Stepper Motors: Operation Modes

Stepper motors can be operated in four different operation modes:

Pictures below show the execution of a step, moving the rotor by 90° (simplified, 2 poles only).

 

Full step operation

This is the most common operation mode.
Current flows through both windings. Rotor magnet turns and aligns along the resultant magnetic field. Picture shows an operation of one full step of 90°.

stepper motors arrow  stepper motors

 

Applicational notes:

  • Highest output power versus motor size. As full winding coil material is utilized, current losses are low.
  • Simplest driver circuitry.
  • Step angles can be slightly different, resulting from any difference between both stator systems.

 

Half step operation

Current flows alternately through both windings and through one winding only.
Step angle is half of full step.
Picture shows an operation of two half steps, both 45°.

stepper motors

 

Applicational notes:

  • Step angle resolution is doubled.
  • Smoother running at low step frequencies (clock rates).
  • Lower torque when one winding powered up only (running torque as well as holding torque). *

&* This torque can be increased by applying higher current (current thermally permissible is by factor √2).
But due to iron saturation the increase of torque might be less.
This mode is called “compensated half step operation”.
Disadvantage: Driver circuitry is more complex.

 

Wave mode operation

Current generally flows through one winding only.
Step angle resolution is same as for full step operation.
Picture shows an operation of one step of 90°.

stepper motors  arrow stepper motors 

 

Applicational notes:

  • This mode can be applied, if current supply is a limiting factor (battery supply).
    It generates maximum torque with minimum current, but provides lower torque.
  • Lower output power versus motor size compared to 2 winding full step operation.
  • Less step angle distortion resulting from stator system differences.

 

Microstepping operation

Smaller step angles can be commanded by variation of the current level.
This requires a more complex driver circuitry.

Applicational notes:

  • Smoother running at low step frequencies (clock rates).
  • Step angle resolution can be increased, but step angle accuracy not so much.