03000EE308052001

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Max. Marks: 100

b)

APJ ABDUL KALAM TECHNOLOGICAL UNIVERSITY

Sixth semester B.Tech degree examinations (S), September 2020

Course Code: EE308
Course Name: Electric Drives

PARTA
Answer all questions, each carries 5 marks.

How are the load torques classified? Give an example for each type of load
torque.
Derive the speed-torque (@-T) equation of a separately excited DC motor. Plot
the -T characteristics of the motor.
Compare and contrast Class-C and Class-D choppers.
List and explain the merits of constant V/f control of Induction Motor.
Explain the differences between the switching devices used for Voltage Source
Inverter and Current Source Inverter.
Write the transformation matrix which converts phasor in three-phase system to
an orthogonal, stationary reference frame.
List down the salient features of “True Synchronous Mode” of operation of a
synchronous motor.
Draw a neat labelled block schematic diagram of microcontroller based
Permanent Magnet Synchronous Motor (PMSM) drive.

PART B

Answer any two full questions, each carries 10 marks.

A motor-drive system has the following specifications:

Polar moment of inertia of motor-load system referred to the shaft, J = 5 kg-m?
Motor torque 1പ- 50 - 0.17, and Load Torque, 11 = 0.025N

where, “14 is the speed of the motor in rpm. Calculate the start-up time of the
drive.

Draw and explain the closed loop speed control scheme widely used in electric

drives.

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Duration: 3 Hours

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