Implement Winder Tension Control on SINAMICS DCM 6RA8031

Implement Winder Tension Control on SINAMICS DCM 6RA8031

This application note explains how to commission a winder (rewind/unwrap) drive based on the SINAMICS DCM 6RA8031-6DV62-0AA0 with a SIMATIC S7-1511 controller. It addresses the most common field question that arises during a retrofit: can the original strategy of armature-current torque regulation combined with diameter-dependent field-current (excitation) trimming be implemented in a modern SINAMICS DC drive, and which software or hardware option modules are required to do so without buying unnecessary licenses.

The reference hardware is a six-pulse two-quadrant unit with the standard SINAMICS Control Unit. The DCC (Drive Control Chart) winder example, shipped at no cost through Siemens Industry Online Support, contains a fully engineered winder DCC chart (diameter calculation, taper-tension, torque reference distribution, friction/ inertia compensation). The article walks through identifying the unit, installing the DCC option, acquiring the Winder example, deciding whether a DCC Engineering license is needed, wiring the S7-1511 PROFINET interface, and verifying tension at the load cell.

1. SINAMICS DCM Hardware Identification

The SINAMICS DCM product line is described in the official SINAMICS DC Converters product page and the SINAMICS DCM DC Converter Operating Instructions (PDF). The order number 6RA8031-6DV62-0AA0 follows the standard Siemens DC-converter mnemonic:

The SINAMICS DCM family uses a modular structure. The base unit ships with a Basic Operator Panel (BOP) and a CU320-2-based Control Unit. For most winder retrofits, no additional power-section hardware is required. Optional add-ons that may be required depending on the winder mechanics are listed in Section 6.

2. Winder Control Strategy Recap

The mechanical relationship that the winder must satisfy at every instant is:

F = (M − J · dω/dt) / r

where F is web tension, M is motor torque, J is total inertia referred to the motor shaft, dω/dt is angular acceleration, and r is the running roll radius. The field-retrofit is built on the natural properties of a separately-excited DC machine:

• Armature current ↔ torque (T = kT · Ia, with negligible field interaction at constant flux).
• Field current ↔ flux ↔ base speed (EMF Eb = kE · Φ · ω).

The original control circuit on the legacy drive does exactly that: a tension (or diameter) trim modifies the field setpoint, while the armature current loop closes against the load-cell reference. On the SINAMICS DCM this is realised by combining the standard armature current controller (closed at the firmware level) with a DCC chart that:

1. Calculates the running diameter from line-speed / winder-speed ratio, or accepts an external diameter sensor value.
2. Generates a field-current setpoint through a flux-profile table (constant-flux region, then field-weakening region) plus a tension-trim offset.
3. Adds taper-tension (linear tension reduction as diameter grows) when the application is a rewinder.
4. Builds a torque-reference setpoint from F_ref · r + M_accel + M_friction and feeds it to the armature-current setpoint input of the closed-loop speed/torque control.

3. SINAMICS DCC: What It Is, How It Is Installed

SINAMICS DCC (Drive Control Chart) is a Siemens engineering extension that adds a CFC (Continuous Function Chart) editor to the STARTER / Startdrive commissioning tool. The DCC option lets the user assemble signal-processing blocks (multipliers, integrators, function tables, state machines, etc.) inside the drive firmware, execute them in real time on the Control Unit, and interconnect them with the standard drive signals.

3.1 Installation procedure

1. Insert the STARTER installation medium. The same STARTER version that supports the SINAMICS DCM 6RA8031 (current: STARTER V5.x and Startdrive in TIA Portal V16 SP1 and later) must be used.
2. Select Custom / Expert installation.
3. Tick the option "CFC for SINAMICS Drives (DCC)". The installer also places the DCC libraries into the system and registers them with the STARTER toolbox.
4. Finish the installation and start STARTER. The DCC editor becomes available under the drive node → Configuration → DCC charts.

