Inertia Ratio

Even though your system may meet speed/torque requirements, then inertia ratio of the system helps understand the ability to control the mechancics/load of the system. The overall settling time, system response to commanded changes, etc.

INERTIA RATIO = J load / J motor

• J load = inertia of load as seen by the motor.

• J motor = inertia of the rotor of the motor.

As a general rule of thumb for systems, we recommend for performance reasons that the Inertia Ratio be equal to or less than the following:
Stepper: 10
Servos: 10
DirectDrive: 50 to 100

The ideal Inertia Ratio is a 1:1 ratio. This is when the motor is the most efficient. Less that a 1:1 ratio is slightly less efficient that a 1:1 ratio.