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2-Phase
and 5-Phase Step Motor Comparison
Accuracy
/ Repeatability
Accuracy has two components,
electrical and mechanical. Electrical error is caused by phases
being out of balance. For example, the motor's winding resistance
has a spec of ± 10%, it is possible that although the motor
is rated at 10W, one phase could be 9.2W and another phase could
be 10.6W. This difference between the phases would cause the rotor
to align more towards one phase than another.
There are several
components to mechanical error, the major one is tooth configuration.
Although the teeth on a motor are supposed to be square, the stamping
process and age of the die can cause some of the teeth, or portions
of the teeth to be rounded. Instead of the magnetic flux flowing
directly, it can flow elsewhere when the teeth are rounded. So these
factors contribute to the accuracy of the motor.
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A
5-phase motor is most accurate every 10th step and
nearly perfect every 500th step in full step mode.
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Using a Full-Step drive, a 2-phase motor repeats states every 4th
step, while in a 5-phase motor the states repeat every 10th step.
Any electrical error caused by imbalances in the phases is negated
every 4th step in a 2-phase and every 10th
step in a 5-phase, leaving only mechanical error.
Once the motor
completes a full 360° rotation, the same tooth is now lined
up at the original starting point, eliminating mechanical error.
Since a 2-phase motor takes 200 steps per revolution it is almost
perfect every 200 steps, while the 5-phase motors take 500 steps
per rev and are nearly perfect every 500 steps.
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