Download GTU (Gujarat Technological University) BE/BTech (Bachelor of Engineering / Bachelor of Technology) 2019 Summer 4th Sem New 2140906 Ac Machines Previous Question Paper
Seat No.: ________ Enrolment No.___________
GUJARAT TECHNOLOGICAL UNIVERSITY
BE - SEMESTER ?IV(NEW) ? EXAMINATION ? SUMMER 2019
Subject Code:2140906 Date:15/05/2019
Subject Name: AC Machines
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) Explain only constructional difference between squirrel case and
wound rotor 3 phase Induction Motor
03
(b) Derive the torque equation of 3 phase Induction Motor 04
(c) List the types of starters for a 3 Phase Induction Motor. Explain any
two starters in brief.
07
Q.2 (a) What is Linear Induction motor? Explain in brief with its application 03
(b) Draw Slip Torque characteristic of 3 phase Induction motor and
explain in brief
04
(c) A 30 KVA 2400/120-V, 50 Hz transformer has a high voltage winding
resistance of 0.1 ohm and a leakage reactance of 0.22 ohm. The low
voltage winding resistance is 0.035 ohm and the leakage reactance is
0.012 ohm. Find the equivalent winding resistance, reactance and
impedance referred to the (1) High voltage side and (ii) the low voltage
side.
07
OR
(c) Describe the procedure to construct the circle diagram of induction
motor. Also Explain the method to determine losses, Motor efficiency
and slip at full load condition using circle diagram.
07
Q.3 (a) What do you mean by Synchronous Condenser and how it?s different
than Synchronous motor?
03
(b) Explain V-curves and Inverted V-curve of synchronous motor in
brief
04
(c) List the types of Single Phase induction motor. Explain the operational
principal of any one split phase induction motor with necessary sketch
and vector diagram
07
OR
Q.3 (a) Why synchronous motor is not self starting? Describe in brief 03
(b) What is auto synchronous motor and how it is different than
synchronous motor.
04
(c) Draw the schematic diagram and explain the construction and
working of shaded pole single phase motor.
07
Q.4 (a) What is Hunting of Synchronous machine and how it prevents 03
(b) Which are the conditions need to satisfy for successful parallel
operation of 3 ph Alternator?
04
(c) What is synchronization? Explain two bright one dark lamp method
and all dark lamp method of synchronization in brief.
07
OR
Q.4 (a) Derive the EMF equation of an alternator 03
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Seat No.: ________ Enrolment No.___________
GUJARAT TECHNOLOGICAL UNIVERSITY
BE - SEMESTER ?IV(NEW) ? EXAMINATION ? SUMMER 2019
Subject Code:2140906 Date:15/05/2019
Subject Name: AC Machines
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) Explain only constructional difference between squirrel case and
wound rotor 3 phase Induction Motor
03
(b) Derive the torque equation of 3 phase Induction Motor 04
(c) List the types of starters for a 3 Phase Induction Motor. Explain any
two starters in brief.
07
Q.2 (a) What is Linear Induction motor? Explain in brief with its application 03
(b) Draw Slip Torque characteristic of 3 phase Induction motor and
explain in brief
04
(c) A 30 KVA 2400/120-V, 50 Hz transformer has a high voltage winding
resistance of 0.1 ohm and a leakage reactance of 0.22 ohm. The low
voltage winding resistance is 0.035 ohm and the leakage reactance is
0.012 ohm. Find the equivalent winding resistance, reactance and
impedance referred to the (1) High voltage side and (ii) the low voltage
side.
07
OR
(c) Describe the procedure to construct the circle diagram of induction
motor. Also Explain the method to determine losses, Motor efficiency
and slip at full load condition using circle diagram.
07
Q.3 (a) What do you mean by Synchronous Condenser and how it?s different
than Synchronous motor?
03
(b) Explain V-curves and Inverted V-curve of synchronous motor in
brief
04
(c) List the types of Single Phase induction motor. Explain the operational
principal of any one split phase induction motor with necessary sketch
and vector diagram
07
OR
Q.3 (a) Why synchronous motor is not self starting? Describe in brief 03
(b) What is auto synchronous motor and how it is different than
synchronous motor.
04
(c) Draw the schematic diagram and explain the construction and
working of shaded pole single phase motor.
07
Q.4 (a) What is Hunting of Synchronous machine and how it prevents 03
(b) Which are the conditions need to satisfy for successful parallel
operation of 3 ph Alternator?
04
(c) What is synchronization? Explain two bright one dark lamp method
and all dark lamp method of synchronization in brief.
07
OR
Q.4 (a) Derive the EMF equation of an alternator 03
2
(b) Define pitch factor and distribution factor of an alternator with
necessary equations.
04
(c) Mention the methods of determination of voltage regulation of an
alternator. Describe the Synchronous impedance (EMF) method in
detail.
07
Q.5 (a) What is short circuit ratio of synchronous machine and how it?s effect
to machine performance.
03
(b) Explain the construction and working of universal motor 04
(c) A 3-phase, 16-pole alternator has a star-connected winding with 144
slots and 10 conductors per slot. The flux per pole is 0.03 Wb,
Sinusoidally distributed and the speed is 375 r.p.m. Find the Line and
phase EMF. Assume full-pitch coil (Kc=1).
07
OR
Q.5 (a) Describe Induction Generator in brief 03
(b) Explain the construction and working of Repulsion motor 04
(c) A three phase star connected alternator is rated at 1600 KVA, 13.5 KV.
The per phase armature effective resistance and synchronous reactance
are 1.5 ohm and 30 ohm respectively. Calculate voltage regulation for
a load of 1.280 MW at power factor of (i) Unity p.f and (ii) 0.8 lagging.
07
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This post was last modified on 20 February 2020