Special Electrical Machines Multiple Choice Questions
1. A single-stack, 4-phase, 6-pole VR stepper motor will have a step angle of
Ans - 15ºFormula Used:
2. In a three-stack 12/8-pole VR motor, the rotor pole pitch is
Ans - 45º
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3. A three-stack VR stepper motor has a step angle of 10º. What is the number of rotor teeth in each stack ?
Ans - 12
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
Ans - 4
5. What is the step angle of a permanent-magnet stepper motor having 8 stator poles and 4 rotor poles ?
Ans - 45º
6. A stepping motor is a ________ device.
Ans - incremental
7. Operation of stepping motors at high speeds is referred to as
Ans - slewing
8. Which of the following phase switching sequence represents half-step operation of a VR
stepper motor ?
Ans - A, AB, B, BC ....and so on.
9. The rotational speed of a given stepper motor is determined solely by the
Ans - step pulse frequency
10. A stepper motor may be considered as a .................. converter.
Ans - digital-to-analogue
11. The rotor of a stepper motor has no
(a) windings
(b) commutator
(c) brushes
Ans - all of the above.
12. Wave excitation of a stepper motor results in
Ans - half-stepping
13. A stepper motor having a resolution of 300 steps/rev and running at 2400 rpm has a pulse
rate of— pps.
Ans - 6000
14. The torque exerted by the rotor magnetic field of a PM stepping motor with unexcited stator is called ..................torque.
(a) detent
(b) holding
Ans - either (a) or (b)
15. A variable reluctance stepper motor is constructed of .................. material with salient poles.
Ans - ferromagnetic
Next Page - MCQ ( Q16-30 )
understood clearly
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