SINAMICS G120 CU240B-2 Online Commissioning with STARTER V4.3.2

SINAMICS G120 CU240B-2 / CU240E-2 Online Commissioning with STARTER V4.3.2: Troubleshooting Reference

This engineering reference consolidates the failure modes encountered when bringing a SINAMICS G120 modular drive online with the legacy STARTER commissioning tool. The documented symptom pattern - "No device found" with STARTER V4.2, a power unit overcurrent on first run, a persistent "OFF1 enable missing" status, and a drive that rotates in only one direction - is the canonical commissioning sequence for a CU240B-2 or CU240E-2 control unit paired with a PM240 power module. The article covers STARTER version compatibility, online connection procedure, the SINAMICS enable cascade, F30001 root cause analysis, single-direction rotation caused by terminal wiring errors, factory reset, and the CU240E-2 firmware 4.4 device-description gap.

1. System Overview and Topology

The SINAMICS G120 is a modular frequency inverter built from two components: a Control Unit (CU) and a Power Module (PM). The CU is the intelligence of the drive - it runs the closed-loop vector control, manages the digital and analog I/O, and hosts the fieldbus interface. The PM is the power section containing the rectifier, DC link, and IGBT inverter stage. The drive cannot run without both components, and a drive that responds to the Basic Operator Panel (BOP-2) but does not appear in STARTER is a CU / toolset compatibility problem, not a hardware failure.

Control units covered in this reference:

• CU240B-2 - Standard variant, USS / Modbus RTU on RS485, six digital inputs, two digital outputs, one analog input, one analog output.
• CU240B-2 PN - Adds PROFINET interface with two ports for line topology.
• CU240E-2 - Adds Safety Integrated (STO, SS1) and PROFIsafe over PROFINET.
• CU240S-2 / CU240S-2 PN - US / PROFINET standard variant, predecessor of the B/E series.
• CU240E-2 DP - PROFIBUS variant with Safety Integrated.

The standard commissioning tool for the G120 family through firmware 4.7 SP3 is STARTER (SIMATIC Automation Tool for Engineering and Commissioning). Firmware 5.x and later move commissioning to Startdrive inside TIA Portal. The legacy STARTER V4.3.2 / V4.4 remains the supported path for the V4.x firmware stream.

2. STARTER Version Compatibility and Online Connection

STARTER version selection is the single largest source of "No device found" and "Accessible nodes empty" faults on a control unit that the BOP-2 reports as healthy. Each STARTER release embeds device description (EDD) files for a defined set of firmware versions. When the control unit firmware is newer than the EDD bundled with the installed STARTER, the tool cannot interpret the device's online response and silently discards it.

2.1 Compatibility Matrix

2.2 Online Connection Procedure

1. Install STARTER V4.3.2 or V4.4 on a Windows 7 SP1 / Windows 10 workstation. Restart the PC after installation so the S7DOS service for the access point is loaded.
2. Set the access point: Options → Set PG/PC Interface. For USB select S7USB; for PROFINET select the Intel / Siemens TCP/IP adapter that is bound to the drive network; for RS232 select the COM port of the PC-inverter connection kit (6SL3255-0AA00-2AA0).
3. Power the control unit: 24 V on terminals 31 / 32 (CU240B-2) or 9 / 28 (CU240E-2). Wait for the CU to complete its boot sequence - the READY LED on the CU transitions from flashing green to solid green, and the BOP-2 displays the drive state.
4. In STARTER, open or create a project, then select Online → Accessible Nodes. The detected drive appears with its IP address (PROFINET), USS address, or COM port identifier (RS232).
5. Highlight the drive and click Accept to add the device to the project tree. Right-click the drive and select Connect to Target System. STARTER uploads the parameter set from the device and shows the online indicator in the project tree.

