PERMENANT MAGNET VARIABLE RELUCTANCE
PERMANENT MAGNET MOTOR
Cutaway diagram of a typical permanent magnet stepper motor.
Canstack rotor that is used in permanent magnet stepper motors.
VARIBLE RELUCTANCE STEPPER
• 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
• Since this type of motor does not have
permanent magnets, it cannot use the same
type of stepper controller as other types of
• The hybrid stepper motor is the most widely
used and combines the principles of the
permanent magnet and the variable
• Most hybrid stepper motors have two phases
and operate on the principle used to explain
the 12-step motor previously.
Hybrid stepper motor combines features of the permanent magnet
stepper and the variable reluctance stepper motors.
STAPPER MOTOR ADVANTAGE
• The rotation angle of the motor is proportional to
the input pulse.
• The motor has full torque at standstill (if the
windings are energized).
• Precise positioning and repeatability of movement
since good stepper motors have an accuracy of 3 to
5% of a step and this error is non-cumulative from
one step to the next.
• Excellent response to starting/stopping/reversing.
• Very reliable since there are no contact brushes in
the motor. Therefore the life of the step motor is
simply dependent on the life of the bearing.
• The stepper motors response to digital input pulses
provides open-loop control, making the motor
simpler and less costly to control.
• It is possible to achieve very low speed synchronous
rotation with a load that is directly coupled to the
• A wide range of rotational speeds can be realized as
the speed is proportional to the frequency of the