Inertia

The "inertia" is a quantity that prevents an object from changing its state of motion, and in a rotating body, it indicates the difficulty of turning or stopping. Unit is kg·m².

Inertia Visualized

When driving a rotating object that serves as a load, the acceleration and deceleration torques increase in proportion to the value of the inertia.
In the figure below, assuming that the two wheels have the same mass, the one with the larger diameter has a larger inertia.

Motor Selection and Inertia

For motors and gears, permissible inertia and numerical values are provided to ensure normal operation and to prevent damage. As a precaution in selection, the following guideline should be used.
If the load inertia is large, it may be possible to use a gearhead to reduce the speed. Through the gearhead, the inertia applied to the motor shaft is reduced by the square of the speed reduction ratio. As an example, if the gear speed reduction ratio is 2, the rotation speed is halved and the motor can drive a load four times its permissible inertia.