Special Electrical Machines Multiple Choice Questions
16. Though structurally similar to a control transmitter, a
control receiver differs from it in
the following way :
Ans - it has a mechanical damper on its
shaft
17. The control ........................ synchro has three phase winding both
on its stator and rotor.
Ans - differential
18. Regarding voltages induced in the three stator windings of a synchro, which
statement is
false ?
Ans - they are polyphase voltages.
19. The low-torque synchros cannot be used for
Ans - robot arm positioning.
20. Which of the following synchros are used for error detection in a servo
control system ?
(a) control transmitter
(b) control transformer
Ans - both
21. For torque transmission over a long distance with the help of electrical
wires only, which of the following two synchro’s are used ?
Ans - CX and CR
22. The arrangement required for producing a rotation equal to the sum or
difference of the
rotation of two shafts consists of the following coupled synchros.
(a) control transmitter
(b) control receiver
(c) control differential transmitter
Ans - all of the above.
23. Which of the following motor would suit applications where constant speed
is absolutely
essential to ensure a consistent product ?
Ans - permanent-magnet synchronous motor
24. A switched reluctance motor differs from a VR stepper motor in the sense
that it
Ans - rotates continuously
25. The electrical displacement between the two stator windings of a resolver
is
Ans - 90º
26. Which of the following motor runs from a low dc supply and has permanently
magnetized
salient poles on its rotor ?
Ans - permanent-magnet D.C motor
27. A dc servomotor is similar to a regular d.c. motor except that its design
is modified to cope with
(a) slow speeds
(b) static conditions
(d) both
28. One of the basic requirements of a servomotor is that it must produce high
torque at all
Ans - speeds
29. The most common two-phase ac servomotor differs from the standard ac
induction motor
because it has
Ans - higher rotor resistance
30. Squirrel-cage induction motor is finding increasing application in
high-power servo
systems because new methods have been found to
Ans - decouple its torque and flux.
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