Adding Motor Modules to a SINAMICS D425 Without Re-Configuration

Overview

The Siemens SINAMICS D425 is a member of the SINAMICS S120 modular drive platform. It integrates a CU320-2-class control intelligence and a CompactFlash card into one chassis-format module, and it typically sits behind a Smart Line Module (SLM) for regenerative line-side infeed. In the field case that drives this article, the existing installation has one Motor Module in operation; the engineer must add two additional Motor Modules via Drive-CLiQ without triggering a full automatic re-configuration that would overwrite the commissioned project.

This article documents the field-proven procedure for adding new SINAMICS Motor Modules to an existing D425 system via Drive-CLiQ while preserving the live project. The method relies on the SCOUT topology view and the SINAMICS drive configuration wizard, both of which let the engineer manipulate the topology and parameter sets incrementally. The article covers the architectural background, the reasons automatic configuration is the wrong tool for expansion, the physical installation rules for Drive-CLiQ, the step-by-step parameter and topology work in SCOUT, the RAM-to-ROM persistence step, and the verification procedures that confirm the new drives are operational.

Prerequisites

Before starting the expansion, confirm the following prerequisites are met:

• An existing commissioned SINAMICS S120 project with a D425 control unit in service.
• SCOUT (the legacy commissioning tool) or TIA Portal with the Startdrive option (the current engineering environment) installed on the engineering station. SCOUT V4.x or V5.x remains the most common tool for S120 work; Startdrive V15 or later is the path Siemens now recommends for new projects. Both can read and edit the SINAMICS Integrated project tree.
• An online connection to the D425. PROFINET, PROFIBUS, or the Ethernet service interface (X127) are all supported. The service interface is the most convenient for engineering work because it does not require a network change.
• DRIVE-CLiQ cables of the correct length. Siemens supplies 0.11 m, 0.2 m, 0.3 m, 0.5 m, 1 m, 2 m, 3 m, 5 m, 10 m, 20 m, 30 m, 40 m, 50 m, and 70 m variants. Cables longer than 70 m are not supported on a single segment.
• New Motor Modules with known article numbers. Common Single Motor Module examples for S120 booksize: 6SL3120-1TE31-xAA3 (3 A), 6SL3120-1TE31-xAA4 (5 A), 6SL3120-1TE31-xAA5 (9 A), 6SL3120-1TE31-xAA6 (18 A). Double Motor Module examples: 6SL3120-2TE31-xAA3 (2 x 3 A), 6SL3120-2TE31-xAA4 (2 x 5 A), 6SL3120-2TE31-xAA5 (2 x 9 A). The trailing digit varies by hardware revision and connector variant. Always confirm the article number on the nameplate.
• The firmware version of the SINAMICS Integrated must support the new Motor Module. Verify with parameter r0018 (firmware version of the SINAMICS Integrated) and r0158 / r0159 (firmware version of each Motor Module). The Siemens Industry Online Support portal publishes the release notes for each SINAMICS firmware that list the supported component matrix.
• A backup of the current D425 CompactFlash image. Use SCOUT's Upload to PG with the access level set to Expert or higher, or copy the contents of the CF card with a card reader before changing anything.

SINAMICS D425 Architecture

The D425 is a chassis-format SINAMICS S120 controller that combines the SINAMICS Integrated control intelligence (architecturally equivalent to a CU320-2 PN plus an internal PROFINET interface) with a CompactFlash card that stores parameters, the runtime license, and the topology descriptor. A typical D425 system is structured as shown in the table below.

Drive-CLiQ is the proprietary digital backplane that the D425 uses to identify and parameterise connected components. Each Motor Module, Line Module, Sensor Module, and Terminal Module has an electronic nameplate that is read through Drive-CLiQ at startup. The D425 builds its topology map from this nameplate data and compares it against the project stored on the CompactFlash card. Any discrepancy is reported as a topology fault (F0135) or a topology difference alarm (A0135).

The D425 supports up to 6 servo drives or 3 vector drives (V/f, vector without encoder, or vector with encoder) per Control Unit. Beyond that, a CX32-2 controller extension is required. The exact per-firmware limit is documented in the SINAMICS S120 Function Manual and the matching release notes for the firmware in use. Refer to the Siemens Industry Online Support portal for the latest release notes.

