16
|
State the main
disadvantage of the VR stepper motor.
|
|
Disadvantage
of VR stepper motor
- The
main disadvantage of the VR stepper motor is that it hasn’t any Detent torque
( which is necessary to retain the rotor at main position in the case of
power failure)
|
17
|
Explain the term :
Multi stack VR stepper motor
|
|
Multi stack VR
stepper motor
- It
consists of number of axially isolated sections or stacks along its axial
length.
- Each stack is excited by a separate winding.
|
18
|
Give reason : The
variable reluctance stepper motor is capable at high stepping rate.
|
|
Due
to high torque to weight ratio
|
19
|
State the other name
of permanent magnet step motor.
|
|
Stamped
construction or sheet metal step motor
|
20
|
Give reason : The PM
stepper motor is called as stamped step motor.
|
|
PM
stepper motor
- The
rotor of the PM consists of smooth cylindrical permanent magnet radially
magnetized with alternate N and S poles therefore it is also called as
stamped step motor.
|
21
|
Compare drive
circuit : Bipolar and Unipolar
|
|
Bipolar ( Monofilar )
- Single
winding per bobbin
- Drive
circuit requires in order to reverse the direction of current in the winding
- Positive
and negative supply or bridge inverter requires.
Unipolar ( Bifilar )
- Two
windings per bobbin
- Drive
circuit energized only one winding at a time
- Only
one power supply and two switches per bobbin requires to operate a motor
|
22
|
Which type of stator
and rotor does the Permanent magnet stepper motor consist of?
|
|
PM stepper motor
- Stator : It consists of wound
projecting poles.
- Rotor : It is made of
cylindrical permanent magnet.
|
23
|
State the salient
features of the PM stepper motor.
|
|
Features of PM
stepper motor
- High
detent torque as compared to VR stepper motor
- It
requires low power as compared to VR stepper motor.
- High
inertia
- Low
acceleration
- It
produces more torque / stator current as compared to VR stepper motor.
|
24
|
Which type of rotor
construction the hybrid stepper motor consists of?
|
|
Hybrid
stepper motor - Rotor
- The
rotor of the stepper motor is made of three sections.
- The
two outer sections are similar to variable reluctance rotor and in between a
magnet is placed.
- The
two outer sections are offset circumferentially from each other by one half
tooth pitch.
|
25
|
What is reason
behind the name ‘ Hybrid stepper motor ’?
|
|
Hybrid stepper motor
- The
rotor of the hybrid stepper motor is made of both combined variable
reluctance and permanent magnet therefore it is termed as ‘ Hybrid stepper
motor ’.
|
26
|
Describe the
function of permanent magnet rotor in the Hybrid stepper motor.
|
|
The
permanent magnet rotor provides good damping characteristics in the hybrid
stepper motor.
|
27
|
Which type of shape
the holding torque curve of the stepper motor consists of?
|
|
The
shape of the holding torque curve is inverted sinusoidal. It is graphically
representation of holding torque versus rotor displacement.
|
28
|
Which type of data
the specification sheet of a stepper motor consists of?
|
|
Specification
data sheet
- Voltage
- Number
of phases
- Maximum
Speed
- Maximum
holding torque
- Step
angle
- Step
accuracy
- Types
of drive : Unipolar and Bipolar
|
29
|
Explain the term :
Cogging torque or Detent torque
|
|
Cogging torque
- The
residual torque in the permanent magnet or hybrid stepper motor is called as Cogging torque.
|
30
|
At which condition
the torque versus rotor displacement curve is sinusoidal?
|
|
The
torque versus rotor displacement curve is sinusoidal below holding torque.
|
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