Resolving SIMOTION D425-DP F30002 Fault and SMC30 Encoder 2 Setup

1. Problem Overview

The SIMOTION D425-DP controller integrates a SINAMICS S120 drive line on a single hardware platform (catalog 6AU1425-0AA00-0AA0 / 6AU1425-0AD00-0AA0). When paired with an external SMC30 Sensor Module Cabinet-Mounted (catalog 6SL3055-0AA00-5CA2), the integrated axis expects two encoder interfaces:

• Encoder 1 – motor encoder used for position and commutation feedback (typically a DRIVE-CLiQ-mounted or resolver module).
• Encoder 2 – external machine encoder wired into the SMC30, used as speed reference for synchronous motion or load-side position feedback.

Two field failures recur in this configuration:

1. Fault F30002 (DC link overvoltage) triggered intermittently during homing or any axis deceleration with an unloaded or lightly loaded motor.
2. Encoder 2 not visible in the SIMOTION SCOUT topology, leaving the speed feedback path broken.

The root causes are distinct but linked: the missing braking unit produces the overvoltage trip, and the missing SMC30 node in the DRIVE-CLiQ topology prevents Encoder 2 from being assigned. This guide covers parameter-level root-cause analysis, hardware mitigation, and the correct SCOUT commissioning sequence.

2. System Architecture and Topology

A correct D425-DP topology for dual-encoder operation must contain the following DRIVE-CLiQ nodes, in this order from the controller:

1. Control Unit – D425-DP (acts as CU320-2 equivalent for the integrated axis).
2. Line Module – e.g., Smart Line Module 6SL3130-6AE15-0AB0 (not regenerative by default).
3. Motor Module – Single Motor Module sized to the motor (e.g., 6SL3120-1TE13-0AA0 for 3 A).
4. Motor with Encoder 1 – connected via DRIVE-CLiQ or via a SMC10/SMC20 if the motor has no DRIVE-CLiQ.
5. SMC30 (Encoder 2) – last node in the chain, connected through the second DRIVE-CLiQ port of the Motor Module or via daisy-chain from the Line Module.

If the SMC30 is missing from the topology tree under SCOUT → Drive → Topology, the drive will not publish p0400[1], p0430[1], or the associated fine resolution / pulse count parameters. The axis in SIMOTION cannot reference Encoder 2 because the drive object has only one encoder interface instantiated.

3. Fault F30002 – Root Cause Analysis

F30002 is the standard SINAMICS fault for DC link overvoltage. The default trip thresholds (firmware V4.x / V5.x, integrated drive) are:

When the integrated Smart Line Module (or any non-regenerative Line Module) is used, the energy returned by the motor during OFF1/OFF3/Ramp-down cannot flow back to the mains. The energy has only two sinks: the DC link capacitance and a braking resistor. If neither is sized to absorb the regeneration, F30002 trips.

3.1 Energy Balance

Regenerative energy per deceleration event:

E_regen = 0.5 * J_total * (ω_start² − ω_end²) [Joules]

where J_total = motor inertia + load inertia reflected to the motor shaft, and ω is angular velocity in rad/s.

DC link capacitance of a typical 3–5 kW Motor Module (e.g., 6SL3120-1TE15-0AA0) is approximately C_dc ≈ 110 µF. Stored energy ceiling above nominal DC link voltage (560 V at 400 V AC input):

E_dc = 0.5 * C_dc * (V_trip² − V_nom²) ≈ 0.5 * 110e-6 * (760² − 560²) ≈ 14.5 J

For a motor/load combination with J_total = 0.005 kg·m² decelerating from 3000 rpm (ω = 314 rad/s) to zero:

E_regen = 0.5 * 0.005 * 314² ≈ 246 J

This is roughly 17× the DC link absorption capacity. The fault is therefore a physical certainty without external dissipation hardware.

