## 24/12/2021

### Multi Stack Variable Reluctance ( VR ) Stepper Motor

The construction, step angle, advantages and disadvantages of variable reluctance stepper motor is given in this theory.

# Construction of Variable Reluctance Stepper Motor

• Figure shows four stack variable reluctance stepper motor.
• We can achieve low step angle by multi stack variable reluctance stepper motor.
• The stator frame and rotor shaft are common in the multi stack variable reluctance stepper motor.
• Each stack is parallel to shaft axis and its excitation is given by separate winding.

## Step angle in Variable Reluctance Stepper Motor

• The number of stator poles is equal to number of rotor poles.
• If there are 20 teeth in the four stack VR stepper motor, the step angle becomes 4.50.
• Step angle ( Θ ) = 3600 / S

Where S = 4 ( Number of stacks ) × 20 ( Number of rotor teeth )

= 80

• Therefore, Step angle ( Θ ) = 3600 / S = 3600 / 80 = 4.50

• Higher stepping rate is possible
• Low inertia of rotor
• Light weight
• Freely rotation of rotor