CS/B.TECH(PWE)/SEM-8/PWE-803B/2012
2012
ELECTRIC DRIVES
Time Allotted : 3 Hours Full Marks : 70
The figures in the margin indicate full marks.
Candidates are required to give their answers in their own words
as far as practicable.
GROUP – A
( Multiple Choice Type Questions )
1. Choose the correct alternatives for any ten of the following :
10 × 1 = 10
i) The field control scheme of DC separately excited motor
is applied when
a) controlling the speed below base speed
b) controlling the speed above base speed
c) stopping the motor from running
d) none of these.
ii) In a controlled rectifier the voltage is controlled by
changing
a) the duty cycle b) firing angle
c) both (a) and (b) d) none of these.
iii) A motor driving a passive load is said to be steady state
stable if
a) 
> b)
c) < d) none of these.
iv) In static Kramer drive method
a) slip power can flow in both directions
b) slip power can flow only in one direction
c) slip power cannot flow
d) none of these.
v) Viscous friction is
a) directly proportional to the speed of the motor
b) directly proportional to the square of the speed of
the motor
c) inversely proportional to the speed of the motor
d) not related to the speed of the motor.
vi) In an induction motor drive the regenerative braking
takes place when
a) the rotor rotates in the same direction as that of
stator magnetic field
b) the rotor speed equals synchronous speed
c) the rotor speed is greater than synchronous speed
d) none of these.
vii) The speed-torque characteristics of a DC shunt motor is
a) hyperbolic in nature
b) parabolic in nature
c) a straight line with negative slope
d) none of these.