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Multiple Choice Interview Questions On Special Motor Part 1

Ques.[1] A variable reluctance stepper motor is constructed of .................. material with salient poles.

(a) paramagnetic
(b) ferromagnetic
(c) diamagnetic
(d) non-magnetic
Answer: B

Ques.[2] In a three-stack 12/8-pole VR motor, the rotor pole pitch is

(a) 15º
(b) 30º
(c) 45º
(d) 60º
Answer: C

Ques.[3] A stepper motor having a resolution of 300 steps/rev and running at 2400 rpm has a pulse rate of— pps.

(a) 4000
(b) 8000
(c) 6000
(d) 10,000 
Answer: C

Ques.[4] If a hybrid stepper motor has a rotor pitch of 36º and a step angle of 9º, the number of its phases must be

(a)4
(b)2
(c)3
(d)6
Answer: A

Ques.[5] The rotor of a stepper motor has no

(a) windings
(b) commutator
(c) brushes
(d) all of the above.
Answer: D

Ques.[6] A stepping motor is a .................. device.

(a) mechanical
(b) electrical
(c) analogue
(d) incremental
Answer: D

Ques.[7] The rotational speed of a given stepper motor is determined solely by the

(a) shaft load
(b) step pulse frequency
(c) polarity of stator current
(d) magnitude of stator current. 
Answer: B

Ques.[8] Which of the following phase switching sequence represents half-step operation of a VR stepper motor ?

(a) A, B, C, A .......................
(b) A, C, B, A .......................
(c) AB, BC, CA, AB .......................
(d) A, AB, B, BC .......................
Answer: D

Ques.[9] A stepper motor may be considered as a .................. converter.

(a) dc to dc
(b) ac to ac
(c) dc to ac
(d) digital-to-analogue
Answer: D

Ques.[10] What is the step angle of a permanent-magnet stepper motor having 8 stator poles and 4 rotor poles ?

(a) 60º
(b) 45º
(c) 30º
(d) 15º
 Answer: B

Ques.[11] Wave excitation of a stepper motor results in

(a) microstepping
(b) half-stepping
(c) increased step angle
(d) reduced resolution.
Answer: B

Ques.[12] The torque exerted by the rotor magnetic field of a PM stepping motor with unexcited stator is called ..................torque.

(a) reluctance
(b) detent
(c) holding
(d) either (b) or (c)
Answer: D

Ques.[13] A single-stack, 4-phase, 6-pole VR stepper motor will have a step angle of

(a) 15º
(b) 30º
(c) 45º
(d) 90º
Answer: A
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