13-12-2012, 06:25 PM
Stepper Motors
Stepper Motors.ppt (Size: 100.5 KB / Downloads: 110)
A stepper motor is a “pulse-driven” motor that changes the angular position of the rotor in “steps”
Define
β = the step angle (per input pulse)
Resolution = the number of steps/revolution
θ = total angle traveled by the rotor
= β X # of steps
Variable-Reluctance Stepper Motor
Principle of Operation:
Reluctance of the magnetic circuit formed by the rotor and stator teeth varies with the angular position of the rotor
Here, energize coils A and A’ (Phase A)
Rotor “steps” to align rotor teeth 1 and 4 with stator teeth 1 and 5
Typical Switching Circuit
Decoder provides logic output to turn QA On/Off
Amplifier A “conditions” the logic pulses
When QA turns On, it conducts current in the motor phase A winding
When QA turns Off, D and RS conduct current to “discharge” the phase winding