Resolving SINAMICS S120 CU310-2 F07802 in Simulation Mode

Overview

The SINAMICS S120 drive family from Siemens supports a hardware-in-the-loop simulation mode that exercises the closed-loop control, setpoint channel, and diagnostic readouts of the Control Unit without firing the IGBTs of the connected power section. The mode is intended for factory acceptance testing, software validation, drive commissioning without line voltage, and training environments. On the CU310-2 DP/PN control unit paired with a PM340 blocksize power module, the simulation is enabled by setting p1272 = 1, but field experience shows that the drive can latch fault F07802 (power unit not ready) and the engineer is left looking at r0026 and r0070 reporting 560.2 V even though only a 24 V DC control supply is connected to the CU.

This reference documents the configuration sequence, the parameter dependencies (p1272, p020, p864, r0026, r0070, p0210), the firmware-specific behavior on SINAMICS V2.5.x, the STARTER 4.1.1.0 commissioning workflow, and the documented CU310-2 simulation limitations. It also clarifies the source of the 560.2 V reading, which is normal simulated behavior rather than a hardware fault.

SINAMICS S120 Architecture and Simulation Mode

The S120 family uses a modular topology that separates the closed-loop control from the power conversion stage. The relevant blocks are:

• Control Unit (CU310-2): Hosts the firmware, the speed/torque/current controllers, the setpoint channel, and the PROFIBUS/PROFINET interface to the PLC.
• Power Module (PM340): Contains the six-pulse line rectifier, the DC link capacitors, and the IGBT inverter stage. For a single-axis CU310-2 system the PM340 also functions as the Motor Module.
• Sensor Module (SMC10/SMC20/SMC30): Optional, mounted on the motor, connected back to the CU310-2 via DRIVE-CLiQ.

In simulation mode the control unit runs the full vector/servo control algorithm using synthesized feedback values, but the gate signals to the IGBTs are inhibited. Parameters such as p1272, p020, and p0210 define the simulated power section. The drive's status word (r0899) reports the operating state including the simulation flag (bit 2).

The simulation mode was originally designed for the CU320-2 multi-axis controller. On the CU310-2 it is supported as a secondary feature, and the implementation is reduced compared to the CU320-2. This is the primary source of the F07802 fault observed on CU310-2 firmware 2.5.x.

Reference: SIMIT Drive Simulation - SINAMICS S120 via Basic Positioner (Siemens Support, Entry ID 109761007)

CU310-2 Control Unit and PM340 Power Module

The CU310-2 is a stand-alone control unit available in two variants:

• CU310-2 DP (6SL3040-1LA00-0AA0) - PROFIBUS interface
• CU310-2 PN (6SL3040-1LA01-0AA0) - PROFINET interface with two ports

Key interfaces and terminals on the CU310-2:

The PM340 blocksize power module is available in frame sizes A through F with rated currents from 1.3 A to 200 A at 400 V class (and equivalent 690 V class ratings). The PM340 contains the rectifier, DC link, and inverter in a single chassis. The PM340 is selected in the firmware through p020, which stores the Siemens MLFB (order number) of the unit. If the PM340 is unpowered, p020 reads as 0 and the CU310-2 cannot determine the simulated power section parameters.

Fault F07802 - Definition and Trigger Conditions

F07802 in the SINAMICS S120 fault system indicates that the power unit is not in the ready state. The exact wording varies by firmware version; on V2.5.x it is typically logged as "Power unit: not ready" or "Power unit: identification failed". The fault is set when one of the following conditions is detected:

1. The CU310-2 cannot complete a DRIVE-CLiQ handshake with the PM340 (topology fault, cable fault, or PM340 unpowered).
2. The 24 V supply to the PM340 electronics is missing or below the threshold (typically 21 V minimum).
3. p020 is set to 0, meaning no power unit has been identified.
4. The PM340 reports an internal fault that prevents transition to the ready state.

