Stepper Motors Flashcards
What is a stepper motor
a rotor and stator that moves in discrete rotary steps in fixed angles
What is the basic principle behind a stepper motor
converts electrical impulses to discrete mechanical movements, one pulse per step
what does a stepper motor require
requires an electrical converter and a control system
shaft speed and direction of rotation are dictated by…
sequencing and frequency of input impulses
What conditions are needed for precise open loop control
- non-accumulative position-error
- known position by counting input step impulses
- torque
what 3 types of stepper motors are there
Variable reluctance (VR) Permanent magnet (PM) Hybrid
in VR what causes the rotor motion
minimisation of magnetic reluctance between rotor and stator poles
what is the rotor made of in VR
soft, non-magnetised iron
what is the stator made of and what does it have in VR
made of soft-iron with phase coils
in PM what causes rotor movement
electrical circuit switching the stator poles’ polarity (-1,0,1). causes the rotot PM field to match induced stator field and reach stable equilibrium (detent position)
in PM what step angles are possible?
90 and 45
in Hybrid how does the rotor move
combines principles of VR and PM:
axially magnetised coreand toothed motor
what are the benefits of hybrid
- better holding detent
- better dynamic torque characteristics
- concentrate air gap flux
- very small step size
what step size range is hybrid capable of and how many steps per rev
0.9-3.6 and 100-400steps per rev
