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October 3, 2006

Stepper Motor Sizing

Filed under: Stepper Motors — mota @ 4:20 pm

Load Torque + (Acceleration Torque x Inertia) will give you the correct result for choosing a stepper.

Inertia = (Rotor Inertia + Load Inertia).  Formulas for calculating load inertiaFormulas for calculating torque.

A rule of thumb for choosing a stepper based on inertia ratios is to choose a rotor inertia that is not less than 1/10 of the load inertia (10:1 ratio, load to rotor) and not less than 1/3 (3:1 ratio, load to rotor) of the load inertia for quick acceleration/deceleration moves.  Use a gearhead if your load inertia ratio is too high.  Formula for choosing a gearhead for inertia ratio: Inertia Ratio = Total Inertia / Rotor Inertia * Gear Ratio^2. 

There is one exception: the AlphaStep series uses a resolver for closed-loop control so you can choose motors with 30:1 or 9:1 load to rotor inertias without losing stalling.


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