Stepper Motors Objective Questions & Answers
1. A variable reluctance stepper motor is constructed of ______________ material with salient poles.
a) Paramagnetic
b) Ferromagnetic
c) Diamagnetic
d) Non-magnetic
Answer: b
Explanation: A variable reluctance stepper motor is the motor that has motion in steps with respect to increase in time and constructed of ferromagnetic material with salient poles.
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
Explanation: Pole pitch is defined as the number of armature slots to the pole pitch and here this has been converted into degrees.
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
Explanation: Pulse per second is mathematically given as PPS = (Rpm/60)*(number of steps per minute).
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
Explanation: Step angle is defined as =(Ns-Nr)/(Ns+Nr)*360.
5. The rotor of a stepper motor has no
a) Windings
b) Commutator
c) Brushes
d) All of the mentioned
Answer: d
Explanation: The rotor is the rotatory part of the motor of a stepper motor and has no windings, commutator and brushes.
6. A stepping motor is a ____________ device.
a) Mechanical
b) Electrical
c) Analogue
d) Incremental
Answer: d
Explanation: A stepping motor is a motor in which the motion in the form of steps and is a incremental device i which as the time increases the steps are increased.
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
Explanation: The stator part of a motor is the stationary part of the motor and rotational speed of a given stepper motor is given by the step pulse frequency.
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
Explanation: In the half step operation of a Variable reluctance motor physical step resolution is multiplied by 2 and control signals appear to be digital rather than analog.
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
Explanation: A stepper motor is a motor in which the motion is in steps and it is an increemental device and may be considered as a digital to analog converter.
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
Explanation: Step angle is defined as =(Ns-Nr)/(Ns+Nr)*360 where Ns is the number of stator poles and Nr is the number of rotor poles.