Troubleshooting SINAMICS G130 F30027 F7802 DC Link Faults

1. Problem Overview

A SINAMICS G130 chassis drive built from catalog number 6SL3310-1GF34-7AA reports active faults F30027 and F7802 after a sudden supply-side power event (outage, blackout, or unintentional disconnect). Operators and commissioning engineers typically observe that the line contactor closes, 525 V AC is measured at the drive line terminals (three-phase, phase-to-phase), the pre-charging resistors are heard engaging, but the bus never reports a DC link voltage. In many cases the physical DC link does charge to the expected peak value (≈ √2 × V_LL ≈ 742 V DC for a 525 V line) but parameter r0070 (or r0070[0]) stays at 0 V, which is the unmistakable signature of a broken sensing path rather than a charging failure.

This reference walks through the fault chain, the hardware elements that make up the voltage-sensing path inside a G130, a structured diagnostic procedure using Siemens STARTER / Startdrive and the AOP30 advanced operator panel, and the field-proven replacement workflow for the CIM (Control Interface Module) and the VSM (Voltage Sensing Module) when those components are the root cause.

2. Fault Code Definitions

Both fault numbers are part of the SINAMICS drive-side fault system and have well-defined semantic meanings inside the firmware. Always read the cause field stored alongside the fault message via r0949/r0948 or the diagnostics buffer, since fault value interpretation depends on the firmware version loaded.

2.1 F30027 — Power unit monitoring

F30027 belongs to the F3xxxx fault class reserved for faults originating inside the power unit (the IGBT stack / line-side inverter module). In G130 firmware V5.x and later the message is registered as:

• F30027 — Power unit: power supply voltage monitoring faulty.

The drive's internal plausibility check between the measured DC link voltage and the expected value (derived from the line voltage via the VSM/line voltage sense path) has failed. Typical recorded cause values of F30027 include:

• Cause value 0: Undervoltage — measured V_DC dropped below the configured threshold.
• Cause value 1: Overvoltage — measured V_DC above the configured ceiling.
• Cause value 10: Power unit voltage sensing faulty (signal implausible).
• Cause value 11: Hardware detected no supply after pre-charging completed.

2.2 F7802 — Drive readiness fault

F7802 sits in the F7xxxx class which covers drive-level coordination faults. On most G130 firmware revisions this becomes:

• F7802 — Drive not ready / readiness missing.

Internally, F7802 is raised when one or more subordinate objects (including the basic operator panel loops and power unit readiness) report ZSW1.2 (ready) as false. In the scenario covered here, F7802 is a cascaded consequence of the underlying F30027; once the power unit can correctly report a valid V_DC, F7802 clears automatically on the next OFF1 → ON transition.

3. Affected Hardware Architecture

The 6SL3310-1GF34-7AA is a frame-size FS-FSG SINAMICS G130 chassis unit rated for the 3 AC 380–480 V range with a peak DC link class of 720 V DC. The DC link voltage sensing path travels through four functional blocks, in order:

1. VSM (Voltage Sensing Module) — line-side sensing board mounted on the right-hand side of the power block; measures the incoming three-phase voltage.
2. DC sensing branch — internal resistor-divider and isolation amplifier on the power block PCB.
3. CIM (Control Interface Module) — board-level adapter that conditions the analog V_DC signal and passes control signals between the power block and the Control Unit over the DRIVE-CLiQ ribbon cable.
4. Control Unit (CU320-2 or CU310-2) — receives the scaled V_DC value and exposes it as r0070.

Each of these blocks is a candidate failure point. Field experience on the FSG frame shows that the failure mode (physical DC charging present, but r0070 reads 0 V) collapses to one of three causes:

4. Failure Mechanism

After a real-world power outage, three failure-causing phenomena appear at the FSG frame drive end:

1. Insulation stress — the missing 525 V AC line can be replaced by transient overvoltages as grid reclosure propagates through transformer inductance. The first surge hits the in-rush limiter and capacitor bank.
2. Loss of the DRIVE-CLiQ link — the ribbon connecting CIM to the CU can pick up radiated transients in the cabinet. The DRIVE-CLiQ protocol includes CRC checking; if the CRC fails repeatedly, the drive drops the channel and the CU declares a power unit monitoring fault.
3. Damaged sense resistor chain — a high-energy surge on the DC link can blow the high-impedance resistor divider that feeds the isolation amplifier, leaving the analog front-end reading 0 V while the link is physically still alive.

In the case described, replacing the CIM did not clear the fault because the actual damage was further upstream (the resistor-divider / sense front-end on the power block). The next replacement candidate in the chain is the power block or its VSM daughter board, depending on frame and build variant.

