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down again by an input variable with a negative sign. This reduces possible overshooting of
the output variable.
In this implementation, the digital 6RA80 can make use of its advantages over older analog
controls.
Technological controls with the SINAMICS DCM
Various options for technological controls can be implemented for the SINAMICS DCM.
These can be implemented on the basic module using free function blocks or the DCC.
Furthermore, SIMOTION can also be used.
Current / torque limitation control:
There is sometimes a requirement to limit to a certain speed and torque at the same time.
This cannot be implemented without further complications.
The following options for closed-loop control exists: Speed control, with the speed kept
constant at a certain speed setpoint and the current / torque is set to a suitable value, so that
the speed is kept constant.
Torque control, with the motor torque kept constant and the speed set to a precisely the
value that compensates for this torque while remaining constant.
The current limitation control or torque limitation control is a possible compromise. In the
armature setting range (no field weakening), the variables for the current and the torque are
equal (100% of field current). In the weak field range, the torque is kept constant and the
current setpoint necessary to maintain the constant torque in the weak field range is
calculated by division of the torque setpoint by the flux . See parameters p50169 and
p50170.
For this type of control, the speed setpoint is overdriven by a small percentage, say, 5% of
the additional speed setpoint. The drive would like to rotate faster but the speed is kept at the
somewhat lower actual value by the web. The speed controller goes to the torque limit. This
torque limit can now be set to the desired torque limit value by an external variable. Input of
the additional speed setpoint via the connector number set in p50645.
Input of the desired torque limit setpoint via the connector number set in p50605[0].
This type of control is often used for axial winder and tension controls.
With this torque limit at the overdriven speed controller output, control now results in
precisely the desired torque value.
If the material now tears, the speed controller will depart from the torque limit because of the
missing load torque of the web and the driver will not turn faster than the speed setpoint plus
the, for example, 5% additional overdrive setpoint. This prevents a high overspeed and the
resulting damage to the winder reel.
No additional option is required for this type of control.
Master-slave switchover
With this type of control, a variable-speed master drive and one or more torque-controlled
slave drives are used.
The possible applications are motors on a common shaft, e.g., for line shafts of printing
machines or DC motors with a common shaft (tandem drive) or if multiple drives are inputting
to a common transmission.
http://support.automation.siemens.com/WW/view/en/48957735
Load sharing control
If drives are coupled via a common web and they are to be controlled to a specific load
distribution across the motors, e.g. S roll drives on a foil plant or to implement a converter
tilting drive, load sharing control is used instead of master-slave switchover.
http://support.automation.siemens.com/WW/view/en/47216918