What are the load types of stepper motors?

There are four types of industrial automation motor loads:

Variable horsepower and constant torque
Variable torque and constant horsepower
Variable horsepower and variable torque
Positional control or torque control.

Variable horsepower and constant torque applications include conveyors, cranes, and gear-type pumps. In these applications, the torque is constant because the load doesn't change. The required horsepower may vary depending on the application, which makes constant speed ac and brushless dc motors a good choice.

An example of a variable torque and constant horsepower application is a machine rewinding paper. The material speed remains constant, which means the horsepower doesn't change. The load does change, however, as the roll diameter increases. 

In small systems, this is a good application for dc motors or a servo motor. Regenerative power also is a concern and should be considered when sizing the linear stepper motors or choosing the energy control method. 

AC motors with encoders, closed-loop control, and full quadrant drives may be beneficial for larger systems.

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