Motor selection

The motor is selected on the basis of the required torque which is defined by the application, e.g. traveling drives, hoisting drives, test stands, centrifuges, paper and rolling mill drives, feed drives or main spindle drives. Gear units for movement conversion or for adapting the motor speed and motor torque to the load conditions must also be considered.

As well as the load torque which is determined by the application, the following mechanical data are among those required to calculate the torque to be provided by the motor:

• Masses to be moved
• Diameter of the drive wheel/diameter
• Leadscrew pitch, gear ratios
• Frictional resistance data
• Mechanical efficiency
• Traversing paths
• Maximum velocity
• Maximum acceleration and maximum deceleration
• Cycle time

You must decide whether synchronous or asynchronous motors (induction motors) are to be used.

Synchronous motors should be selected for compact construction volume, low rotor moment of inertia and therefore maximum dynamic response.

Asynchronous motors can be used to increase maximum speeds in the field-weakening range. Asynchronous motors (induction motors) for higher power ratings are also available.

The following factors are of prime importance during configuration:

• The line supply configuration, when using specific types of motor and/or line filters on IT systems (non-grounded systems)
• The ambient temperatures and the installation altitude of the motors and drive components

The motor-specific limiting characteristics provide the basis for defining the motors.

These define the torque or power characteristic over speed and take into account the motor limits based on the DC link voltage of the Power Module or Motor Module. The DC-link voltage in turn is dependent on the line voltage and, with multi-motor drives, on the type of Line Module.

Typical speed/power graph for asynchronous motors

Torque characteristics of synchronous motors

For detail engineering information, please refer to the motor configuration manuals.

An updated overview of configuration manuals is available in a number of languages on the Internet at: http://www.siemens.com/motioncontrol

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