3.2 Diagnostic Path

To confirm F30002 is energy-related and not a supply issue:

1. Open SCOUT → Drive → Diagnostics → Fault Buffer; record fault value r0949 and additional info r0948. For F30002, r0948 typically reads 1 (DC link overvoltage).
2. Check r0070 (DC link voltage) and r0029 (current) at the moment of trip. If r0070 > 760 V on a 400 V line, the trip is energy-driven.
3. Inspect the fault history pattern. If F30002 appears only on OFF1 or OFF3, the ramp generator is dumping kinetic energy too quickly for the available absorption.

4. Software-Only Mitigation (Temporary)

Three parameter changes can suppress or delay F30002 without additional hardware. These are commissioning compromises, not permanent solutions for production because they extend cycle time and reduce dynamic performance.

4.1 Enable Vdc_max Controller

The Vdc_max controller extends the ramp automatically when DC link voltage approaches the warning level:

p1240[0] = 1     ; Vdc_max controller enabled
p1243[0] = 100   ; dynamic factor of Vdc_max controller (default 100%)
p1245[0] = 1     ; Vdc_min controller enabled (also helpful for line dips)
p1247[0] = 1     ; Vdc_max controller dynamic factor (default 100%)

Reference: SINAMICS S120/S150 List Manual, parameter p1240.

4.2 Extend Ramp-Down Time

p1121[0] = 5.0   ; ramp-down time, was probably 1.0 s; raise to 5–10 s

Longer ramps reduce ω_start² − ω_end² per unit time, lowering instantaneous regenerative power.

4.3 Set Regenerative Torque Limit

p1531[0] = -3.0  ; negative torque limit (regen), in Nm, scaled to motor

Limiting regenerative torque to a value the DC link can absorb prevents overshoot.

5. Hardware Solution – Braking Resistor Sizing

For a non-regenerative Line Module, install a braking module and braking resistor matched to the Motor Module peak and continuous ratings. Common Siemens part numbers:

Sizing formulas (verify against local code and Siemens application guidelines):

P_peak >= E_regen / t_decel_min

P_continuous >= (cycle_factor) * P_peak

where cycle_factor = fraction of cycle time the resistor is active (typically 0.05–0.20 for indexing axes).

Once the hardware is installed, configure the drive to recognize it:

p0219 = 1     ; braking module configuration: internal (SBM)
p0217 = 1     ; braking resistor configuration: internal, present
p1240 = 1     ; Vdc_max controller enabled
p1247 = 1     ; Vdc_max dynamic response on

Reference: SINAMICS S120 Equipment Manual – Braking Modules.

6. Encoder 2 Setup via SMC30

The SMC30 is a stand-alone encoder interface module that supports TTL, HTL, and SSI encoders. It is connected to the drive via DRIVE-CLiQ and exposes one encoder channel in the topology.

6.1 Hardware Wiring

Use twisted-pair shielded cable, shield bonded at the SMC30 end only. For HTL encoders, set the supply voltage (5 V or 24 V) via the rotary switch on the SMC30 front panel.

6.2 Drive-Side Parameter Configuration (Encoder 2)

Once the SMC30 is detected in the topology, the second encoder is mapped to parameter indices [1] (Encoder 1 is index [0]).

; --- Encoder 2 type (HTL unipolar, bipolar, TTL, SSI) ---
p0400[1] = 3001     ; 3001 = HTL unipolar, 3002 = HTL bipolar, 3003 = TTL
p0401[1] = 0        ; 0 = incremental
p0404[1] = 0        ; 0 = voltage sense, 2 = bipolar
p0405[1] = 0        ; square-wave (default)
p0408[1] = 2500     ; pulses per revolution (set to encoder nameplate)
p0420[1] = 0        ; encoder connection type (0 = standard SMC30)
p0425[1] = 0        ; fine resolution via p0418/p0419
p0410[1] = 0        ; encoder inversion: 0 = not inverted
p0430[1] = 0        ; zero mark enable: 0 = off, 1 = on
p0431[1] = 0        ; zero mark tolerance window

6.3 SIMOTION Axis Configuration

In SCOUT, open the axis configuration:

1. Project navigator → right-click the TO axis → Properties → Encoder.
2. Set Encoder 1 (position feedback) to the drive's internal motor encoder.
3. Set Encoder 2 (speed feedback) to the SMC30 input.
4. Assign the SIMOTION technology object type: _TO_SynchronousAxis if the load is geared to the motor, or _TO_SpeedAxis for speed-only use.

