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