An 8 stator pole design could have an air gap variation of up to twice as much as compared to the 16 pole design even if both motors were built with the same manufacturing capabilities.
However there are additional drawbacks to each stator design. Due to space constraints of the 16 pole design, manufacturers are only able to wind half as many turns when compared to an 8 pole design. Therefore, inductance is reduced by about half. Low inductance is mainly good for high speed applications. Torque will also be lower in the 16-pole design due to this constraint in space. With less space, there are less windings per pole (turns per coil). Typical 1.8° step motors use the 8-pole stator design, which explains for the higher torque but lower accuracy when comparing it to a 0.9 degree stepper motor.
However there are additional drawbacks to each stator design. Due to space constraints of the 16 pole design, manufacturers are only able to wind half as many turns when compared to an 8 pole design. Therefore, inductance is reduced by about half. Low inductance is mainly good for high speed applications. Torque will also be lower in the 16-pole design due to this constraint in space. With less space, there are less windings per pole (turns per coil). Typical 1.8° step motors use the 8-pole stator design, which explains for the higher torque but lower accuracy when comparing it to a 0.9 degree stepper motor.
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As shown above with the 12 pole design, more teeth can be added to the stator due to simple mathematics. The higher number of teeth allows for added torque and, because there are more poles, the air gap variation is not as large as the 8 pole design making the step accuracy better as well.
When step motors are designed into your next application, it would be wise to choose accordingly: traditional 0.9° stepper motor for high speeds and high accuracy, 1.8° stepper motor for more torque and less accuracy, and the 417 series 0.9° steppers for both torque and optimal accuracy.
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