Map the Encoder 2 actual value in the program:

// ST snippet
axis1.encoder2.interface.address := 16#0800; // I/O address of SMC30 PZD
velocity_actual := axis1.encoder2.velocity.actual / 1000.0; // scaling

7. Step-by-Step Commissioning Procedure

1. Hardware verification. Confirm SMC30 is powered (LED green), DRIVE-CLiQ link active (LED yellow/green at both ends), and the encoder supply is correct (5 V or 24 V at terminal X520).
2. Topology check. In SCOUT, go online and open Drive → Topology. The SMC30 should appear with the correct article number and firmware version. If it appears red, check DRIVE-CLiQ cable routing and termination rules.
3. Configure braking unit. Set p0217 = 1, p0219 = 1, and physical presence of the resistor confirmed before energizing the line.
4. Download parameters. Right-click the drive → Download to target device (RAM), then save to ROM (CF card of D425-DP).
5. Encoder test. In Drive → Diagnostics → Trace, record r0061[1] (Encoder 2 actual speed). Hand-rotate the load and verify the sign and magnitude match the mechanical rotation.
6. Test motion. Run a low-speed jog (v = 100 mm/min) in both directions. Monitor r0029 (current), r0070 (DC link), and r0061[0..1] for both encoders.
7. Deceleration test. Command OFF1 at full velocity. Monitor r0070 – it must not exceed the warning level (720 V at 400 V AC). If it does, verify the braking resistor is firing (test point across the resistor with an oscilloscope, or check r1239.0 brake chopper status).
8. Save to ROM and back up the project to the engineering station.

8. Verification Checklist

9. Common Pitfalls and Field Notes

• Sign of Life errors (F30001, F08501) often appear in parallel with F30002 on a D425-DP running without a braking unit. They are not the root cause but a downstream symptom of drive firmware entering safe state during a fault.
• Encoder 2 visible but reading zero: check p0404[1] – if set to 2 (bipolar) with a unipolar HTL signal, the SMC30 will reject counts. Use a scope to verify both A and B are toggling.
• Direction reversed: do not invert mechanically; flip the encoder direction with p0410[1] = 1. This avoids mistakes in the mechanical assembly.
• Loss of SMC30 on power cycle: the D425-DP CF card may not contain the topology of the SMC30 if it was added after the last save-to-ROM. Re-save the project and re-clone the CF card before shipping.
• Braking resistor duty cycle: for high-cycle applications, oversize the resistor by 2× continuous rating. Thermal failure of the resistor is a common field cause of repeated F30002.
• Single-phase line input: if the integrated SLM is fed from a 1-phase 230 V source, the DC link nominal is roughly 320 V and the trip threshold is reduced. Confirm supply topology with the actual installation drawings before any current calculation.

10. Alternate Platforms and Migration Notes

For new installations where regenerative energy dominates (vertical axes, high-inertia centrifuges), consider replacing the Smart Line Module with an Active Line Module (ALM) to return energy to the mains:

• 6SL3130-7AE15-0AB0 (5 kW ALM, 400 V)
• 6SL3130-7AE21-0AB0 (10 kW ALM, 400 V)

Set p0217 = 0 to disable the braking chopper integration when the ALM is used. The ALM also requires a line filter (6SL3000-0BE31-0AA0 or similar) to meet EMC requirements.

For SIMOTION D445-DP or D455-2 DP/PN (catalog 6AU1450-...), the same parameter map applies, with the additional benefit of two axis objects available – Encoder 1 and 2 of axis 1 and 2 can be assigned independently.

11. Related Fault Codes

Reference: SINAMICS S120/S150 List Manual – Faults and Alarms.