Resolving STARTER V4.3 Missing CU240S in Drive Unit Selection

Resolving STARTER V4.3 Missing CU240S in Drive Unit Selection

Symptom: STARTER release V4.3.1.2 (or any V4.3.x build) does not list CU240S directly in the Create New Drive Unit dialog when commissioning a SINAMICS G120. The CU type label on the physical drive clearly shows CU240S, but the dropdown only lists CU240, CU240B-2, CU240E, CU240E-2, CU250S, and similar entries. The drive is reachable online, yet no exact CU240S line item exists for selection.

This article documents the root cause, the correct selection path, the firmware/build matrix, and the verification steps to bring a legacy CU240S online under STARTER V4.3 and later without re-flashing the control unit.

1. Affected Products and Versions

2. Root Cause

STARTER V4.3 reorganized the SINAMICS G120 device catalog. The CU240S (without the "-2" suffix) was removed from the top-level dropdown because:

1. Production of the legacy CU240S hardware ceased. Tooling reflects the new cataloging convention used by the G120C, G120P, and the CU2xx-2 families.
2. The CU240S hardware family spans four variants: CU240S, CU240S DP, CU240S PN, and CU240S F. STARTER consolidates these into a single "CU240" parent entry so that the firmware loader, parameter set, and I/O configuration can be applied consistently across all four variants without re-selecting the device type per variant.
3. The commissioning wizard provides a second screen where the actual CU240S variant (DP, PN, F, standard) is selected based on the connected drive's online identification.

Result: The drive is not "missing" from STARTER. The CU240S is intentionally hidden behind the generic CU240 selection node.

3. Correct Selection Procedure

3.1 Step-by-Step: Offline Configuration

1. Open STARTER V4.3.1.2 and create a new project.
2. Right-click the project node → Insert New Object → Drive Unit.
3. In the Create New Drive Unit dialog, navigate to: Sinamics → Drives → SINAMICS G120 → Control Units → CU240
   • Do not select CU240B-2 or CU240E-2. These are the "-2" generation with a different firmware parameter set and hardware I/O layout.
4. Assign a device name (e.g. G120_CU240S_Pump1) and confirm.
5. The drive unit appears in the project tree. Open it → Configure Drive Unit.
6. In the wizard, the second screen lists all CU240 variants. Select the entry matching the physical label:

7. Continue through the wizard, selecting the Power Module (PM240, PM250, PM260) that matches the connected motor module.
8. Finish the configuration. The offline project now contains the correct CU240S variant.

3.2 Step-by-Step: Online Detection via Live List

If the drive is connected via PROFIBUS or PROFINET and visible on the bus, STARTER's Live List can identify the CU240S automatically:

1. Connect the programming PC to the same subnet as the G120.
2. In STARTER: Project → Accessible Nodes (or the magnifier icon).
3. STARTER broadcasts DCP/PROFINET discovery. The CU240S returns its identification (vendor ID 0x002A, device ID 0x010A).
4. Right-click the detected node → Load to Project.
5. STARTER auto-creates a drive unit with the correct CU240S sub-variant already selected. The wizard step is skipped because the tool reads the device identification directly.

4. CU240S vs CU240B-2 / CU240E-2 — Functionality Comparison

The original poster asked whether selecting CU240 (instead of CU240B-2) yields the same I/O and functionality. It does — but only when the actual physical CU is a CU240S. Selecting CU240 for a CU240B-2 physical unit, or vice versa, results in mismatched parameters and I/O errors at runtime.

Summary: When the physical label is "CU240S" (no "-2"), selecting the parent "CU240" entry in STARTER is correct. STARTER will not present the CU240S in the top-level dropdown because the catalog was consolidated; the sub-variant selection occurs inside the configuration wizard.

5. Firmware and STARTER Build Matrix

6. STARTER Installation Verification

Before troubleshooting the missing CU240S, confirm the STARTER installation includes the G120 device description packages:

1. Open STARTER → Help → About. Confirm the build number (e.g. V4.3.1.2).
2. Navigate to Start → Siemens Automation → STARTER → Information System.
3. Search for "SINAMICS G120". If the search returns no results, the Drive ES Basic or G120 support package was not installed.
4. Reinstall via the original STARTER DVD or download from Siemens Support (STARTER downloads).
5. After reinstall, restart the PC and verify the G120 catalog is populated.

