Siemens SINAMICS S120 CU320-2 Replacement

Overview

In the Siemens SINAMICS S120 modular drive system, the Control Unit (CU) serves as the central intelligence of the multi-axis drive network. It executes the closed-loop speed and current control loops, coordinates vector and servo motion control profiles, hosts system firmware, and manages real-time fieldbus communications.

The CU320-2 is the standard, high-performance Control Unit utilized in complex multi-axis industrial machinery. Whether you are dealing with a component failure, upgrading from the legacy first-generation CU320, or transitioning from PROFIBUS to PROFINET, replacing this critical component requires a precise understanding of physical connections, DRIVE-CLiQ topologies, license transfers, and firmware compilation. This guide outlines the technical specifications, selection matrices, and step-by-step procedures required to execute a seamless replacement.

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Legacy Product Information

The first-generation Control Unit (CU320, without the "-2" suffix) was introduced in the early years of the SINAMICS S120 product line. This legacy unit possessed lower processing throughput, smaller RAM, and was limited to older firmware branches (V2.x).

The modern replacement platform is the CU320-2, which is divided into PROFIBUS (DP) and PROFINET (PN) communication variants.

Legacy Part Numbers & Technical Specifications

• Obsolete 1st Gen Control Unit: 6SL3040-0AA00-0AA0, 6SL3040-0AA00-0AA1 (CU320)
• Legacy Lifecycle Status: Phase-out declared; support ended. Replaced entirely by the CU320-2 family.

Current CU320-2 Specifications

• Input Voltage: 24 V DC (20.4 V to 28.8 V) via a 4-pole terminal block
• Current Consumption: 1.0 A (excluding external DRIVE-CLiQ nodes, Option Slots, and digital outputs)
• Digital Inputs: 12 isolated digital inputs (optocoupler-graded)
• Bidirectional Digital Inputs/Outputs: 8 non-isolated channels configured via parameterization (p0728)
• DRIVE-CLiQ Interfaces: 4 onboard RJ45 sockets providing 100 Mbit/s serial communication to Power Modules, Motor Modules, and Sensor Modules
• Option Slot: 1 slot designed for Communication Board Ethernet CBE20 or Terminal Board TB30
• Fieldbus Interface:
  • DP Variant: 1x Sub-D 9-pin connector for PROFIBUS DP (up to 12 Mbit/s)
  • PN Variant: 2x PROFINET RJ45 ports (integrated 2-port switch, Real-Time RT and Isochronous Real-Time IRT)

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Recommended Replacements

When upgrading or replacing an S120 Control Unit, select the appropriate model based on your communication protocol requirements.

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Compatibility Considerations

Before replacing a CU320 or an older CU320-2, several crucial compatibility factors must be addressed:

1. CompactFlash (CF) Card Generation

The physical size of the CF card is identical across generations, but you cannot run a CU320-2 Control Unit using a V2.x CF card from a first-generation CU320.

• First-generation CU320 firmware supports V2.1 to V2.6.
• CU320-2 hardware requires a minimum of Firmware V4.3. The maximum firmware supported is dependent on the hardware revision but generally extends up to V5.2.
• When upgrading from a CU320 to a CU320-2, you must purchase a new CompactFlash card (e.g., 6SL3054-0...) preloaded with firmware V4.3 or higher.

2. Software Licensing and Web License Manager

SINAMICS S120 drives enforce license tracking via the serial number of the CompactFlash card. Licenses (such as Multiaxis/Performance expansions, Safety Integrated Extended Functions, and basic positioner licenses) are bound tightly to the original CF card's serial number.

• If you are just replacing a failed CU320-2 hardware unit and retaining your original CF card, no license transfer is needed. Simply insert the old card into the new hardware.
• If you must replace both the CU320-2 and the CF card, you must perform a license transfer. Use the online Siemens Web License Manager to re-assign the software licenses from the old CF card serial number to the new CF card serial number. Be sure to note down both serial numbers before beginning.

3. DRIVE-CLiQ Topology Limits

The CU320-2 has enhanced computing capabilities, allowing it to handle more control loops (up to 6 servo or vector axes, or up to 12 V/f axes under specific sampling time matrices). Ensure the DRIVE-CLiQ connection paths map exactly to their designated ports (X100, X101, X102, X103) because the drive parameters rely on structural topology recognition. Altering physical ports during a swap will trigger topology fault codes (e.g., F01360).

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Upgrade Benefits

Upgrading legacy CU320 units to the modern CU320-2 yields several operational advantages:

• Lower Sampling Times: Faster processor execution allows task time configuration reduction in current, speed, and position loops, improving dynamic motor response.
• Integrated Web Server: The CU320-2 features diagnostic and maintenance pages accessible over standard Ethernet for commissioning and servicing without requiring the STARTER or TIA Portal engineering suite.
• Dual-Port PROFINET Switches: The CU320-2 PN layout allows daisy-chained line topology systems without needing external physical switches.
• Larger Diagnostic History & Status Display: Dual 7-segment display on the front face provides rapid diagnostic codes (LED sequences indicate system boot, operational, and fault states).

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Common Migration Challenges

An automation engineer must prepare for these common hurdles during a replacement project:

1. Firmware Device Mismatch in Project Configuration: If replacing an older CU320-2 running V4.4 with a unit preloaded with V5.2, your offline STARTER or TIA Portal project must be updated or compiled to match the online drive firmware version. Alternatively, flash the CF card format back down to match the offline project configuration.
2. IP and Profinet Device Name Loss: PROFINET systems rely on the configured device name to assign IP addresses. When swapping the hardware, the new unit will not have a device name. You must assign the correct hardware device name using STEP 7, TIA Portal, or Prim Primary Setup Tool (PST).
3. Safety Integrated Checksums: If safety functions (STO, SBC, SS1, SLS) are active over PROFIsafe, swapping a control unit or updating firmware recalculates safety CRC checksums. This requires a safety commissioning unlock and diagnostic re-validation to generate and confirm the new safety parameters.

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Step-by-Step Replacement Procedure

Follow this technical procedure to replace a faulted CU320-2 or migrate a legacy CU320 unit.

+-------------------------------------------------------------+
| SAFETY WARNING:                                             |
| HIGH VOLTAGE PRESENT IN MOTOR/LINE MODULE DC LINK.          |
| Ensure all power sources are isolated, locked out, and all  |
| residual DC link voltages have discharged (<20V DC) before  |
| starting physical work.                                     |
+-------------------------------------------------------------+

Phase 1: Software & Configuration Backup

1. Connect to the active Control Unit using Siemens STARTER or TIA Portal.
2. Perform an online upload of the hardware parameter parameters: Click Target System -> Copy RAM to ROM.
3. Upload the configuration to your computer and save the project file as a diagnostic backup.
4. Locate the card serial number via the software diagnostic view or by physically reading the inscription on the CF card. Save this for Web License verification if changing CF cards.

Phase 2: Isolation & Safe Disassembly

1. Open the main line circuit breaker and lock out the inbound power supply. Verify zero voltage on the 24V DC terminal blocks and the main three-phase system feeding the power modules.
2. Open the physical front cover of the CU320-2 unit to expose the DRIVE-CLiQ ports and the 24V supply connector.
3. Label and disconnect the local isolated 24 V DC supply plug (terminals 1 through 4) from the top-left section.
4. Label each DRIVE-CLiQ cable clearly with its assigned port identifier (X100, X101, X102, or X103). Disconnect the RJ45 DRIVE-CLiQ cables.
5. Unplug the Profibus Sub-D connector (from interface X126) or PROFINET cables (from X150 P1/P2).
6. Unscrew the terminal blocks containing direct-wired digital inputs and outputs (X122, X132), keeping the wiring terminal intact.

Phase 3: Hardware Removal & Replacement

1. Loosen the protective PE grounding connection terminal strap situated on the bottom section of the Control Unit housing.
2. For side-by-side booksize module setups, press the plastic release latches on top and pull the CU320-2 forward off the mounting plate or standard PM-IF adapter module.
3. Gently pull the standard CompactFlash Card out of its dedicated slot (lower half of the center compartment).
4. Extract option boards (e.g., CBE20, TB30) by releasing their retention screws and lifting them straight out.
5. Fit the option board into the option slot of the New CU320-2 unit, securing the retention screws firmly.
6. Insert the compatible CompactFlash Card into the front-facing CF slot of the new unit until it snaps into place.
7. Mount the new CU320-2 back onto the booksize module side-frame or DIN rail. Ensure the metallic grounding plates on the back of the housing sit flush against the control panel backplate.