2.3 PROFINET Name and IP Assignment

For CU240B-2 PN and CU240E-2 PN, the PROFINET device name must match the configured name in the TIA Portal hardware configuration or be assigned ad hoc. To assign a temporary name: open Online → Accessible Nodes, right-click the device, and select Assign PROFINET Name. The default IP is 0.0.0.0; assign a static IP via Assign IP Address before the controller can route cyclic I/O to the drive.

Reference the SINAMICS G120 with CU240B-2 / CU240E-2 operating instructions in the Siemens Industry Online Support portal for the full pinout of the X200 PROFINET port and the X1 / X2 terminal block.

3. Enable Cascade and "OFF1 Enable Missing"

After the online connection is established and a run command is applied, the drive often reports "OFF1 enable missing" in the missing-enables list. This is the expected power-on inhibit state of the SINAMICS enable cascade, not a hardware fault. The drive will not close its IGBT gates until every enable in the chain is asserted.

3.1 Enable Signal Source Table

3.2 Diagnostic Procedure for OFF1 Missing

1. In STARTER online, open Commissioning → Drive Functions → Drive States to read the live missing-enables list. The same list is shown on the BOP-2 under Menu → Diagnostics → Missing enables.
2. Open the Expert List (right-click the drive, Expert List) and add r002 (status word 1) and r003 (status word 2) to the watch list. Decode the bits with the standard SINAMICS status word mapping; bit 0 = ready to switch on, bit 1 = ready, bit 2 = operation enabled, bit 3 = fault present, bit 4 = OFF2 active, bit 5 = OFF3 active, bit 6 = switch-on inhibited.
3. Watch r722 (status of digital inputs). Bit 0 of r722 is DI 0 - the default ON/OFF1 source. Apply the field run command and verify r722.0 transitions 0 to 1.
4. If r722.0 stays at 0, the digital input is not energized. Check the wiring: 24 V on the DI terminal, common (terminal 28 or 9) on the reference, the DI is configured as a digital input (p0728 for DI 0) and not overridden by a BICO source.
5. If r722.0 toggles correctly but the OFF1 missing flag persists, check p0840[0] assignment. In some configurations, p0840 is set to a fieldbus control word (e.g., r2090.0) and the fieldbus is not yet in cyclic data exchange. Temporarily force p0840[0] = 722.0 to confirm the wiring path, then restore the fieldbus source.

3.3 OFF2 and Safety Integrated on CU240E-2

On a CU240E-2, OFF2 is hard-wired to the Safe Torque Off (STO) inputs. Terminal 16 (EP +24 V enable), terminal 17 (STO input 1), and terminal 18 (STO input 2) must all be at 24 V for the drive to enable. If only one STO channel is energized, the drive will pulse-inhibit and report "OFF2 enable missing." Use the supplied factory jumper between 16 / 17 / 18 to disable STO during commissioning, or wire each input to a safety relay contact rated for the application.

4. Power Unit Overcurrent (F30001)

The error message "power unit over current" on the first run command corresponds to fault code F30001 in the G120 fault buffer. The drive detected an output current that exceeded the IGBT module's rated peak. F30001 is a power-electronics protection event and is almost always a wiring or motor-data issue, not an inverter failure.

4.1 F30001 Root Cause Matrix

4.2 Motor Data Verification

Enter the motor nameplate data into p0301 (motor type), p0304 (rated voltage), p0305 (rated current), p0307 (rated power), p0310 (rated frequency), p0311 (rated speed), p0335 (motor cooling). A 10% error in p0305 will produce F30001 on the first ramp because the field-weakening and current-limit calculations are scaled against this value.

4.3 Motor Identification Routine

1. Acknowledge F30001 (set p3981 = 1 or pulse the fault acknowledge DI configured on p2103).
2. Set p1900 = 2 (full motor identification with rotation). The drive displays a warning that the motor will spin during identification.
3. Apply the ON command. The drive accelerates to ~80% of rated speed, measures stator resistance (R_s), leakage inductance (L_sigma), and rotor time constant (T_rot), then stops. The duration is typically 30-90 s for a standard induction motor.
4. If identification completes without fault, p1910, p1912, p1913, p1959, p1960 are written with the measured values. Save with RAM to ROM (copy RAM to ROM) so the values survive a power cycle.

