| Motor type | Linear | Rotary | Direct drive | Vacuum |
|---|---|---|---|---|
| Servo motor | with spindle | Yes | Yes | No |
| Outer rotor motor | with spindle | Yes | Yes | No |
| Kit motor | No | Yes | Yes | No |
| Torque motor | No | Yes | Yes | No |
| Linear motor | Yes | No | Yes | Yes |
Electric drives with theoretically unlimited travel are available in many variants. A conventional servomotor can rotate endlessly in one direction. With a linear motor , a corresponding number of magnetic rails are required for the linear travel path.
Another distinguishing feature is the motor design. Torque motors, for example, have a very high torque. Alternatively, motors can also be designed for a high speed. The external rotor is a suitable example here.
The place of use then plays a decisive role in the selection. In moving or narrow systems, the housing is dispensed with and the kit motor (rotor and stator) is installed directly. This reduces weight and saves space. In other cases, a housing makes sense as it protects against dirt and other influences.
The use of a stepper motor offers several advantages. The speed can be easily determined and controlled by remembering that the speed corresponds to steps per revolution divided by the pulse frequency. Stepper motors can also perform fine incremental movements and do not require a feedback encoder. They are therefore operated in an open control loop. Stepper motors also have high acceleration and non-cumulative positioning error. In addition to excellent low speed and high torque characteristics without gear reduction, stepper motors can also be used to hold loads in a stationary position. In this case they will not overheat. All stepper motors can be operated in a wide speed range.
