Servo systems are used to control a load. In order for the servo to do this
properly per the system requirements, it must be appropriately sized. The servo
system needs to be able to provide the required torque, the required speed, and
the required accuracy in order for the entire system to perform as designed.

The type of load, the mechanical transmission, the duty cycle of the system
(how often it starts and stops its operation), how fast the system needs to go
during operation, and how accurate the system needs to be all play a part in
deciding what system should be selected. Generally when replacing an existing
servo system, the same power size can be selected even though the motor may
be a different physical size.

When deciding on a servo system for a new application, sizing software is often
used to help the process. This software contains all the required mathematical
formulas used to determine the inertia of the load which is a critical parameter
used in selecting a servo.