## 30/03/2020

### Stepper Motor Interview Question Answer - 3

Which type of stepper motor is generally operated by two phases?

• PM stepper motor

Whether the direction of the stepper motor depends upon polarity of stator current?

• The direction of the stepper motor is independent of polarity of stator current.

Which factors greatly affects the torque in the stepper motor?

• The torque in the stepper motor depends upon the step rate, types of drive and the drive current in the winding.

State the value of step accuracy of the step motor.

• 3 to 5 % of one step

Explain the term : Step position error

Step position error

• It is maximum positive or negative error when the stepper motor has rotated one step form its holding position.

Explain the term : Holding torque

Holding torque

• It is maximum torque developed by the stepper motor at standstill.

Explain the term : Detent torque

Detent torque

• It is maximum torque which can be applied to the shaft of the non – energized stepper motor without causing rotation.

Explain the term : Pull in torque and pull-out torque

Pull in torque

• It is maximum torque that can be applied to that shaft of a stepper motor without losing out of step.

Pull out torque

• It is maximum torque at which the stepper motor can start, stop and reverse the direction of rotation without losing out of step.

Explain the term : Accuracy

Accuracy

• It is difference between theoretical and actual rotor position expressed as a percentage of step angle.

Explain the term : Maximum slew rate

Maximum slew rate

• It is defined as maximum operating frequency of the stepper motor at no load.

Describe the importance of pull in and pull-out curve of the stepper motor.

Importance of Pull in curve

• It is area referred to as start – stop region of the stepper motor. It indicates the maximum frequency at which the step motor can start / stop.

Importance of Pull-out curve

• It is area referred to as slew region. It indicates the maximum frequency at which the motor operated without losing synchronism.

What is resonance frequency in the stepper motor?

Resonance frequency

• When an input pulse is given to the stepper motor, its rotor must accelerate then decelerate and finally stop.  This will cause oscillation, overshoot and vibrations. The speed at which the stepper motor does not run is known as resonance frequency.

How to eliminate effect of resonance in the stepper motor?

• The effect of resonance is eliminated by using mechanical dampers, drive circuit, electronic circuit or changing step angle.

State the applications of the stepper motor.

Applications

• Textile industries
• Typewriters, Line printers, Tape drives, Floppy disc drives, X – Y plotters
• IC fabrications
• Control in computer peripherals
• Commercial, medical and military applications