1
Seat No.: Enrolment
GUJARAT TECHNOLOGICAL UNIVERSITY
PDDC SEMESTER-VIII EXAMINATION WINTER 2018
Subject Code:X80903 Date: 26/11/2018
Subject Name: Electrical Drives Traction
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.
Q.1

State the main requirements for an ideal traction system. Give merits and demerits of electric traction over steam engine traction.
07

What do you mean by drive? Explain multi quadrant operation of electric drive
07
Q.2

Explain group drive, individual drive and multi motor drive.
07

Enlist different methods of speed control of three-phase induction motor. Explain any of them.
07
OR

Explain plugging and regenerative breaking. Also mention difference between them.
07
Q.3

Discuss advantages and dis advantages of electric drives.
07

Explain speed time curves for main line traction services.
07
OR
Q.3

Using the simplified trapezoidal speed time curve, derive an expression for the maximum speed in kmph in terms of acceleration, retardation, distance between stops and actual time of run between stops.
07

Explain speed time curves for urban and sub urban traction services.
07
Q.4

Write short notes on different class of duties of electrical motor.
07

Define average speed, crest speed and schedule speed. Discuss the factors, which affect schedule speed of a train
07
OR
Q.4

Write technical note on heating and cooling curves.
07

What is specific energy consumption? Derive equation for specific energy consumption.
07
Q.5

Explain series parallel starting of d.c. series traction motors
07

Explain different methods for speed control of induction motor.
07
OR
Q.5

Explain Types of enclosures used in electric motor.
07

Draw and explain AC locomotive
07