5. Step-by-Step Diagnostic Procedure

1. Verify safe state. Apply the lockout/tagout procedure to the line supply. Wait until the DC link discharges — monitor r0046 (sequence bit 6) until it is false, and verify zero voltage on the link before opening the cabinet.
2. Re-energise under STARTER observation. Connect a programming device to the G130 via the X127 service port. Open the project, go online with the CU, and place the drive in S6 — Commissioning state.
3. Trace the bus voltage. Watch r0070 in real time while issuing the line contactor close command. If r0070 stays at zero while a multimeter at the DC terminals shows ≈ 740 V DC, the sensing path is broken.
4. Read the diagnostics buffer. Open Menu → Diagnostics → Diagnostics buffer. Note r0945 (fault number), r0948 (timestamp), and r0949 (fault value / cause). Save the buffer.
5. Check the VSM state. If the system has an external VSM (line voltage sense), navigate to the VSM object and check r0026[1] (line voltage actual) and the VSM fault/alarm screen. A VSM that reports V_DC but lost line sense still triggers F30027 via the cross-check.
6. Inspect the DRIVE-CLiQ diagnostics. Look at Topology → Component status. Any CIM or DRIVE-CLiQ node flagged red confirms communication loss.
7. Hardware inspection. Power down. Open the cabinet. Visually inspect the CIM (front of the power block) and the sense resistor chain on the right-hand side of the power module. Look for discoloration, cracked components, or burnt smell.

5.1 Quick Triage Matrix

6. Hardware Replacement Procedure

6.1 CIM Replacement

1. Power down and discharge. Verify r0046.6 = 0.
2. Remove the front cover of the power block to access the CIM mounting bracket (FS FSG: front-right of the power module).
3. Disconnect the DRIVE-CLiQ ribbon cable and the signal ribbon to the CU.
4. Remove the two retaining screws and lift out the CIM in the keyed slot.
5. Install the replacement CIM with the same index/version order. Check the spare part number — the FSG frame accepts CIM part number 6SL3352-3AG77-8AA0 (or the equivalent successor in current catalog data, e.g. 6SL3352-3AG78-2AA0) for the 3 AC 380–480 V range.
6. Reconnect ribbon cables to the drive modules. Note the cable orientation arrows.
7. Reapply supply, go online with STARTER, accept the new CIM topology. If the firmware identifies a new component, follow the recommended commissioning sequence.
8. Run a no-load ON/OFF cycle and confirm that r0070 rises with the AC line.

6.2 VSM Replacement

1. Identify the VSM — on frame FSG chassis units it is usually attached to the right-hand side of the power block, behind a cover plate.
2. Disconnect the sense lead pair (line side) and the signal connector to the CIM.
3. Release the latch and pull the VSM straight out.
4. Insert the new VSM. Spare part number for the 525 V / 690 V line voltage range: 6SL3353-3AG78-1AA0 (verify against current catalog).
5. Reconnect signal connector. Tighten sense lead terminals to 0.6 N·m.
6. Power up, run diagnostic, confirm r0070 tracks the line voltage.

6.3 Power Block Replacement

If the resistor divider on the power block itself has been damaged, the entire power block must be replaced. Power block replacement is a heavy-lift operation and should be carried out by service personnel with G130 chassis certification. The simplified sequence is:

1. Withdraw the power block from the cabinet onto a service trolley.
2. Disconnect DC link busbars from the rear.
3. Swap CIM, VSM, and IGBT modules onto the new power block to retain the commissioning context.
4. Install replacement part number 6SL3320-1GF34-7AA0 or current equivalent.
5. Recommission the drive using the original STARTER project.

7. Control Unit Reconfiguration

After any CIM, VSM, or power block swap, the Control Unit topology will detect new components. Always run the following to avoid stale topology errors:

• p949 — read DRIVE-CLiQ faults.
• p9906 and p9907 — activate / parameterize on PROFINET (where applicable).
• Inspect topology under STARTER Configuration → Topology.

8. Verification and Commissioning

1. Apply supply without enable command. Monitor r0070 and r0026[1] as pre-charge completes; both must rise to expected peak and hold steady.
2. Issue OFF1 no-enable cycle. Watch for new faults in the diagnostics buffer.
3. Issue a low-speed jogging reference using P1071 (function generator) where permitted by the application. Confirm r0027 matches r0062 within tolerance.
4. Take the drive into speed control with reduced torque limit (set p1530 = 50% momentarily). Confirm normal response, then restore p1530.
5. Save parameters with RAM → ROM (copy RAM to ROM) and back up the project.

9. Preventive Measures

• Install proper surge protection (Class B + Class C combined arresters) upstream of the drive line feeder. The G130 chassis does not include line-side overvoltage arrestors as standard.
• Use shielded DRIVE-CLiQ cables with the drain wire bonded at both ends to ground.
• Verify that the cabinet ground bus is bonded to plant ground at sub-1 Ω impedance. Surge energy commonly discharges through the cabinet safety ground.
• For installations in regions with frequent sags and swells, parameter p0210 should be set to the actual line class (typically 525 V / 50 Hz) so the internal DC link threshold matches reality. Refer to the SINAMICS G130 Parameter Manual (Document 6SL3097-4AF00-0BP0) for the correct value selections.
• Log r0070 continuously into the SCADA historian. A falling or noisy r0070 trending can predict CIM degradation before a power outage escalates it to F30027.

10. Spare Part Reference Catalog

11. Operational State Word Diagnostics

The G130 reports drive readiness via ZSW1 bits; knowing which bit is still 0 helps diagnose lingering faults after a hardware swap: