The Siemens SIMOREG 6RA7085-6DS22-0 is a fully digital DC MASTER converter from the legacy 6RA70 series, sized for the 600 A armature current class. In extruder service the unit normally follows a master speed reference, applies a torque (current) limit, and reports both shaft speed and armature current to the operator panel or to a higher-level PLC. This reference documents the shortest practical path from an unconfigured unit to a running extruder using only the integrated PMU/OP1S operator panel, an external potentiometer for the speed setpoint, and the drive's own analog outputs for indication. The procedure covers motor data entry, analog reference scaling, current limit, feedback wiring, manual speed controller optimization (the auto-optimization run is unsafe for a coupled gearbox load), and verification.
1. Drive Identification and Hardware Ratings
Before applying power, confirm the unit physically matches the order code on the rating plate. The 6RA7085-6DS22-0 designation decodes as follows within the SIMOREG 6RA70 family:
| Code segment | Meaning |
|---|---|
| 6RA70 | SIMOREG DC MASTER, fully digital, BICO parameter system |
| 85 | Frame size / current class (600 A armature, 30 A field typical) |
| 6 | Three-phase 400 V / 460 V armature supply class |
| D | Field supply configuration (single-quadrant field) |
| S22 | Build / option suffix (verify against rating plate) |
| 0 | Standard firmware, no special options |
Cross-check the rating plate values (armature current, field current, line voltage, firmware version) against the cabinet drawing and the SIMOREG 6RA70 documentation on the Siemens Industry Online Support portal before commissioning. The EPROM label inside the door also reports the firmware build, which determines the available parameter set.
2. Required Tools and Materials
- OP1S operator panel (or the integrated PMU three-key pad on the basic unit)
- Insulated screwdrivers for terminal blocks X1–X4 (digital), X6/X7 (analog), X9 (field)
- Calibrated 10 kΩ multi-turn potentiometer for the speed reference, or 4-20 mA source
- Two panel meters (analog or digital) for current and speed indication
- Hand tachometer or strobe for mechanical speed verification on first run
- DC clamp meter or use of the internal 600 A / 60 mV shunt for armature current verification
- Copy of the SIMOREG 6RA70 parameter list (function diagrams and parameter manual) from Siemens Industry Online Support
3. Control Terminal Layout (Standard CUD1 Board)
All low-voltage wiring lands on the front-access terminal strip. The exact pinout depends on the CUD1 / CUD2 option board installed; the drawing inside the cabinet door is the only authoritative source. Standard assignments for the 6RA7085-6DS22-0 with the stock CUD1 board are:
| Terminal | Signal | Function in this application |
|---|---|---|
| X1-1, X1-2 | Digital input 1 (enable / ON) | Wire to the contactor string; high = release |
| X1-3 | Digital input 2 (fault reset) | Connect to a normally-open pushbutton |
| X1-7, X1-8 | Digital output 1 (ready) | Connect to the operator's "drive ready" lamp |
| X2-1, X2-2 | Speed actual value (analog tacho) | Connect to the analog tacho (skip if using EMF feedback) |
| X3-1, X3-2 | Encoder channel A/B | Connect to the optional pulse encoder if used |
| X4-A, X4-B | Serial RS485 (USS) | Optional link to a higher-level PLC or SCADA |
| X6-1, X6-2 | Main setpoint (analog input 1) | Connect to the wiper of the 10 kΩ potentiometer |
| X6-3, X6-4 | Analog input 2 | Current-loop input, e.g., for current limit override |
| X7-1, X7-2 | Analog output 1 (current) | Connect to the panel ammeter (0-10 V proportional to armature current) |
| X7-3, X7-4 | Analog output 2 (speed) | Connect to the panel tachometer |
| X9-1, X9-2 | Field output (F+, F-) | Field winding of the DC motor |
4. Parameter Structure, Access, and BICO Routing
SIMOREG 6RA70 uses the BICO (Binector / Connector) parameter system. Numbers beginning with P are write parameters (setpoints), numbers beginning with r are read-only actual values, and numbers beginning with n are binectors/connectors used for signal routing. Pxxx(yy) denotes parameter Pxxx, index yy. Most commissioning parameters are protected until you open the parameter set with the access key.
- On the OP1S, navigate to P051.
- Set P051 = 21 to enable open access for the commissioning engineer.
- Set P052 to select the parameter set you want to edit (set 1 is the default active set).
- To put the drive back into production, set P051 = 0 to lock the parameter set. This prevents an operator from accidentally changing commissioning values.
