GUJARAT TECHNOLOGICAL UNIVERSITY
SEMESTER-IV(NEW) - EXAMINATION - SUMMER 2019
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Subject Code:2140906 Date:15/05/2019Subject Name: AC Machines
Time:02:30 PM TO 05:00 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) Explain only constructional difference between squirrel case and 03
wound rotor 3 phase Induction Motor
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(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 07
two starters in brief.
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 04
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explain in brief(c) A 30KVA 2400/120-V, 50 Hz transformer has a high voltage winding 07
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
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impedance referred to the (1) High voltage side and (ii) the low voltageside.
OR
(c) Describe the procedure to construct the circle diagram of induction 07
motor. Also Explain the method to determine losses, Motor efficiency
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and slip at full load condition using circle diagram.Q.3 (a) What do you mean by Synchronous Condenser and how it’s different 03
than Synchronous motor?
(b) Explain V-curves and Inverted V-curve of synchronous motor in 04
brief
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(c) List the types of Single Phase induction motor. Explain the operational 07
principal of any one split phase induction motor with necessary sketch
and vector diagram
OR
Q.3 (a) Why synchronous motor is not self starting? Describe in brief 03
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(b) What is auto synchronous motor and how it is different than 04
synchronous motor.
(c) Draw the schematic diagram and explain the construction and 07
working of shaded pole single phase motor.
Q.4 (a) What is Hunting of Synchronous machine and how it prevents 03
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(b) Which are the conditions need to satisfy for successful parallel 04
operation of 3 ph Alternator?
(c) What is synchronization? Explain two bright one dark lamp method 07
and all dark lamp method of synchronization in brief.
OR
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Q.4 (a) Derive the EMF equation of an alternator 03
(b) Explain the term pitch factor and distribution factor of an alternator with 04
necessary equations.
(c) Mention the methods of determination of voltage regulation of an 07
alternator. Describe the Synchronous impedance (EMF) method in
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detail.Q.5 (a) What is short circuit ratio of synchronous machine and how it’s effect 03
to machine performance.
(b) Explain the construction and working of universal motor 04
(c) A 3-phase, 16-pole alternator has a star-connected winding with 144 07
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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).
OR
Q.5 (a) Describe Induction Generator in brief 03
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(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. 07
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.
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This download link is referred from the post: GTU BE 2019 Summer Question Papers || Gujarat Technological University
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