Drive-CLiQ Topology Rules

Before physical installation, respect the following rules for Drive-CLiQ wiring on a D425:

• Each SINAMICS component has a fixed number of Drive-CLiQ ports. Line Modules, Motor Modules, Sensor Modules, and Terminal Modules typically have two ports (X200, X201) so they can be daisy-chained. The Control Unit has a port labelled X100 (or X200 in some configurations) and additional ports for connecting to multiple parallel branches.
• Maximum cable length between any two Drive-CLiQ nodes is 70 m for standard cables. Longer distances require a fibre-optic DRIVE-CLiQ connection with a DQI fiber-optic repeater.
• Maximum number of nodes per D425 is firmware-dependent. With current firmware, the typical limit is 16 nodes including the line module, the motor modules, and any terminal modules.
• The Smart Line Module must occupy the line-side Drive-CLiQ port on the D425 (typically port X100 or the dedicated LINE port). Failing to place the line module in the correct port is a common cause of F08501.
• Port numbering is significant: a wrong port assignment causes F0135 Topology: component missing or unexpected or F08501 PROFIdrive: drive object not assigned.
• A Drive-CLiQ hub (DMC20 or DME20) can be used to create a star topology instead of a daisy-chain, but each hub counts against the node count and must be configured in the topology view.

Why Automatic Configuration Is the Wrong Tool for Expansion

The Automatic Configuration or Automatic Device Configuration function in SCOUT is intended for the first commissioning of a new system. When activated, SCOUT clears the existing project, reads the electronic nameplate of every component detected on Drive-CLiQ, creates a new drive object for each Motor Module, and assigns default parameters based on the detected hardware. The previous parameter set, the user's tuning values, and any application-specific configuration are overwritten.

For an expansion case, this is the wrong behaviour. The existing drive is in service; the user is adding capacity, not replacing the system. Running automatic configuration would:

1. Reset all parameters of the existing drive to factory defaults.
2. Force the user to re-run motor identification and encoder commissioning for the existing motor.
3. Require the safety configuration to be re-applied, which on Safety Integrated drives means the user must repeat the safety acceptance test.
4. Lose the application-specific telegram mapping to the PLC (e.g., Siemens telegram 1, 2, 3, 4, 5, 6, 102, 105, 106).
5. Force the PLC project to be re-built and re-downloaded.

Instead, the correct procedure is to keep the existing project in place and add the new drive objects incrementally through the SINAMICS_Integrated → Drives wizard, then route the new Drive-CLiQ connections in the topology view. The existing drives remain untouched, the parameter set is preserved, and the safety and PLC configuration are unaffected.

Step-by-Step Physical Installation and Drive-CLiQ Cabling

1. Prepare the Cabinet

1. Lock out and tag out the line supply to the Smart Line Module per local safety procedure. Verify zero voltage on the line-side terminals with a properly rated meter.
2. Wait for the DC link discharge time. The D425 and the SLM display a warning label with the discharge time; for a typical 5 kW SLM the discharge time is 5 minutes. Touch the DC bus bar with a properly insulated discharge wand before handling the bus bar hardware.
3. Open the cabinet and verify the existing wiring. Take a photograph of the existing Drive-CLiQ cabling for reference.

2. Mount the New Motor Modules

1. Mount each new Motor Module on the rack per the cabinet layout drawing. The Motor Modules typically attach to a mounting rail with M6 screws and must be grounded to the cabinet earth bar with a short, low-impedance bond.
2. Verify the cooling airflow direction matches the arrows on the module. Reversed airflow causes the modules to overheat under load.
3. Verify the 24 V DC control supply is available at the new modules. The X124 connector on each Motor Module provides the 24 V input; a green LED confirms presence.

3. Wire the DC Bus Bars

1. Connect the DC bus bars (DC+ and DC-) from the last existing Motor Module in the daisy-chain to the new Motor Module 1. Use the bus bar links supplied with the new module.
2. Connect the bus bars from Motor Module 1 to Motor Module 2.
3. Torque the bus bar screws to the value stated on the module label. Typical values are 2.5 Nm for 50 mm² bars, 6 Nm for 95 mm² bars, and 12 Nm for 150 mm² bars. A loose bus bar connection is one of the most common causes of F07004 DC link overvoltage or F07002 DC link overcurrent faults.
4. Verify the protective conductor (PE) is bonded to the cabinet earth bar with a short, low-impedance connection.