               [New CU320-2 Control Unit Mounting]
              +-----------------------------------+
              |  [==== 24V DC POWER TERMINAL ====]|
              |                                   |
              |   [X100] [X101] [X102] [X103]     |  <-- Reconnect in 
              |     |      |      |      |        |      EXACT order
              |                                   |
              |   +------------+   +------------+ |
              |   | X122 DI/DO |   | X132 DI/DO | |
              |   +------------+   +------------+ |
              |                                   |
              |   +-----------------------------+ |
              |   | CF Card Slot (Bottom Cover) | |  <-- Transfer original
              |   +-----------------------------+ |      or install updated
              |                                   |      licensed CF card
              +-----------------------------------+

Phase 4: Termination & Re-Wiring

1. Secure the physical PE grounding strap to the backplate/unit ground point.
2. Plug the digital terminal blocks back matching the labeled locations (X122, X132).
3. Connect the DRIVE-CLiQ communication cables to their exact match sockets (X100 to X100, etc.). Improper port connection will result in critical topology faults.
4. Re-insert the fieldbus cables (Profibus/Profinet).
5. Securely plug in the terminal block for the 24V direct current logic supply.

Phase 5: Power-Up and Software Commissioning

1. Power up the local 24 V DC logic supply before powering up the main three-phase line modules.
2. Observe the onboard LED indicator status:
   • RDY (Ready) LED: Should change from Orange to flashing/steady Green during normal startup stages. If it flashes Red/Green, the database configuration on the CF card differs from the physical hardware generation.
   • DP/PN LED: Should stay Green once connection to the PLC Master is established.
3. Open STARTER or TIA Portal. Open your saved backup project.
4. Establish an online connection. If the software prompts a firmware comparison mismatch, you must either:
   • Write-down upgrade: Downgrade the firmware binary on the CF card to match your offline program.
   • Project Upgrade: Perform a "Device Replacement" inside the TIA Portal hardware catalog config viewer to raise the configured version to the actual installed version.
5. Download your project configuration parameter file.
6. Run safety validation procedures if using Safety Integrated components. Ensure safety parameters are synchronized and verify safety CRC checksums.
7. Perform target configuration commit steps: execute Copy RAM to ROM to store the active parameter set into permanent non-volatile memory block.

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Frequently Asked Questions

Can I insert a non-Siemens CompactFlash card into the CU320-2?

No. The CU320-2 relies on dedicated formatted Siemens CompactFlash cards. The system check routines block general commercially available cards because the system requires the security partition keys generated during manufacturing to execute standard SINAMICS software licenses.

How do I identify if physical hardware on my CU320-2 PN has failed versus a software corruption?

If the 7-segment display on the front face remains dead or displays a constant static "8.8." while the 24V supply runs within range, the microprocessor hardware or internal regulator circuit has likely failed. If the dual display shows alternating codes or a red flashing RDY led, check the firmware database on the CF card or look for a corrupted system parameter file.

Do I lose my program parameters if I replace the CU320-2?

Parameters are stored directly on the removable CompactFlash card. Swapping out a failed CU320-2 box while installing your original functional CF card will restore exact system memory registers, maintaining program configurations and physical setups untouched.

What causes a DRIVE-CLiQ topology error after replacing a Control Unit?

This fault (typically code F01360) happens if DRIVE-CLiQ cables are reconnected to incorrect port destinations (for example, putting the Motor Module wire into port X102 instead of X100). The unit detects a routing path network change that does not match the active parameter block stored in memory. Re-route the physical lines to solve this error.

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Related Products & Families

• SINAMICS S120 Motor Modules: Booksize format, Single/Double Motor Modules (e.g., 6SL3120-...)
• SINAMICS S120 Line Modules: Active Line Modules (ALM), Smart Line Modules (SLM), Basic Line Modules (BLM)
• DRIVE-CLiQ Cabling: Prefabricated RJ45 connectivity cords (e.g., 6FX2002-1DC00-...)
• Control Unit Adapters: CUA31 (6SL3040-0PA00-0AA1) and CUA32 (6SL3040-0PA01-0AA0) for single-power module interfacing
• Communication Option Boards: CBE20 PROFINET interface cards (6SL3055-0AA00-2EB0)

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Need Help?

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All components provided by our team come complete with comprehensive functional warranties to ensure your facility maintains peak uptime. Contact Palm Parts Solution today to procure replacement hardware or to speak directly with an application engineer.