GUJARAT TECHNOLOGICAL UNIVERSITY
BE - SEMESTER- V (New) EXAMINATION - WINTER 2019
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Subject Code: 2150904 Date: 06/12/2019Subject Name: Elements of Electrical Design
Time: 10:30 AM TO 01:00 PM Total Marks: 70
Instructions:
1. Attempt all questions.
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2. Make suitable assumptions wherever necessary.3. Figures to the right indicate full marks.
MARKS
Q.1 (a) Define the following terms used in armature winding design: 03
(1) back pitch (2) Commutator pitch (3) winding pitch
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(b) Explain the use of dummy coils and equalizer connections in d.c. 04armature windings.
(c) Design a mush winding for 3-phase, 4-pole and 24 slots stator. Also 07
show winding diagram for phase R only.
Q.2 (a) Give the classification of insulating materials on the basis of maximum 03
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permissible temperature rise.(b) Derive the equation of gap contraction factor for slots. 04
(c) Determine the air gap length of a DC machine from the following data: 07
Gross core length=0.10m, No. of ducts=1, Width of duct=10mm, slot
pitch=24mm, slot width=12mm, Carter’s co-efficient for slots and
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ducts=0.3, gap flux density at pole centre=0.65wb/m?, Field mmf perpole=3800A , mmf required for iron parts of magnetic circuit=600A.
OR
(c) Define real and apparent flux densities in the tooth of d.c. machine 07
armature and give the difference between them. Also derive the
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relation between them. Q.3 (a) Describe how to calculate the magnetizing current in a machine with 03
distributed winding.
(b) Write short note on use of field regulator in case of DC motor and DC 04
generator.
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(c) Find the Front pitch; back pitch, winding pitch and commutator pitch 07for a simplex wave wound 13 slots, 4-pole d.c armature with 13
commutator segments. Draw the winding diagram in developed form.
Also draw the sequence diagram to indicate the position of brushes.
Assume number of coil sides per slot =2
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OR
Q.3 (a) Give the definition of the following terms with respect to load 03
assessment:
(1) demand factor (2) load factor (3) diversity factor
(b) Compare mush winding and double layer winding for three phase AC 04
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machine.(c) Explain the grading of starting resistance for DC Shunt motor starters. 07
Q.4 (a) List any three guidelines for estimation of internal wiring. 03
(b) Discuss briefly the different types of loads with examples. 04
(c) Give design steps for small single phase transformer. 07
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OR
Q.4 (a) Discuss the necessity of starter in DC motors and Induction motors. 03
(b) Explain the working of capacitor start capacitor run single 04
phase induction motor.
(c) Give the design steps for single phase variable chock coil. 07
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Q.5 (a) Explain working of three point starter for DC motor. 03
(b) Discuss types of electrical wiring. 04
(c) Explain the grading of starting resistance for three phase induction 07
motor starters.
OR
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Q.5 (a) List various methods for calculating mmf required for the 03
tapered teeth and explain any one method in detail.
(b) Compare Simplex lap winding & Simplex wave winding. 04
(c) Calculate the steps in a 4 section rotor resistance starter for a 3-phase 07
induction motor having full load slip 2.5%. Maximum starting current
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= full load current and rotor resistance/phase=0.02O.--- Content provided by FirstRanker.com ---
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