Variable Reluctance Stepper Motor : Construction & Working

 

Variable Reluctance Stepper Motor

In the VR stepper motor, the stator consists of winding whereas the rotor has salient poles. The position of rotor depends upon magnetic reluctance between stator and rotor therefore it is called as – Variable reluctance stepper motor.

DC Servo Motor : Characteristics

• The construction of DC Servo motor is similar to that of separately excited DC Motor or Permanent Magnet DC Motor. 
• The speed control of DC Servo motor is done by armature voltage control.  

Permanent Magnet Stepper Motor

 

Permanent magnet ( PM ) Stepper Motor

• The stator of the PM stepper motor consists of two project poles which is wound by separate windings. 
• The rotor is made of permanent magnet. 

Hybrid Stepper Motor

 

The characteristics of Hybrid stepper motor is combined that of variable reluctance ( VR ) stepper motor and permanent magnet ( PM ) stepper motor.

Construction

• Its stator is similar to that of single stack VR stepper motor. 
• The phase winding of stator is either Mono-filar or Bifilar. 

Multi Stack Variable Reluctance ( VR ) 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 has common frame and rotor has common shaft in the multi stack variable reluctance stepper motor. 

Micro-stepping in Stepper Motor

 

Principle of Micro-stepping

• The rotor of the stepper motor does not rotate smoothly in the half step as well as full step operation but rotor rotates with some jerk when step angle changes.  
• The operation of stepper motor with micro step driving result in less vibration and low noise.  

Construction & Working of PMDC Motor

 

Principle

‘Interaction between current carrying conductor and rotating magnetic field in the rotating machine produces torque. ’ The construction of Permanent Magnet DC Motor is similar to that of DC Motor except the stator of PMDC motor is made of permanent magnet in place of field winding.