在siemens bridle t400的3.9章节说明里面看到如下描述：

The tension can be set in four different ways. With each method, the converter is operated in the “speed control” mode, i.e. vector control with speed actual value encoder.

1) Tension control (without actual value)
Torque-controlled tension setting for the speed controller output limitation. The speed controller is operated as a PI-controller and over-modulated with a Dv. The limitation of the speed controller corresponds to the tension torque.

2) Direct tension control (with actual value)
Torque-controlled tension setting for the limitation of the speed controller output with a supplement from the tension controller. The speed controller is operated as a PI-controller and over-modulated with a Dv. The  limitation of the speed controller corresponds to the tension torque. The tension controller corrects this limitation.

3) Direct tension control (with actual value)
Variant with additional torque

4) Expanded mass flow concept ( V_MODE )
The coiler is operated speed-controlled and receives supplementary setpoints from the thickness control.
The supply coiler or the S-roll are rigidly speed-controlled like a stand drive (Stand 0). This is used in tandem mills. The speed controller operates as a PI-controller with delayed setpoint for the I-component. The limitation of the speed controller is set to maximum motor torque.
The threading tension is controlled by TENS (master tension controller) via the gap control of the first stand.