Seat No.: ________ Enrolment No.
___________
GUJARAT TECHNOLOGICAL UNIVERSITY
BE - SEMESTER–V (NEW) EXAMINATION – WINTER 2023
Subject Code:3150910 Date:07-12-2023
Subject Name:Electrical Machine- II
Time:10:30 AM TO 01:00 PM Total Marks:70
Instructions:
1. Attempt all questions.
2. Make suitable assumptions wherever necessary.
3. Figures to the right indicate full marks.
4. Simple and non-programmable scientific calculators are allowed.
MARKS
Q.1 (a) Explain term hunting for synchronous motor, also explain method to 03
reduce this effect.
(b) Explain working principle of induction motor. Give detail classification 04
of induction motors, and its advantages and disadvantages.
(c) Explain frequency of rotor current in induction motor. Derive torque 07
equations for starting and running condition of induction motor.
Q.2 (a) Explain power stages of an induction motor in detail. 03
(b) Draw and explain relation between torque and slip of induction motor. 04
(c) Which tests required to draw circle diagram for induction motor? Explain 07
steps to draw the circle diagram of an induction motor in detail.
OR
(c) Explain necessity of starters in three induction motor also draw and 07
explain star-delta starter in detail.
Q.3 (a) Explain cogging and crawling. 03
(b) Draw and explain circuit diagram and vector diagram of an induction 04
motor.
(c) Why does rotor rotates in three phase induction motor? Explain in detail 07
production of Rotating Magnetic Field.
OR
Q.3 (a) Write methods of speed control of universal motor. 03
(b) What is the use of centrifugal switch in single phase induction motor? 04
Explain working of capacitor start induction run single phase induction
motor with vector diagram.
(c) Write types of single-phase induction motor, explain working of shaded 07
pole induction motor.
Q.4 (a) Explain working of Switched reluctance motor. 03
(b) Explain working and applications of Permanent magnet brushless DC 04
motor.
(c) Derive EMF equation of an alternator, also explain pitch factor and 07
distribution factor.
OR
Q.4 (a) Write advantages and applications of linear induction motor. 03
(b) Explain vector diagrams of alternator in loaded condition. 04
(c) What is voltage regulation of an alternator, list the methods of voltage 07
regulation. Explain ZPF method.
1
Q.5 (a) Explain application, advantages and disadvantages of stepper motor. 03
(b) Explain conditions for parallel operation of alternators. 04
(c) What is synchronizing of an alternator? Explain all dark lamp method in 07
detail.
OR
Q.5 (a) What will be the effect on synchronous motor if it is over excited and 03
under excited, explain with vector diagram.
(b) Draw and explain V-curve and inverted V-curve for synchronous motor. 04
(c) With vector diagram explain effect of change in excitation and effect of 07
change in steam supply for alternators connected to bus bar.
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