On the CU310-2, setting p1272 = 1 (simulation) does not bypass the requirement for a valid p020. The simulation still needs a power unit code because the firmware uses p020 to compute the simulated IGBT current limits, thermal model, and DC link voltage. If p020 = 0 when p1272 = 1 is set, the drive reports F07802 with the OFF1/OFF2/OFF3 inhibit bits set in the status word.

Key Parameters for Simulation Mode

Root Cause Analysis - Why F07802 Occurs on CU310-2

When p1272 = 1 is set on a CU310-2 + PM340 system and the drive reports F07802, the most likely root causes are:

1. Missing or invalid p020 (power unit code): After a parameter reset, p020 defaults to 0. The drive cannot start simulation without a power unit reference.
2. PM340 not powered: The PM340 requires both 24 V at terminal X1 and the main line voltage at the line input. If only the CU310-2 is powered, the CU cannot read the PM340 identification via DRIVE-CLiQ and the power unit remains unknown.
3. DRIVE-CLiQ wiring fault: The cable between CU310-2 port X100 and the PM340 DRIVE-CLiQ port must be a Siemens DRIVE-CLiQ cable (6FX2002-1DC00-xxxx or 6FX5002-1DC00-xxxx). Third-party cables or damaged cables will fail the handshake.
4. Firmware version mismatch: Firmware 2.5.x on the CU310-2 has known simulation limitations. The simulation mode was designed primarily for CU320-2 systems with Motor Modules.
5. Commissioning filters active: If p0009 or p0010 is non-zero (e.g., p0009 = 30 for reset or p0010 = 1 for quick commissioning), the drive blocks normal operation and may report F07802.

The 560 V DC Link Voltage Anomaly - Expected Simulation Behavior

A common point of confusion during simulation mode is the value displayed in r0026 and r0070. When the CU310-2 is supplied with only 24 V DC (no main line voltage to the PM340) and p1272 = 1 is set, the DC link voltage readouts show 560.2 V instead of the expected 24 V. This is the correct simulation behavior:

• Simulation mode generates a synthetic DC link voltage based on the configured line supply voltage (p0210) and the power unit code in p020.
• For a 400 V three-phase system, the simulated DC link voltage equals 400 V × √2 ≈ 565.7 V (peak of the rectified line-to-line voltage). The 560.2 V reading is the simulated value that would be present if a real 400 V three-phase supply were connected.
• When p1272 = 0, the drive reads the actual DC link voltage through the PM340's voltage sensing circuit, which shows the 23-24 V supplied to the CU terminals.

The simulated DC link voltage for a six-pulse rectifier follows the relationship:

V_DC = V_LL × √2 × (1 / cos(α))

For a line voltage of 400 V and a firing angle α = 0, V_DC = 400 × 1.414 = 565.7 V. For a 690 V class system, V_DC = 690 × 1.414 = 975.7 V. The 560.2 V reported by r0026 corresponds to a 400 V class PM340 with line voltage set slightly below 400 V (around 396 V), which is within the tolerance of a nominal 400 V European industrial supply.

Pre-Commissioning Prerequisites

1. STARTER commissioning software version 4.1.1.0 or later installed on a Windows PC (Windows 7 SP1 or later).
2. SINAMICS S120 firmware version 2.5.x on the CU310-2 (verify with r0018).
3. PROFIBUS or PROFINET connection between PC and CU310-2, terminated according to the bus standard.
4. 24 V DC power supply to CU310-2 terminal X1 (PE, M, P24) with adequate current margin (the CU310-2 draws approximately 1.5 A at 24 V).
5. PM340 connected via DRIVE-CLiQ to CU310-2 X100, with the PM340's own 24 V supply and line voltage applied.
6. Parameter access level set to "Expert" in STARTER (default access level is "Standard").
7. Commissioning filters p0009 = 0 and p0010 = 0.
8. p020 populated with the correct power unit code, either via automatic identification or manual entry.