3.2 DCC license tiers

The DCC Engineering license is sold per workstation (floating license through the Siemens Automation License Manager). The exact order number is published in the Siemens catalog "PM 21" (DCM catalog) and in the catalog "ST 70" (SINAMICS drives). Confirm the actual order number through your local Siemens sales contact or the Siemens Industry Mall before ordering.

4. DCC Winder Application: Acquisition and Use

Siemens publishes the DCC Winder as an application example, which contains a DCC chart that implements the complete winder functionality (diameter calculator, taper tension, torque reference, inertia and friction compensation) plus the parameter list and a short commissioning document. To obtain the example:

1. Open the Siemens Industry Online Support portal.
2. Search for the entry "SINAMICS DCC Winder" or browse the application examples for SINAMICS DCM.
3. Download the ZIP archive that contains the STARTER project (*.dnx), the pre-compiled DCC chart, the parameter list, and the documentation PDF.

If the entry is not visible directly, request it from your local Siemens contact (or through the Siemens Industry Online Support feedback form). Siemens publishes several DCC Winder variants, one for each common winding layout:

4.1 Loading the example into the drive

1. Open the example project in STARTER.
2. Connect online to the SINAMICS DCM 6RA8031-6DV62-0AA0 via PROFINET or PROFIBUS.
3. Carry out a standard drive commissioning first (motor data, encoder, current limits, field current limits).
4. Open the drive in STARTER, navigate to Configuration → DCC charts, right-click and choose Import chart. Select the chart file from the example project.
5. Compile the drive project and load it to the device. STARTER automatically generates the DCC block parameters in the expert list.
6. Open the expert list and parameterise the winder application (see Section 8).

5. Required Additional Hardware

The 6RA8031-6DV62-0AA0 is delivered with a Control Unit that contains the basic analog and digital I/O plus the encoder and field-current interfaces required for a winder. No additional option boards are required for the winder functionality as such, but the following may be needed depending on the mechanical retrofit:

The CU320-2 used in the 6RA8031-6DV62-0AA0 has a fixed analog input for the load cell and a fixed analog input that the DCC chart can read as the diameter sensor signal. If both analog channels are needed (e.g. dancer position plus diameter sensor) and the built-in channels are already used, add a TM31 (one extra analog input and one extra analog output).

6. S7-1511 Integration Through PROFINET

The S7-1511 is configured in TIA Portal. The SINAMICS DCM is exposed in the TIA hardware catalog through its GSDML file. The integration sequence is:

1. Install the SINAMICS DCM GSDML into TIA Portal (Options → Manage general station description files (GSD)).
2. Add the SINAMICS DCM 6RA8031 device to the PROFINET topology. The default IP is assigned automatically by the IO controller.
3. Select a PROFIsafe or standard telegram. For a winder, the most common choice is a free telegram or Siemens telegram 1 for the basic speed/torque interface, with the additional DCC interconnection handled through BICO connectors mapped to PROFINET words (Telegram 999 in the SINAMICS DCM).
4. Place the SINAMICS DCM drive object in the S7 program. Use either direct I/O access (LAD/FBD PEW / PAW), the SINA_SPEED function block for speed-controlled operation, or the LAcycCom_Config block for acyclic parameter access (used for the DCC winder parameters).

The mapping of control word 1 (STW1) and status word 1 (ZSW1) is defined in the SINAMICS DCM Operating Instructions. Bit 0 of STW1 is ON/OFF1; bit 3 is Enable Operation; bit 11 enables the torque-controlled mode that the DCC winder chart uses. The winder-specific diameter, tension setpoint, and tension actual-value are mapped to the free connectors of telegram 999.

