Gujarat Technological UniversityWinter 2025 examination

GTU BE03009021 Electrical Machines I Winter 2025 Question Paper & PDF

B.E. · Electrical Engineering · Semester 3 · Subject code BE03009021
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Total
70 marks
To pass
23 marks (33%)
Duration
2.5 Hours 10:30 AM – 1:00 PM
Questions
5 with internal choice
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Q.1

14 Marks
(a)
3 marks
Derive the EMF equation for single-phase transformer
(b)
4 marks

List out the conditions require to fulfill for parallel operation of the single-phase transformers.

(c)
7 marks

Determine the parameters to draw the equivalent circuit of transformer having below given data 100/200 volts, 50 Hz, single-phase open circuit test (O.C. test)- 100 volts, 0.4 Amp, 20 watts conducted from LV side Short circuit test (S.C. test) - 15 volts, 5 amp, 42.5 watts conducted from HV side

Q.2

14 Marks
(a)
3 marks
Discuss star-star connection of three phase transformers.
(b)
4 marks
Discuss Auto transformer.
(c)
7 marks
Discuss and analyze the Scott connection of the transformers.
(c)
7 marks

Discuss comparative analysis of different cooling systems used for cooling of transformers.

Q.3

14 Marks
(a)
3 marks
Discuss the phasor diagram of transformer operating at lagging power factor.
(b)
4 marks
Discuss online tap changer of the transformer.
(c)
7 marks
Discuss the torque-slip characteristic of an induction motor.
(a)
3 marks
Analyze the term "All day efficiency " for single-phase transformer.
(b)
4 marks
Discuss any two protective devices used for the protection of transformer
(c)
7 marks
Discuss cogging and crawling of an induction motor.

Q.4

14 Marks
(a)
3 marks
Discuss the working principle and types of construction of transformers.
(b)
4 marks
Analyze the effect of rotor resistance on the starting toque of the induction motor.
(c)
7 marks
How to determine
i)output line,
ii)torque line, and
iii)Power scale from the circle diagram of three-phase induction motor.
(a)
3 marks
Discuss different types of losses occurred in transformer.
(b)
4 marks
Derive the condition for the maximum running torque for induction motor.
(c)
7 marks

An induction motor has below mentioned data Three-phase, 50 Hz, slip= 0.03, synchronous speed of stator magnetic field is 750 rpm, useful torque (shaft torque) is of the order of 192 Nm. Determine

i)rotor frequency,
ii)speed of rotor,
iii)number of poles, and output power.

Q.5

14 Marks
(a)
3 marks
Discuss the classification of single phase AC motors.
(b)
4 marks
Discuss the different power stages of an induction motor.
(c)
7 marks
Discuss shaded pole single phase induction motor.
(a)
3 marks
Discuss equivalent circuit of single-phase AC motor.
(b)
4 marks

Discuss the effect of change in supply voltage on torque slip characteristic of an induction motor.

(c)
7 marks
Discuss capacitor start and capacitor run type single-phase induction motor.

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About this paper

Official Gujarat Technological University (GTU) examination paper for Electrical Machines I (Winter 2025, B.E. · Electrical Engineering, Sem 3). Features complete 70-mark regular & remedial examination pattern, official marking distribution across all 5 questions, and direct 1-click official PDF download.

Transcribed for student exam preparation from Gujarat Technological University official examination archives. Questions, syllabus guidelines, and curriculum marking schemes remain the intellectual property of Gujarat Technological University.

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