Step-by-Step Activation Procedure

1. Connect and go online with STARTER: Launch STARTER 4.1.1.0, open the project (or create a new S120 project), insert the CU310-2 device, insert the PM340 under the CU, configure the PROFIBUS/PROFINET address, and click "Online" → "Connect to target system" (Ctrl+Shift+8). Confirm the target device matches the expected MLFB.
2. Run basic commissioning: Right-click the drive object → "Commissioning" → "Wizard". Select the control mode (Servo or Vector), enter the motor data, configure the encoder, and set the limits. Save the parameter set to the CF card and the PC.
3. Configure the power unit code (p020): In the expert list, search for p020. If the PM340 is connected and powered, p020 auto-populates after POWER ON. If it is still 0, enter the PM340 MLFB manually. Click "Change" to write and then "Copy RAM to ROM" to save non-volatility.
4. Verify the topology: Open the topology view (Configuration → Topology). Confirm the CU310-2 and PM340 are connected correctly. Red icons indicate topology errors that must be resolved before continuing.
5. Enable simulation mode: Set p1272 = 1 in the expert list. Press "Change" to write the value to the drive. The drive transitions to "Simulation active" after a short processing delay. Check r0899.2 in the expert list to confirm simulation bit is set.
6. Test the simulation: Issue the pulse enable (set the EP terminal on X124 or use STARTER's "Control panel"). Apply a small speed setpoint via p1155 or the control panel. Verify r0021 (speed actual) follows the setpoint, r0026/r0070 show ~560 V DC link, and r0031 (torque actual) responds.
7. Save and document: Right-click the drive object → "Target device" → "Copy RAM to ROM". Export the parameter set to a file. Document p020, p1272, and p864 in the project file for traceability.

Verification with STARTER

After enabling simulation mode, run the following verification checks in the expert list:

If any check fails, refer to the Troubleshooting Matrix below.

Firmware Compatibility and CU310-2 Simulation Limitations

For firmware 2.5.x on the CU310-2, Siemens technical support has indicated that simulation mode is not fully supported. Engineers requiring robust simulation should consider one of the following paths:

• Upgrade firmware to 4.4 SPx or later to gain full simulation support on the CU310-2.
• Replace the CU310-2 with a CU320-2 control unit and a separate Motor Module (e.g., Single Motor Module 6SL3120-xxxx-xxxx). The CU320-2 has full simulation support across all firmware versions and is the primary architecture for which simulation mode was designed.
• Use SIMIT simulation for PC-based emulation of the SINAMICS S120 at the PROFINET/PROFIBUS level. SIMIT supports Basic Positioner, EPOS, and Speed Control modes with higher fidelity than the firmware simulation.

Reference: SIMIT Drive Simulation - SINAMICS S120 via Basic Positioner (Siemens Support, Entry ID 109761007)

Alternative Approaches for High-Fidelity Simulation

When the CU310-2 firmware simulation is insufficient, the following alternatives provide more complete drive emulation:

1. SIMIT with SINAMICS S120 application: The most accurate Siemens-offered simulation. SIMIT runs on a separate PC, communicates with the PLC via PROFINET, and emulates the SINAMICS S120 drive object. Supports commissioning with STARTER offline, then live simulation with the S7 controller. The application is documented in the Siemens support entry ID 109761007.
2. TIA Portal S7-1500 with SINAMICS Startdrive: The Startdrive plug-in in TIA Portal includes a SIMIT integration that allows the SINAMICS S120 to be emulated within the TIA Portal environment. Suitable for projects migrating from S7-300/400 to S7-1500.
3. S7-PLCSIM with the real CU310-2: For S7-300/S7-400 control programs, PLCSIM can emulate the S7 side and send test setpoints to a real CU310-2 in simulation mode. This combines real drive firmware simulation with emulated PLC control.
4. CU320-2 with separate Motor Module: The most robust hardware-in-the-loop simulation. The CU320-2 supports full simulation including Sensor Module emulation, thermal model, and safety function exercise (excluding actual STO/SS1/SS2 output).

Troubleshooting Matrix

Frequently Asked Questions