4. Route the Drive-CLiQ Cables

1. From the spare Drive-CLiQ port (X201) of the last existing Motor Module, route a DRIVE-CLiQ cable to port X200 of the first new Motor Module.
2. From port X201 of the first new Motor Module, route a DRIVE-CLiQ cable to port X200 of the second new Motor Module.
3. Keep DRIVE-CLiQ cables away from VFD motor output cables. The minimum separation is 200 mm for parallel runs under 1 m, and more for longer runs. DRIVE-CLiQ is sensitive to EMI from the motor output PWM waveform.
4. Do not exceed the maximum cable length of 70 m. If a longer distance is required, use a DMC20 hub and a fibre-optic DRIVE-CLiQ link.

5. Initial Power-Up and Topology Detection

1. Close the cabinet. Restore the line supply.
2. The D425 powers up and reads the electronic nameplate of every component on Drive-CLiQ. The new Motor Modules are detected and reported as topology difference.
3. Expect alarm A0135 Topology comparison: component difference detected or fault F0135 Topology fault depending on the firmware version and the severity configuration.
4. Verify the existing drive is still operational. The existing motor should continue to respond to setpoints as before the expansion.

Step-by-Step SCOUT Topology View and Drive Wizard

1. Open the Online Project

1. Start SCOUT and open the project for the D425.
2. Establish an online connection to the target. The D425 should appear in the project tree with the existing project loaded from the CompactFlash card.
3. In the project navigator, locate the SINAMICS_Integrated object. This is the entry point to the integrated drive objects and contains the Drives, Line Module, and any other components.

2. Open the Topology View

1. Right-click SINAMICS_Integrated and choose Topology. The topology view shows a graphical representation of all detected Drive-CLiQ nodes and their port assignments.
2. The existing components (Smart Line Module, Motor Module 1, sensors, terminal modules) appear with green status. The two new Motor Modules appear with red status and a Difference label because they are detected on the wire but not yet in the project.
3. Check the port assignment of each new module. The view shows the source port and the destination port for each Drive-CLiQ cable. If the new modules are daisy-chained at the end of the existing chain (the recommended installation), the topology comparison will accept the order and the difference is components added at the end of the chain.
4. If the wiring does not match the project, click on the DQ connection in the topology view and re-assign the port numbers. Save the topology changes locally before continuing.

3. Insert a New Drive Object

1. In the project navigator, expand SINAMICS_Integrated → Drives.
2. Right-click the Drives folder and choose Insert new drive (or Insert DO - Drive Object).
3. The drive configuration wizard opens. The wizard guides the user through selecting the drive type, the Motor Module, and the motor.

4. Select the Drive Type

The drive type determines the closed-loop control structure and the available functionality. The valid options on a D425 are:

5. Select the Motor Module and Motor

1. The next wizard step lists every Motor Module detected on Drive-CLiQ. Select the new Motor Module that corresponds to the new drive. The wizard shows the article number, serial number, and firmware version of the selected module. Verify these match the nameplate on the physical module.
2. If the motor is a Siemens 1FK, 1FT, 1PH, 1PM, 1FN, or similar motor with a DRIVE-CLiQ interface, the motor is identified automatically through Drive-CLiQ. The wizard shows the motor article number and the electrical parameters read from the nameplate.
3. If the motor is a Siemens motor without DRIVE-CLiQ, select the motor from the list in the wizard. The motor data is populated from the SINAMICS motor database.
4. If the motor is a third-party motor, enter the motor parameters manually. Required parameters include the rated voltage (p0304), rated current (p0305), rated power (p0307), rated speed (p0311), rated frequency (p0310), rated power factor (p0308 for asynchronous), pole pair number, and motor cooling method. Save the motor data set for future reference.

6. Select the Encoder

1. If the encoder is connected via DRIVE-CLiQ (e.g., a Siemens motor with integrated DRIVE-CLiQ encoder), the encoder is identified automatically. Parameters p0141, p0142 (encoder type), and the entire p0400 ff. parameter set are pre-populated.
2. If the encoder is a third-party encoder connected to a Sensor Module (SMC10, SMC20, SMC30, SME20, SME25, SME120, SME125), select the Sensor Module article number and the encoder type code. Common encoder type codes are listed in the parameter manual. Verify the encoder resolution, signal level, and protocol.
3. For HTL/TTL encoders, set p0400 = encoder type code and complete the encoder parameter set per the encoder manual. For HTL encoders, the input voltage level is critical: a 24 V HTL encoder on a 5 V TTL input will damage the Sensor Module.