// Example: S7-1500 SCL snippet to send a winder command
// via PROFINET to the SINAMICS DCM
#DCM_PIW  := "SINAMICS_DCM"~>PEW;          // process input words
#DCM_PQW  := "SINAMICS_DCM"~>PAW;          // process output words
#DCM_PQW[0] := 16#047E;                       // STW1: ON/OFF1 + Enable + torque mode
#DCM_PQW[1] := REAL_TO_WORD(#Diameter_mm);  // free connector: diameter setpoint
#DCM_PQW[2] := REAL_TO_WORD(#TensionSet_N); // free connector: tension setpoint
#DCM_PQW[3] := 0;                            // free connector: ramp

7. Commissioning Procedure

1. Mechanical pre-checks. Verify motor nameplate, field voltage, encoder polarity, and that the load cell is mounted according to the manufacturer specification. Confirm the dancer / diameter transducer travel range.
2. Basic drive commissioning. In STARTER, run the offline → online → Automatic calculation sequence (drive data, motor data, encoder data, current controller, speed controller, field current controller). The standard tuning sequence of the SINAMICS DCM calculates the controller gains from the motor and encoder data.
3. Activate DCC. In STARTER, enable the DCC option: Drive → Configuration → DCC → Activate. Save and load to the device.
4. Import the winder chart. Right-click the DCC charts node, import the pre-compiled chart from the example project. Compile and load to the device.
5. Parameterise the winder. Open the expert list and populate the DCC parameters. Typical parameters are listed in Section 8.
6. Wire DCC connectors. Map the DCC chart outputs (torque setpoint, field setpoint) to the corresponding BICO inputs of the standard SINAMICS DCM control structure: p50681 (torque setpoint source), p50682 (field-current setpoint source). The exact connector numbers depend on the winder chart variant; the example project includes a wiring sheet.
7. PLC side. In TIA Portal, configure the PROFINET connection, build the program, and download.
8. Dry run, no web. Turn the drive on in speed-controlled mode first. Verify direction, maximum speed, ramp behaviour, and emergency stop. Switch to torque-controlled mode (STW1 bit 11) and verify the torque reference.
9. Dry run with web. Thread the web with the line stopped, then run the line at minimum speed. Verify the diameter tracking and the field-current behaviour in the trace.
10. Load test. Run a build-up cycle (unwind to rewind) and check tension stability at the load cell.

8. Winder Parameter Reference

The exact parameter numbers depend on the winder chart variant. The list below is the most common subset encountered on SINAMICS DCC Winder examples. Always cross-check against the documentation of the version you downloaded.

9. Control Structure Overview

The DCC chart contains the closed-loop tension controller, the diameter calculator, the field profiler, the friction / inertia compensator, and the torque-reference distribution. The SINAMICS DCM standard control closes the inner armature current loop and the field current loop. The PROFINET interface exchanges the load-cell reference, the actual tension, the diameter and the line speed with the S7-1511.

10. Verification

11. Troubleshooting Matrix

12. Field-Proven Commissioning Notes

• Run the speed-controller auto-tuning on an empty winder (no web, no roll) so the inertia is correct. Re-tune with the heaviest roll once the line is built up, and store the result in a parameter set that the DCC chart can switch.
• Tension-controller bandwidth should be at most 1/5 of the speed-controller bandwidth. The DCC winder chart implements a PI controller with limited output slew rate to prevent interaction with the speed loop.
• The first start-up is best done in open-loop diameter, constant-tension mode. Once the diameter is tracking correctly, switch to the closed-loop diameter sensor if the line has one.
• For tapered-tension rewinders, the taper table is set as a 2-point linear segment in the DCC winder chart. Verify the sign of the slope by running an empty roll to a built-up roll and observing the tension trace.
• Keep a STARTER trace of the field current, armature current, diameter, line speed and tension setpoint / actual. A 10-second, 100 ms sample rate covers most start-up transients.
• Save the working project to a versioned folder. Each parameter set change can be documented with a version number; the SINAMICS DCM supports eight parameter sets (p7000 …) that the S7-1511 can switch via PROFINET.

13. Frequently Asked Questions