5. Single-Direction Rotation on CU240E-2 / CU240B-2

A drive that rotates only in the forward direction and ignores the reverse command is almost always a wiring issue. The standard terminal assignment on a CU240B-2 / CU240E-2 dedicates DI 1 to the reverse command, fed into the BICO source for the negative setpoint (p1113 for the analog setpoint, or directly to the setpoint inversion bit for the fieldbus control word).

5.1 Default Terminal Map (CU240B-2 / CU240E-2, factory setting)

5.2 Diagnostic Procedure

1. Watch r722 in the expert list. Apply the reverse command and verify r722.1 transitions 0 to 1.
2. If r722.1 does not change, the DI is not wired. Check the terminal block: 24 V on terminal 6, common on terminal 28 (CU240B-2) or 9 (CU240E-2).
3. If r722.1 toggles correctly but the drive still runs in one direction, check p1113 (setpoint inversion) and p1035 / p1036 (motor potentiometer raise / lower if used). For fieldbus control, verify bit 11 of the control word (r2090) is being set by the controller.
4. Check p1082 (maximum frequency) and confirm the setpoint is reaching the ramp function generator. Watch r0020 (frequency setpoint) and r0021 (actual frequency) in the expert list. A setpoint of 0 Hz on the negative side of the ramp will not produce reverse motion.

6. Factory Reset and Recovery Procedures

A factory reset clears the entire parameter set back to the as-shipped state. Use this when the drive has been configured with unknown parameters, when transitioning the drive to a new application, or as a recovery step when the parameter set is corrupted.

6.1 BOP-2 Factory Reset

1. Navigate to Menu → Parameters → Filter → Expert.
2. Set p0010 = 30 (commissioning parameter filter, factory settings).
3. Set p9761 = 1 to start the factory reset (firmware 4.4 and later) or p0970 = 1 (older firmware).
4. Wait for the BOP-2 to display "Factory reset completed." The drive will display fault F0160 if the reset fails.
5. Power cycle the drive (24 V off / on, then line voltage off / on).

6.2 STARTER Factory Reset

1. Connect online to the drive.
2. Right-click the drive in the project tree and select Online → Restore Factory Settings.
3. Confirm the prompt. The drive will reset, disconnect, and reappear in Accessible Nodes.
4. Power cycle and re-accept the drive into the project.

6.3 Recovery from Failed Reset

If the factory reset is interrupted (USB disconnected, power loss, STARTER crash), the drive may enter a state where it does not respond. Recovery sequence:

1. Disconnect all bus cables (PROFINET, RS485, USB).
2. Open the line contactor to remove mains voltage from the PM. Leave the 24 V supply on the CU powered.
3. Wait 30 seconds for the internal capacitors to discharge.
4. Close the line contactor and wait for the CU to boot.
5. Retry the factory reset via BOP-2 (more reliable than STARTER after a failed reset).
6. If the second reset also fails, attempt a deep reset: p0970 = 10 on firmware versions that support it (4.4 and later). This clears all parameter partitions including the safety and SD card partitions.
7. As a last resort, remove the optional SD card and reformat it in a PC. Reinsert the SD card and retry the factory reset.

7. CU240E-2 Firmware 4.4 STARTER Detection Issue

CU240E-2 control units shipped from Siemens after the firmware 4.4 release (4.4.0.4 and later) do not appear in STARTER's Accessible Nodes list when using STARTER V4.3.2. The fault is a device description (EDD) version mismatch - STARTER V4.3.2 does not embed the EDD for the 4.4 build. The drive is healthy: BOP-2 parameterization and run commands work normally.

7.1 Resolution Options

7.2 Verifying the Firmware Version

Read the firmware version from BOP-2: navigate to Menu → Parameters → r0018. r0018 is formatted as a packed value where the high byte is the major version, the next byte the minor version, the next byte the build, and the low byte the hotfix. For example, r0018 = 4.4.0.4 indicates firmware V4.4, build 4. Alternatively, read r0018 in STARTER once the EDD is updated.