5. Motor Data Entry
Before any speed controller optimization, the motor nameplate values must be written into the drive. The auto-optimization run uses these to compute the firing angle, the field-weakening breakpoint, and the controller defaults. Manual optimization uses them to size the test pulses.
| Parameter | Meaning | Extruder example (600 A motor) |
|---|---|---|
| P100 | Rated armature current (A) | 600 |
| P101 | Rated armature voltage (V) | 460 |
| P102 | Rated field current (A) | Read from nameplate, e.g., 25 |
| P103 | Minimum field current for field-weakening (A) | 0.5 × P102 typical |
| P104 | Speed at end of constant-torque range (rpm) | Nameplate base speed, e.g., 1500 |
| P105 | Maximum speed (rpm) | Mechanical limit, e.g., 1750 |
| P106 | Armature resistance (mΩ) | From motor data sheet |
| P107 | Armature inductance (mH) | From motor data sheet |
| P108 | Field resistance (Ω) | From motor data sheet |
Enter the field current last because the field regulator cannot pre-magnetize correctly until the field data is in the converter. Verify P102 against the motor's actual field terminal current using a clamp meter on the field lead at the X9 terminals before proceeding.
6. Speed Reference from an External Potentiometer
The 6RA70 expects the main speed setpoint on its first analog input by default. The task is to connect the potentiometer to the right terminals and tell the drive which input to use.
- Wire the 10 kΩ potentiometer: wiper to X6-1, one end to X6-2 (internal +10 V reference), other end to X6-3 (internal 0 V reference). For 4-20 mA operation, loop-power the input and select current mode in P401.
- Set P401 to the desired mode: 0 = voltage 0–10 V (default), 1 = current 0–20 mA, 2 = current 4–20 mA.
- Set P100 (speed setpoint source) to the connector of analog input 1 (typically K0001 in the BICO list for the stock CUD1 build). The exact connector number depends on the firmware build; the OP1S parameter help shows the available connectors.
- Set the maximum speed at full-scale reference with the speed setpoint normalization parameter (P113/P114 in the 6RA70 firmware). Verify by rotating the pot to maximum and reading r001 (speed setpoint after ramp) on the OP1S.
Test the reference chain with the enable signal OFF. The setpoint on the OP1S should track the pot smoothly from 0 to 100% of the maximum speed. If the response is inverted, swap the connections to X6-2 and X6-3.
7. Current Limit Configuration
The 600 A armature rating of this frame allows continuous operation up to the nameplate current, with brief excursions into the overload region defined by the i²t integrator. For an extruder the load is steady but the cold-start torque is high, so the current limit is typically set to 110–130% of the rated armature current.
| Parameter | Meaning | Recommended value |
|---|---|---|
| P150 | Positive torque limit (system 1) | 110–130% of P100, e.g., 700 A |
| P151 | Negative torque limit (system 1) | Match P150 unless the extruder forbids reverse |
| P152 | Positive torque limit (system 2) | Same as P150 if only one parameter set is used |
| P153 | Negative torque limit (system 2) | Match P152 |
| P154 | Torque limit source | Fixed value (default) |
| P155 | Additional torque limit | 100% for a 6-quadrant non-regenerative frame |
For an extruder that must never run in reverse, set the negative torque limits to 0% or wire a digital input to enable/disable the reverse direction in the parameter-set bit field. Verify on the rating plate whether the 6RA7085-6DS22-0 is a two-quadrant (6DS) or four-quadrant (6DF) frame before assuming regeneration is possible.
8. Speed and Current Feedback Indication
Two analog outputs on terminal block X7 are used in this application: one to drive a panel ammeter, one to drive a panel tachometer. The outputs are 0–10 V referenced to drive common and can drive a 10 mA load directly.
| Parameter | Meaning | Value for extruder indication |
|---|---|---|
| P740 | Analog output 1 source (connector) | Armature current actual (% of P100) |
| P741 | Analog output 1 normalization | 10.0 = 100% of P100 (600 A) = 10 V out |
| P742 | Analog output 2 source | Speed actual (% of P105) |
| P743 | Analog output 2 normalization | 10.0 = 100% of P105 (e.g., 1750 rpm) = 10 V out |
To scale a 0–10 V panel meter directly in amperes, use a 0–1 mA movement with a 10 kΩ series resistor so the meter reads 0–1000 mA full-scale. Relabel the scale plate as 0–600 A. For 4–20 mA transmission to a higher-level PLC, drop a 500 Ω resistor across the output to convert 0–10 V to 0–20 mA, or use the USS protocol on terminals X4-A / X4-B and map r001 / r002 into USS register words.
9. Manual Speed Controller Optimization
The auto-optimization run is by far the fastest path to a working speed loop — it injects test signals, measures the motor response, and sets P600 (Kp) and P601 (Tn) automatically. However, the auto run requires the motor to be uncoupled from the load OR to be coupled to a load that can absorb the test torque reversals. For an extruder with a heavy gearbox, the test torque reversals can damage the gear teeth, the shear pin, or the screw. Manual optimization is the field-proven alternative:
- Open the access key (P051 = 21).
