Types of Stepper Motors
Three basic types of stepper motors include the permanent magnet motor, the variable re-luctance motor, and the hybrid motor, which is a combination of the previous two.
The rotor for the permanent magnet motor is called a canstack rotor. The canstack rotor shows that the permanent magnet motor can have multiple rotor windings, which means that the shaft for this type of stepper motor will turn fewer degrees as each pulse of current is received at the stator. For example, if the rotor has 50 teeth and the stator has 8 poles with 5 teeth each (total of 40 teeth), the stepper motor is able to move 200 distinct steps to make one complete revolution. This means that shaft of the motor will turn 1.8° per step. The main feature of the permanent magnet motor is that a permanent magnet is used for the rotor, which means that no brushes are required. The drawback of this type of motor is that it has relatively low torque and must be used for low-speed applications.
The variable-reluctance motor does not use permanent magnets, so the field strength can be varied. The amount of torque for this type of motor is still small, so it is generally used for small positioning tables and other small positioning loads. Since this type of motor does not have permanent magnets, it cannot use the same type of stepper controller as other types of stepper motors.
The hybrid stepper motor is the most widely used and combines the principles of the permanent magnet and the variable reluctance motors.
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