7. Complete the Wizard and Repeat

1. Click Finish to close the wizard. The new drive object appears in the project navigator under SINAMICS_Integrated → Drives → Drive_2 (or the next free number).
2. Repeat the wizard for the second new Motor Module.
3. Save the project to the local hard drive. The project file is still the engineering station's copy; the target is not yet updated.

Parameter Assignment and Telegram Mapping

After the drive objects are inserted, verify and adjust the application-specific parameters for each new drive.

1. Speed and Current Limits

The SINAMICS default limits are set conservatively, but the application usually requires tighter or looser limits. Configure the following parameters for each new drive:

2. Speed Controller Tuning

For servo and vector drives, the speed controller gain and integral time must be tuned for the mechanical load. The recommended procedure is to use the SINAMICS auto-tuning function (p1959 = 1, then p1960 = 1) which performs a one-time measurement of the mechanical system and writes the resulting Kp and Tn to p1460 and p1462 respectively. The auto-tuning must be run with the motor uncoupled from the load or with the load in a safe state, because the motor will perform several test movements during the measurement.

For applications that require manual tuning, start with Kp = 0.3 × (motor rated torque / motor rated current) and Tn = 200 ms, then increase Kp until the speed loop shows approximately 5% overshoot in a step response.

3. Telegram Mapping

If the drive exchanges cyclic data with a PLC over PROFINET or PROFIBUS, the telegram must be configured to match the PLC project. Common telegrams are:

Select the telegram per drive via parameter p0922. The PLC project must reference the same telegram number. The drive and the PLC must be consistent; a mismatch causes a PROFINET alarm IO device failure or Configuration mismatch on the PLC side.

Download, RAM-to-ROM, and Verification

1. Compile the Project

1. Right-click the project root and choose Compile. SCOUT checks for parameter consistency and reports any errors in the output window.
2. Resolve any compilation errors before continuing. The most common errors are duplicate drive object numbers, missing component assignments, and invalid parameter values.

2. Download to the Target

1. Select Download → Download to Target Device (or press the F8 keyboard shortcut). SCOUT writes the new project to the D425 RAM.
2. During the download, the D425 briefly stops processing. The existing drives may fault briefly; the user must reset them after the download if this happens. Most modern SCOUT versions transfer only the changes and do not stop processing, but the behaviour depends on the firmware version and the access level.
3. After the download, the new drive objects are operational in RAM. The existing drives are unchanged.

3. RAM-to-ROM (Persist the Configuration)

1. In SCOUT, choose Target System → Copy RAM to ROM. This copies the current parameter set from volatile RAM to non-volatile CompactFlash storage.
2. Wait for the copy to complete. The progress is shown in the status bar. A typical project takes 10-30 seconds to write to the CF card.
3. After the copy is complete, the D425 retains the new drives across a power cycle. Without this step, the new drives are lost on the next restart.

4. Verification Procedures

Perform the following checks in order. Each check confirms a different aspect of the expansion.

Topology check. Open the topology view in SCOUT and verify all components show green status, the Drive-CLiQ cable assignments match the physical wiring, no Difference labels are present, and the number of detected components matches the number in the project.

Diagnostic buffer check. Open the diagnostic buffer of each new drive (right-click the drive object → Diagnostics → Diagnostic buffer) and verify no F-class faults are present at startup, no A0135 Topology comparison incomplete alarm remains, and the drive transitioned from Commissioning to Operation state.

Motor rotation test. Use the SCOUT control panel (right-click the drive → Control panel) to issue a small speed setpoint (e.g., 50 rpm). Verify the motor follows the setpoint without overshoot or oscillation. Check parameter r0021 (actual speed in rpm) and r0027 (actual current in A) in the SCOUT online view. Stop the motor with the control panel Stop button.

Power-cycle test. Power off the D425 completely, wait 30 seconds for the DC link to discharge, then power on the D425. Verify both new drives come up in RUN state automatically, without operator intervention. This confirms that the RAM-to-ROM step was successful and the configuration is persistent.

PLC communication check. If the drives exchange cyclic data with a PLC over PROFINET or PROFIBUS, re-run the device configuration in TIA Portal so the IO controller sees the new slots, compile and download the PLC project, verify the IO device is in Operational state on the PLC side, and from the PLC read a few process data items (e.g., status word, actual speed) and confirm the values update.

