when
i) The readings are +ve
ii) The second reading is obtained after reversing pressure coil terminals. 8
b) State and explain following factors in connection with illumination :
i) Utilization factor
ii) Space to height ratio
iii) Depreciation factor
iv) Beam factor. 8
OR
4. a) Explain with the help of a neat circuit diagram how one wattmeter can be used
for measurement of total three phase reactive power of three phase balanced
circuit. Also draw the necessary phasor diagram. 8
b) State and explain requirements of good lighting scheme. 8
5. a) Following tests are obtained when a 200 V/400 V, 5 KVA transformer is tested
as follows :
O.C. test – 200 V, 0.8 A, 72 W, (L.V. Side)
S.C. test – 16 V, 20 A, 80 W (L.V. side)
Calculate the efficiency and regulation at full load 0.8 p.f. lag. 8
b) With the help of neat circuit diagram explain procedure to determine regulation
of three phase alternator by synchronous impedance method. 8
OR
6. a) Three phase synchronous generator (alternator) has 10 poles, no. of slots = 60,
conductor per slot = 4, coil span of 150° and flux per pole 0.12 Wb. If
winding is sinusoidally distributed and star connected, determine line voltage
generated if frequency is 50 Hz. 8
b) Write short note on ‘current transformer’ and ‘potential transformer’. 8
SECTION – B
7. a) From first principle, derive the expression for torque developed by induction
motor. Also derive condition for maximum torque. And hence draw torque-slip
characteristic of induction motor. 10
b) A three phase, six pole, 50 Hz induction motor develops 5 H.P. at 950 rpm.
What is the stator input and efficiency of the motor if the stator losses are 300 W
total. (Note neglect mechanical losses and take 1 HP = 735.5 Watt). 8
OR
8. a) Draw the rotor construction diagram of slip ring motor and squirrel cage
motor. Also state their merits, demerits and applications. 10
b) Explain with suitable diagram star-delta starter used for three phase induction
motor. 8
9. a) Why single phase motor is not self started ? With neat diagram explain
construction, working, characteristic of capacitor slit phase induction single
phase motor. 8
b) With the help of neat diagram explain construction, working and applications
of a.c. servomotor. 8
OR
[3962] – 268 -4-
10. a) Explain construction and working with the help of neat diagram of single
phase split pole motor. State its merits, demerits and any two applications. 8
b) Universal motor – construction, working, applications and its characteristics. 8
11. a) State and explain in details the various factors considered while selection of
electrical drive for particular application. 8
b) State the properties of good heating element. Explain the procedure to design
a strip type heating element used in resistance ovens. 8
OR
12. a) State the merits, demerits and applications of group drive and individual drive
system. 8
b) With the help of neat diagram explain construction and working of coreless
induction heating furnace. 8
————————
S.E. (Mechanical) (Semester – II) Examination, 2011
ELECTRICAL TECHNOLOGY
(Common to Mech. S/W, Industrial, Production, Prod. S/W)
(2003 Course)
Time : 3 Hours Max. Marks : 100
Instructions : 1) Answer any 3 questions from each Section.
2) Answers to the two Sections should be written in separate
books.
3) Neat diagrams must be drawn wherever necessary.
4) Black figures to the right indicate full marks.
5) Your answers will be valued as a whole.
6) Use of electronic pocket calculator is allowed.
7) Assume suitable data, if necessary.
SECTION – I
1. a) Draw sectional view of two pole d.c. machine (label the various parts). 6
b) A shunt motor takes 20 A at 220 V and run at 1500 rpm. Motor has armature
resistance 0.5Ω and field resistance 110Ω . If machine has stray losses = 150 W.
Calculate
i) Back emf
ii) Mechanical power develop
iii) Gross torque developed
iv) Loss torque
v) Net torque
vi) BHP. 8
c) States the necessity of a starter in D.C. motors. 4
OR
2. a) State the various speed control methods used for d.c. series motor. Explain
any one of them with diagram. 6
b) A d.c. shunt motor runs at 1000 rpm by drawing 8 A current at no load from
250 V supply. If motor has armature and field winding resistances 0.2Ω and
250Ω respectively. Calculate the speed when motor takes 50 A. (Assume
flux remains constant) 8
c) Draw only electrical and mechanical characteristics of d.c. shunt motor. 4
3. a) The three phase power is measured by a two wattmeter method. The reading
of wattmeters are W1 = 2000 W and W2 = 500 W. Calculate the total power
and power factor when
i) The readings are +ve
ii) The second reading is obtained after reversing pressure coil terminals. 8
b) State and explain following factors in connection with illumination :
i) Utilization factor
ii) Space to height ratio
iii) Depreciation factor
iv) Beam factor. 8
OR
4. a) Explain with the help of a neat circuit diagram how one wattmeter can be used
for measurement of total three phase reactive power of three phase balanced
circuit. Also draw the necessary phasor diagram. 8
b) State and explain requirements of good lighting scheme. 8
5. a) Following tests are obtained when a 200 V/400 V, 5 KVA transformer is tested
as follows :
O.C. test – 200 V, 0.8 A, 72 W, (L.V. Side)
S.C. test – 16 V, 20 A, 80 W (L.V. side)
Calculate the efficiency and regulation at full load 0.8 p.f. lag. 8
b) With the help of neat circuit diagram explain procedure to determine regulation
of three phase alternator by synchronous impedance method. 8
OR
6. a) Three phase synchronous generator (alternator) has 10 poles, no. of slots = 60,
conductor per slot = 4, coil span of 150° and flux per pole 0.12 Wb. If
winding is sinusoidally distributed and star connected, determine line voltage
generated if frequency is 50 Hz. 8
b) Write short note on ‘current transformer’ and ‘potential transformer’. 8
SECTION – B
7. a) From first principle, derive the expression for torque developed by induction
motor. Also derive condition for maximum torque. And hence draw torque-slip
characteristic of induction motor. 10
b) A three phase, six pole, 50 Hz induction motor develops 5 H.P. at 950 rpm.
What is the stator input and efficiency of the motor if the stator losses are 300 W
total. (Note neglect mechanical losses and take 1 HP = 735.5 Watt). 8
OR
8. a) Draw the rotor construction diagram of slip ring motor and squirrel cage
motor. Also state their merits, demerits and applications. 10
b) Explain with suitable diagram star-delta starter used for three phase induction
motor. 8
9. a) Why single phase motor is not self started ? With neat diagram explain
construction, working, characteristic of capacitor slit phase induction single
phase motor. 8
b) With the help of neat diagram explain construction, working and applications
of a.c. servomotor. 8
OR
[3962] – 268 -4-
10. a) Explain construction and working with the help of neat diagram of single
phase split pole motor. State its merits, demerits and any two applications. 8
b) Universal motor – construction, working, applications and its characteristics. 8
11. a) State and explain in details the various factors considered while selection of
electrical drive for particular application. 8
b) State the properties of good heating element. Explain the procedure to design
a strip type heating element used in resistance ovens. 8
OR
12. a) State the merits, demerits and applications of group drive and individual drive
system. 8
b) With the help of neat diagram explain construction and working of coreless
induction heating furnace. 8
————————
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