1. STEPPER MOTOR J. Belwin Edward Assistant Professor Senior
School of Electrical Engineering
VIT University
Vellore

2. Applications Computer peripherals Textile industries IC fabrications
Robotics
Applications requiring incremental motion
Typewriters
Line printers
Tapedrives
Floppy disk drives
Numerically-controlled machine tools
Process control systems
X-Y plotters

3. Applications contd…. Commercial, military and medical applications
Mixing, cutting, striking, metering, blending
Application in manufacture of packed food stuffs
Application in manufacturing of commercial end
products
Production of science fiction movies.

4. Step Angle - β As small as 0.78o to 90o
Most commonly used – 1.8o, 2.5o, 7.5o, 15o
β = (Ns-Nr) x 360o = 360o
Ns.Nr mNr
Ns – No. of Stator poles (teeth)
Nr – No. of Rotor poles (teeth)
m - No. of stator phases

5. Resolution
Resolution = No. of steps/revolution
= 360o/β

6. Types
Variable Reluctance - VR
Permanent Magnet - PM
Hybrid

7. VR, PM and Hybrid types

8. Variable Reluctance ( VR) stepper motor
Wound Stator poles
Single Stack
Multiple Stack – smaller step angle
Rotor poles – ferromagnetic material
Direction – stator current polarity
Reluctance of the magnetic circuit formed by rotor and stator teeth varies with angular position of the rotor

9. Variable Reluctance stepper motor
Single Stack

10. VR – Multi stack

11. VR-Operation

12. Modes of operation –VR type
1-phase ON – full step operation
2-phase ON
Half-step – alternate 1-phase & 2-phase mode
Micro stepping

13. 2-phase ON mode

14. Half step mode

15. Half step operation

16. Permanent Magnet (PM) Stepper Motor

17. Permanent Magnet stepper motor
Wound Stator poles
Single Stack
Multiple Stack – smaller step angle
Rotor poles – permanent magnet
Rotor Shape - Cylindrical
Direction – stator current polarity

18. PM - operation

19. PM - operation

20. Modes of Operation – PM type
1-phase ON mode
2-phase ON mode
Half step mode

21. Modes of Operation – PM type

22. Hybrid Stepper Motor

23. Hybrid stepper motor Combination of VR and PM
Wound Stator poles – (similar to VR)
Single Stack
Multiple Stack – smaller step angle
Rotor poles – permanent magnet
Rotor shape – not Cylindrical
Direction – stator current polarity