2-Phase and 5-Phase Step Motor Comparison

Synchronism

Because the 5-phase motor only moves 0.72° per step it is nearly impossible for the 5-phase motor to miss a step due to overshooting/undershooting. A motor will lose synchronism or miss a step when the teeth on the rotor don't line up with the correct teeth on the stator. What will cause the teeth not align properly? First, in order for a rotor tooth to not align properly another tooth must have aligned where it was supposed to. In order for this to happen the rotor must have either overshot (went past the correct stator tooth) or undershot (not moved far enough to line up with the correct stator tooth) by more than 3.6°. Why 3.6°? Well, because the rotor teeth are magnetically attracted, the correct tooth needs to be more than halfway between the teeth on the stator to align (7.2° between rotor teeth divided by 2 gives you 3.6°). So when the rotor overshoots the correct stator tooth by more than 3.6° the next tooth will align in its place, causing you to skip a step. Conversely, if the rotor fails to move more than 3.6° the current rotor tooth will remain lined up with the stator tooth and the rotor will not rotate, meaning you missed a step.

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