- Verify the speed setpoint source (P100) is the analog input wired to the pot.
- Start with a very low P600 (e.g., 0.5) and a very high P601 (e.g., 1000 ms) — almost no integral action, very low proportional gain.
- Close the access key (P051 = 0) and release the enable signal.
- Apply a small setpoint step (2–5% of maximum speed) and observe r001 (speed actual) and r002 (armature current) on the OP1S.
- If the speed response is sluggish, increase P600 in 0.5 steps. If the speed overshoots or oscillates, decrease P600 or reduce P601.
- Repeat until the step response reaches 90% of the final speed in approximately 200–400 ms with less than 5% overshoot — typical extruder tuning target.
During manual optimization, the motor is on load (the gearbox is connected, the screw is turning through plastic). The test setpoint steps must therefore be small (2–5% of maximum speed) to avoid stalling the screw or popping a shear pin. The drive's i²t integrator (P159, P160) will tolerate these short pulses at currents above P150, but continuous operation at high torque will trip the overload.
10. Extruder-Specific Commissioning Procedure
Follow this sequence at the first start-up. Allow at least 30 seconds between the enable signal and the first setpoint step to let the field pre-magnetize to its rated value.
- Verify main contactor, field contactor, and any input isolator are open. Measure zero potential at the DC link.
- Connect a hand tachometer to the non-drive end of the motor shaft.
- Close the main contactor with the enable signal OFF. The drive should display a "ready, no enable" state on the OP1S.
- Read r004 (field actual) and confirm it matches P102 ±5%.
- Apply the enable signal. The drive should display "run" with zero setpoint.
- Slowly rotate the pot to 5%. The motor should turn at approximately 5% of the maximum speed. Verify on the hand tachometer.
- Continue to 25%, 50%, 75%, and 100% in turn, holding each step for 30 seconds. Watch the armature current on the panel ammeter and on r002. The current should be less than the no-load value of the motor (typically 5–15% of rated) when the extruder barrel is empty.
- Feed plastic into the hopper. The current should rise smoothly to the running load level. If the current oscillates, reduce P600 (Kp) and re-test.
- Engage the gearbox-driven load (if it was disconnected for the no-load test) and re-test the step response with a 5% setpoint step. The 600 A current limit should never be reached during normal running; if it is reached, the screw is jammed and must be cleared before continuing.
11. Verification Checklist
| Check | Pass criterion |
|---|---|
| Enable ON, setpoint 0 | Armature voltage 0, motor stationary, r000 = run |
| Setpoint 50% | Speed = 50% of P105, current < 15% of P100 (no load) |
| Setpoint 100% | Speed = P105 ±2%, current < nameplate |
| Reverse enable attempted (if allowed) | Speed = 0, drive stays in run, no fault |
| Reverse enable attempted (if not allowed) | Drive trips or stays at zero, depending on configuration |
| Pot wiper lifted | Speed setpoint drops to 0, drive ramps to stop, no fault |
| Enable removed during run | Drive stops, contactor stays closed, fault display clear |
| Field current during run | r004 within 5% of P102 |
| Panel ammeter at full load | Matches shunt reading within 1% |
| Panel tachometer at full load | Matches hand tachometer within 1% |
12. Troubleshooting Matrix
| Symptom | Most likely cause | Action |
|---|---|---|
| Display dead after power-up | Internal 24 V supply failed, or PMU ribbon disconnected | Check 24 V at X1, reseat PMU cable, replace CUD1 if internal supply shorted |
| Display "o0.0" but motor does not turn | Enable signal missing on X1-1 | Measure 24 V on X1-1, trace back to the contactor string |
| Display fault on enable | Field current not established (r004 < 50% of P102) | Check field wiring, verify P102 matches motor nameplate, check field thyristor firing |
| Armature overcurrent trip | i²t integrator tripped | Reduce P150 if set too high, check for jammed screw, allow 5 min cooldown |
| DC link overvoltage on stop | Single-quadrant drive back-driven by load | Install dynamic brake or use 4-quadrant frame; ramp setpoint down before stop |
| Motor runs at full speed regardless of pot | Setpoint source mis-routed to a constant connector | Re-set P100 to the analog input connector, verify wiring on X6 |
| Motor runs at full speed in reverse | Pot wiper wired to wrong terminal, setpoint inverted | Swap X6-1 / X6-2 wiring, or set P100 normalization to negative |
| Speed oscillates at constant load | Speed controller P600 too high | Reduce P600 by 0.5 increments, retest step response |
| Speed drifts up or down under constant load | P601 too long (integral wind-up) or P600 too low | Reduce P601 (faster integral), increase P600 slightly |
| Panel ammeter reads zero with motor running | P740 source set to wrong connector, or X7-1/X7-2 wiring reversed | Verify P740 source, check wiring, measure voltage on X7-1 with multimeter |
| Panel tachometer reads 2× actual speed | Analog tacho polarity inverted on X2 | Swap X2-1 and X2-2 |
| Panel tachometer reads half actual speed | Encoder pulse count set wrong in P143 | Adjust P143 to match the encoder's pulses-per-revolution |
| Drive trips immediately on enable | Motor stalled or armature wiring reversed | Check armature polarity at A+/A-, verify motor is free to turn, check for ground fault |
| Field current reads 0 after enable | Field thyristor not firing, or field wiring open | Measure field voltage at X9, check F+ / F- polarity, inspect field thyristor board |
13. Field-Weakening Range Verification
If the extruder runs above base speed, the field-weakening range must be commissioned separately from the constant-torque range. Run the motor to the maximum speed in P105 and verify that the field current r004 has dropped to P103. If the field current has not dropped, the field-weakening controller is not active; check that P104 is set above the running speed and that P103 is below the field current at that speed.
