MULTISTACK STEPPER MOTOR

•     As mentioned earlier, these are used to obtain small step size, typically ranging between

•     2 to 15°.

•     In a m stack motor, the motor is divided into a m number of magnetically isolated sections called stacks, along its axial length.

•     The m stacks of stator have a common frame while the rotors are mounted on a common shaft. The stators and rotors have the same number of poles (teeth).

•     The stator poles in m stacks are aligned while the rotor poles are shifted by (1/rn) of the pole pitch from one another.

•     All the stator windings in a stator stack are excited simultaneously hence each stator stack forms a phase.

•     So number of stator phases is equal to number of stator stacks. Generally three stack stepper motors are used.

•     The Fig. 7.10 shows the arrangement in three stack stepper motor along with shifting of the rotor poles by (1/3) of the pole pitch from one another.