APJ ABDUL KALAM TECHNOLOGICAL UNIVERSITY
SECOND SEMESTER M.TECH DEGREE EXAMINATION, MAY 2016

Electrical & Electronics Engineering

(Electrical Machines, Power Control and Drives)
018186302 Electric Drives

Max. Mark: 60 Duration: 3 Hours

Answer anp two full quesfions from each Par!
PART A
1.A motor drives 2 loads. One has rotational motion. It is coupled to the motor through a
reduction gear ratio 0.1 and efficiency of 90%. The load has a moment of inertia of 10 kgm
and a torque of 10 Nm. Other load has translational motion and consists of 1000 KgiM to
be lifted up at a uniform speed of 1.5 m/s. Coupling between this load and motor has an 11

of 85%. Motor has an inertia of 0.2 kg-m 2 and runs at a constant speed of 1420 rpm.
Determine equivalent inertia referred to motor shaft and power developed by the

motor. (9)
2. a) Obtain the dynamic behaviour of separately excited de motor in constant flux mode,
during starting. (4)

b) A 220V 1500 rpm -SOA separately excited 0௦ motor with armature resistance of 0.5 Q
is fed from a 3+ full convertor .Available ac source has a line voltage of 440V, 50 Hz.
A star —delta connected transformer is used to feed the armature so that the motor
terminal voltage equals rated terminal voltage when converter firing angle is zero.
Determine the value of firing angle when motor is running at 1200rpm and rated torque.
(5)
3; Explain two quadrant operation of single phase full converter for continuous and

discontinuous mode of operation and obtain the boundary between two modes. (9)

PART 8
4. a) Draw and explain the implementation of closed loop v/f control strategy with slip
compensation for induction motor drive. (6) b) With phasor diagram, explain the

principle of vector control in three phase induction motor. (6)