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STEPPER MOTORJ. Belwin Edward
Assistant Professor SeniorSchool of Electrical Engineering
VIT UniversityVellore
Applications
Computer peripheralsTextile industriesIC fabricationsRoboticsApplications requiring incremental motion
TypewritersLine printersTapedrivesFloppy disk drivesNumerically-controlled machine toolsProcess control systemsX-Y plotters
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.
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
Resolution
• Resolution = No. of steps/revolution = 360o/β
Types
•Variable Reluctance - VR•Permanent Magnet - PM•Hybrid
VR, PM and Hybrid types
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
Variable Reluctance stepper motor
Single Stack
VR – Multi stack
VR-Operation
Modes of operation –VR type
• 1-phase ON – full step operation
• 2-phase ON• Half-step – alternate 1-phase & 2-phase mode
• Micro stepping
2-phase ON mode
Half step mode
Half step operation
Permanent Magnet (PM) Stepper Motor
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
PM - operation
PM - operation
Modes of Operation – PM type
• 1-phase ON mode• 2-phase ON mode• Half step mode
Modes of Operation – PM type
Hybrid Stepper Motor
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