It works on the principle of ‘variable reluctance’ and doesn’t have any permanent magnet either in the rotor or in the stator. The stator and the rotor are made up of silicon steel stamping with inward and outward projected poles, respectively. There are odd or even number of teeth or poles on the stator and each stator pole has field coil as an exciting coil.
The number of stator and rotor poles is not same so that the motor has self- starting capability. However, the width of teeth in both rotor and stator is the same.
Multi-stack-variable reluctance-stepper motor-
This type of stepper motor is also known as cascade type stepper motor. It is used to achieve small step sizes that range from 2 to 15 degrees. Usually, three stacks are common, but it can employ 7 stacks at a maximum.
The multi-stack variable reluctance stepper motor can be considered as an identical single stack variable reluctance stepper motor mounted on a single shaft. There is same number of poles in stator and rotor in multi-stack variable reluctance stepper motor.
Hybrid stepper motor-