MULTIPLE CHOICE QUESTIONS
Q.1 The series-parallel system of speed control of
series motors widely used in traction work gives a speed range of about
(A) 1 : 2
(B) 1 : 3
(C) 1 : 4
(D) 1 : 6
Q.2 In practice, regenerative braking is used when
(A) quick motor reversal is desired
(B) load has overhauling characteristics
(C) controlling elevators, rolling mills and printing
presses etc.
(D) other methods can not be used.
Q.3 Statement 1. A direct-on-line (DOL) starter is used
to start a small d.c. motor because
Statement 2. it limits initial current drawn by the
armature circuit.
(A) both statement 1 and 2 are incorrect
(B) both statement 1 and 2 are correct
(C) statement 1 is correct but 2 is wrong
(D) statement 2 is correct but 1 is wrong
Q.4 Ward-Leonard system of speed control is NOT
recommended for
(A) wide speed range
(B) constant-speed operation
(C) frequent motor reversals
(D) very low speeds
Q.5 Thyristor chopper circuits are employed for
(A) lowering the level of a d.c. voltage
(B) rectifying the a.c. voltage
(C) frequency conversion
(D) providing commutation circuitry
Q.6 An invertor circuit is employed to convert
(A) a.c. voltage into d.c. voltage
(B) d.c.voltage into a.c. voltage
(C) high frequency into low frequency
(D) low frequency into high frequency
Q.7 The phase-control rectifiers used for speed of
d.c. motors convert fixed a.c. supply voltage into
(A) variable d.c. supply voltage
(B) variable a.c. supply voltage
(C) full-rectified a.c. voltage
(D) half-rectified a.c. voltage
Q.8 If some of the switching devices in a convertor
are controlled devices and some are diodes, the convertor is called
(A) full convertor
(B) semiconvertor
(C) solid-state chopper
(D) d.c. convertor
Q.9 A solid-state chopper converts a fixed-voltage
d.c. supply into a
(A) variable-voltage a.c. supply
(B) variable-voltage d.c. supply
(C) higher-voltage d.c. supply
(D) lower-voltage a.c. supply
Q.10 The d.c. motor terminal voltage supplied by a
solid-state chopper for speed control purposes varies...........with the duty
ratio of the chopper
(A) inversely
(B) indirectly
(C) linearly
(D) parabolical