For an extruder that runs only in the constant-torque range (speed always below base speed), leave the field at its rated value (r004 = P102) at all times. Do not enable field-weakening unnecessarily — the field regulator is more efficient with a constant setpoint.
14. Putting the Drive into Production
After verification, close the access key (P051 = 0) and verify that all commissioning parameters are still in their written values by browsing the P000 list on the OP1S. Back up the parameter set to the OP1S memory card (or to a PC running SIMOVIS / DriveMonitor via the serial port) and store the backup with the cabinet documentation.
Print the as-commissioned parameter list and tape it inside the cabinet door. Record the final P600, P601, P150, and P104 values along with the date and the commissioning engineer's initials — these are the values that will be needed if the drive is ever replaced and must be re-entered on the spare unit.
15. Parameter Cross-Check and Documentation
Before handing the drive over to operations, walk through the parameter set one more time and confirm the following against the cabinet schematic:
- Armature and field supply voltages match the rating plate and the motor nameplate.
- P100, P101, P102 (armature current, voltage, field current) match the motor nameplate exactly.
- Speed setpoint source and normalization match the wiring on X6.
- Speed actual value source and normalization match the wiring on X2 (tacho) or X3 (encoder).
- Torque limits in P150–P155 match the gearbox shear pin rating and the process requirement.
- Analog output 1 (P740, P741) and analog output 2 (P742, P743) match the panel meter ranges.
- All digital inputs on X1 are wired per the cabinet schematic; the enable and fault-reset inputs are confirmed working.
- Fault memory cleared, r000 reads "run" with enable applied and zero setpoint.
Store the final parameter dump on the OP1S memory card and on a PC connected via the X4 USS port. The complete SIMOREG 6RA70 function diagram and parameter manual is published by Siemens at the Siemens Industry Online Support portal. Always cross-check the parameter numbers in this article against the as-built manual for the firmware version printed on the EPROM of your unit before any parameter change.
FAQ
Can I commission the 6RA7085 with the gearbox and extruder screw connected?
Yes, but use the manual speed controller optimization path. The auto-optimization run injects test signals that reverse the motor torque and can damage the gearbox teeth, shear pin, or the screw. Manual optimization uses small forward-only setpoint steps and is safe for a coupled load.
What current limit should I set for a 600 A extruder motor?
Set P150 to 110–130% of the motor's rated armature current (660–780 A for a 600 A nameplate) to absorb the cold-start and screw-fill transients. The drive's i²t integrator will protect the motor from continuous overload. If the gearbox has a shear pin rated below the motor's peak torque, size the current limit to match the shear pin, not the motor.
Why does the drive trip on DC link overvoltage on stopping?
The 6RA7085-6DS22-0 is a single-quadrant (6DS) frame and cannot regenerate. When the extruder screw is gravity-loaded or the plastic is still flowing, the motor acts as a generator and pumps current back into the DC link, raising the voltage until the drive trips. Either fit a dynamic braking resistor across the DC link, ramp the setpoint down before the stop command, or replace the drive with a four-quadrant (6DF) frame.
How do I scale the panel ammeter to read directly in amperes?
Set P740 (analog output 1 source) to the armature current connector and P741 to 10.0 so that 100% of the rated current (P100, e.g., 600 A) produces 10 V at X7-1. Use a 0–1 mA movement with a 10 kΩ series resistor. Relabel the scale plate to read 0–600 A directly.
Where is the official parameter list for the SIMOREG 6RA70?
The complete parameter list, function diagrams, and firmware release notes are published by Siemens at the Siemens Industry Online Support portal. The same site hosts the operating instructions, the function-block library, and the firmware notes for the 6RA70 firmware versions. Always cross-check the parameter numbers in this article against the as-built manual for the firmware version printed on the EPROM of your unit before any parameter change.