7. Configuration Wizard Walk-Through (Annotated)

For documentation purposes, here is the complete wizard sequence with the screens you should see:

1. Screen 1 — Drive Family: Select SINAMICS G120.
2. Screen 2 — Control Unit: Select CU240 (parent node). This is the key step. Do not panic if CU240S is not listed at this level.
3. Screen 3 — CU Sub-Variant: Now CU240S, CU240S DP, CU240S PN, and CU240S F appear. Pick the match.
4. Screen 4 — Power Module: PM240, PM250, or PM260, based on motor module label.
5. Screen 5 — Power Module Rating: Select kW rating that matches the PM nameplate.
6. Screen 6 — Summary: Review and confirm. Click Finish.

After completion, the offline project tree will display the full CU240S identification. You can then go online and load the project to the drive.

8. Verification — Bringing the Drive Online

1. Connect STARTER to the CU240S via USB (cable 6SL3255-0AA00-2HA0) or the fieldbus interface.
2. Right-click the drive unit → Go Online.
3. STARTER compares offline vs. online configuration. A mismatch in the control unit variant triggers fault F0135 (drive object type inconsistent) or F0136 (control unit type detected).
4. If a fault appears, the offline selection was wrong. Re-run the wizard, pick the correct CU240S sub-variant, and reload.
5. On successful online connection, open Commissioning → Drive Functions and verify parameters:

6. Open the control panel, jog the motor at low speed (5–10 Hz), and confirm direction. If rotation is reversed, swap p1820 (direction of rotation reversal) from 0 to 1.
7. Perform an identification run (p1910 = 1 for motor data identification with the motor at standstill, or p1960 = 1 for rotating measurement).
8. Save the project to the CU's RAM/ROM and to the PC: Target → Copy RAM to ROM and Project → Save.

9. Troubleshooting Matrix

10. Migration Path: CU240S → CU240x-2

Since the CU240S is phase-out, many sites will migrate to CU240B-2 or CU240E-2. Key migration points:

1. Mechanical: The CU240B-2 and CU240E-2 share the same form factor and mounting footprint as CU240S. Direct swap in the cabinet.
2. Terminal mapping: The control terminals are renumbered. Use the Siemens migration guide for terminal-by-terminal mapping. Reference: SINAMICS G120 CU240S → CU240x-2 migration.
3. Parameter set: Most r/p parameters are retained, but parameter numbers shift in the safety and fieldbus groups. Use STARTER's Project Migrator or TIA Portal Startdrive to convert projects.
4. Firmware: Re-flash to V4.7 SP3 (latest LTS for CU240x-2) before commissioning.
5. Functional safety: CU240S F (basic STO) maps to CU240E-2 F with extended Safety Integrated (STO, SS1, SLS, SDI, SSM). Re-validate the safety function per IEC 61800-5-2.

11. Alternative: TIA Portal Startdrive

For new installations and migrations, TIA Portal Startdrive is the preferred tool. The G120 device catalog in Startdrive shows CU240B-2, CU240E-2, and all PN/DP/EIP variants explicitly. Startdrive V16+ also supports project migration from legacy STARTER V4.x projects containing CU240S configurations.

1. Open TIA Portal → Devices & Networks → Add new device.
2. Search "SINAMICS G120". The catalog lists CU240B-2, CU240E-2, and the G120C variants.
3. Drag the required CU into the project. Online detection works similarly via PROFINET DCP.
4. Use Project → Migrate to import legacy STARTER projects.

12. Safety and Documentation References

• SI 58378053 — CU240S Phase-Out Notice
• SINAMICS G120 CU240S Migration to CU240x-2
• SINAMICS G120 Operating Instructions (compact)
• SINAMICS G120 List Manual (parameter reference)
• STARTER Commissioning Tool Documentation