Configuring CU320-2PN S120 Line Module and Mixed Servo/Vector

Configuring Siemens CU320-2PN with Mixed Servo/Vector Axes and Line Module Control

1. System Overview and Scope

The SINAMICS S120 drive platform uses the CU320-2 Control Unit to execute communication, open-loop control, and closed-loop control for one or more Line Modules and Motor Modules. Two CU320-2PN variants are commonly deployed on multi-CU systems where the infeed (Line Module) must be controlled cooperatively with motor-side axes. This reference covers a representative architecture:

• Two CU320-2PN controllers on PROFINET
• ET200S PLC with IM151-8F PN/DP fail-safe CPU
• Three dual Motor Modules on the second CU320-2PN
• Mixed induction (vector) and 1FK7042 (servo) axes on shared Double Motor Modules
• STO via PROFIsafe over PROFINET
• Keyence XG7000 vision system on the same PROFINET segment

The reference design demonstrates how to wire DRIVE-CLiQ, select telegrams (110 vs 352), control the Line Module via p864, and resolve field-typical faults (F07410, F07900).

2. Hardware Topology and DRIVE-CLiQ Layout

DRIVE-CLiQ is the internal point-to-point serial bus between the CU320-2, Line Module, and Motor Modules. Each CU320-2 port supports a maximum of 16 DRIVE-CLiQ nodes (subject to firmware-version constraints). A common pitfall is to "chain" Motor Modules through X100→X101→X102. While legal, this topology drastically reduces diagnostic reach because a single cable break disconnects the entire downstream chain.

Recommended topology (star from CU320-2 ports):

1. CU320-2PN Port X100 → Line Module (mandatory; Line Module always occupies the first DRIVE-CLiQ node on port 0)
2. CU320-2PN Port X101 → Motor Module 1, X100
3. CU320-2PN Port X102 → Motor Module 2, X100
4. CU320-2PN Port X103 → Motor Module 3, X100
5. If a fourth Motor Module is needed, jumper Module 1 X101 → Module 2 X101 (a single bridge, not a daisy chain)

The key constraint is that the topology configured in STARTER / SINAMICS Startdrive must exactly match the physical wiring. Any mismatch triggers topology errors (F01360, A01360) at commissioning and the configuration is rejected.

For guidance on physical mounting of the CU320-2 on a Line Module, see the S120 Control Units and Additional System Components Manual.

3. Mixed Servo/Vector Configuration Rules

The CU320-2 allows combination of synchronous (servo) and asynchronous (vector) motors on the same Control Unit, but the automatic configuration wizard in STARTER / Startdrive defaults all axes to servo mode. The dialog "Select closed-loop control structure" must be invoked per axis to switch vector axes back to induction operation.

Field-proven rule: On any given CU320-2, if you mix motor types, select all axes as servo during automatic configuration and then manually reconfigure the induction motor axes by entering nameplate data into p0300–p0350. Manually setting motor type to "induction" while leaving the configuration class at "servo" produces inconsistent controller clocking and trips F07410 on the affected axis at first enable.

Configuring all axes uniformly during auto-configuration and then adjusting parameters afterwards is preferred over mixing config classes in the same wizard pass.

4. Telegram Selection: 110 (EPOS) vs 352 (Standard Vector)

Two telegrams dominate this class of application:

Telegram 110 carries the EPOS control word (STW1), status word (ZSW1), MELDW (message word), position setpoint/actual (XERR, POSISTW, POSISTW), and velocity setpoint/actual. It is the standard for the basic positioner integrated into SINAMICS S120.

Telegram 352 is the standard telegram for closed-loop speed/torque control with vector drives and provides extended diagnostics (NSOLL, NIST, MIST, IAIST, MELDW).

If the user's PLC function blocks are written for 352 (vector) and 110 (servo), the telegram must be set per axis and the corresponding PZD mapping in the SIMATIC project must match exactly. Telegram 999 (free BICO) is supported but should only be used when 110/352 cannot satisfy the application; debugging free-configured telegrams in a multi-axis PROFINET environment is a known commissioning time sink.

5. Line Module Control via p864 (Infeed Operation Enable)

On a SINAMICS S120 system with a CU320-2 plus Smart/Active Line Module, the infeed must be energized before any Motor Module can close its pulse enable. The parameter that interlocks the motor modules to the infeed is p0864 (note: the param number is p0864, not p864 as commonly typed) — "Power unit, infeed operation enable."

By default, each Motor Module's p0864 is BICO-interconnected to the Line Module's "Infeed ready" status bit. When two CU320-2 controls are present and only one Line Module exists, p0864 must be cross-wired between CUs:

1. On CU320-2 #1 (the one connected to the Line Module): expose the Line Module status bit (r863.0 = "Infeed ready") on a digital output or to PROFINET via a free telegram bit.
2. On CU320-2 #2 (no Line Module): bring this signal into p0864 of every Motor Module.
3. Inside STARTER, use BICO to connect r863.0 → p864 of each Motor Module on CU320-2 #2.

If p0864 is left at default, Motor Modules on the second CU will display "Switch-on inhibit" indefinitely after the first pulse enable because the Line Module status bit is not visible to the second CU.

6. PROFIsafe and STO Over PROFINET

The ET200S IM151-8F PN/DP CPU supports PROFIsafe. With no hard-wired enable paths in the cabinet (no separate STO terminal block wiring), STO must be propagated to SINAMICS S120 over PROFIsafe. This requires:

1. Adding the PROFIsafe telegram (typically telegram 30) to each servo/vector axis in the drive configuration.
2. Configuring a PROFIsafe slot in the SIMATIC hardware configuration with F-destination address matching the drive (set via p9810 on the drive side).
3. Wiring the F-CPU's F-Periphery DB to drive STW1 bit 0 (OFF1) or to the dedicated PROFIsafe control word.