8. Diagnostic Parameter Reference

9. Communication Interface Setup

9.1 PROFINET (CU240B-2 PN / CU240E-2 PN)

1. Set the PROFINET device name via Online → Accessible Nodes → Assign PROFINET Name. The name must match the TIA Portal hardware configuration (e.g., "g120cu240b2").
2. Assign a static IP address: 192.168.0.10 / 255.255.255.0 is a common default for G120 cells.
3. Verify the Telegram selection: standard telegrams 1, 20, 350, 352, 353, 354 are supported. Telegram 1 (speed control, 2 words each direction) is the default.
4. Configure p0922 = 1 (IF1 PROFIdrive telegram selection).
5. Map the fieldbus control word to p0840 / p0844 / p0845 via p2051[0] = p2080[0] = r2050[0] (control word 1 from PROFINET).
6. Map the fieldbus speed setpoint to p1070 (main setpoint) via p2051[1] = r2050[1].

9.2 RS485 USS / Modbus RTU (CU240B-2 base)

1. Set p2030 = 2 (USS protocol) or p2030 = 4 (Modbus RTU).
2. Set p2020 (baud rate): 6 = 9600, 7 = 19200, 8 = 38400, 9 = 57600, 10 = 115200.
3. Set p2021 (USS address) or p2021 (Modbus address): range 1 - 247.
4. Wire the RS485 bus: terminals 1 / 2 (P+ / N-) for the bus, with termination resistors on the first and last node.
5. Set p2040 (process data monitoring time) to 1000 ms or longer to prevent bus-failure faults during commissioning.

9.3 USB Service Port

The CU240B-2 / CU240E-2 have a USB-C service port on the front face. This port is for STARTER commissioning only - it does not support cyclic process data. The driver is the Siemens S7USB driver, installed automatically with STARTER. Use a shielded USB cable of less than 3 m.

10. Migration to Startdrive / TIA Portal

For new projects, Siemens recommends migrating to Startdrive in TIA Portal V15 and later. Startdrive supports CU240B-2 / CU240E-2 firmware up to 4.7 SP3 and all firmware 5.x releases. Key differences from STARTER:

• Project tree is integrated into the TIA Portal hardware catalog. Devices are dragged from the catalog to the device configuration, not added via accessible nodes.
• Online connection uses the TIA Portal device proxy, which holds the PROFINET name and IP address from the offline configuration.
• Safety Integrated configuration is in the TIA Portal Safety Administration editor, not a standalone STARTER screen.
• Firmware update is performed via TIA Portal / Startdrive, not the legacy SINAMICS firmware update tool.

Existing STARTER projects can be migrated: open the STARTER project, save it as a TIA Portal compatible XML, then import it via TIA Portal → Project → Migrate STARTER project. The migration preserves parameters, BICO connections, and drive functions, but rewrites the hardware configuration to the TIA Portal format.

11. Verification Checklist and Troubleshooting Matrix

11.1 Commissioning Verification

1. STARTER reports the drive online - green check in the project tree, no red fault indicator.
2. r002 status word shows operation enabled (bit 2 set) when the ON command is active.
3. Motor identification (p1900 = 2) completes without fault; values written to p1910, p1959, p1960.
4. Forward run command produces rotation in the correct direction (verify with tachometer or mechanical observation).
5. Reverse run command produces rotation in the opposite direction (when DI 1 wired).
6. Fault buffer (r0947) is empty after a 10-minute run at rated load.
7. PROFINET cyclic data exchange is active (yellow LED on port, status "OK" in controller diagnostic buffer).
8. Setpoint and actual frequency match within the configured ramp (r0020 vs r0021).

11.2 Field Troubleshooting Matrix

11.3 Status Word 1 (r852) Bit Decode

FAQ