Fault Diagnosis and Troubleshooting

The following table summarises the most common faults encountered during a D425 Motor Module expansion and the corresponding remedies.

PLC Integration and Safety Considerations

PLC Telegram Mapping

If a SIMATIC PLC controls the new drives over PROFINET or PROFIBUS, the PLC project must be updated to reference the new drive slots.

S7-1500 with TIA Portal. Open the TIA Portal project, expand the PROFINET IO system, select the D425 IO device, right-click and choose Device configuration. TIA Portal reads the current slot configuration from the device. Verify that the new drive slots appear in the device view. Add the new telegram data items to the PLC tags and any function blocks (e.g., SINA_SPEED, SINA_POS, SINA_INFEED). Compile and download.

S7-300 / S7-400 with STEP 7 Classic. Open HW Config, select the D425 IO device, and read the slot configuration from the device. Update the cyclic I/O in OB1 or the PROFIdrive function blocks. Compile and download.

For standard applications, Siemens provides the SINAMICS connection block library including SINA_SPEED (speed setpoint and actual value interface), SINA_POS (position control), SINA_INFEED (line module control), and LAcycCom (cyclic data processing). Refer to the SINAMICS Blocks for SIMATIC Controllers documentation on the Siemens Industry Online Support portal for the specific library version and call interface.

Safety Integrated Drives

For Safety Integrated drives, the addition of Motor Modules changes the safety configuration and requires additional steps. The safety acceptance test must be repeated for the new drives, even if the existing drives are unchanged.

Key safety parameters to set on each new safety drive:

Field Commissioning Tips and Platform Notes

• Always take a backup of the D425 CompactFlash card image before expanding the topology. Use SCOUT's Upload to PG with access level Expert. Store the backup on a network share that is backed up nightly.
• If the SINAMICS Integrated firmware does not recognise the new Motor Module, verify the firmware version is supported. Upgrade via the SINAMICS support package in SCOUT, or downgrade the Motor Module firmware to a compatible version.
• For DRIVE-CLiQ cable routing, use Siemens supplied cables. Third-party cables may not meet the impedance specification and cause intermittent F0135 faults. The Siemens cable part number is on the cable label.
• If two new Motor Modules are added at the end of the existing daisy-chain, the topology view accepts the order without manual port reassignment. If the new modules are added in parallel (e.g., from a hub), manual port reassignment is required.
• For PROFIsafe or Safety Integrated drives, additional parameter p9601 ff. must be set on each new drive. Adding safety drives changes the commissioning scope significantly and requires a safety acceptance test.
• The D425 supports up to 6 servo drives or 3 vector drives per Control Unit. Beyond that, a CX32-2 controller extension is required. The exact limit depends on the firmware version and the closed-loop cycle clock selected.
• For multi-axis applications, the SINAMICS closed-loop cycle clock (current controller clock, speed controller clock) must be set to a value that all drives can achieve. If one drive requires a fast cycle (e.g., 125 us), all drives run at that cycle.
• After the download, always perform the power-cycle test to confirm that the new drives come up automatically without operator intervention. This is the definitive test that the RAM-to-ROM step was successful.
• For complex topologies with many drives, consider using a DMC20 hub instead of a long daisy-chain. A hub reduces the maximum cable length per segment and improves serviceability.
• Document the final topology with a screenshot from the SCOUT topology view and store it with the project. This is the single most useful piece of documentation for future service work.

Differences from D410 and D445

For reference, the D425 is the mid-range SINAMICS S120 chassis-format controller. The lower-end D410 is used for single-axis applications with reduced functionality, and the higher-end D445 is used for high-performance applications with more servo axes per CU. The procedure described in this article is largely the same for the D410 and D445, but the per-CU drive count limit differs. Refer to the SINAMICS S120 Function Manual for the exact limit per model.

Migration to TIA Portal Startdrive

New projects should be engineered in TIA Portal with the Startdrive option, which is Siemens' current commissioning environment for SINAMICS S120. SCOUT remains supported for legacy projects but is no longer being extended. The procedure described in this article is functionally identical in Startdrive; the menu names and the project navigator structure differ slightly, but the topology view, the drive wizard, and the RAM-to-ROM step are all present. Existing SCOUT projects can be migrated to TIA Portal via the Migrate project function; the migration transfers the SINAMICS configuration but may not transfer every parameter, so always take a full backup before migrating and review the comparison report after migration.

FAQ