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

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