Download GTU (Gujarat Technological University) BE/BTech (Bachelor of Engineering / Bachelor of Technology) 2019 Summer 5th Sem New 2150904 Elements Of Electrical Design Previous Question Paper
Seat No.: ________ Enrolment No.___________
GUJARAT TECHNOLOGICAL UNIVERSITY
BE - SEMESTER ?V (NEW) EXAMINATION ? SUMMER 2019
Subject Code: 2150904 Date: 17/06/2019
Subject Name: Elements of Electrical Design
Time: 02:30 PM TO 05:00 PM Total Marks: 70
Instructions:
1. Attempt all questions.
2. Make suitable assumptions wherever necessary.
3. Figures to the right indicate full marks.
MARKS
Q.1 (a) Define: (1) Field form factor (2) Gap contraction factor for slots. 03
(b) How Magnetizing current is calculated for 3 phase induction motor? 04
(c) Explain different types of wiring used in Electrical installation? 07
Q.2 (a) Define Real and apparent flux density and write the equation for relation
between them.
03
(b) What is carter?s fringing curves? Why it is used? 04
(c) A 15 kW 230 volt, 4 pole d.c. machine has the following data: armature
diameter= 0.25m; armature core length=0.125m, length of air gap at pole
centre= 2.5mm,
flux per pole = 11.7 mWb, ratio Pole arc/pole pitch = 0.66.
Calculate the mmf required for the air gap (i) if the armature surface is
treated as smooth ii) if the armature is slotted and gap contraction factor is
1.18.
07
OR
(c) Calculate the mmf required for the air gap of a machine having core
length=0.32m, including 4 ducts of 10mm each , pole arc =0.19m, slot
pitch = 65.4 mm , slot opening = 5mm, air gap length = 5 mm, flux per
pole = 52 mWb. Given Carter?s coefficient is 0.18 for slot opening/gap
length =1 , and is 0.28 for duct width/ gap length = 2.
07
Q.3 (a) Classify the various types of a.c. armature windings. 03
(b) What is the function of field regulator in case of d.c. shunt motor? Explain
briefly.
04
(c) Design a suitable 5 section starter for a 7.5 kW, 250 V, 1000 rpm DC
shunt motor from the following data:
Maximum starting torque = 1.5 times the full load torque
Armature circuit resistance = 0.5 ?
Full load efficiency = 85%
07
OR
Q.3 (a) Explain in brief the progressive and retrogressive lap windings.
03
(b) What is the function of field regulator in case of d.c. shunt generator?
Explain briefly.
04
(c) Find the resistance of each section of a rotor resistance starter of a slip-
ring induction motor having a rotor resistance of 0.02 ? per phase and a
full load slip of 3%. Use 9 studs. Assume maximum starting current = Full
load current.
Also determine the slip at various studs.
07
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1
Seat No.: ________ Enrolment No.___________
GUJARAT TECHNOLOGICAL UNIVERSITY
BE - SEMESTER ?V (NEW) EXAMINATION ? SUMMER 2019
Subject Code: 2150904 Date: 17/06/2019
Subject Name: Elements of Electrical Design
Time: 02:30 PM TO 05:00 PM Total Marks: 70
Instructions:
1. Attempt all questions.
2. Make suitable assumptions wherever necessary.
3. Figures to the right indicate full marks.
MARKS
Q.1 (a) Define: (1) Field form factor (2) Gap contraction factor for slots. 03
(b) How Magnetizing current is calculated for 3 phase induction motor? 04
(c) Explain different types of wiring used in Electrical installation? 07
Q.2 (a) Define Real and apparent flux density and write the equation for relation
between them.
03
(b) What is carter?s fringing curves? Why it is used? 04
(c) A 15 kW 230 volt, 4 pole d.c. machine has the following data: armature
diameter= 0.25m; armature core length=0.125m, length of air gap at pole
centre= 2.5mm,
flux per pole = 11.7 mWb, ratio Pole arc/pole pitch = 0.66.
Calculate the mmf required for the air gap (i) if the armature surface is
treated as smooth ii) if the armature is slotted and gap contraction factor is
1.18.
07
OR
(c) Calculate the mmf required for the air gap of a machine having core
length=0.32m, including 4 ducts of 10mm each , pole arc =0.19m, slot
pitch = 65.4 mm , slot opening = 5mm, air gap length = 5 mm, flux per
pole = 52 mWb. Given Carter?s coefficient is 0.18 for slot opening/gap
length =1 , and is 0.28 for duct width/ gap length = 2.
07
Q.3 (a) Classify the various types of a.c. armature windings. 03
(b) What is the function of field regulator in case of d.c. shunt motor? Explain
briefly.
04
(c) Design a suitable 5 section starter for a 7.5 kW, 250 V, 1000 rpm DC
shunt motor from the following data:
Maximum starting torque = 1.5 times the full load torque
Armature circuit resistance = 0.5 ?
Full load efficiency = 85%
07
OR
Q.3 (a) Explain in brief the progressive and retrogressive lap windings.
03
(b) What is the function of field regulator in case of d.c. shunt generator?
Explain briefly.
04
(c) Find the resistance of each section of a rotor resistance starter of a slip-
ring induction motor having a rotor resistance of 0.02 ? per phase and a
full load slip of 3%. Use 9 studs. Assume maximum starting current = Full
load current.
Also determine the slip at various studs.
07
2
Q.4 (a) What is armature winding? Define following term with respect to it (1)
Turn (2) Coil (3) Coil side
03
(b) Define : (1) Coil pitch (2) Commutator pitch (3) Back pitch (4) Front
pitch
04
(c) Find and give comments whether the following wave windings are
symmetrical or not:
(i) 4-pole, 25-slots, 2 coil sides per slot
(ii) 4-pole, 14-slots, 2 coil sides per slot
07
OR
Q.4 (a) Differentiate between integral and fractional slot windings also state
advantages of fractional slot windings.
03
(b) What do you mean by ?dummy coil?? What is its application? Also
explain the use of equalizer connections in d.c. armature winding.
04
(c) Workout an arrangement for equalizer connection for 16 slots, 4 pole, 16
coils simplex lap wound d.c. machine. Use 4 equalizer rings.
07
Q.5 (a) State the condition for designing a single layer mush winding. 03
(b) Explain the importance of current carrying capacity and voltage drop
while determine the size of conductor.
04
(c) Discuss the design procedure of single phase variable choke coil.
07
OR
Q.5 (a) What is the purpose of estimating and costing? 03
(b) What are the factors that should be considered while selecting the type of
wiring system?
04
(c) Define wiring diagram, schematic diagram and single line diagram.
Explain using suitable example.
07
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This post was last modified on 20 February 2020