The ET200S local F-modules (3 fail-safe DI and 1 fail-safe DO) handle the 6 E-stops and 6 guard doors. The F-runtime program passes the safety result to the drives via PROFIsafe. The PLC vendor must provide function blocks for telegrams 110 and 352; safety integration requires a separate PROFIsafe block.

For a working PROFIsafe sample on SINAMICS S120 with ET200S, search the Siemens support site for application example 68624711 referenced in the official SINAMICS S120 documentation.

7. Fault Diagnosis Matrix

Two drive-side faults dominate commissioning of mixed-axis CU320-2PN systems:

7.1 F07410 Deep Diagnosis

F07410 indicates the current controller output has reached the limit (typically the torque limit p1520/p1521 or current limit p0640). At slow speeds in the Control Panel with no mechanical load, this points to:

1. Phase sequence reversed: Swap any two of U, V, W at the motor terminal box or at the motor module output.
2. Encoder direction reversed: If r61 increments in the opposite direction from commanded motion, set p0410 = 1 (or change encoder inversion).
3. Brake not releasing: Check holding brake wiring and 24 V supply to the brake. If brake remains engaged, the motor draws locked-rotor current → F07410.
4. Drive defective: After confirming wiring and encoder, default the drive (Restore factory settings), re-run automatic configuration, and retry. If F07410 persists with a known-good motor/cable on a known-good axis configuration, the Motor Module itself is suspect.

7.2 F07900 Deep Diagnosis

F07900 typically fires when the speed controller output saturates and the actual speed diverges from the setpoint beyond the monitoring window. Mechanical blockage (jam) or wrong motor data are the usual culprits. Field remedy: free the shaft, verify U-V-W, replace the motor cable (a known intermittent failure mode on 6FX5002-2DC10-1AF0), and confirm the motor module's current measurement is not biased.

8. Cable and Motor Module Verification Procedure

When a single axis faults persistently while identical axes on the same Motor Module work, follow this procedure before replacing the Motor Module:

1. Confirm encoder increments: open Control Panel, manually spin shaft, observe r61 (speed actual). Must increment positively for one direction and negatively for the other.
2. Swap motor power cable with a known-good identical axis.
3. Swap feedback cable (6FX5002-5CN01-1AF0) with a known-good axis.
4. Swap motor with a known-good identical 1FK7042-2AK71-1RA0.
5. Default the entire drive (p0970 = 1 or "Restore factory settings" in STARTER).
6. Re-run automatic configuration; verify p0864 source.
7. Enable in speed control (n-control) via Control Panel.
8. Run a slow open-loop speed command; if F07410/F07900 do not reappear, the original failure was in the cable or motor.
9. If fault persists, replace the Motor Module (6SL3120-2TE15-0AA4).

9. ET200S Integration with SIMATIC

The IM151-8F PN/DP CPU has 3 PROFINET ports and 256 Kbyte of program memory. All I/O is local to the rack. With 3 fail-safe DI, 1 fail-safe DO, 6 E-stops, and 6 guard doors, the F-runtime library handles all safety logic. The remaining PROFINET bandwidth is consumed by:

• 2 × CU320-2PN (each with telegrams 30 + 110/352 per axis)
• 1 × Keyence XG7000 vision system (typically 8-byte cyclic I/O + acyclic parameter channel)

Recommended PROFINET update time for this configuration: 2 ms (cyclic), with reduction ratio 1. PROFIsafe requires ≤ 4 ms update time to satisfy SIL3 watchdog limits.

10. Commissioning Checklist

1. Wire DRIVE-CLiQ in star topology from CU320-2PN X100/X101/X102/X103 to each Line/Motor Module X100.
2. Apply 24 V to CU320-2PN and confirm green DRIVE-CLiQ LEDs on all nodes.
3. Connect STARTER / Startdrive via PROFINET (TCP) or via the CU320-2PN X120 service port.
4. Run automatic configuration; select "All servo" then manually convert induction axes.
5. Assign telegrams: 352 for vector, 110 for servo, 30 for PROFIsafe.
6. Configure p0864 cross-wiring between CUs.
7. Download configuration; perform RAM → ROM copy (p0977 = 1).
8. Test each axis in Control Panel with speed setpoint only (no position).
9. Enable PROFIsafe and verify STO/SS1 response.
10. Test full coordinated motion under PLC control.

11. Edge Cases and Field Notes

11.1 Why "All Servo" First, Then Convert Vector Axes

The STARTER wizard generates identical controller clocking across all axes when one closed-loop structure class is selected. If the wizard is allowed to mix classes (some servo, some vector from the start), the resulting per-axis sampling rates differ and the system clocking becomes inconsistent. This often manifests as F07410 on the first vector axis, not because the axis is defective but because the current controller is sampled at the wrong rate.

11.2 Line Module Takeover in Control Panel

When commissioning motor modules without PLC intervention, the Control Panel "Take control" dialog presents a drop-down for the infeed. If only the motor axis is taken under control, the Line Module stays in switch-on inhibit and the axis faults with "Switch-on disable of the drive is active." This is not a hardware fault — it is correct behavior. To take complete control, select "With infeed" in the dialog.

11.3 Identical Hardware, Different Behavior

When three identical servo axes on the same Double Motor Module show identical parameters and identical wiring but one faults while the others work, suspect (in order): cable, motor, Motor Module half-side. Defaulting the entire drive resolves configuration corruption but not hardware defects.

12. Frequently Asked Questions